COMBINING ABILITY OF RESPONSE TO PHOTOPERIOD IN PEANUT

Photoperiod insensitivity plays an important role in the adaptation of peanut (Arachis hypogaea L.) genotypes across environments. However, little is known of its genetic control. The objective of this study wa s to determine the combining ability of response to photoperiod in pea nut. The F-1 progenies from a six-parent diallel cross excluding recip rocals were studied together with their parents for response to photop eriod under short and long day conditions in the field for three seaso ns. The experiment was conducted in a split plot design with photoperi od as main plots and genotype as subplots. The response to photoperiod (D-SL) was computed as the difference in harvest index (adjusted pod weight/adjusted biomass) between short and long day treatments, The me an square for response to photoperiod was highly significant for paren ts and their crosses, Season by cross interaction was the only signifi cant interaction effect. The response to photoperiod was mainly associ ated with general combining ability variance, ICG 2405 and ICGV 86031 were good general combiners for insensitivity to photoperiod, All cros ses of sensitive x sensitive and sensitive x insensitive parents were sensitive to photoperiod, However, in several cases, this response was not consistent across seasons and resulted in a significant season x cross interaction. The F-1 between insensitive parents was insensitive to photoperiod in the three seasons tested. A comparison of F-1 respo nse with parents and midparent value of crosses between photoperiod se nsitive and insensitive parents suggested additive gene action in some crosses and partial dominance to dominance in others.