SNAP BEAN BREEDING IN EASTERN AFRICA

KENNETH TEMBE ODUORA56/69956/2013

MSC. AGRONOMY

DEC 2013

CONTENT

1. INTODUCTION2. ORIGIN AND CYTOGENETICS3. REPRODUCTIVE SYSTEMS4. BREEDING OBJECTIVES5. BREEDING METHODS6. WORK DONE IN EASTERN AFRICA, MAJOR

ACHIEVEMENTS AND LESSONS LEARNT7. CONCLUSIONS AND FURTHER WORK8. LIST OF REFERENCES

INTRODUCTION• Green bean is the immature green pod of the P.vulgare primarily grown for export .

• major export vegetable commodity in Eastern Africa with the main producing countries being Kenya, Tanzania, Uganda and more recently Rwanda. Kenya exported about 44 thousand metric tonnes of snap beans in 2012 valued at about KES 1.7 billion. (HCDA 2012)

• estimated that over 90% of the crop produced in Eastern Africa is exported to regional and global markets (CIAT 2006).

• grown by both small- and large-scale farmers in Eastern Africa for fresh and processing markets (KARI 2004).

cont’ introduction

• Compared to dry beans, snap beans have a high market value, mature much earlier and have a longer harvest duration (Ugen et al. 2005)

• snap beans with quality characteristics demanded by target markets is vital to increasing consumption and export value (Ndegwa et al. 1999; Muchui et al. 2006; Ndegwa et al. 2008; Kimani et al. 2009;).

• high seed costs, lack of high yielding pest and disease resistant commercial snap bean varieties is perhaps the most critical constraint to snap bean production (Kimani et al. 2004).

cont’ introduction• snap beans grown in Eastern Africa were developed in

temperate regions particularly North America and Europe and are therefore not well adapted to biotic and environmental conditions in Kenya and other countries in Eastern Africa.

• foreign varieties are very susceptible to bean rust, angular leaf spot, root rots and bean common mosaic virus among other diseases and pests, especially bean stem maggot, thrips, spiny bugs, pod bores, bean aphids, red spider mites and white flies (Nderitu et al. 1996; Kimani et al. 2004)

• to depend on very expensive fungicides and insecticides to reduce production and post-harvest losses associated with disease and pests. However, this option is not viable because of the recently instituted maximum residual limits (CIAT 2006)

ORIGIN AND CYTOGENETICS• Domesticated in central and south America more than

6000years ago. Mexico and Guatemala, and Peru and neighbouring countries

• Dry seeds were introduced and planted in Spain during the 16thC . It was taken to France. The unripe pods soon became popular as a vegetable in Europe.

• use of the green pods was made possible by a considerable reduction of ‘parchment’ consisting of cross-intersecting fibres in the fruit wall.

• This character, polygenic in heredity, was improved by breeding in Europe during the 18th and 19th centuries.

• hard fibres along both satures (strings) were first eliminated by a dominant mutation, which appeared spontaneously during the 19th

Cont’ orgn and cytgn• Presently French beans is produced all over

the world and can be found in all countries of tropical Africa.

• Popular in Francophone than Anglophone countries, more in urban than in rural areas, more in highlands than lowland regions, and more during the cool season than during the hot season.

• Snap bean just like other bean varieties have a chromosome number of 2n=22

REPRODUCTIVE STRUCTURE• The Inflorescence forms an axillary or terminal

raceme up to 15(–35) cm long,• Flowers are bisexual, hence snap bean is

autogamous in nature. • corolla is white to pale purple or red-purple,

hood-shaped, of about 1.5 cm long, wings ; • has 10 stamens , 9 fused and 1 free;The

ovary is superior and laterally compressed.

SNAP BEAN BREEDING OBJECTIVES IN EASTERN AFRICA (CIAT 2006)

• Regional snap bean programme supported in 2006 by ASARECA, was initiated to develop improved snap bean varieties with :

high yield potential,

resistant to biotic stresses, and

high pod quality for smallholder producers .

objectives of the snap bean breeding in Kenya (Kimani 2010):

1. To select bush snap beans with multiple resistances to rust, angular leaf spot and anthracnose.

2. To evaluate advanced bush snap bean lines for pod quality, marketability, shelf life and high productivity, and resistance to aphids, thrips and bean stem maggot.

3. To select climbing snap bean lines with multiple resistances to rust, angular leaf spot and anthracnose.

4. To evaluate advanced snap climbing bean lines for pod quality, marketability, shelf lifeand high productivity and resistance to nematodes and root rots

BREEDING METHODOLOGY IN SNAP BEAN

• pedigree method- developing new snap bean cultivars -effective for traits with moderate to high heritabilities

• The disadvantage is that by selecting traits with high heritability in early generations, genetic variation with low heritability is lost (Fouilloux and Bannerot, 1988).

Cont’ breeding method• single seed descent and bulk breeding methods

(Fouilloux and Bannerot, 1988) - more efficient for cultivar development than pedigree in preserving genetic variation with low heritability

• Bulk breeding is more efficient than single seed descent when labour costs and land use were considered (Fouilloux and Bannerot, 1988). Single seed descent allows genetic analysis of traits in a population whereas bulk breeding does not.

