Testing local cocoa selections in three provinces in Sulawesi: (i)Productivity and resistance to cocoa pod borer and Phytophthora podrot (black pod)
Peter McMahon a, *, Hussin bin Purung b, Smilja Lambert b, Sahardi Mulia c, Nurlaila c,Agung W. Susilo d, Endang Sulistyowati d, Sri Sukamto d, Muhajir Israel b, Ashar Saftar b,Arman Amir b, Agus Purwantara e, Arief Iswanto e, David Guest f, Philip Keane a
a Department of Botany, La Trobe University, Australiab Mars Inc., Jln Kima 10, Kav. A6, Kima, Daya, Makassar, Sulawesi 90241, Indonesiac BPTP Sulsel, Makassar, South Sulawesi, Indonesiad Indonesian Coffee and Cocoa Research Institute, Kaliwining, Jember, East Java, Indonesiae Biotechnology Research Institute for Estate Crops, Indonesiaf Faculty of Agriculture and Environment, University of Sydney, Australia
a r t i c l e i n f o
Article history:Received 8 June 2014Received in revised form27 December 2014Accepted 2 January 2015Available online
Keywords:Multi-locationCocoa selectionsClonesResistanceBean qualityCocoa pod borerPhytophthora pod rot (black pod)
Trials were established on smallholder cocoa farms in three provinces in Sulawesi to assess productivityand constitutive responses of local cocoa clones to cocoa pod borer (CPB) and Phytophthora pod rot (Ppr)in different environmental situations. Twelve clones per trial (local farmer-assisted selections or clonesproduced by hybridisation programs in East Java and Malaysia) were tested in the districts of Pinrang,Polewali-Mandar and North Kolaka, including four standards common to the trials: the Malaysian clone,PBC123, and three selections from Sulawesi farms. The clones were evaluated from the time they startedfruiting in 2010 (about two years after planting) for two years during which time chemical pesticideswere not applied. Otherwise farms were managed according to recommended practices, includingharvesting each fortnight, fertiliser application and heavy and light pruning, depending on the season.Butter fat content was generally lower than 50% but was higher in three local selections in Pinrang, M04,RB and Panimbu Red. While strongly dependent on genotype, fat and shell content and pod values in thecommon standards showed some variation between sites. The bean size and fat content of PBC123 waslow, but this clone yielded better than most of the clones tested. For the common standards, yield es-timates obtained from average yield per tree were higher in Pinrang (735e1100 tons/ha/annum) than inN. Kolaka (342e894 ton/ha/annum) or Polewali-Mandar (485e899 tons/ha/annum) indicating a markedsite-effect. The number of flowers produced was higher in the common standards in Pinrang. Soil pa-rameters including pH and exchangeable calcium, magnesium and potassium were higher in Pinrangthan in Polman, although both sites were deficient in soil nitrogen and organic carbon. Lower averageCPB infestation rates in ripe pods for the two-year evaluation period occurred in Pinrang (48e66%) andPolewali-Mandar (19e68%) than in N. Kolaka (77e80%). In most of the clones, total and severe CPBincidence decreased during the high pod season but some selections, such as M04 and TR01, maintaineda low total and severe CPB incidence in both the low and high pod seasons, indicating partial resistance.In the ripe pods of common standards, the highest average Ppr incidence (ranging from 10 to 14%)occurred in N. Kolaka, which had a higher annual rainfall than the other sites. In ripe pods in the Pinrangtrial, Geni J, M06 and Panimbu Red had a low Ppr incidence (4.4e4.8%) while M04 was Ppr-susceptible(23%). Incidence of Helopeltis spp. was high in the immature pods of some clones (exceeding 30% of thetotal harvest in M01 and Geni J in Pinrang). The results show that the performance of clones is affected bythe locality in which they are grown, as well as their genotype, indicating the importance of testingclones under different environmental conditions. While the trials confirmed the efficacy of farmer-assisted selection, they also indicated that clones resistant to CPB, were susceptible to Ppr or otherpests/diseases, and vice versa. For example, local selection, M04, was highly susceptible to Ppr, yet
P. McMahon et al. / Crop Protection 70 (2015) 28e39 29
1 The 6th Indonesian International Cocoa Conferencfor a sustainable cocoa industry, Askindo, May 15Indonesia.
resistant to CPB. Therefore, the results indicate the importance of efforts to screen the progeny of hybridcrosses that combine resistance and yield traits.
Table 1Clones, their origin (district in Sulawesi or region outside Sulawesi), purpose ofselection and the districts in Sulawesi in which they were tested: Pinrang (Tiroang),North Kolaka (Tiwu) and Polman (Anreapi). i, included in trial; r, resistance; PBC,Prang Besar clone (PBC123 is known locally as Sul1, Sulawesi1); M, Muhtar; Geni J,Genin Jasi; Pan R, Panimbu Red; DRC, Djati Roenggo clone; RB, Rahim Burau; TR,Torea; ICCRI, Indonesian Coffee and Cocoa Institute; PCK, Puang Caddik; KKM, KlonKoko Mardi; NR, Nasir Rauf; PwPg, Polewali-Pinrang; ILH, Ilham; BR, Balong River(BR25 is known locally as Sul2, Sulawesi 2); KW, Kaliwining.
Clone Pod colour Trial site Origin Selected for
Pinrang N.Kolaka
Polman
PBC123(Sul1)
Red i i i Malaysia Yield
M01 Green i i i N. Luwu YieldM05 Pale Red i i i N. Luwu VSDrGeni J Red i i i E. Luwu VSDrPan R Redeorange i i N. Luwu YieldM04 Green i N. Luwu Yield/
qualityM06 Redeyellow i i N. Luwu YieldDRC15 Pale green i E. Java VSDrRB Orange i E. Luwu YieldTr01 Redeorange i N. Luwu YieldICCRI04 Green i E. Java YieldPCK Green i Mamuju YieldKKM22 Yellowered i Malaysia YieldNasir Rauf Green i i Soppeng YieldMuhtar Yellowered i i Soppeng YieldPwPg Redeorange i Pinrang YieldDarno Green
eyellowi Soppeng Yield
ILH Greeneyellow
i i Soppeng Yield
BR25 (Sul2) Red i Malaysia Yield
1. Introduction
In Indonesia, cocoa (Theobroma cacao), originating in SouthAmerica, has a long history of various introductions with the Cel-ebes (or Sulawesi) being the first island in which cocoa, brought bySpanish sailors via the Philippines, was planted (Durand, 1995).However, it is only relatively recently (beginning in the early 1980s)that cocoa production has expanded to global proportions inSulawesi (Ruf and Yoddang, 2000, 2004a). This expansion, due to aboom in smallholder production, has led to the island contributingto over 60% of the total production of Indonesia (currently theworld's third largest cocoa producer). Following an early ‘honey-moon’ period, relatively free of pests/diseases and with sufficientlyfertile soils (Keane, 1992; Ruf and Yoddang, 2000, 2004b), farmers,processors and exporters of cocoa in Indonesia are now facing adecline in productivity and in bean quality, an issue addressed bythe 6th Indonesian International Cocoa Conference1. The declinecan be accounted for by a number of factors, including decreasingsoil fertility and organic matter content and an increased incidenceof pests/diseases. Cocoa bean quality in Sulawesi is compromisedby infestation by cocoa pod borer (CPB), Conopomorpha cramerella,now widespread in Indonesia. A large proportion of beans ininfested pods becomes unusable and with heavy infestation thewhole pod must be discarded. Losses also are incurred by Helopeltisspp. although attack is more localised. In addition, during the wetseason the incidence of Phytophthora pod rot (Ppr) or black podcaused by Phytophthora palmivora (Guest, 2007) rises markedly sothat losses of 50% and above may occur during periods that areparticularly wet. If Ppr incidence is high in the main harvest seasonthis can become the most serious pest/disease problem for farmers.Diseases impacting on vegetative plant parts, especially vascular-streak dieback (VSD), also incur major losses. These problems arecurrently driving Indonesian farmers to replace cocoa with othercrops, particularly oil palm.
