Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

1

ISSN 1023-1072

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1): 13-23

HETEROSIS OF SOME YIELD AND ITS RELATED CHARACTERS IN AROMATIC RICE (ORYZA SATIVA L.) VARIETIES AND THEIR F1 HYBRIDS UNDER LOWLAND

AND UPLAND ENVIRONMENTS 1

A. D. Jarwar1, Q. D. Dela Cruz2 and G. S. Junejo1

1Rice Research Station, Thatta Sindh, Pakistan 2Department of Crop Sciences, Institute of Graduate Studies, Central Luzon

State University, Nueva Ecija Philippines

ABSTRACT

Heterotic performance of twenty-one F1 hybrids and their 10 parents were evaluated in a randomized complete block design with three replications in two environments. Significant differences were observed among parents, hybrids and hybrids versus parents for most of the yield and yield related characters in both environments. Under lowland environment, grain yield showed the high relative mid parent heterosis that varied from 12.69 to 17.45%. F1 hybrids, Sugdasi x Basmati 370 (16.52%), Bengalo x Pandan (16.39%), JJ77 x Pandan (12.88%) and DR65 x Vertin (12.69%) showed high mid parent heterosis. Under upland environment, grain yield showed the high relative mid parent heterosis that varied from 13.37 to 27.69%. F1 hybrids, Bengalo x Pandan (27.69%), DR65 x Vertin (24.27%), Rataria x Vertin (21.25%), Sugdasi x Pandan (17.38%), Sugdasi x Basmati 370 (13.42%) and LR2 x Basmati 370 (13.37%) showed high mid parent heterosis. F1 hybrids, Sugdasi x Pandan, LR2 x Basmati 370, Bengalo x Pandan, Bengalo x Basmati 370 and DR65 x Vertin showed higher yield ha-1 in both environments. Keywords: Aromatic rice, environments, F1 hybrids, heterosis, yield traits.

INTRODUCTION The current levels of rice production do not meet future demand. Since 2000, annual withdrawals from rice stocks have been necessary to bridge the gap between rice production and demand. The world population is projected to increase from 6.13 billion in 2001 to 7.21 billion in 2015 and 8.27 billion in 2030, indicating a corresponding increase in rice demand from 680 million tons in 2015 to 771 million tons in 2030 (Badawi, 2004). The challenge of overcoming hunger, poverty and malnutrition in rice-consuming countries while maintaining productivity and protecting the environment will require coordinated efforts.

Corresponding author: adjarwar@yahoo.com

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

2

Increased awareness at national, regional and global efforts to secure sustainable rice production. In addition, rice research plays a major role in the efficient utilization of cultivated area, improved rice varieties, and the minimization of losses during milling. The major focus of rice research in the next decade must emphasize on the development of high-yielding and early-maturing varieties in order to ensure sustainable production of rice (Swain, 2005). Rice, the second most widely-grown cereal crop after wheat and gifted with rich genetic repositoire, is the staple food for more than half of the global human population. More than one hundred thousand landraces and improved cultivar collections available in the rice germplasm world wide largely contribute to the rich genetic diversity of rice. Driven by natural selection of varieties distributed in diverse agro-ecoclimatic conditions coupled with continuous selection by man for his diverse in quality and aesthetic preferences, a unique rice varietal group has emerged, which became known as basmati rice, a specialty rice all over the world (Singh et al., 2000). Heterosis is a phenomenon in which F1 hybrids derived from diverse parents show superiority over their parents. Two major hypotheses have been proposed to explain the genetic basis of heterosis: the dominance hypothesis (Davenport, 1908) and over dominance hypothesis (East, 1908, 1936). The heterozygote (Aa) is more vigorous and productive than either homozygote (AA or aa). This over- dominance theory is proven for traits controlled by a single or a few genes. The heterozygote performs a given function over a range of environments more efficiently than either homozygote (East, 1936). Studies on the genetic basis of heterosis for polygenic traits in various crops have shown that heterosis is the result of partial to complete dominance, over dominance, epistasis, and may be a combination of all these (Comstock and Robinson, 1952). Evidence of real over dominance for quantitative traits is hard to find. However, apparent overdominance caused by non allelic interaction and linkage disequilibrium are common contributors to heterosis (Jinks, 1983). The presence of heterosis and SCA effects for yield and its related traits in rice are reported by Saleem et al. (2008). Faiz et al. ( 2006) evaluated four genotypes (2 lines and two testers) and their F1’s to estimate heterosis and combining ability effects in yield and yield influencing traits like plant height, number of productive tillers plant-1, number of spike-lets panicle-1, number of filled grains panicle-1, sterility %age and grain yield. Significant differences were observed in lines, testers and line x testers. The highest positive heterosis over better parents was observed for grain yield (41.83 %), number of productive tillers plant-1 (11.04 %) and number of filled grains panicle-1 (7.39 %) in the cross IR69616A x Basmati 385. GCA effects were found higher for filled grains and number of spike-lets panicle-1. Except plant height, mean performance of the parents was positively and strongly correlated with GCA effects. Nuruzzaman et al. (2002) reported the presence of heterosis and SCA effects for yield and its related traits. Vanaja and Babu (2004) pointed out that yield increase in rice was due to favorable heterosis in flag leaf area, number of spikelets panicle-1 and number of grains panicle-1. Tiwari et al. (2011) studied three CMS lines and 20 elite restorers to identify the best heterotic combination. Their results indicated manifestation of heterobeltiosis in grain yield for 43

