Nearly Isogenic Cucumber Genotypes Differing in Leaf Size and Plant Habit Exhibit Differential Response to Water Stress

Abstract

Four nearly isogenic cucumber lines (Cucumis sativus L.) differing in leaf size [standard leaf (LL) vs. little leaf (ll)] and plant habit [indeterminate (DeDe) vs. determinate (dede)] were compared for their response to high soil moisture tensions in 1990 and 1996. Comparisons were made between lines for aboveground vegetative and fruit response, between two irrigation regimes, and among three postharvest treatments. Differences in vegetative plant response between lines were documented by wilting ratings, plant dry weight, fruit number and fresh weight, and fruit quality [i.e., fruit shape, seed size, seed cavity size, and pillowy fruit disorder (PFD)] ratings depending upon the stress environment. Postharvest treatment affected the quality of fruit recovered from plants subjected to water stress. Exposure of fruit at 15 °C and 85% relative humidity (RH) for 4 days after hydrocooling, resulted in lower PFD than storage of fruit at 26 °C and 60% RH for 2 days without hydrocooling. Cucumber genotypes showed differential response to water stress indicating that plant habit and leaf size can be important genetic determinants of plant response to water stress. Although plant productivity was not affected by water stress, PFD, shape, seed size, and seed cavity size of fruit from lldede plants were more severely affected by water stress than its llDeDe counterpart. Plants homozygous ll, in either a determinate or indeterminate background, were less susceptible to wilting under water stress conditions than their normal leaf (LL) counterparts. However, plant dry weight and fruit number and weight were higher in LLDeDe plants when compared to their llDeDe counterparts. Fruit recovered from LLDeDe plants were of higher quality than those recovered from llDeDe plants. Thus, wilting response to water stress is not necessarily indicative of a cucumber plant's tolerance to water stress in the reproductive stage.