Efficient and reproducible somatic embryogenesis and micropropagation in tomato via novel structures - Rhizoid Tubers

Abstract

A dual in vitro regeneration system consisting of indirect organogenesis and somatic embryogenesis (SE), applicable to several varieties of tomato— Solanum lycopersicum (cv. Riogrande , cv. Roma , hybrid 17905 and model cv. M82 ) has been established. This system is both improved and highly reproducible compared to current methods. Callus initiation, plant regeneration and SE was developed for one-week-old cotyledon explants. Indirect organogenesis via callus induction (CI) was developed for all four varieties of tomato used in this study. One-week-old tomato seedlings were used as a source of cotyledon and hypocotyl segments as explants. The explants were subsequently cultured on Murashige and Skoog (MS) medium supplemented with different combination and concentrations of plant growth regulators (PGRs). Substantial trends in regeneration and propagation response were observed among the varieties and treatments. For commercial varieties cvs. Riogrande and Roma , maximum CI was observed at 2 weeks in CIMT 9 (0.5 mg/L NAA, 1 mg/L BAP) and CIMT 12 (2 mg/L IAA, 2 mg/L NAA, 2 mg/L BAP, 4 mg/L KIN). However, cv. M82 responded after 4 weeks to a combination of treatments CIMT 9 (0.5 mg/L NAA + 1 mg/L BAP) and CIMT 13 (2 mg/L IAA + 2 mg/L NAA + 2 mg/L BAP + 4 mg/L ZEA) for the production of calli. Subsequent shoot and root organogenesis were optimized for all four varieties. Cv. Riogrande , exhibited fastidious in vitro regeneration potential and selected for induction of somatic embryos via SE involving novel structure: rhizoid tubers (RTBs). Numerous fine hair like rhizoids (~23/explants) were first developed from cotyledon and hypocotyl explants cultured on MS medium supplemented with 0.5 or 2 mg/L NAA at pH 4.0 in dark conditions. Further incubation of each rhizoid under light conditions on MS media supplemented with 5 mg/L TDZ or BAP at pH 4.0 led to the formation of a novel structure—rhizoid Tubers (RTBs). Thus, as evident from histology, SE in Riogrande tomato species requires a medium with pH of (4.0) and higher concentration of cytokinins (BAP/TDZ) to form on average 40–45 RTBs from both explants. Histological and morphological studies revealed that RTBs develop through different stages of embryogenesis to multiple plantlets, on MS medium with 5 mg/L TDZ/BAP at normal pH (5.8). The results obtained indicated that the induced somatic embryos of tomato with lower pH are a more efficient mode of propagation than the organogenesis with or without callus formation. The RTBs led to a complete plantlets regeneration in 45 days compared to indirect organogenesis at 60 days.

A Novel and Efficient In Vitro Organogenesis Approach for Ajuga lupulina Maxim

“…BA was the most effective among the four cytokinins employed in axillary shoot regeneration in A. lupulina similar to that reported by Sivanesan and Park [ 18 ]. TDZ is believed to be the best synthetic cytokinin present for the regeneration of numerous plant systems [ 19 , 20 ]. High cytokinin activity of TDZ inhibits shoot elongation; however, it is conducive to the formation of somatic embryos [ 15 , 21 ].…”

Highly efficient Agrobacterium-mediated transformation and plant regeneration system for genome engineering in tomato

“…Cytokinins in plants stimulate cell division, bud initiation, and proliferation ( Van Staden et al, 2008 ). In vitro regeneration of tomato has been significantly affected by the explants, genotypes, and PGR concentrations and combinations used in the culture medium ( Alatar et al, 2017 , Prihatna et al, 2019 , Saeed et al, 2019 , Vinoth et al, 2019 ).…”

“…The results confirmed that ZEA was a superior cytokinin concerning multiple shoot induction among three plant growth regulators tested. Successful regeneration procedures have been reported using different explant types of many tomato genotypes on medium augmented with ZEA ( Gupta and Van Eck, 2016 , Saeed et al, 2019 ). In shoot induction medium containing ZEA, all the explants generated the optimum number of shoots (from 2.86 to 26.76 shoots) after two successive subcultures ( Table 1 , Table 2 , Table 3 ).…”

Piriformospora indica employs host’s putrescine for growth promotion in plants

“…No study so far assigns a functional role for a specific metabolite in P. indica mediated growth promotion across plants. Tomato ( Solanum lycopersicum L.) is one of the most important vegetables grown worldwide with 177 million ton production (Saeed et al, 2019). However, Tomato has been least explored for its interaction with P. indica and beneficial effects.…”