Genotypic differences and water-deficit induced enhancement in epicuticular wax load in peanut

The epicuticular wax load (EWL) on leaves reduces surface transpiration and thus improves crop water use efficiency. The objectives of this study were to evaluate peanut (Arachis hypogaea L.) genotypes for their ELW and also to determine the influence of water deficit stress on EWL. Peanut genotypes were grown in fields in two dry seasons (2000 and 2001) and one rainy (2000) season. Withholding irrigation water resulted in a significant increase in water saturation deficit in the stressed crop. At 45 d after sowing (DAS), significant genotypic differences were observed in EWL of 12 genotypes grown in the rainy season (2000). The values of EWL ranged from 0.91 mg dm(-2) in Chico to 1.74 mg dm(-2) in PBS 11049, with a mean of 1.27 mg dm(-2). Among six genotypes, which were also sampled subsequently, the mean values were 1.10, 1.58, 2.05 mg dm-2 at 45, 75, and 95 DAS, respectively. In both dry seasons, significant genotypic differences were found in the EWL. In the dry season of 2001, the effect of various moisture deficit treatments and their interactions with the genotypes were highly significant. The values ranged from 0.653 to 2.878 mg dm(-1). On an average, the highest EWL was found in PBS 11049 (2.24 mg dm(-2)). Even under irrigated conditions, in summer 2001, the EWL increased with increased age of the crop. However, there was a greater increase in the treatments that were subjected to moisture deficit stress. It was concluded that genotypic differences exist in EWL of peanut and also that EWL increases with increased crop age. This increase is more pronounced in plants that are subjected to protracted moisture deficit stress.