Most of the cocoa in Sulawesi has been derived from parentmaterial introduced from seed gardens established in Sumatra andJava, or from Malaysia brought back to Sulawesi by returning itin-erant labourers. This has led to a moderately genetically diversepopulation on farms as well as considerable diversity in produc-tivity, quality and pest and disease resistance. Therefore, the di-versity of the cocoa currently planted in smallholdings is a soundbasis for local selection and hybrid crossing for pest/disease resis-tance and improved yield and quality. With the techniques of side-and top-grafting, now widely adopted in Sulawesi, there is a greatpotential to select improved genotypes and propagate them clon-ally. Potentially, employing improved planting material and selec-tion of genotypes that are suitable for particular environments(with input and cooperation from local farmers) could help toaddress the decline in productivity and quality, and discouragefarmers from turning to crops with higher nutrient requirements,such as maize, or crops that are less environmentally sustainable,such as oil palm. In an Australian Centre for International Agricul-tural Research (ACIAR) project conducted jointly with Mars Inc. this
e: Empowering smallholderse16, 2014, Nusa Dua, Bali,
approach was tested in different locations in southern Sulawesiusing a range of local selections from Sulawesi, clones from hybridcrosses conducted in Jember by the Indonesian Coffee and CocoaResearch Institute (ICCRI) and two Malaysian clones, PBC123 andBR25, which are now planted widely in Sulawesi.
To test genotypes identified as promising for particular charac-teristics by smallholder farmers, trials were established on cocoasmallholder farms in three provinces in Sulawesi. The mainobjective of this research was to identify local genotypes suited topropagation in Sulawesi under local conditions of natural pest/disease infestation. Data obtained could be used to recommendselected clones as farmers' planting material or for using asparental material in hybrid crosses. An additional aim of the trialswas to provide more information about the performance ofselected clones in different geographical locations. Here we reporton the performance of the selected clones, in particular their podand bean properties and variations in response to CPB and Ppr. Awide range of responses was found between the different clonesindicating an urgent need to combine promising characters inbreeding programs. Site-specific effects were also evident pointingto the necessity of testing promising material in situ since genotype
KW617 Red i E. Java YieldKW523 Reddish
greeni E. Java PPRr
KW516 Green i N.Sumatra YieldHusbitori Green i Bone Quality
P. McMahon et al. / Crop Protection 70 (2015) 28e3930
performance is strongly affected by local environment and pest/disease conditions.
2. Materials and methods
2.1. Clone selection
Promising cocoa clones were selected for testing in multi-location trials in Sulawesi. Selections were obtained locally fromfarms by Mars Inc., a previous ACIAR project and the IndonesianCoffee and Cocoa Research Institute (ICCRI) in East Java whichprovided some clones obtained from crosses that combined pro-ductivity and resistance traits. Most of the genotypes were selectedinitially based on the knowledge of farmers.
The clones included in the trials and the locations in which theywere tested are shown in Table 1. In each trial 12 clones were grownand evaluated: these were mainly local farmer selections but alsoincluded PBC123 and BR25, now locally renamed ‘Sulawesi 1’ andSulawesi 2, respectively, Malaysian hybrid offspring cloned fromthe progeny of breeding programs (see Chong, 1984; Chong andShepherd, 1986), and clones obtained from hybrid crosses con-ducted by ICCRI in East Java. Clones tested in common in all of thetrials were PBC123, and three local clones selected by Mars Inc.with the cooperation of farmers in South Sulawesi: M01, M05 andGeni J (see Table 1).
Fig. 1. Typical layout of a clone testing trial. Each clone (designated by a letter) was plantedfour trees. A list of the clones in each trial is given in Table 1.
2.2. Trial establishment
A trial was established in each of three provinces in Sulawesi:South Sulawesi in Alla Calimpo, Tiroang, Pinrang District (Latitude030470046.24S; Longitude 1190410010.3E; altitude 25 m), West Sula-wesi in Beluak, Anreapi, Polewali-Mandar (or Polman) District(Latitude 03�2300.3500S; Longitude 119�20041.2000E; altitude 45 m)and South-East Sulawesi in Tanggeawo, Tiwu, N. Kolaka District(Latitude 03�18059.2900S; Longitude 120�58057.3900E; altitude 38 m).The latter trial was separated from the others by the Gulf of Bone.
The trials were established by planting 4e5 month-old top-grafted seedlings (clonal budwood grafted onto locally availablerootstock seedlings) of the clones in early 2008 using an 8-tree plotdesignwith four replicate blocks (Fig. 1). Therefore, each trial beganwith 384 trees; some trees were lost but most of the plots in eachtrial retained at least 6e8 trees for evaluation with a few plotshaving less than this. The trials were kept free of chemical pesti-cides (including herbicides) except in the early stage of establish-ment. In the Pinrang and N. Kolaka trials pesticide applications re-commenced in mid-2012, but during the period of evaluation re-ported here (2010e2012) no pesticide chemicals were applied.Otherwise, the trial sites were managed with normal farm practiceas recommended by field extension officers. NPK fertiliser (250 gper tree) was applied twice per year. Heavy pruning was conductedin the early wet season and lighter pruning towards the end of the
in rows of 8-tree plots in each of four blocks. In Pinrang, plots consisted of two rows of
P. McMahon et al. / Crop Protection 70 (2015) 28e39 31
wet season. Pruning was avoided in the dry season. Regular com-plete harvesting (Wood et al., 1992) was practiced in all of the trialsbut once per fortnight rather than every 10 days, and all infectedpod husks and immature pods were buried or removed from thesite: this forms part of a cultural strategy to control CPB.
