Standardization of embryo rescue technique and bio-hardening of grape hybrids (<i>Vitis vinifera</i> L.) using Arbuscular mycorrhizal fungi (AMF) under sub-tropical conditions

Abstract

In-ovulo embryo rescue in grape breeding programme assures breeding efficiency by curtailing 6 to 8 years in the development of seedless grape cultivars. Effect of different growth regulators, culture media, ovule age, cultivars and mycorrhizal strains on successful in-ovulo embryo rescue were studied in this experiment. With respect to mean ovule age (days after pollination), maximum ovule-embryo growth (2.13 mm²) were obtained when ovules were cultured at 24 days after pollination (DAP) but maximum germination (12.67 %) was obtained when ovules were cultured at 28 DAP. The concentration of IAA (4 mg) + GA3 (0.5 mg) proved to be most effective for germination (13.84 %). Among various media used for culturing ovules on modified MS medium (1/2 macro + 1/1 micro) required minimum days to germinate (96.67) and registered highest germination (13.75 %). Chilling treatment was proved to be one of the important factors for embryo maturation and 60 d of chilling treatment at 4 °C improved embryo germination. With respect to the effect of different growth regulators on various rooting and shooting parameters IBA (1.0 mg·L^-1) and NAA (1.5 mg·L^-1) were found superior. While comparing different hardening strategies, a glass jar with polypropylene cap (GPP) was found to be most effective as far as hardening success (66.67 %) was concerned. One of the serious impediments in the success of in vitro rescued plantlets is very high field mortality, field survival of rescued plantlets can be effectively increased by using different mycorrhizal strains (AMF) as bio-hardening agents. Among the various strains used for hardening of rescued plantlets T3 inoculated plantlets registered highest survival percent (88.00).