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

3

hybrids ranging from 11.63 to 113.04% and 46 hybrids over standard variety, ranging from 10.48 to 71.56%. Most of the crosses which exhibited superiority over better parent or standard variety for grain yield also showed significant heterosis for number of fertile spikelets and number of spikelets panicle-1. The hybrid rice programe depends upon the magnitude of heterosis which also helps in the identification of potential cross combinations to be used in the conventional breeding programes to create wide array of variability in segregating generations. A good hybrid should manifest high heterosis for commercial exploitation. This study is therefore aimed at estimating the heterotic effects and aids in selecting the desirable parents and crosses for the exploitation of heterosis in newly introduced basmati varieties of Indica rice. MATERIALS AND METHODS This study was conducted at the experimental area of the Research office, Central Luzon State University, Science city of Munoz, Nueva Ecija, Philippines. Hybridization was done to produce F1 hybrid seed during summer and wet seasons of April, 2010. Evaluation of genotypes was carriedout during the dry season of July 2011. Ten selected genotypes of which seven were used as lines and three as testers while one was kept as check. Line (males) Local Roosi-2, Sugdasi, Mehak, JJ77, Rataria, DR65, and Bengalo were originated from Pakistan through selection. Whereas Testers (Females) Pandan and Vertin were originated from Philippines and Basmati 370 from India through selection. Variety Basmati 370 was used as check. The seeds were sown in plastic pails for the production of crosses in the dry/summer season-2010. Staggard planting was done to synchronize flowering, to obtain the planned crosses. Hybridization was done as soon as the flowering appeared in the parental material. The crosses were made in line x tester mating fashion, thus 21 F1 hybrids were developed. The pails were filled with garden soil and organic compost in a ratio of 9:1 which was thoroughly mixed. Approximately 10 kg of the medium was used in each pail. Three to five seeds were hand dibbled in each pail. The seeds were covered with thin layer of fine soil and kept wet to the level of saturation. Four to five days after emergence watering was done when required. Fertilizers were applied following the recommended rate into two splits 1st at seedling and 2nd at panicle initiation stage. Flowers of female parents were emasculated by cutting the tip of each floret with scissor and the immature anthers were removed with an automatic sucker or by hand with forceps, taking care that stigma is not damaged. Emasculation was done in the afternoon between 4-6 p.m, one day before the anther is expected to dehisce and the stigma is likely to become fully receptive. The emasculated flowers were then covered with butter paper bags to avoid natural cross pollination. Pollination of emasculated flowers of each floret was done in the morning between 10 and 11 a.m. when the anthers were fully matured and ready to dehisce. Dehisced anthers were collected from the male parents and were shed onto the female parents (emasculated panicle). After pollination, the panicles were again properly covered, to protect from foreign pollen and were tagged just after bagging. The tags were marked with the date of

