An Introgression from Wild Tomato (Solanum habrochaites) Affects Tomato Photosynthesis and Water Relations

Abstract

ABSTRACTA quantitative trait locus (QTL) stm9 (shoot‐turgor maintenance; located on chromosome 9) from chilling‐tolerant Solanum habrochaites S. Knapp & D.M. Spooner maintains plant water status via stomatal closure in response to root chilling, which induces a rapid onset form of root water stress. Here we examined the effect of an introgressed S. habrochaites chromosome 9 region, which contains QTL stm9, on water relations, photosynthesis, and yield in the field. Three near‐isogenic lines (NILs) of cultivated tomato (Solanum lycopersicum L.) with and without S. habrochaites chromosome 9 introgressions, and their parent cultivar T5, were evaluated in 2 yr of field experiments in Davis, CA. The NILs with a S. habrochaites introgression exhibited predawn and midday leaf conductances that were 23 and 10% smaller, respectively, than those of the NIL without the S. habrochaites introgression and the parent cultivar. This resulted in the NILs with the S. habrochaites region having 23% higher predawn leaf water potential, 13% higher midday leaf water potential, and 13% lower net photosynthesis than the NIL without the S. habrochaites introgression and the parent cultivar. Yield in the NILs containing small (NIL175) and large (NIL1322) introgressions of S. habrochaites decreased an average of 42 and 71%, respectively, compared with the NIL without the introgression and the parent cultivar. The effect of the introgression from S. habrochaites under nonchilling conditions may prove useful for understanding tradeoffs between productivity and transpiration.