Combining ability of biomass and harvest index under short- and long-day conditions in groundnut

Abstract

Photoperiod insensitivity plays a significant role in ensuring wide adaptability of genotypes across environments. The effect of photoperiod in groundnut (Arachis hypogaea) is manifested in post-flowering development including partitioning. The partitioning of assimilates, as measured by harvest index (HI), has the greatest effect on pod yield. The F1 progenies (excluding reciprocals) and their parents from a six-parent diallel cross were studied to estimate combining ability for biomass and HI under short day (SD) and long day (LD) conditions, and to identify good combiners with high biomass and HI for use in breeding programmes. The experiment was conducted for three seasons in a split plot design with two photoperiods as main plots and 21 genotypes as subplots. The two photoperiod treatments were SD (defined as normal-day light period) and LD (defined as normal-day light period extended by 4 h using incandescent lamps). The multi-environment analogue of Griffing's Method 2 - Model 1 was modified to analyse data for combining ability. While biomass was controlled by both GCA and SCA effects, HI was predominantly controlled by GCA effects. GCA and SCA effects for biomass and HI interacted with environments (six factorial combinations of photoperiods and seasons). SCA effects remained insensitive to variation in photoperiod both for biomass and HI. However, GCA effects for HI were sensitive to photoperiod. ICG2405 was a good general combiner for both biomass and HI across environments. None of the crosses showed positive and significant SCA effects for both biomass and HI. Photoperiod influenced the sensitivity of GCA effects of ICGV86694 and ICG2405 for HI. However, the differences between SCA effects in ICGV86694 × ICG2405 were not significant. The results of this study emphasise the need for further studies utilising random genotypes and a range of photoperiods