The genetic and physiological basis of water use efficiency in tomatoes

Abstract

Drought and heat stress are the major abiotic constraints to plant survival and productivity. This study focused on the estimation of genetic variability in response to water deficit conditions, evaluated the use of carbon isotopes to measure water use efficiency (WUE), and identified SNP marker associations with traits linked to higher genotypic performance under water deficit stress. The diverse plant materials were subjected to two irrigation regimes in two planting seasons and characterized for various morphological and fruit quality traits to explain the genetic variance. The study suggests fruit length to diameter ratio, number of fruits and fruit setting should be considered for selection under water deficit environments. The accessions were genotyped using SNPs to identify marker trait associations (MTAs) under water deficit conditions. About 20% markers were found to be significantly associated with the various traits. Being growth condition specific, these MTAs will need to be validated in a wider set of materials and environments. A subset including six genotypes was used to investigate WUE under controlled conditions at Purdue University, West Lafayette. The WUE was assessed using gravimetric measurements, leaf isotopic composition and diurnal gas exchange measurements. Strong association among ∆13C and other traits including assimilated weighted average intracellular CO2 concentration, intrinsic and instantaneous WUE under varied water deficit levels was observed. The results demonstrated the efficacy of carbon isotopes in predicting changes in WUE as well as substantial variation in WUE among Solanum lycopersicum accessions. The information generated from the present study will advance knowledge to understand the genetic, physiological, and fruit quality response under water deficit stress conditions and help tomato industry develop better adapted tomato genotypes.