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

4

emasculation, date of pollination, and the names of male and female parents. Seeds of the crossed material were harvested after 21-25 days of pollination and kept in the cold storage. Harvesting of the crossed plants were done 25 days after pollination. Evaluation of hybrids alongwith their parents and a check variety was done in two environments, low land and upland conditions in three replications, during the dry season in December 2010. Lowland conditions were characterized by continuous presence of water during the growing period, while in the upland condition, the genotypes were grown under controlled irrigation. In each environment, each genotype was planted in a row plot of 1 meter length with a distance of 30 cm between rows and 20 cm between plants. The field was prepared thoroughly by alternate plowing and harrowing until the desired soil tilth was attained under lowland environment, whereas in upland environment, field was prepared with disc plowing and harrowing twice. Thirty day- old seedlings were pulled and one seedling hill-1 were transplanted in the prepared plots and sprayed with mollusicide at the rate of 1L ha-1 right after transplanting in the lowland. Whereas in the upland condition, irrigation was applied in the prepared plots at the time of transplanting. The experimental plots in both the environments were fertilized at the rate of 132-42-42 NPK kg ha-1 at 7 days after transplanting, while the remaining dose was applied into two splits at 30 and 45 DAT. During transplanting, water level was maintained at 2-3cm depth until 25-30 DAT in the lowland condition. In upland condition, irrigation was applied as alternate dry and wet. Aside from irrigation, weeding and appearance of insect pests and diseases were monitored regularly and no infestation was observed in the experiments. In the upland condition, manual weeding was done to control the weeds. Harvesting was done when the plants reached at maturity. Five plants were randomly selected by cutting the stem close to the soil surface for determining the agronomic traits and yield components. Proper labels were used to tag the index plants. The data were collected for panicle length (cm), number of spikelets panicle-1, number of filled grains panicle-1, percent filled grains, weight of 1000 grains (g) and grain yield (kg ha-1). Data for yield and its related characters were subjected to the following biometrical analysis methods. The data collected from the experiment were subjected to statistical analysis for analysis of variance appropriate for RCBD. Mean squares were tested against error variance by the usual “F” test. The least significant difference (LSD) was computed by multiplying the standard error of the difference with “t” values for (r-1) (t-1) degres of freedom at 5% and 1% level of significance. Heterosis was expressed as the percent deviation of the hybrids (F1) from each of the relative parent i.e. increased or decreased vigor of the F1 hybrids over their mid parent value as under:

Where: = Mean performance of F1 hybrids

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

5

= Mean value of the two corresponding parents

P1 = mean performance of male parent, P2 = mean performance of female parent Estimates of heterosis was tested for their significance by the following formula:

Where:

r = number of replications

f = number of female (testers)

m = number of males (lines)

Means were compared with least significant difference (LSD) which was computed by multiplying the standard error of the difference with the respective “t” value for error degree of freedom at 5% and 1% levels of significance.

RESULTS AND DISCUSSION One of the essential factors needed in hybrid development is the high magnitude of heterosis available through specific combinations. In the present study, heterosis was calculated as deviation of hybrids from mid parental values of each of the crosses for yield and its component. Significant variation for all characters studied except for number of non-productive tillers plant-1 and length of panicle among the crosses. For parents versus crosses, all the characters were significant except percent filled grains panicle-1. In the present study, the parents of diverse origin were used which indicate a variable heterosis from higher to lower degrees in their F1 hybrids under lowland and upland environments. The heterotic effect of the crosses for different yield traits, for two environments studied are presented in Table 1. The character wise results are given here under: Panicle length Under lowland conditions, heterotic values ranged from -8.03 to 7.64. Out of 21 crosses, seven showed significantly positive heterosis over their mid parents, while eight crosses showed significantly negative heterosis. The highest positive heterosis was observed on the cross combinations Sugdasi x Basmati 370 (7.64%) followed by cross Rataria x Vertin (6.51%). The significant positive heterotic effect indicates that those hybrids gave increased panicle length.

