In vitro pollination, embryo rescue and germination studies in ginger

Abstract

Investigations were carried out for the refinement of in vitro pollination techniques in ginger developed at the Plant Tissue Culture laboratory, Department of Plantation Crops and Spices, College of horticulture, mainly to identify the conditions required for the germination of in vitro produced seeds of ginger. The study was carried out from 1994 to 1996. Investigations were carried to study the effect of season, cultivars and position of flowers in the inflorescence on pollen fertility and viability. The results showed that pollen fertility and viability were influenced by the season and genotype but not by the position of flowers on the inflorescence. The pollen viability was high in inflorescences produced during the early and mid period of the flowering seasons. So scheduling the pollination works for the early and mid period of the flowering seasons may lead to more seed set. The cultivars SG-66 and Rio-de-Janeiro exhibited more pollen fertility and viability. So chances of seed set will be more in crosses involving these cultivars as male parents. Crossing studies showed that Rio-de-Janeiro as female parent can be crossed with Kuruppampady, SG-66, Nadia and as a male parent can be crossed with Kuruppampady, Nadia, SG-66 and Bajpai. So the high yield potential of Rio-de-Janeiro can be transferred to cultivars suitable for dry ginger production. Selfing studies showed that the cultivars viz., Rio-de-Janeiro, Kuruppampady, SG-66, Nadia, Bajpal, SG-603 and SG-543 can be selfed by the in vitro pollination and fertilization techniques. The in vitro fertilized ovules developed into mature seeds in the medium of ½ MS with 2, 4-D 0.1 to 1.0 mg 1-1 and BAP 5 to 20 mg 1-1. The effect of 2, 4-D could be replaced by NAA 0.5 to 2 mg 1-1 or IAA 0.05 to 0.2mg 1-1. The results of seed viability test with tetrazolium salt showed that seeds of 40 and 80 DAP are viable so seeds from 40 DAP onwards can be subjected to germination studies. The studies on germination of ginger seeds showed that primary treatments like water soaking, incubating on moist filter paper, moist sand or basal medium (both solid and liquid state) did not favour germination of ginger seeds. Incubating the seeds in ½ MS + 6 per cent sucrose along with 2, 4-D 0.1 to 1.0 mg 1-1 or NAA 0.5 to 2.0 mg 1-1 and BAP 5 to 20 mg 1-1 had no influence on germination of ginger seeds. The combination of NAA 0.5 mg 1-1 or IAA 0.05 to 0.2 mg 1-1 with 2iP 2.5 to 5 mg 1-1 had no influence on seed germination. GA3 5 to 10 mg 1-1 and ethylene 5 to 10 mg 1-1 also did not favour seed germination. Seed treatments like chemical and mechanical scarification, stratification, washing the seeds in running water and subjecting the embryos to stress condition by dehydrating hydrated seeds for 12 h or soaking the seeds in 12 per cent each of Mannitol and PEG-4000 solution did not influence germination. Embryo rescue involving transfer of embryo along with endosperm to culture media with varying combinations of auxins and cytokinin also did not promote development of embryo to seedling.