2.2.1. Climate zonesThe trial sites occur in climate zones A and C according to the
criteria of Schmidt and Ferguson (1951) who identified eightclimate zones (AeH) in Indonesia. According to their mapped zones(see Whitten et al., 2002), North Kolaka is within zone A (perma-nently humid with at least 100 mm rainfall per month) and thePinrang and Polewali-Mandar trial sites lie within zone C (seasonalwith approximately three consecutive dry months receiving lessthan 60mm rainfall). In 2011, the total annual rainfall in the vicinityof the trial sites in Pinrang, North Kolaka and Polewali-Mandar was1229 mm, 1869 mm and 1363 mm, respectively (Bureau of Mete-orology, Indonesia).
Table 2Yield (kg dry beans per 1000 trees per annum) of some of the clones in the threetrials in Sulawesi, including those common to the trials (see Materials andmethods).Pods were harvested and the beans extracted, dried and weighed each fortnight fortwo years (2010e2012). Pod production was variable between the four replicateblocks. The mean production per tree (kg) of dry beans (±SEM) per annum wasextrapolated to 1000 trees to give the approximate yield/ha/annum.
Geni J 824.3 ± 39.6 331.2 ± 79.3 735.1 ± 151.3M05 639.6 ± 26.6 64.3 ± 23.4 485.0 ± 35.3Pan R 735.1 ± 84.7 341.6 ± 80.3 niM06 900.9 ± 272.7 412.6 ± 72.6 niBR25 ni ni 451.6 ± 81.6KW516 ni ni 935.1 ± 68.0a
KW523 ni ni 1284.0 ± 406.8a
KW617 ni ni 1176.3 ± 264.0a
a Data taken from 2 replicates.
2.3. Evaluation
Evaluation began in May 2010 (in Pinrang and Polman) and June2010 (in North Kolaka) when the trees had begun to produce pods.All ripe pods were harvested each fortnight as well as damagedimmature pods. Pods harvested in each plot were pooled for eval-uation. The proportion of pods infested with CPB, Ppr and or Hel-opeltis spp. was determined. Pods were cut open and evaluated forseverity of CPB infestation as follows: 1, nil: no CPB infestation orhealthy pods; 2, light infestation: <10% and all beans still extract-able by hand; 3, moderate infestation: >10%with some of the beansunextractable by hand; 4, heavy infestation: all beans unextractableor 100% loss.
The severity of infestation by Helopeltis spp. was evaluated byvisual inspection of the pod surface for lesions or their scars(Stonedahl, 1991) as follows: N, nil: no signs of infestation; L, lightinfestation: <10 lesions; M. moderate infestation: 10e50 lesions; H,heavy infestation: >50 lesions and pod shape changes.
Phytophthora pod rot (Ppr) was scored by estimating the pro-portion of the pod coveredwith the brown discolouration typical ofa Ppr lesion: N, no lesion; L (light) >10%; M (moderate), 10e50%; H(heavy), over >50% of the pod surface discoloured. Many pods wereaffected by both CPB and Ppr and some by Helopeltis spp. as well.Pods with multiple infections were evaluated separately. To obtainoverall incidence and severity for each pest/disease the sum of thepods infected with a single pest/disease was taken.
At each harvest, wet weight of beans for each clone was deter-mined. The beans were then dried to at least 38% of the wet beanweight (usually taking about 4e5 days) and the dry weightsdetermined.
In each of the trials, beans collected from a few consecutiveharvests in 2010 were dried and then pooled for analyses. Beanquality characteristics including fat and shell content were deter-mined in the cocoa quality laboratory at Mars Symbioscience,Makassar.
The number of flowers on each tree was estimated once permonth and allocated one of the following scores: 1, 0 flowers; 2,1e50 flowers 3, 50e100 flowers, 4, >100 flowers per tree. A flow-ering index representing the degree of flowering for each clone ineach block was obtained as follows:
(N1 �1 þ N2 � 2 þ N3 � 3 þ N � 4)/(N1 þ N2 þ N3 þ N4), wherefor each plot N1 is the number of trees scored as 1, N2 is the numberof trees scored as 2 etc.
Mean flowering, standard deviation and SEM were calculatedfrom the flowering indices obtained for the four replicate blocks.
2.4. Measurements of soil parameters
Analyses of the top soil in the Polman and Pinrang trials wereconducted. In three blocks of the Polman trial, four soil subsamples(200e300 g) were collected about 0.5 m away from the base ofdifferent cocoa trees to a depth of approximately 5 cm and com-bined into one sample. The three samples were analysed separately.In Pinrang sub-samples collected from different parts of the trialsite were combined into one sample for analysis. Average soilparticle composition, pH, organic matter content and nutrientcontent were determined at the Assessment Institute for Agricul-tural Technology (AIAT) certified soil laboratory, Maros, SouthSulawesi for the samples from the two sites.
2.5. Data analysis
Some plots were missing trees, and therefore all data collectedfrom the plots were adjusted to reflect yield and pest/diseaseincidence per tree. Since the cocoa was grown at a density ofapproximately 1000 trees per hectare, yield per ha was estimatedbymultiplying average yield per tree by 1000. Data was analysed toobtain means, standard deviations and standard errors and sub-jected to one-way ANOVA (IBM SPSS Statistics19). Means wereseparated using the Tukey's b test (in cases where variance washomogenous) or the GameseHowell test. Interactions betweengenotype and location were analysed by two-way ANOVA (GLM,IBM SPSS Statistics19). For ANOVA, the total numbers of pods perclone were transformed to their log10 values and the proportions ofinfested or infected pods for each clone were converted to angles(in radians) by arcsine square root transformation. However, resultswere reported in the original data format.
3. Results
3.1. Flowering and yield
Yield was extremely variable, not only for the same clone indifferent trial locations but also between replicate blocks in theindividual trials (see Table 2). For each clone, the number of ripepods harvested per tree also varied considerably within plots (datanot shown). Flowering was significantly higher in Pinrang, than inthe other two trials (Fig 2). For the clones tested in common at thethree sites, yields, estimated by extrapolating yield per tree to1000 trees (approximating one hectare) were slightly higher in
Fig. 2. The average flowering score from 2010 to 2012 for the four clones common to all three trials: dotted bars, Pinrang; dashed bars, N. Kolaka; hatched bars, Polman. Floweringwas scored each month (see Materials and methods). Means and SEM of 4 replicates are shown for the cumulative data of two years: means with different letters are significantlydifferent (p ¼ 0.05, GameseHowell test). The data indicate that significantly higher flower numbers occurred in Pinrang.