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

6

Under upland conditions, heterosis values varied from -10.27% to 7.23%. Six crosses exhibited significantly positive heterosis and five exhibited significant negative heterosis among 21 F1 hybrids. The positive significant heterotic effect indicates the length of panicle has increased. In upland environment, the highest significant positive heterosis was found in cross combinations JJ77 x Vertin (7.23%) followed by LR2 x Basmati 370 (6.82%) and Sugdasi x Vertin (6.65%). The average heterosis in two environments ranged from -5.74 to 4.95. Out of 21 hybrids, 10 exhibited positive heterotic effects and the rest exhibited negative effects. Number of spikelet panicle-1 Under lowland condition, only one cross Sugdasi x Basmati 370 showed significantly positive heterotic effect (23.66%), while hybrid DR65 x Vertin was recorded significantly negative heterosis (-24.69%).While under upland conditions, the heterosis ranged from -22.72 to 27.04. The highest positive heterosis was shown by cross of Bengalo x Pandan (27.04%) followed by Sugdasi x Basmati 370 (12.73%). Out of 21 crosses, 12 showed positive heterotic effects and nine expressed negative effect. The positive heterotic effect exhibited increase in the number of spikelets panicle-1 due to hybrid vigour. Average values of two environments ranged from -18.30 to 18.19. Out of 21 cross combinations, 11 showed mean positive heterotic effects while 10 showed negative effects. Hybrid Sugdasi x Basmati 370 exhibited the highest average heterotic value of 18.19%. These results agreed with the findings of Faiz et al. (2006) who observed highest positive heterosis for this trait. Number of filled grains panicle-1 Under lowland environment, the heterotic effects showed that among the crosses, Sugdasi x Basmati 370 and DR65 x Pandan exhibited maximum significant positive heterosis (27.03 and 27.06%, respectively). Such higher values indicated complete dominant gene action in these crosses. Under upland environment, out of 21 cross combinations, only Bengalo x Pandan showed highest positive heterosis (34.73%), while JJ77 x Basmati370 showed the highest negative heterosis (-30.87%) over their mid parental values. The heterosis values ranged from -30.87 to 34.73%. In combined environments, mean values ranged from -23.25 to17.00. Out of 21 F1 hybrids, 11 hybrids exhibited positive heterotic effect. The highest mean value (20.21%) was observed in cross Sugdasi x Basmati 370, followed by Bengalo x Pandan (17.00%) and DR65 x Pandan (12.87%). Percent filled grains panicle-1 Under lowland condition, all cross combinations showed insignificantly negative and also positive heterotic effects, except cross of DR65 x Pandan, which exhibited significantly positive heterosis over their mid parental value (5.09%).

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

7

Table 1. Heterotic effects for different yield and its related characters under two environments.

F1 hybrids Length of panicle (cm) Number.of spikelets panicle-1

Number of filled grains panicle-1

Lowland Upland Mean Lowland Upland Mean Lowland Upland Mean

LR2 x Pandan -3.47** -2.73 -3.10 -4.73 -10.37 -7.55 -10.04 -10.71 -10.37

LR2 x Basmati 370 3.09* 6.82** 4.95 4.69 3.15 3.92 5.10 6.87 5.98

LR2 x Vertin -2.82* -5.23** -4.02 1.85 5.87 3.86 3.07 5.17 4.12

Sugdasi x Pandan -5.56** -2.11 -3.83 -7.91 -7.26 -7.58 -9.67 -6.55 -8.11

Sugdasi x Basmati 370 7.64** -4.19* 1.72 23.66* 12.73 18.19 27.03* 13.40 20.21

Sugdasi x Vertin -0.58 6.65** 3.03 -0.32 1.97 0.82 0.37 2.84 1.60

Mehak x Pandan 0.89 -7.48** -3.29 -0.02 -8.95 -4.48 -2.75 -14.41 -8.58

Mehak x Basmati 370 0.05 0.13 0.09 -15.75 7.74 -4.01 -15.83 11.26 -2.28

Mehak x Vertin -4.35** -1.11 -2.73 -2.18 -1.11 -1.64 -0.55 -2.22 -1.38

J J 77 x Pandan -8.03** -3.45* -5.74 -2.61 4.58 0.98 -5.33 5.97 0.32

J J 77 x Basmati 370 5.69** -10.27** -2.29 -13.00 -22.72* -17.86 -15.63 -30.87 -23.25

