Heritability and correlation for nitrogen (N2) fixation and related traits in peanut (Arachis hypogaea L.).

The objectives of this study were to estimate broad sense heritability for N2 fixation and related traits and agronomic traits and evaluate correlations among these traits. Seventy four progenies in the F, generation previously selected in the F4 generation for high and low performance for N fixation and related traits were tested for N2 fixation and related traits and their agronomic performances. A non-nodulating line was also included as a reference crop for nitrogen determination. The experiment was carried out under limited soil nitrogen conditions. A randomized complete block design with four replications was used. Data were recorded for leaf color score, nodule dry weight, top dry weight, fixed nitrogen, pod number, pod weight, seed weight, seed size, shelling percentage and harvest index. Most heritability estimates for N2 fixation and related traits were moderate and high ranging from 0.33 to 1.00 except one low estimate (0.33). Most heritability estimates for agronomic traits were also moderate and high ranging from 0.37 to 1.00 except two low estimates (0.37 and 0.50). High heritability estimates in the F5 generation indicated that genetic variations of this population after divergence selection in the F4 generation are conserved and further selection for N2 fixation and agronomic traits in this population is possible when individual characters are considered. High and positive correlations among fixed nitrogen and its components were found indicating that increase in one trait can increase others. Correlations between N2 fixation and pod yield were low and varied depending on crosses suggesting that selection for both N2 fixation and pod yield is essential.

Gene effects for parameters of peanut bud necrosis virus (PBNV) resistance in peanut.

The objective of this study was to determine relative importance of gene effects for PBNV incidence and PBNV severity evaluated at 30, 40, 50 and 60 days after planting. Eight generations of three crosses involved three parental lines were evaluated for disease incidence (percentage of infected plants) and disease severity under natural occurrence of PBNV infection in a randomized complete block design with six replications. Evaluations were carried out at 30, 40, 50 and 60 Days After Planting (DAP). The analysis followed Hayman's model and Gamble's notations were used to describe parameters of gene effects. Joint scaling test was used to determine adequacy of the model. Additive gene effect was the most important contribution to genetic variation in generation means for both disease incidence and disease severity in the cross ICGV 86388 x IC 10. Selection for lower disease incidence and disease severity in this cross is promising. Additive gene effect and additive x additive epistatic gene effect were also important but in lower magnitude in the cross ICGV 86388 x KK 60-1 for disease incidence at 60 DAP. The presence of significant dominance gene effect in this cross for disease incidence might hinder the progress from selection. The consistent and significant additive gene effect for disease severity might provide a better selection strategy. Additive gene effect was significant for disease incidence only in the cross IC 10 x KK 60-1 at 60 DAP. Additive x dominance epistatic gene effect was also significant at 40 DAP, but no genetic parameter was significant for disease severity. This cross is considered less promising.