B. C. Ajay

Genetic association and frequency distribution in segregating generations derived from pigeonpea crosses

Correlation and presence of genetic interactions was studied using F2 and F3 generations in three pigeonpea crosses for yield and its component traits. Most of the characters studied were positively skewed and were being governed by several genes indicating quantitative inheritance. Variance, skewness and kurtosis have also indicated that homozygosity has increased over the generation in pigeonpea crosses. Cross BRG 1 x ICP 8863 was found better than other two crosses (TTB 7 x ICP 8863 and TTB 7 x ICPL 87119) in providing high yielding segregants displaying parental diversity. Seed yield and other associated characters such as plant height and number of pods per plant had complementary gene action with other genes governing these characters. Yield increase is possible by following rigid selection for yield and its component characters. A shift in correlation coefficients between the generations was recorded which is likely to be attributed to difference in gene complementation of linkage blocks and an indication of unstable nature of breeding population.

Identification of AFLP markers linked to Fusarium wilt disease in pigeonpea [Cajanus cajan (L.) Millsp.]

An experiment was conducted to identify markers linked to Fusarium wilt disease resistance, Parents namely TTB 7 and ICP 8863 were screened using 151 SSRs markers and 16 AFLP primer combinations. Parental screening revealed five SSR primers and 12 AFLP primer combinations polymorphic between parents. Bulk segregant analysis identified five AFLP primer combinations generating seven markers polymorphic between resistant and susceptible bulks while, none of the SSR markers were polymorphic. This indicates that, these markers are putatively linked to wilt disease. Screening of F2 segregating population of cross TTB 7 x ICP 8863 with these putatively linked markers revealed four markers (E-AAT/M-CTG850, ETCG/M-CTT650, E-TCG/M-CTA730 and E-TCG/M-CTT230) which segregated in 3:1 mendelian pattern. Simple linear regression performed on these four markers had identified two markers namely E-TCG/M-CTT650 and E-TCG/M-CTA730 linked to disease.

Response of different peanut genotypes to reduced phosphorous availability

Performances of 23 peanut genotypes comprising of popular varieties and few widely used germplasm accessions were compared under P-unfertilized and Pfertilized conditions during kharif and summer seasons to identify P-efficient and P-inefficient genotypes. Yield parameters and P concentrations in different plant parts at maturity were recorded and P-efficiency indices calculated. Significant differences among peanut genotypes, P levels and P × genotype interactions were observed for all the traits. LP caused 33% and 23% yield reduction during kharif and summer season respectively. However, performance of genotypes varied with the season and P supply. Genotypes FeESG-10, GG-7, GG-20 and TG-37A with high yield, kernel P-uptake and P concentration in leaf were Pefficient. On the contrary genotypes NRCG-162, GPBD-4, NRCG-7320 and NRCG-7085 were identified as P-inefficient. As an immediate solution to P deficient soils, the P-efficient genotypes could be directly grown in the LP soils with/without using P to get high yield.

Genetic appraisal of F2 generation of Dolichos bean for yield and yield attributing traits

In the present study F 2 generation was evaluated for yield and yield contributing traits to understand genetic variability and association among yield contributing traits in dolichos bean. High phenotypic and genotypic coefficient of variability (PCV and GCV) was observed for first flowering initiation and total seed weight per plant in both the crosses. The differences between PCV and GCV values were narrow for all the traits studied, which indicates the low level of environmental influence in the expression of these traits. High heritability and GAM was noticed for all the traits studied in both the crosses indicating that influence of additive gene effects in expression of these characters. Skewness and kurtosis indicate that seed weight per plant (SW/P) was governed by complementary gene interaction with fewer numbers of dominant genes. Hence, SW/P could be increased either by increasing 100SW or seeds per pod among the crosses studied.

Multivariate analysis for yield and its component traits in rice (Oryza sativa L.) under alkaline soil condition

A study was undertaken to assess the response of rice genotypes grown under alkaline soil condition using various multivariate analytical tools. ANOVA and MANOVA revealed significant differences among 33 genotypes for different traits. Principal component analysis (PCA) grouped the traits into three components, which jointly explained 67% of the total variation. Largest variation was explained by total biomass, spikelet per panicle and grain yield per panicle. When different alkalinity groups were compared in pairwise fashion using SIMPER analysis, it was found that there is no common trait to differentiate between the groups. Considering all traits together, Vikas and KMR 3 were identified as the most suitable genotypes which can be utilized as donors for tolerance to alkalinity.