P. McMahon et al. / Crop Protection 70 (2015) 28e3932
Pinrang (Tables 2 and 3). For example, potential yields of PBC123and M01 were over 1 ton/ha/annum in Pinrang, but less than thisat the other sites (Table 2). In North Kolaka in 2010, fruiting in thetwo-year old trees commenced about a month later than the othertwo locations. All of the trials were heavily impacted by vascular-streak dieback, which in the more susceptible clones was detri-mental to pod production and overall performance. Of the localselections, Geni J and MO5, with PBC123, proved to be the mostVSD resistant clones in the trials. However, M05 performed poorlyin N. Kolaka with a yield at this site 10-fold lower than M05 inPinrang. Since this selection is self-incompatible (observation byHussin bin Purung) this might account for the very low yieldsobtained for this clone in N. Kolaka, compared to the other loca-tions. The M05 trees in other locations may have been proximal tocompatible clones in Pinrang and Polman. In the Polman trial, theyields obtained from the clones selected from progeny hybridcrosses in East Java (KW series) gave relatively high yields(Table 2) but this was very variable between blocks. In at least twoof the blocks yields were much lower. Block 4 in the Polman trialhad a higher density of coconut shade trees than the other blocksand the cocoa trees had consistently had lower pod numbers andyields, possibly due to competition for nutrients.
Relatively high proportions of healthy pods in the ripe podharvest for the two years were obtained in Pinrang and Polman forPBC123 and M05 (Table 3). The high proportion of healthy pods in
Table 3Healthy pods: proportion of ripe pod harvest (%) for selected clones in the trials. Datashown are cumulative for a two year period 2010e2012. Means of four replicates(±SEM) are given except in Polman where the data were taken from pooled repli-cates. The average number of ripe pods harvested per tree for the two years is givenin parentheses. ni, clone not included in trial.
Clone % Healthy pods ± SEM (average no. ripe/tree/annum).
Pinrang N. Kolaka Polman
PBC123 37.8 ± 4.7 (38.6) 9.6 ± 1.4 (27.7) 42.1 (27.1)M01 20.9 ± 2.2 (27.8) 5.4 ± 1.2 (25.4) 26.3 (28.7)Geni J 12.4 ± 1.8 (28.9) 2.6 ± 0.6 (14.3) 25.7 (27.4)M05 45.1 ± 0.9 (49.2) 3.0 ± 1.1 (10.4) 48.5 (21.9)Pan R 45.6 ± 7.6 (12.1) 5.3 ± 1.4 (9.1) niM06 39.1 ± 5.0 (23.1) 12.1 ± 1.7 (14.1) niBR25 ni ni 55.2 (16.6)KW516 ni ni 39.3 (17.3)KW523 ni ni 33.6 (30.2)KW617 ni ni 33.7 (25.2)
BR25 (tested in Polman) indicates partial resistance to CPB or PPR orboth. The clones of the KW hybrid crosses also had a moderatelyhigh proportion of healthy pods. However, the proportion ofhealthy pods in the common standards was very low in N. Kolakaindicative of high rates of infestation/infection in this trial. N.Kolaka also receives a higher annual rainfall on average than Pin-rang and an extendedwet season. This might account for the higherPpr rates at this site (see below).
3.2. Bean characteristics and pod values
Key characteristics of the clones grown at each of the trial sitesare given in Table 4. In the common standards, the differencesbetween clones, such as bean count, fat content, pod value etc. wereslight between the different sites suggesting a mainly geneticcontrol over these characters. For example, the particularly lowbean count and large bean size that accounts for the popularity ofM01 was maintained in each of the sites. Accordingly, the podvalues (no. pods per kg dry beans produced) of PBC123 (which hada smaller bean size) and M01 were relatively high and low,respectively, at each of the sites (Table 4). Highest butter contentswere obtained in M04, RB and Pan R in Pinrang exceeding 50% ineach case (Table 4). Consistent with this Pan R in N. Kolaka had thehighest butter content of the clones tested in the trial.
3.3. Pest/disease incidence in pods
Cocoa pod borer (CPB) and Phytophthora pod rot (Ppr)accounted for nearly all pod damage in both immature and ripepods. Table 5 shows the incidence of total CPB for some of theclones tested in the three trials and Fig. 3 shows the proportion ofpods with light, moderate or severe infestation in N. Kolaka andPinrang. Total CPB incidence was generally higher in North Kolakathan in Pinrang or Polman. However, since a large proportion ofinfested pods had light levels of infestation most of the beans couldstill be harvested (Fig 3).
The local clone, M05 had a consistently lower average CPBincidence in the trials, while Geni J was consistently the most CPB-susceptible clone in the three trials. M01 was also one of the mostCPB-susceptible clones in each of the trials (Table 5, Fig. 3). Otherclones with a relatively low incidence were BR25 (locally known asSulawesi 2), M04, TR01 and Panimbu Red (Table 5). Husbitori testedin Polman had one of the lowest rates of CPB infestation (19%) ofclones tested in any of the trials. This clone was, however, also the
Table 4Bean characteristics and pod values of the clones tested in three locations in Sulawesi. The clones common to the three trials are shown in bold italics. Bean count, no. drybeans/100 g; pod value, no. pods per kg dry beans; na, data not available; Ilham (ILH) in Polman produced no pods.
Trial Clone Bean count Bean moisture (%) Bean size (g) Fat content (%) Shell content (%) Pod value (healthy) Pod value (total)
N. Kolaka PBC123 104.00 10.92 0.96 47.70 14.96 31.39 32.35M.01 59.00 8.67 1.69 48.50 11.47 16.51 18.20M.05 74.00 8.99 1.35 47.90 15.82 44.55 45.91Geni J 71.00 10.69 1.41 48.90 15.46 18.50 19.91KKM22 na na Na Na na 29.27 naNR 81.67 8.04 1.22 48.70 13.55 19.27 20.50PwPg na na Na Na na 9.30 naM06 84.67 9.60 1.18 48.20 16.88 26.35 27.53Pan R 63.00 na 1.59 49.30 12.17 15.71 17.29Darno 83.67 8.79 1.20 47.70 13.11 25.81 27.00Muhtar 79.00 9.31 1.27 48.30 17.74 27.96 29.23ILH 128.33 8.95 0.78 48.30 11.46 34.55 35.33
Polman PBC123 128 7.31 0.78 45.40 17.51 na 44.37M 01 62 na 1.60 48.20 22.11 na 30.43M 05 97 na 1.03 42.60 17.90 na 44.82Geni J 100 na 1.00 46.70 17.03 na 41.98KW523 95 na 1.06 48.90 20.36 na 43.15KW617 65 na 1.55 48.50 21.17 na 34.28Nasir rauf 67 na 1.49 na na na 38.69KW516 61 na 1.65 49.40 27.64 na 32.27Husbitori 92 na 1.09 45.30 na 24.29BR 25 93 na 1.07 46.50 14.96 na 39.98Muhtar 61 na 1.63 na na na 42.42
Table 5Incidence of total CPB in ripe pods of some clones harvested from the three trials inSulawesi (see Materials and methods). Pods were harvested each fortnight andevaluated for pest/disease damage. Total CPB incidence (%) was calculated as theproportion of the cumulative ripe pod harvest of two years (2010e2012) infestedwith CPB. Incidence is given for clones grown in at least two of the locations,including the common standards, PBC123, M01, Geni J. and M05. ni, not included inthe trial; na, data not available.
