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

Abstract

Summary.Photoperiod insensitivity plays a significant role in ensuring wide adaptability of genotypes across environments. The effect of photoperiod in groundnut (Arachis hypogaea L.) 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 Fi progenies (excluding reciprocals) and their parents from a six‐parent diallel cross were studied to estimate combining ability for biomass and HI under short (SD)‐ and long (LD)‐day 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. V6 (ICG 2405) 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 V2 (ICGV 86694) and V6 for HI. However, the difference between SCA effects of V2 × V6 was not significant. The results of this study emphasise the need for future experiments with random genotypes over a range of photoperiods.