Heterosis and Combining Ability in CMS Based Hybrid Chilli ( Capsicum annuum L . )

Field experiments were conducted during kharif 2009-2010 to identify the most heterotic CMS based hybrids in chilli. The heterosis for dry fruit yield and yield components of 51 F1 hybrids were derived from crosses between three females (line) and seventeen males (tester) crossed in line x tester fashion. The cross ACA1/LCA334 exhibited significant heterosis over mid parent 493.44% as well as better parent 402.78%. The F1 hybrid JNA1/BVC-37 registered significant standard heterosis (48.47%) for dry fruit weight plant. The highly significant gca effect revealed that LCA960, BVC37, LCA334, PantC1 and JNA1 were good general combiner among the male and female, respectively. The hybrid JNA1/BVC37 gave the highest yield for dry as well as green fruits along with highly significant sca effects.


Introduction
India is the largest producer of chilli in the world owing to the availability of improved varieties.The role of hybrid seed in India is limited and the production of hybrid cultivars can be successful only if adequate quantities of hybrid seeds are produced at reasonably low cost.The hybrid seed production in chilli requires tedious process of emasculation and pollination.Chilli flowers are delicate in nature, resulting in flower drop or poor fruit set after emasculation.Moreover hand pollination increases the cost of hybrid seed production due to high labour cost.In the recent years hybrid cultivars have become popular and many farmers are producing hybrid seeds of hot pepper based on nuclear male sterility (Dash et al., 2001).Development of male sterility system is the only alternative to reduce the cost of seed production as it is being practiced in other vegetables.The male sterile (S-) cytoplasm has so far been most commonly utilized for commercial hybrid development in South Korea, China and India (Kim & Kim, 2005;Kumar et al., 2007).However, rapid transfer of male sterile cytoplasm (nuclear diversification of CMS) in Indian genotypes has been a handicap due to the limited availability of maintainer allele (rf) in chilli genotypes (Kumar et al., 2007) leading to restriction in the choice of the parents (Zhang, 2000).A major fertility restorer locus (Rf) is known to restore fertility of this S-cytoplasm, but it is influenced by temperature, quantitative trait loci (QTLs)/modifiers (Wang et al., 2004) and conditioned by an additional partial restoration (pr) locus (Lee et al., 2008a).This pr locus is suspected to be either tightly linked to Rf locus or is third allele of Rf locus (Lee et al., 2008b).In Capsicum, very few stable nuclear-cytoplasmic male sterile (CMS) lines are known because male sterility expressions in CMS lines have been found to be temperature sensitive (Shifriss, 1997).Temperature alteration may induce a degree of variation in male sterility, ranging from complete to partial.Selfing as well as crossing of the male sterile individuals can be achieved through temperature manipulation.Therefore, breeders must use restorer as well as maintainer lines for various environments to secure a completely sterile female parent, but fully fertile hybrid.
One important aim of hybrid breeding is to exploit the heterosis effect appearing in the F 1 .In development of high yielding varieties and hybrids of crop plants, the breeder often faces the problem of selecting parents and crosses.Common approach of selecting parents on the basis of per se always does not lead to fruitful results (Allard, 1960).The selection of parents has thus to be based on complete genetic information and knowledge of combining ability of potential parents.
Combining ability analysis in this respect is considered to be an efficient technique not only for selection of desirable parents and crosses but also characterizes nature and magnitude of gene action in the expression of a trait.Knowledge about the type and amount of genetic effects is required for an efficient use of genetic variability of crops.The concept of good combining ability refers to the potential of a parental form for producing superior offspring by crossing with another parent for the breeding process.Information and exact study of combining ability can be useful in regard to selection of breeding methods and selection of lines for hybrid combination.Due to the numerous theoretical and practical advantages of this method, in recent years the choice of parental forms on the basis of combining ability has been extended.
Keeping in a view the present investigation was undertaken to identify the most heterotic male sterility based hybrids and generate information on general and specific combining ability effects for selection of parents (male sterile and restorer lines) for promising hybrid combinations.

