Analysis of low-temperature tolerance of a tomato (Lycopersicon esculentum) cybrid with chloroplasts from a more chilling-tolerant L-hirsutum accession

Growth and photosynthesis of an alloplasmic tomato (cybrid), i.e. line AH47 , containing the nuclear genome of the chilling-sensitive cytoplasmic albin o mutant of L. esculentum Mill. 'Large Red Cherry' (LRC) and the plastome o f a more chilling-tolerant high-altitude accession of the related wild spec ies L, hirsutum Humb. & Bonpl. LA 1777, were investigated at an optimal (25 /20 degrees C) and suboptimal (16/14 degrees C) day/night temperature regim e and their performance compared with that of both euplasmic parents. The c ybrid shoot had a similar biomass and development rate to the nuclear tomat o (L. esculentum) parent at both temperature regimes. Compared with the bio mass production of shoots grown at optimal temperature, the reduction in sh oot biomass at suboptimal temperature was smaller for L. hirsutum than for L, esculentum and the cybrid. This difference was related to a stronger inh ibition of leaf area expansion in L, esculentum and the cybrid in the subop timal temperature regime than in L. hirsutum. Irrespective of the temperatu re regime under which the plants were grown, photosynthetic performance and leaf pigment, carbohydrate and soluble-protein contents of the cybrid rese mbled those of the nuclear parent. No advantages of the alien L. hirsutum c hloroplast with respect to growth and photosynthesis-related characteristic s were observed in the cybrid in the suboptimal temperature regime, indicat ing that the temperature sensitivity of the photosynthetic apparatus is reg ulated by nuclear genes, An adverse consequence of interspecific chloroplas t transfer was the increased susceptibility to chill-induced photoinhibitio n of the cybrid. It is concluded that cybridization is not a useful tool fo r improving low-temperature tolerance of tomato. (C) 2000 Annals of Botany Company.