Seasonal responses and genotype-by-season interactions for the growth dynamic and development traits of peanut

Information on the interactions between genotypes and environments for physiological traits of peanut (Arachis hypogaea L.) is limited. The objective of the present study was to evaluate the effects of seasons and genotype x season (G x S) interactions for dynamic growth and development traits of peanut. Fifteen peanut lines varying in maturity duration, seed type and yield level were grown in a field experiment at the Khon Kaen University in Northeast Thailand during the 2002 and 2003 rainy seasons and the 2003 and 2004 dry seasons. Data were recorded on phenological development stages, pod yield and final biomass, and leaf area index (LAI), crop growth rate (CGR), pod growth rate (PGR), partitioning coefficient (PC), pod harvest index (HI), shelling percentage, and specific leaf area (SLA) were determined. Seasonal effects were found for all development and growth traits of the test peanut lines. Crop duration for the dry season was much longer than for the rainy season because of low temperatures during the early growth stage, causing a delay in flowering and a longer period of pod formation. The test peanut lines showed small differences in the duration of vegetative development and pod formation, but varied greatly in the seed filling duration. This period also showed the greatest differential responses to seasons between the peanut genotypes. Crop yields for the 2003 rainy and the 2004 dry seasons were much lower than for the other two seasons because of late leaf spot disease in the 2003 rainy season and cool temperatures at flowering in the 2004 dry season, resulting in poor pod setting, low PGR and low HI. The test peanut lines differed considerably in pod and biomass yields and all the growth traits measured. Significant G x S interactions were also found for all of these traits, though were much smaller than season effect. Regression analyses identified PGR as the dominant physiological trait determining the G x S interaction for pod yield. Exploring marker-assisted selection for this trait is suggested.