• Recurrent backcrossing has also been used as a standard procedure for the introgression of qualitative traits into an elite background. Silbernagel (1986)

Cont’ breeding method lack of recombination in snap bean may be part of the

bottleneck to trait transfer. Common bean chromosomes are small with an average of less than two chiasmata per bivalent (Marechal, 1971).

The low rate of crossing over limits the amount of recombination that can occur in any one reproductive cycle.

determine why quite often in a cross between two separate bean types, types that resemble the parents are recovered in high frequency, with very few that show intermediate or recombinant characters.

breeding methods, such as recurrent selection, and congruity backcrossing and inbred-backcross method can give more opportunities for recombination (Urrea and Singh, 1995; Anderson et al., 1996; Wehrhahn and Allard, 1965; Bliss, 1981).

Cont’ breeding method• The use of molecular markers may help facilitate the transfer of

traits from an unadapted background into snap beans. • Two approaches are conceivable. The conventional approach would

be to use molecular markers to tag genes or QTL of interest such has been done for several traits in bean (Adam-Blondon et al., 1994a; Alzate-Marin et al., 1997a, 1997b)

• Many of these markers for disease resistance have been of interest to some snap bean breeding programs

• The tags would facilitate introgression of the trait of interest during some recurrent crossing procedure (such as backcrossing)

• The advanced backcross QTL analysis proposed by Tanksley and Nelson (1996) may be a useful method for introgressing genes from a dry bean into a snap bean background, particularly where molecular markers for a trait are unknown

Cont’ breeding method

• Molecular maps that have been developed for bean (Adam-Blondon, et al., 1994b; Nodari et al., 1992, 1993a, 1993b; Skroch et al., 1996; Vallejos et al., 1992) have significantly facilitated breeding of snap .

• With the number of RFLP, AFLP, and RAPD markers known, it should be possible to develop a set of polymorphic PCR-based markers to tag a snap bean cultivar’s genome, a process described as Whole Genome Selection (Tanksley and Rick, 1980).

• A marker would be placed on each chromosome arm. From segregating cross progeny, selection for individuals with the most complete set of markers and the trait of interest should result in the recovery of progeny with most of the snap bean traits intact and with the novel trait of interest as well.

WORK DONE IN EASTERN AFRICA

• Work at Kawanda (Uganda) focused on screening snap bean varieties with farmers and developing production packages. Three lines were selected after four years of evaluation with farmers. These are HAB 433, J12 and L3.

• Moi University, Kenya aimed at developing locally adapted snap bean cultivars with improved pod yield, resistance to anthracnose and rust, and marketable pod quality. Four lines were rated resistant to rust,

• had good pod quality, comparable to that of commercial cultivars

•

Cont’ work done in E.A

• At KARI-Thika focused on developing a working collection of snap and runner bean varieties, and on developing segregating populations

• Twenty F4 selections from a cross between a commercial variety and a locally improved rust resistant variety (‘Kutuless’) were made. Two promising F4 lines showed a type 1 growth habit, good ground-pod clearance, high pod load (30-40 pods/plant), acceptable pod characteristics and good snapping ability.

• At the University of Nairobi, crosses were made to transfer rust resistance to three susceptible snap bean varieties

Cont’ work done in E.A

• Availability of public commercial varieties which will increase access to seed by smallholder

• likely to lower production costs due to improved access to seed and

• reduced reliance on fungicides in the region and pesticides-farmers to meet stringent export requirements for residue levels, essential if this crop is to continue providing incomes and employment in rural areas.

FURTHER WORK

• With much of the world bean germplasm adapted to the tropics, problems with daylength-sensitivity, and adaptation to specific temperature regimes can obscure performance at the higher latitudes. One solution to this problem is to convert daylength-sensitive material to daylength insensitivity.

• A process has been initiated to convert tropical dry bean lines .

• A similar process should be used with tropically adapted snap bean lines.

CONCLUSION

• Breeding activities in snap beans in the region have been successful.

• Varieties developed are: high yield potential,

resistant to biotic stresses, and

high pod quality for smallholder producers

REFERENCES• Kimani PM, van Rheenen HA, Mathenge P, Ndegwa A. 2004.

Breeding snap bean for smallholderproduction in East and Central Africa. Annual Report 2004. CIAT, Cali, Colombia. p 49–51.

• CIAT [International Center for Tropical Agriculture]. 2006. Snap beans for income generation by Fouilloux, G. and H. Bannerot. 1988. Selection methods in the common bean (Phaseolus vulgaris). p. 503-542. In P. Gepts (ed.), Genetic Resources of Phaseolus beans. Kluwer, Netherlands

• Silbernagel, M.J. 1986. Snap Bean Breeding. p. 243-282. In Bassett, M. (ed.), Breeding Vegetable Crops. AVI Publ. Co., Westport, CT.

• ASERECA [Association for Strengthening Agricultural Research in Eastern and Central Africa] . 2009 Proceedings of the Regional Stakeholders’ Workshop on Snap Beans Commodity Value Chain by Maureen Katafiire, Michael Ugen and Mwamburi Mcharo

THANK YOU