J J 77 x Vertin -2.63* 7.23** 2.30 -12.54 -11.07 -11.80 -14.78 -11.19 -12.98

Rataria x Pandan 3.54** 4.67** 4.10 -1.71 -4.79 -3.25 -0.62 -9.24 -4.93

Rataria x Basmati 370 -2.67* -0.45 -1.56 5.73 2.67 4.20 5.02 5.23 5.12

Rataria x Vertin 6.51** 1.95 4.23 0.41 7.79 4.10 1.71 9.06 5.38

Bengalo x Pandan 2.79* 0.41 1.60 1.20 27.04 14.12 -0.73 34.73** 17.00

Bengalo x Basmati 370 -0.91 5.07** 2.08 9.74 3.27 6.50 10.61 1.96 6.28

Bengalo x Vertin 0.33 -3.29 -1.48 -3.79 -9.29 -6.54 -1.39 -10.78 -6.08

DR 65 x Pandan -2.98* 1.27 -0.85 21.20 0.32 10.76 27.06* -1.32 12.87

DR 65 x Basmati 370 -1.19 0.82 -0.18 -24.69* -11.91 -18.30 -26.12* -10.48 -18.30

DR 65 x Vertin 3.88** 4.34* 4.11 15.64 5.72 10.68 15.88 4.25 10.06

S.E 1.21 1.64 - 10.91 10.73 - 10.64 10.79 - LSD at 0.5 2.44 3.31 - 22.06 21.69 - 21.50 21.81 - LSD at 0.1 3.26 4.43 - 29.51 29.02 - 28.77 29.19 -

** = Significant at1% level * = Significant at 5% level

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

8

Table 1. Continued.

F1 hybrids Percent filled grains

panicle-1 Weight of 1000 grains (g) Yield (kg ha-1)

Lowland Upland Mean Lowland Upland Mean Lowland Upland Mean LR2 x Pandan -4.95 -0.66 -2.80 0.71 3.21** 1.96 -3.15 -0.01 -1.58 LR2 x Basmati370 0.45 3.34 1.89 -6.69** -8.84** -7.76 16.42 13.37 14.89 LR2 x Vertin 0.45 0.06 0.25 -1.57* -4.60** -3.08 -21.05 -24.42 -22.73 Sugdasi x Pandan -1.29 0.84 -0.22 4.53** 3.71** 4.12 16.52 17.38 16.95 Sugdasi x Basmati 370 2.75 1.33 2.04 -3.36** -3.54** -3.45 17.45 13.42 15.43 Sugdasi x Vertin 1.11 0.78 0.94 7.80** 11.01** 9.40 -13.29 -7.69 -10.49 Mehak x Pandan -2.28 -4.98* -3.63 3.74** 4.71** 4.22 9.42 -3.26 3.08 Mehak x Basmati 370 -0.23 3.46 1.61 -5.38** -7.02** -6.20 -43.71 -34.58 -39.14 Mehak x Vertin 1.80 -0.66 0.57 -1.91** 3.46** 0.77 -9.25 -9.94 -9.59 J J 77 x Pandan -2.68 2.35 -0.16 0.18 -5.54** -2.68 12.88 -12.91 -0.01 J J 77 x Basmati 370 -2.27

