A tomato heat-tolerant mutant shows improved pollen fertility and fruit-setting under long-term ambient high temperature

• Published in: Environmental and experimental botany 2020-10, Vol.178, p.104150, Article 104150
• Main Authors: Pham, Dung, Hoshikawa, Ken, Fujita, Satoshi, Fukumoto, Shoma, Hirai, Tadayoshi, Shinozaki, Yoshihito, Ezura, Hiroshi
• Format: Article
• Language: English
• Subjects: Fruit production; Heat stress; Heat tolerance; Pollen viability; Tomato
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2020.104150

•15 heat tolerant tomato lines screening from over 4000 EMS Micro-Tom mutant populations displayed in two types of fruit-setting: parthenocarpic and seeded fruits.•Long-term heat stress (HS) 35° C increased the deform flowers and damaged 50 % pollen viability.•HT7 mutant produced more viable pollens than WT in HS.•HT7 mutant produced normal fruits containing seeds, while, WT could not produce seeded fruits in HS.•HT7 mutant highly expressed heat shock transcription factor (SlHsfA1b) and heat shock protein (SlHsp101). Heat stress (HS) is a major problem of tomato production worldwide, as it reduces fruit setting due to the adverse effects on pollen development and fertility. In this study, we isolated heat-tolerant (HT) mutants providing improved fruit-setting under long-term ambient high temperature by testing over 4000 lines from the Micro-Tom tomato mutant collection. The HT mutants were categorized into two types, namely those that produced parthenocarpic fruit, and those that produced fruit with seeds. Among the HT mutants, HT7 plants produced fruit with seeds, had a higher fruit number and seeded-fruit yield, and the total pollen number and viability were much higher under HS conditions than those of the WT under both control and HS conditions. HT7 also succeeded at fertilization even under HS conditions due to higher pollen viability than the WT. In addition, HS-related genes, such as SIHsfA1b3 and Hsp101, were more highly expressed in HT7 than in WT. These results suggest that HT7 could be a valuable genetic resource for elucidating heat tolerance mechanisms and a breeding material for improving heat-tolerant fruit-setting in tomato.