Biological hardening of micropropagated tomato plantlets: A case study with Piriformospora indica

Abstract

Aseptic cultures were established from explants (cotyledons, shoot-tips and hypocotyls) in six genotypes (two hybrids-TH802 & TH2312; respective parents Haelani x Accession-2 and VFN8 × Punjab Chuhara) and three male sterile (ms) lines (EC251735, EC 251692 and EC 251752) in tomato (Solanum lycopersicum L.) on MS medium with different concentrations and combinations of hormones. Maximum number of shoots in six genotypes initiated on cotyledons as explants on MS medium supplemented with BAP (2.0 mg/l) while only three male sterile lines initiated on medium with BAP (0.5 mg/l) + Kinetin (0.5 mg/l). Multiple shoot formation on subsequent subcultures was observed on medium with BAP (1 mg/l) + Kinetin (0.5 mg/l). The separated shoots (4-5 cm) in hybrids/parents/ms lines resulted in profuse rooting on half basal MS medium (0.5 × MS media) containing 15 g l_1 sucrose (without hormones). Hardening of in vitro raised plantlets in hybrids/parents/ms lines was done using bioagents and antitranspirants. Maximum survival was recorded on treatment of plantlets with Piriformospora indica (86.6%) followed by Trichoderma viride (75.0%), while minimum survival was observed in untreated control (36.6%). The hardened plant-lets were successfully transferred to field and expressed true-to-type traits (including male sterility). This paper reports an efficient and reproducible protocol for in vitro multiplication and biological hardening of diverse genotypes in tomato.