-9.20** -5.73 -3.78** -0.16 -1.97 -29.97 -48.61 -39.29

J J 77 x Vertin -2.25 -0.54 -1.39 -1.81* -3.56** -2.68 -3.75 -7.04 -5.39 Rataria x Pandan 1.57 -4.81* -1.62 2.30** 6.07** 4.18 -2.23 -11.96 -7.09 Rataria x Basmati 370 -0.50 3.17 1.33 1.66* -8.11** -3.22 -18.99 9.25 -4.87 Rataria x Vertin 1.52 1.45 1.48 1.05 6.97** 4.01 7.01 21.25 14.13 Bengalo x Pandan -1.57 6.86** 2.64 7.98** 0.62 4.30 16.39 27.69 22.04 Bengalo x Basmati 370 1.26 -0.79 0.23 -2.24** -3.20** -2.72 7.56 10.78 9.17 Bengalo x Vertin 2.46 -1.36 0.55 -7.36** 3.89** -1.73 5.01 -14.31 -4.65 DR 65 x Pandan 5.09* -1.39 1.85 5.32** 5.08** 5.20 -1.75 3.41 0.83 DR 65 x Basmati 370 -1.44 1.48 0.02 -2.36** -2.02 -2.19 6.43 3.66 5.04 DR 65 x Vertin 0.57 -1.05 -0.24 -1.10 -5.47** -3.28 12.69 24.27 18.48 S.E 2.31 2.32 - 0.71 1.05 - 711.00 492.29 - LSD at 0.5 4.67 4.70 - 1.43 2.13 - 1436.94 994.90 - LSD at 0.1 6.25 6.25 - 1.19 2.85 - 1922.55 1331.15 - * = Significant at 1% level * = Significant at 5% level

The heterosis values however ranged from -4.95 to 5.09%. Under upland condition, heterosis values for this trait ranged from -9.20 to 6.86. Among 21 crosses, only Bengalo x Pandan showed significantly highest positive heterosis (6.86%), while cross combination JJ77 x Basmati 370 showed highest negative

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

9

heterosis (-9.20%), followed by hybrid Mehak x Pandan (-4.98%). Out of 21 crosses, 11 hybrids showed positive heterosis, whereas 10 showed negative heterosis. Averaged over two environments ranged from -5.73 to 2.64%. Out of 21F1 hybrids, 13 hybrids showed positive effects. Positive heterotic effect revealed that hybrids had increased percent filled grains panicle-1. Among the average positive heterotic effect, the highest value was exhibited by cross Bengalo x Pandan (2.64%), followed by Sugdasi x Basmati 370 (2.04%). However, cross combination DR65 x Basmati 370 showed the lowest heterotic value (0.02%). Weight of 1000 grains Under lowland condition, estimates of heterotic effect for this trait ranged from -7.36 to 7.98%. Significant positive heterosis over mid parent values was observed in seven hybrids out of 21 and 10 expressed significantly negative heterosis. The significantly positive heterotic effects could reflect towards higher grain yield. This also suggests that cross combinations with highest magnitude of positive heterosis like Bengalo x Pandan (7.98%), Sugdasi x Vertin (7.80%) and DR65 x Pandan (5.32%), have heavier seed weight and could be utilized for the exploitation of heterosis in grain weight. Under upland condition, the heterosis values ranged from -8.84 to 11.01. Out of 21 F1 hybrids, 10 showed significantly positive heterotic effect over mid parental values, while eight showed significantly negative heterosis. Hybrid of Sugdasi x Vertin exhibited highest significant positive heterosis (11.01%), followed by Rataria x Vertin (6.97%), Rataria x Pandan (6.07%) and DR65 x Pandan (5.08%). Above crosses, showed higher values for their average performance for this trait. Significantly positive heterosis indicates the heavier weight of 1000 grains, resulting higher yields for these hybrids. Averagedover environments, mean values ranged from -7.76 to 9.40. However positive heterosis values were observed in nine out of 21 F1 hybrids. The positive heterotic effects of those crosses could be reflected for higher grain yield under lowland and upland conditions which suggest that cross combinations with highest magnitude of positive heterotic effects like Sugdasi x Vertin (9.40%), DR65 x Pandan (5.20%), Bengalo x Pandan (4.30%) and Mehak x Pandan (4.22%) have heavier seed weight and can be utilized for the exploitation of heterosis to improve grain weight over both the environments. Yield (kg ha-1) Under lowland conditions, all crosses showed non-significant positive as well as negative heterotic effects. Out of 21cross combinations, 11 crosses exhibited positive heterosis and 10 manifested negative heterotic effects. The heterotic values ranged from -43.71to 17.45. Cross of Sugdasi x Basmati 370 showed highest positive heterosis (17.45%), followed by Sugdasi x Pandan (16.52%) and LR2 x Basmati 370 (16.42%). Under upland condition, all hybrids showed non-significant heterosis. Out of 21, ten crosses showed positive heterosis and 11 negative effects. The heterosis values ranged from -48.61 to 27.69%. Cross combination Bengalo x Pandan, showed highest positive heterosis (27.69%), followed by DR65 x Vertin (24.27%) and Rataria x Vertin (21.25). Over the