Plant Material
The experimental material comprised of fifty one F 1 hybrids developed from three females (CMS lines) viz., JNA1, ACA1 and ACA2 including seventeen male lines viz., SKS, PantC-1, G-4, K1-4C, 9608U, BVC-1, GUK-1, GUK-2, GUK-2-1, LCA334, LCA960, KDC-1-1, P. Jwala, KA-2, K1-4D, PSBR and BVC-37.Seventy one entries including twenty parents and their 51 F 1 hybrids were evaluated in a Completely Randomized Block Design (CRBD) with two replications during kharif season 2009-2010 at JNKVV, Jabalpur (Madhya Pradesh).The plot size for each accession was 6m x 1.2m where in both row-to-row and plant-to-plant spacing was 60 cm x 60 cm.The crop was raised as per the standard package of practice.The experiment was repeated thrice by transplanting the seedlings at the interval of twenty days.Timely management practices were followed to grow a good crop.Five plants were randomly selected/plot for recording data on days to first flower initiation, days to first fruit ripening, days to first harvest, number of pickings, number of fruits plant -1 number of primary branches and plant height (cm), where as ten fruits were selected (two fruits from each randomly selected plant) for fresh weight fruit -1 (g), dry weight fruit -1 (g), fruit length (cm), fruit diameter (cm), pedicel length (cm), petiole length (cm), number of seeds fruit -1 and 1000 seed weight (g).For days to 50% flowering data was recorded on plot basis.

Statistical Analysis
The estimates of heterosis and combining ability were computed on mean performance of hybrids and their parents over two replications for each date of transplanting.Data on three transplanting dates were subjected to analysis for heterosis (Turner, 1953;Fonseca & Patterson, 1968) and Line x Tester (Kempthorne, 1957) for combining ability analysis as per the standard procedure.

Analysis of Variance
The estimates of mean square due to genotypes and parents were significant for all the traits (Table 1) indicating the presence of large amount of diversity among the genotypes and respective group of the material studied.Mean squares due to line, testers, and line x testers were also significant for most of the traits revealed the differences among females and males.The comparison of parents vs crosses was significant for all the traits suggesting presence of hybrid vigour for all the characters.

Mean Performance of Parents and Hybrids
The range for mean performance and various heterotic effects as well as promising crosses identified on the basis of these two parameters are narrated in Table 2.The maximum range of mean performance was observed for number of fruits plant -1 for both, parents (71.67 -388.33) and hybrids (162.33 -565.17)along with high heterotic effects over mid parent (21.75 -658.29),better parent (-1.8 -651.37) and standard check (43.02 -397.94).
Genotypes BVC-37, BVC-1, GUK2-1, LCA960 and K1-4D registered as better parents based on per se performance for dry fruit weight plant -1 .KA-2 exhibited better parent for days to first flower initiation and days to fifty per cent flowering, JNA1 for days to first fruit ripening and days to first harvest, PSBR, K1-4D, KA-2, KDSC1-1 and LCA960 for number of pickings, PantC1 for number of fruits plant -1 , LCA960 for fresh weight fruit -1 , dry weight fruit -1 , number of seeds fruit -1 and 1000 seed weight , SKS for fruit length, GUK2-1 for fruit diameter, G-1 for pedicel length, BVC-37 for petiole length, fresh fruit weight plant -1 and dry fruit weight plant -1 , 9608U for number of primary branches plant -1 .

Heterotic Effects of Crosses
Most heterotic crosses are presented in Table 3 revealed that none of the hybrids showed desirable standard heterosis for days to first flower initiation, days to first fruit ripening, fresh weight fruit -1 , dry weight fruit -1 , pedicel length and number of seeds fruit -1 .However, one hybrid each for days to fifty per cent flowering and days to first harvest registered desirable standard heterosis.While 36 crosses for number of pickings, all 51 for number of fruits plant -1 and number of primary branches, 2 for fruit length, 1 for fruit diameter, 40 for petiole length, 23 for plant height, 26 for 1000 seed weight and 12 each for fresh fruit weight plant -1 and dry fruit weight plant -1 exhibited desirable standard heterosis.For fruit length and fruit diameter, most of the crosses were not consistent for their various heterotic effects.These findings are concordance with Joshi et al. (1995), Patel et al. (1997) and Patel et al. (2001).A perusal of the top heterotic crosses revealed that none of the cross was consistent for all the traits.Among the 51 F 1 hybrids studied 8 crosses viz., JNA1/BVC-37 (48.47%),JNA1/PantC1 (25.76%),JNA1/LCA334 (25.33%),JNA1/LCA960 (24.02%),JNA1/PSBR (22.77%),JNA1/GUK-2-1(16.59%),ACA2/LCA960 (13.10%),ACA1/LCA960 (6.99%) showed significant positive heterosis for dry fruit weight plant -1 over standard check VNR 332 (Table 4).However, other thirty nine crosses registered negative standard heterosis and remnant four crosses recorded non significant positive standard heterosis.

Table 1 .
Analysis of variance for eighteen yield related traits in chilli

Table 2 .
Five bests parents for eighteen characters in chilli

Table 3 .
Most heterotic crosses for eighteen characters in chilli for dry fruit yield

Table 4 .
Heterosis for dry and green fruit yield plant -1 for 8 best hybrids in chilli

Table 5 .
Estimates of gca effects of parents for different traits in chilli