Genetic variation in sugarcane for leaf functional traits and relationships with cane yield, in environments with varying water stress

Abstract

Sugarcane is a major economic crop that is grown mostly where water availability is a dominant limitation to production. However, selection for cane yield under dry conditions is difficult because of variable rainfall and sometimes high experimental error variance. If measurements made under relative non-stress conditions could be used to predict relative yield of genotypes under dry environments it could improve effectiveness of selection, especially in early stage selection trials in breeding programs. In this study, field experiments were conducted to evaluate 31 sugarcane genotypes in rain-fed and irrigated treatments across multiple sites and years in Yunnan province, South China. The aim was to examine relationships between cane yield and several leaf functional traits and determine if measurements made in environments experiencing low water stress could be used to predict relative yield of genotypes in dry environments. The water treatments had a large impact on mean cane yield and all the measured leaf function traits. However, for cane yield genotype×water treatment interactions were relatively small relative to genotype main effects, except when water stress was severe. For the leaf functional traits in most cases, genotype main effects were highly statistically significant while genotype×date and genotype×water interactions were mostly not statistically significant despite contrasting conditions at different dates of measurement. It was found that a combination of high yield and low leaf conductance or high leaf temperature (both of which may be related to reduced rates of water use), all measured under non-stress conditions, was predictive of yield under the limited water treatments, with prediction levels better than either yield or leaf based measurements alone. This is suggestive of a potentially valuable role for this combination of measurements in optimal selection indices in early stages of selection in sugarcane breeding programs. High sampling and error variances and high labour requirements associated with measuring conductance or leaf temperature using traditional methods are a limitation to practical application. However, these may be overcome through emerging technologies enabling related measures through aerial imaging. Development and testing of these approaches is recommended to develop better selection methods in early stage selection trials in breeding programs.