Combining ability analysis in bitter gourd (Momordica charantia L.) for potential quality improvement

Combining ability analysis provides useful information for the selection of parents, also information regarding the nature and magnitude of involved gene actions. Crops improvement involves strategies for enhancing yield potentiality and quality components. Targeting the improvement of respective characters in bitter gourd, combining ability and genetic parameters for 19 characters were estimated from a 6×6 full diallel analysis technique. The results revealed that the variances due to general combining ability (GCA) and specific combining ability (SCA) were highly significant for most of the important characters. It indicated the importance of both additive and non-additive gene actions. GCA variances were higher in magnitude than SCA variances for all the characters studied indicating the predominance of the additive gene effects in their inheritance. The parent P2 (BG 009) appeared as the best general combiner for earliness; P1 (BG 006) for number of fruits, average single fruit weight and fruit yield; P4 (BG 027) for node number of first female flower and days to seed fruit maturity; P3 (BG 011) for fruit length and thickness of the fruit flesh; P5 (BG 033) for 100-seed weight; and P6 for number of nodes per main vine. The SCA effect as well as reciprocal effect was also significant for most of the important characters in different crosses.

The impact of epistasis in the heterosis and combining ability analyses

The current theoretical knowledge concerning the influence of epistasis on heterosis is based on simplified multiplicative model. The objective of this study was to assess the impact of epistasis in the heterosis and combining ability analyses, assuming additive model, hundreds of genes, linkage disequilibrium (LD), dominance, and seven types of digenic epistasis. We developed the quantitative genetics theory for supporting the simulation of the individual genotypic values in nine populations, the selfed populations, the 36 interpopulation crosses, 180 doubled haploids (DHs) and their 16,110 crosses, assuming 400 genes in 10 chromosomes of 200 cM. Epistasis only affects population heterosis if there is LD. Only additive x additive and dominance x dominance epistasis can affect the components of the heterosis and combining ability analyses of populations. Both analyses can lead to completely wrong inferences regarding the identification of the superior populations, the populations with greater differences of gene frequencies, and the populations with maximum variability, when the number of interacting genes and the magnitude of the epistatic effects are high. There was a decrease in the average heterosis by increasing the number of epistatic genes and the magnitude of their epistatic effects. The same results are generally true for the combining ability analysis of DHs. Surprisingly, the combining ability analyses of subsets of 20 DHs showed no significant average impact of epistasis on the identification of the most divergent ones, even assuming a high number of epistatic genes and great magnitude of their effects. However, a significant negative effect can occur.

Combining ability analysis for yield and yield components and quality traits in Indian mustard [Brassica Juncea L. (Czern & Coss)]

Combining ability analysis was performed in a 10× 10 half dialle cross in Indian mustard genotypes for yield and quality traitsduring 2017-18 and 2018-19 at the agriculture research farm R.B.(PG) college Mudi, Agra and IFTM university,Lodhipur Rajput Moradabad.In this study, 45 F1 hybrid and their parents were evaluated for 14 quantitative and qualitative traits. The parents used namely, NRCHB -101, DRMR- IJ- 31, Kanti, Urvashi, Pusa mustard- 25 (NPJ-112), Pusa mustard-26 (NPJ-113), Pusa mustard- 27 (EJ-17), CS- 54, RH- 406, RH -749. The results indicated that both additive and non-additive type of gene actions were responsible in expression of all the 14 characters. Parental genotypes viz., RH -749, RH -406 and CS -54, showed high GCA effects for seed yield per plant and most of the important characters except days to 50% flowering and days to maturity. The other parent’survashi, PM -27, DRMRIJ- 31, NRCHB -101 showed high GCA effects for the remainingtraits. Out of 45 crosses only three crosses RH- 406 × RH -749, PM- 26 × RH -406 and PM -26 × RH -406 had desirable and significant SCA effects with high per se performance for seed yield per plant in F1,s generation. The present study indicated that genetic improvement in the Indian mustard would be achieved by using selected promising crosses having significantly high SCA values coupled with high per se performances.

Combining yield, earliness and plant height in a single genotype: a proposal for breeding in grain sorghum (Sorghum bicolor L.)

Grain sorghum production has expanded during the off-season when rainfall oscillates and becomes insufficient. Aiming to obtain better adapted cultivars, breeding programs have sought new combinations of hybrids with earliness, high grain yield, and ideal plant height for harvesting. This study aimed to estimate de combining ability of grain sorghum lines, proposing a breeding strategy, to identify hybrids gathering high yield, earliness, and desired plant height. Thirty-six hybrids from crosses of 12 lines were evaluated at two sites in the Brazilian region known as Cerrado biome. The evaluated traits were: days to flowering, plant height, and grain yield. For the diallel analysis, Method 4 of Griffing adapted to partial diallel was adopted. By combining ability analysis, we identified promising lines to be used as parents to obtain more yielding, early, and ideal height hybrids. The findings allowed us to propose a breeding strategy, in which complex crosses should be performed to gather favorable alleles in new restorer and male-sterile lines. The hybrids 7, 9, 19, and 22 are the most suitable for growing in the evaluated sites. Highlights: Combining ability analysis allows the identification of promising parents to be used in grain sorghum breeding program. Favorable alleles for each trait are contained in different parents, which makes gene pyramiding a necessary strategy to simultaneously gathering earliness, plant height suitable for harvesting, and high yield in a single hybrid. To improve the R lines, the cross between M2 (good donor for shorter height) x M5 (good donor for earliness) should be performed, and the hybrid resulting from M2xM5 can be crossed with the M4 line (good donor for high grain yield). The hybrid generated by the cross F1-B x F4-B (high earliness) should be crossed with the hybrid derived from F6-B x F5-B (shorter height), and the hybrid resulting should be crossed with the hybrid generated by F2-B x F3-B (high grain yield).