Development of an efficient in vitro plant regeneration system using true leaf explants of processing tomato (Solanum...

Tomato (Solanum lycopersicum L.) is one of the most economically important horticultural crops in China, and Xinjiang is the main region in China for processing tomato production. The establishment of a robust in vitro regeneration system is a fundamental prerequisite for genetic improvement and cultivar innovation in this crop. Among the factors influencing regeneration efficiency, exogenously applied plant growth regulators (PGRs) are the most important because they regulate endogenous phytohormone homeostasis and signaling pathways. In this study, true leaf explants of the processing tomato Ligeer 87-5 were used to optimize combinations of 6-benzyladenine (6-BA) and indole-3-acetic acid (IAA) and to establish an efficient in vitro regeneration system. Full strength MS medium supplemented with 2 mg/L 6-BA and 0.2 mg/L IAA was optimal for callus induction and organogenic competence, resulting in a callus induction rate of 97.00%, an embryogenic cell incidence of 63.88%, and an adventitious bud formation rate of 21.33% after 20 days; the budding rate further increased to 63.00% after 30 days. For rapid shoot induction, a medium composed of MS + 1 mg/L 6-BA + 0.2 mg/L IAA yielded the highest adventitious bud formation rate, reaching 89.00% after 10 days. Rooting was most effective on MS medium supplemented with 0.2 mg/L IAA, achieving a 100% rooting rate after 21 days, an average root length of 11.76 cm, a 76.67% acclimatization rate after 28 days, and a 100% survival rate after hardening and transplantation. Collectively, the stage-specific application of different media substantially improved true-leaf regeneration efficiency in processing tomato plants, providing a robust platform for future genetic transformation and molecular breeding.