Clone Total CPB (%) in ripe pods
Pinrang N. Kolaka Polman
PBC123 47.8 ± 3.3 76.1 ± 1.3 47.3 ± 2.0M01 66.0 ± 3.6 79.4 ± 1.7 61.6 ± 7.9Geni J 80.6 ± 1.6 85.4 ± 0.8 68.0 ± 4.1M05 50.9 ± 1.1 17.7 ± 3.1 39.5 ± 8.8Pan R 46.9 ± 6.3 80.5 ± 2.7 niM04 43.4 ± 5.2 ni niM06 50.1 ± 3.0 76.2 ± 3.0 niBR25 ni ni 40.5 ± 5.0KW516 ni ni 44.8 ± 6.5KW523 ni ni 55.3 ± 7.0KW617 ni ni 51.5 ± 7.3
P. McMahon et al. / Crop Protection 70 (2015) 28e39 33
most VSD-susceptible clone in the trial, explaining in part its verylow productivity (data not shown). The data in Table 6 indicate thatlosses of immature pods were mainly the result pests and diseasesother than CPB. Ppr and Helopeltis spp. caused most of the losses atearlier stages of pod development (Tables 8 and 10).
3.3.1. Seasonal changes in CPB incidenceCPB infestation followed a pattern where incidence increased
during periods of low pod production (Day, 1989). At times of lowpod production the total number of egg laying sites becomes morerestricted (Azhar and Long, 1991). In the Sulawesi trials, during thelow pod seasons total incidence increased markedly in all of thetrials. The increase in total incidence led to disproportionate in-creases in severe CPB (equivalent to 100% losses). Fig. 4 showschanges in total and severe incidence in two clones and the numberof total ripe pods harvested in the trial (providing an estimate of thetotal pods available to the pest). Generally, a higher severe inci-dence (approximating pod loss) occurred in times of low podproduction (e.g. M01 and Panimbu Red, Fig. 4). However, in Pinrangduring the mid-year peak harvest seasons, total CPB incidence inthe more resistant Panimbu Red (Table 5, Fig. 3) decreased to lowerlevels (32% and 44% in 2010 and 2011, respectively) than M01 (50%and 84%, respectively). Fig. 5 compares two other clones in thePinrang trial, one relatively resistant and the other susceptible.When CPB incidence exceeded 90% in the susceptible ICCRI04(upper plot), the incidence of severely infested pods (representing100% losses) exceeded 35% (lower plot). In contrast, total incidencein the more resistant M04 was generally lower than 70% (upperplot) and the incidence of severe infestation in M04 remained lessthan 5% (lower plot). However, in both clones, severe CPB incidencerose in the low pod seasons, increases being particularly marked inthe more susceptible ICCRI04. Additionally, the higher suscepti-bility of ICCRI04 is demonstrated in the peak harvest times (whenoverall infestation drops) as the proportion of severely infestedpods remained at 10% or higher (Fig. 5).
Fig. 3. Average CPB incidence in the cumulative harvest of ripe pods in a two-year period (2010e2012) in the trials in N. Kolaka (upper graph, a) and Pinrang (lower graph, b). Datashown are the mean incidence of four replicates ± SEM for lightly (black with dots), moderately (hatched) or severely (white with dots) infested pods. Different letters indicate totalCPB incidence differs significantly (p ¼ 0.05) between clones.
P. McMahon et al. / Crop Protection 70 (2015) 28e3934
3.3.2. Phytophthora pod rotPpr incidence was linked to monthly rainfall totals and was
especially high in the very wet year of 2010. Total Ppr incidencewasgenerally higher in ripe pods in N. Kolaka (Table 7) than in Pinrangand Polman. Annual rainfall is higher in N. Kolaka than Pinrang orPolman (see Materials and methods, 2.2). Nevertheless in Pinrang,M01 and M04 (both clones with good quality characteristics) sus-tained high losses from Ppr (Table 7). The more susceptible clones,such as M01, responded towet periods with particularly high lossesto Ppr, while increases in incidence also occurred in other clonesbut these were generally smaller, indicating partial resistance(Fig. 6). Immature pods of M04 and PBC123 were also susceptible(Table 8). Incidence of severe Ppr (data not shown) was generallyequivalent to total Ppr perhaps reflecting the rapid progress of thedisease in pods following infection with P. palmivora. In N. Kolaka,relatively susceptible clones in the trial (M01 and PBC123, seeTable 9) had a high Ppr incidence, increasing markedly in particu-larly wet periods, while the more resistant clones, M06 and Ilham,
had a lower incidence in most months (Fig. 6). Ppr incidencegenerally increased with rainfall (Fig. 6a), both total rainfall permonth (Fig. 6b) and the number of rainy days per month (seeFig. 6a). The amount of rainfall in N. Kolaka from February to April2011 totalled 671mm compared to 454mmduring the same periodin 2012, but Ppr incidence was as high in the 2012 wet season as inthe previous wet season, and even higher in M01 (Fig. 6). Therefore,Ppr incidence appears to be affected by number of wet daysoccurring in a particular period, as well as the total amount of rainreceived.
Table 9 groups the clones with lowest and highest incidence ofsevere CPB (which effectively cause 100% losses) and total Ppr intwo of the trials (Pinrang and North Kolaka). M01 which has goodyield and bean characteristics (Table 4) was one of the more sus-ceptible of the clones to both of these pest/disease problems. It wasalso susceptible to VSD, as was M04 (data not shown) but M04proved to be resistant to CPB (Table 5). This illustrates a patternoften found by farmers and researchers, namely that in some
Table 6Losses of immature pods shown as the proportion of the total harvest (ripepodsþ damaged immature pods) damaged by pests/disease. All damaged immaturepods were harvested, evaluated and discarded. The averages (±SEM) of 4 replicatesfor the cumulative harvest of two years are given for the clones included in morethan one of the trials. The columns on the right show the CPB-infestation rate ofimmature pods. The data indicate substantial losses prior to pod ripening werecaused by pest/disease problems other than CPB, mainly Ppr and Helopeltis spp. (seeTables 8 and 10).
Clone All pests diseases (% of totalharvest) in immature pods
Table 7Incidence of Ppr in ripe pods in the three trials in Sulawesi (see Materials andmethods). Pods were harvested each fortnight and evaluated for pest/diseasedamage. Total Ppr incidence (%) was calculated as the proportion of the cumulativeripe pod harvest of two years (2010e2012) infected with P. palmivora. Data shownare the means (±SEM) of four replicates for some clones, including the four commonstandards, which were grown in all three locations. ni, not included in the trial.
