ROOTSTOCK-MEDIATED VARIATION IN TOMATO VEGETATIVE GROWTH UNDER LOW POTASSIUM OR PHOSPHOROUS SUPPLIES

Abstract

Grafting provides a rapid and direct tool to transfer rootstock-mediated abiotic stress tolerance to commercial stress-sensitive cultivars. Nutrient deficiency is a widespread problem in some soils, inhibiting physiological processes and thus reducing crop yield. With the aim of selecting rootstocks conferring tolerance to potassium (K+) or phosphorous (P) deficits, a commercial tomato cultivar (‘Boludo F1’, ‘Monsanto’) was grafted onto 144 different rootstocks: six accessions from S. lycopersicum (‘Cerasiforme’) and S. pimpinellifolium, selected for drought tolerance (sourced from The World Vegetable Center, AVRDC); nine introgression lines from S. lycopersicum A— S. pennellii and A— S. habrochaites, selected for high root/shoot ratio, salinity and drought tolerances (sourced from The Tomato Genetics Resource Center, TGRC); and a population of 129 recombinant inbred lines (RILs) derived from a salt sensitive genotype of S. lycopersicum var. cerasiforme and a salt tolerant line from S. pimpinellifolium L. (sourced from Instituto Valenciano de Investigaciones Agrarias, IVIA). Plants were grown in semi-hydroponics or soil for 4-6 weeks (vegetative stage), under low K+ (1 mM) or low P (0.1 mM) supply. Shoot fresh weight was measured at the end of each experiment. There was a large rootstock-mediated variation in shoot biomass under each low nutrient condition. Some specific lines used as rootstocks performed better under low nutrient conditions than the self-grafted commercial cultivar ‘Boludo F1’. Furthermore, although some rootstocks seemed to perform well under different limiting conditions, no relation was found in shoot fresh weight for the two low nutrient conditions studied, suggesting that the mechanisms that control vegetative vigour seem to work differently depending on the specific nutrient deficiency. Results from this study will help in the future to identify genetic and physiological determinants that allow tomato roots to confer crop resistance to nutrient limitation as well as to improve fruit yield under individual and combined stresses.