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

10

environments, the mean values ranged from -22.73 to 22.04%, however hybrid Bengalo x Pandan exhibited highest heterotic value (22.04%) followed by cross combinations DR65 x Vertin (18.48%), Sugdasi x Pandan (16.95%), Sugdasi x Basmati 370 (15.43), LR2 x Basmati 370 (14.89) and Rataria x Vertin (14.13). Heterosis in grain yield is attributable to increases in number of spikelets and number of filled grains. Most of the parents involved in the crosses showed higher mean values over their parents for those characters. CONCLUSION The increased yield of hybrids with the high heterotic effects observed in this study under lowland environment of growing basmati rice, suggests that these hybrids could be utilized for the exploitation of heterosis.

REFERENCES Badawi, A. T. 2004. Rice-based production systems for food security and poverty alleviation in the Near East and North Africa: New Challenges and Technological Opportunities FAO Rice Conference Rome, Italy. Comstock, R. E. and H. F. Robinson. 1952. Estimation of average dominance of genes. In: Heterosis. Ames, Iowa (USA): Iowa State College Press. pp. 494-516. Davenport, C. B. 1908. Degeneration, albinism and inbreeding. Sci., 28: 454-455. East, E. M. 1908. Inbreeding in corn. Rep. Connecticut Agric. Exp. Stn. for 1907. pp. 419-428. East, E. M. 1936. Heterosis. Genetics, 21: 375-397. Faiz, F. A., M. Sabar, T. H. Awan, M. Ijaz and Z. Manzoor. 2006. Heterosis and combining ability analysis in basmati rice hybrids. J. Anim. Pl. Sci., 16: 1-2. Jinks, J. L. 1983. Biometrical genetics of heterosis. In: Frankel R, editor. Heterosis: reappraisal of theory and practice. Berlin (Germany): Springer-Verlag. Nuruzzamman, M., M. F. Alam, M. G. Ahmed, A. M. Shohad, M K. Biswas, M. R. Amin and M. M. Hossain. 2002. Studies on parental variability and heterosis in rice. Pak. J. Bio. Sci., 5 (10): 1006-1009. Roy, B. and A. B. Mandal. 2001. Combining ability of some quantitative traits in rice. Ind. J. Genet., 61 (2): 162-164. Saleem, M. Y., J. I. Mirza and M. A. Haq. 2008. Heritability, genetic advance and heterosis in line x tester crosses of basmati rice. J. Agri. Res., 46 (1): 15-26.

Pak. J. Agri., Agril. Engg., Vet. Sci., 2013, 29 (1)

11

Singh, R. K., V. S. Singh and G. S. Singh. 2000. Aromatic rices. New Delh: Oxford and IBH publishing Co. Pvt. Ltd. Swain, D. 2005. Rainfed lowland and flood–prone rice a critical review on ecology and management technology for improving the productivity in Asia: Role of Water Scie; in Transboundary River Basin Mangmnt., Thailand. Tiwari, D. K., P. Pandey, S. P. Giri and J. L. Dwivedi. 2011. Heterosis studies for yield and its components in rice hybrids using cms system. Asian J. Plant Sci., 10: 29-42. Vanaja, T. and L. C. Babu. 2004. Heterosis for yield and yield components in rice (Oryza sativa L.). J. Trop. Agri., 42 (2): 43-44.

(Received September 05, 2012; Accepted December 26, 2012)