Clone Total Ppr in ripe pods (%)
Pinrang N. Kolaka Polman
PBC123 7.4 ± 1.0 13.0 ± 1.1 10.2 ± 0.9M01 11.8 ± 3.1 14.2 ± 1.3 9.8 ± 2.6Geni J 4.8 ± 0.6 11.0 ± 1.5 4.7 ± 1.5M05 3.5 ± 0.5 11.7 ± 5.5 11.8 ± 2.7M04 23.7 ± 7.8 ni niM06 4.3 ± 0.8 10.9 ± 1.5 niPan R 4.4 ± 1.5 10.7 ± 1.9 niBR25 ni ni 5.6 ± 1.5KW516 ni ni 15.3 ± 3.6KW523 ni ni 10.8 ± 2.4KW617 ni ni 13.1 ± 2.3
Table 8Ppr in immature pods in Pinrang and N. Kolaka as the proportion of total harvest(ripe pods þ damaged immature pods) in clones common to the two trial sites. Datarepresents the averages (±SEM) of 4 replicates for the cumulative harvest of twoyears. ni, not included in trial.
Table 9Clones with the lowest and highest incidences of severe CPB and Ppr in ripe pods forthe cumulative harvest of two years in the Pinrang and North Kolaka trials. Clonesproducing less than 25 pods per tree have been excluded. NR, Nasir Rauf, ILH, Ilham.
Incidence Severe CPB (%) Total Ppr (%)
Pinrang N Kolaka Pinrang N Kolaka
Lowest in trial(resistant)
1.7 ± 0.6 (M04) 5.5 ± 0.7(ILH)
3.5 ± 0.5 (M05) 8.8 ± 1.7(ILH)
2.5 ± 0.5 (PCK) 6.1 ± 0.6(PBC123)
4.3 ± 0.8 (M06) 9.3 ± 1.4(NR)
4.1 ± 0.7 (PBC123) 6.1 ± 0.6(KKM22)
4.8 ± 0.6 (Geni J) 10.9 ± 1.5(M06)
6.2 ± 1.0 (M06) na 7.4 ± 1.0 (PBC) naHighest in trial
(susceptible)11.2 ± 1.0 (M05) 13.2 ± 1.2
(M06)15.5 ± 2.9 (M01) 13.0 ± 1.1
(PBC123)13.8 ± 1.0 (M01) 14.9 ± 2.2
(NR)15.5 ± 2.9 (PCK) 13.0 ± 1.1
(KKM22)14.3 ± 1.9 (ICCRI4) 25.5 ± 5.0
(Geni J)15.6 ± 2.9 (RB) 14.2 ± 1.3
(M01)23.5 ± 2.6 (Geni J) na 23.7 ± 7.8 (M04) na
Table 10Helopeltis spp. incidence in immature and ripe pods of the common standards in theN. Kolaka and Pinrang trials. Helopeltis infestation of clones in the Polman trial wasnegligible.
Trial location Clone Total incidence of Helopeltis spp. (%)
P. McMahon et al. / Crop Protection 70 (2015) 28e39 35
clones, resistance to one pest/disease is accompanied by suscepti-bility to another.
3.3.3. Incidence of Helopeltis spp.Pod infestation with Helopeltis spp. was high in immature pods
in the Pinrang trial (Table 10), but was negligible in the clonestested in Polman. In North Kolaka, ripe pods of M05 had a partic-ularly high total incidence (52%) with a 41% incidence of severelyinfested pods. In Pinrang, a high proportion of immature pods ofM01, Geni J and PBC123 was infested with Helopeltis spp.: all of
these were infested severely. Similarly, M06, PCK, RB and DRC15had high rates of infestation in immature pods in the Pinrang trial.
3.4. Soil parameters
Soils in the three sites were of alluvial origin with clay loam orsandy loam composition in the top soil. In the North Kolaka trialaverage soil pH was 5.2 (Ashar Saftar's observation). Table 11 showsparticle and nutrient composition, soil pH and cation exchangecapacity (CEC) of the soil in the Polman and Pinrang trial sites. Thesoil in Pinrang had a higher clay component than the Polman soil,which had a high sand component. A relatively high pH, CEC andconcentration of basic cations in Pinrang indicated this soil wasgenerally more fertile, but carbon and nitrogen content weredeficient in both locations. Available phosphorus was quite high inboth sites although Nelson et al. (2011) suggest that the available Pconcentration (6e10 ppm) reported as adequate for cocoa pro-duction by Fahmy (1977) was too low (see third column, Table 11).Total S concentration at both sites was within the normal range ofmost soils. Exchangeable aluminium (Al) was not detected in thesoil of either site. Lead (Pb) levels of 100 ppm were detected inPolman, but were negligible in Pinrang. Base saturation in bothlocations was 100%. Iron (Fe) and manganese (Mn) soil concen-trations were high and greatly exceeded the average concentrationof these elements in cocoa growing areas of Papua New Guineadetermined by Nelson et al. (2011). Data for individual macro- andmicronutrients are given in Table 11.
Fig. 4. Incidence of total (solid line, squares) and severe (broken line, triangles) CPB inthe ripe pods of Panimbu Red (upper plot) and M01 (lower plot) in the Pinrang trialfrom 2010 to 2012. The total number of ripe pods harvested in the trial is indicated bythe shaded area (right axis) for the same period. The incidence of severe CPB (andtherefore pod losses) appears to be linked to both low availability of total pods in thetrial and to total incidence. Pod numbers decreased substantially in August 2010 andthe end of 2011, accompanied by severe incidence of about 80%.
Fig. 5. Incidence of total (upper plot) and severe (lower plot) CPB in the ripe pods ofICCRI04 (continuous line, diamonds) and M04 (dashed line, squares) in the Pinrangtrial from 2010 to 2012. Note the different scales for the upper and lower plots. Thetotal number of ripe pods harvested in the trial is indicated by the shaded area (rightaxis) for the same period. CPB infestation increased in both clones during the periodsof low pod production but this was especially marked in the susceptible ICCRI04 inearly 2012 when the ripe pod harvest decreased to particularly low levels. The rela-tively low incidence of severe CPB in M04 was maintained throughout the two-year
P. McMahon et al. / Crop Protection 70 (2015) 28e3936
3.5. Plot-based heritability estimates
Estimates of broad sense heritability from variance componentsin the plot data in the three trials indicated a low heritability forpod production, while the heritability estimate for yield (kg drybeans) was higher (Table 12). The low broad sense heritabilityvalues for pod production in clones common to the three trials inthis study (Table 12) is indicative of the strong effect of environ-mental factors on pod setting and growth. The effect of non-geneticfactors on productivity (Table 12) is reflected by the higher pro-duction in Pinrang for all four clones (the common standards)included in the analysis. In addition, to determine the variancecomponents by the two-way ANOVA, pooled data for each plot wasused and variation between single trees, therefore, was notaccounted for in the estimates of heritability. Nevertheless, the highheritability estimate obtained for CPB incidence suggests that ge-netic factors account for a large proportion of the variation in CPBincidence among the genotypes in the three sites. A substantialcomponent of phenotypic variance (0.33) also accounted for cloneresponse to Ppr.
4. Discussion
The performance of the clones tested in these trials support thefarmer participatory method adopted in their selection. Most of theclones selected proved to have promising yield or quality attributesor resistance to one of the pest/disease problems as observed byfarmers. In West Africa, Pokou et al. (2008) found a similar con-sistency between farmer observation and selection and perfor-mance in confirmatory tests, so that 63% of cocoa genotypesidentified by farmers as resistant to Ppr were confirmed to showresistance in leaf disc tests. Reports from South-East Sulawesi(McMahon et al., 2009) and Cameroon (Efombagn et al., 2007) alsoshowed the efficacy of farmer-assisted selection, an approach thatis currently adopted by Mars Inc. field programs. In addition, theon-farm testing strategy adopted for these trials proved to enhancethe exposure of other farmers to improved planting material, farmmanagement methods and methods of on-farm testing. The trialswere designed so that each of the clones tested was grown in 8-treeplots, readily accessible for observation by visiting farmers whocould observe clone performance and also access budwood ofpromising clones.
period.
Fig. 6. (a) Ppr incidence (%, left axis) between January 2011 and May 2012 in ripe podsof PBC123 (triangles, continuous line), M01 (squares, continuous line), M06 (opentriangles, dashed line) and Ilham (open squares, dotted line) in the N. Kolaka trial. Datapoints represent mean incidence for two months. The shaded area indicates thenumber of wet days per month (with at least 2 mm rainfall per day) in South Pakuenearby the trial site (right axis). The more susceptible M01 and PBC123 (see Table 9)had a higher average incidence than M06 and Ilham; however, Ppr infection of M06exceeded 25% in June/July 2011. (b) total monthly rainfall in South Pakue in the sameperiod.
Table 11Soil parameters in two trial sites. Soil samples were collected to a depth of 5 cm fromdifferent blocks in the trial sites. Data shown are the means for three measurementsin Polman and a combined soil sample from Pinrang. Note: ppm ¼ mg/kg; C/N,carbon: nitrogen ratio; CEC, cation exchange capacity; Exch., exchangeable; na, notapplicable.
Soil parameter (unit) Polman trial Pinrang trial aAdequate or normal range
a Adequate for cocoa production after Fahmy (1977), and normal range based onconcentrations of soil micronutrient in cocoa producing provinces in Papua NewGuinea (see Nelson et al., 2011).
b Within normal range for S (ppm).c Determined by Olsen-P method.
Table 12Plot-based, broad sense heritability (H2) estimates for yield, pod production, CPBand Ppr incidence in Pinrang, Polman and N. Kolaka. Variance components of theeffects of clone (genotype, s2
g), location (s2l), their interaction (s2
gl) and the errors2
w were determined by two-way ANOVA of the pooled data of 8-tree plots for thefour clones common to the trials: PBC123, M01, M05 and GeniJ. For ANOVA, theaverage numbers of pods per tree produced in the two years by each clone weretransformed to their log10 values and the proportions of pods with CPB and Ppr ineach clone to their arcsine angles.
P. McMahon et al. / Crop Protection 70 (2015) 28e39 37
In this study, local selections showing promise included the Mseries of local clones, such as M06, initially selected from a villagenear Masamba in North Luwu, South Sulawesi. In the Pinrang trial,even in the absence of pesticides, the high yields of M06 (almost aton/ha/annum) confirmed the tests conducted elsewhere by MarsInc. and ACIAR which have proved this to be a vigorous clonedemonstrating tolerance to dry conditions and low soil fertility.Both M01 (with estimated yields from Pinrang of over a ton/ha/annum) and M06 have become highly regarded and are now beingdistributed widely in Sulawesi by grafting. M01 is due to be offi-cially released as Masamba Cocoa Clone 1 (MCC1) by the Indone-sian government. In the Polman trial in West Sulawesi, good yieldswere obtained with the clones selected from a hybrid cross(KW617) and farm selections (KW516 and KW523) by the Indo-nesian Coffee and Cocoa Research Institute in East Java. However, inthe trials in Sulawesi reported here, resistance to one pest/diseasewas generally accompanied by susceptibility to another. Forexample, M04 proved to have good quality characteristics and wasresistant to CPB (Tables 4 and 5; Fig. 5), but was susceptible to Ppr(Tables 7 and 8) and VSD. KW617 inherited VSD-resistance
characteristics from the parental clone, PBC123, but proved to bemoderately susceptible to Ppr. Geni J, a productive clone highlyresistant to VSD was the most CPB-susceptible of the clones in eachof the trials. Such cases indicate the need to combine yield, qualityand resistance characteristics in the same genotype by hybridcrosses: such work is being continued by ICCRI (in Java) and MarsInc. (in Sulawesi).
The high variability in pod production between plots for indi-vidual clones and correspondingly low broad sense heritabilityestimate (Table 12) are in part an outcome of the small plot sizeused (8 trees). In Ghana pod yield between individual trees of thesame clone have been reported previously to be highly variable,while resistance traits such as Ppr resistance show greater herita-bility (Lockwood et al., 2007). In the present study, the broad senseheritability estimate for Ppr incidence for four clones at the threesites (0.33, Table 12) suggests a strong genetic component in-fluences this parameter, notwithstanding the importance of envi-ronmental factors (especially the amount of rainfall). While theheritability value obtained in this study was based on pooled plotdata rather than single tree data, in Ghana a moderately high her-itability for Ppr resistance (0.26) was also determined by Lockwoodet al. (2007) from single tree records. The authors suggested that
P. McMahon et al. / Crop Protection 70 (2015) 28e3938
this justified on-farm selection for Ppr resistance from promisingtrees and this was confirmed by Pokou et al. (2008) e see above. Inthe present study, clear differences in Ppr infection rates could befound during both wet and dry periods (Fig. 6): the more resistantclones could be used for crosses with more productive (but sus-ceptible) clones. Nevertheless, the higher Ppr incidence found inripe pods of the common standards in N. Kolaka than the other sitesreflects the higher rainfall in this district, which falls within climatezone A according to the criteria of Schmidt and Ferguson (1951).
During the evaluation period the trials were kept free of pesti-cide use. However, estimated yields exceeded 1 ton/ha/annum forPBC123, as for M01, in Pinrang and these clones proved to be amongthe highest yielding in the two other trials. The comparativelyhigher yield of PBC123 in the three trials was at least partly an effectof its proven resilience to pest and diseases. Its well-known resis-tance to VSD (Chong and Shepherd, 1986) was confirmed in thetrials. The comparative resistance of PBC123 to CPB in the Pinrangand N. Kolaka trials (Tables 5 and 9; Fig. 3), indicated by a lowincidence of severe CPB, might be partly due to the relatively highpod production of this clone (therefore creating a ‘dilution’ effect).However, Teh et al. (2006) reported larval exit rate from PBC123was the lowest among eight genotypes examined, and the scleroticlayer among the hardest suggesting other resistance factors mayaccount for the performance of PBC123, such as high larvalmortality.
PBC123 has been called ‘a wonder clone’ (Dr Ho Cheng Tuck,pers comm). It is now widely propagated in Sulawesi as ‘Sulawesi1’. This clone was selected from the progeny of an Upper Amazon(UA) � Trinitario cross at Prang Besar in Malaysia for yield andmultiple resistance traits, particularly against VSD and Ppr (Chong,1984; Chong and Shepherd, 1986). However, a disadvantage is itsrelatively high bean count and small bean size, shown by beananalyses for harvests from the three trials (see Table 4) which wasconsistent between sites. The pod value for PBC123 realised in thetrials (approx. 30, see Table 4) differs from the 22 pods per kg drybeans reported in Malaysia by Chong (1984). The same applies tothe 53% butter fat content for PBC123 reported by Chong whichdiffers substantially from the average fat content of PBC123 beansin the three Sulawesi trials being consistently quite low (between45.4 and 48.9%). Genetic, rather than environmental, factors largelyregulate bean count and other characteristics (Lachenaud andZhang, 2008), so, for example, relatively consistent butter con-tents were found between trial sites for M01 and Panimbu Red(Table 4). However, bean fat content in the same clone has beenobserved to increase in areas with higher rainfall in East Java(observation by Agung Susilo) suggesting environmental factorscontribute to this bean quality characteristic. Nevertheless, thevarying productivity between the same clones in different locationsindicates, in general, that pod production and yield, more thanother clone characteristics, are influenced by environmentalfactors.
The higher average flower numbers in Pinrang (Fig. 2) couldpartly account for the higher yields in this trial. Soil fertility wasgenerally higher in the Pinrang trial site, than in the Polman site,with a higher CEC and concentration of exchangeable basic cations,and a higher pH which improves availability of many cations forplant uptake. In the North Kolaka trial, the low soil pH (5.2) wouldalso decrease cation availability. On the other hand, the generallylower yields obtained in North Kolaka (Tables 2 and 3) perhapsreflect a later date for the production of the first pods in 2010(despite the trees being a similar age to those in the other trials) orexposure to pests/diseases in the absence of chemical controlmeasures. Both Ppr and CPB incidence were higher in N. Kolaka,than the other Sulawesi sites. The high rainfall in N. Kolaka,compared to the other two sites, might account for the higher CPB
incidence in the clones of this trial, in addition to the higher Pprincidence in this location. Furthermore, particularly high rainfall in2010 which continued into the usual dry season is likely to haveimpacted on pod production in the following year by decreasingflowering rates and/or destroying flowers. Lower yields might alsobe a result of limited pollination success. Groeneveld et al. (2010)conducted a study on pollination of cocoa in Central Sulawesi,concluding that limitations to pollination, as much as other factors,had a consequent negative effect on yield. They suggested cocoayield, even when trees are grown under well-managed conditions,may be limited by insufficient pollination.
In each of the three trials, nearly all ripe pod damage wasaccounted for by attack by CPB or Ppr. Day (1989) reported that podinfestation by CPB at rates of 60% or lower resulted in little loss,while losses increased markedly above this threshold. Lim andPhua (1986) identified a similar relation between total incidenceand pod losses, but found losses increased dramatically when totalincidence exceeded 70%. The data on CPB infestation in Sulawesireported here are consistent with these findings but indicate that,in addition to the total rate of infestation, the number of total podsin the area (in this case the trial area) and the level of resistance hasa strong influence. Fig. 4 compares M01 to the more resistantPanimbu Red clone, showing that severe incidence in both of theseclones increases with total incidence but that particularly largeincreases occurring at times of low pod production. Geni J, the mostCPB-susceptible clone in each of the trials, and M01 (Fig. 4), eachmaintained a high total incidence throughout most of the evalua-tion period but particularly high losses (due to severe infestationwith CPB) were suffered only in the low pod seasons. Therefore, therelation reported by Day (1989) and Lim and Phua (1986) is qual-ified by the level of susceptibility or resistance. While a clear in-crease in losses to severe CPB in Panimbu Red occurred when totalincidence increased during the low pod season at the end of 2011(Fig 5), it was evident that resistance was maintained in M04.Generally, the data support an exponential relation between totalincidence and severity above a certain threshold (Day, 1989; Limand Phua, 1986) at times of low pod production, but this relationbecomes less clear at times of higher pod production as shown inthe case of the susceptible M01 and Geni J or in clones that expressconstitutive resistance.
Clone performance indicated clear differences in the levels ofresistance to CPB (Table 5). Although CPB incidence generallydropped in the high pod season and increased markedly in the lowseason, consistent with previous reports (see Day, 1989), incidencein more resistant clones such as M04 and Panimbu Red wasconsistently lower than susceptible clones such asM01 and ICCRI04(Figs. 4 and 5) or Geni J. Furthermore, a high heritability value wasobtained for infestation rates by CPB for the four clones common tothe trials (0.71, Table 12) suggesting clone susceptibility to CPBdamage is strongly influenced by the host genotype. Whether therelative CPB resistance of these clones is a constitutive property,causing high larval mortality, or an effect of ‘escape’ from infesta-tion in a multi-clonal situation remains uncertain. Possibly, non-preference may account for the different levels of infestation be-tween some of the ‘resistant’ clones, such asM06whichwas rankedas one of the more CPB-resistant clones in Pinrang, but as suscep-tible in N. Kolaka (Table 9). Furthermore, the greater CPB resistanceapparent in Panimbu Red in the Pinrang trial, compared to M01(Table 5, Fig. 3), can be accounted for at least partly by the largerdecrease that occurred in total CPB incidence in Panimbu Redduring the peak harvest seasons (Fig. 4). In the case of Geni J, whichwas the most CPB-susceptible clone irrespective of the locationtested, it appears that its susceptibility is due to an inherentattractiveness to the moth. In contrast to the apparently stronggenotypic effect in Geni J, CPB infestation of other clones appeared
P. McMahon et al. / Crop Protection 70 (2015) 28e39 39
to be affected more by environmental conditions as in the case ofM06 and Panimbu Red. ‘Resistance’ in these clones might be partlyexplained by lower infestation rates at times of high pod produc-tionwhen the pest exercises preference for pods of some genotypesover others (McMahon et al., 2009).
The data in Table 9 suggests that potential resistance to CPB orPpr is not linked since some clones with a low CPB incidence (e.g.PCK and M04) also had a high Ppr incidence. In general, the multi-location trials indicate the importance of testing cocoa selections inparticular localities of cocoa production. Clones selected in Javawhere they show promising characteristics, for example, mayperform differently in Sulawesi or on other islands. Similarly, localSulawesi selections should be tested in the particular region ofintroduction before they are recommended to local farmers.
Acknowledgements
This research was supported by the Australian Centre for Inter-national Agricultural Research (ACIAR) (grant no: SMAR/2005/074).The authorswould like to thank the farmerswhoparticipated in andhelped with the on-farm trials, in particular, Pak Syamsuddin,Haminggo and Syukur. Sincere thanks are also due to Mars Inc. fieldstaff who contributed to the management and evaluation of thetrials, including Pak Abidin, Jasi, Kaisar, A. Ariayanto and others.
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