Induced mutagenesis in rose under in vivo and in vitro culture

Abstract

Investigations were carried out at the Department of Agricultural Botany and Tissue Culture Laboratory attached to the Department of Horticulture, College of Agriculture, Vellayani during the period from 1989-1993 on “Induced mutagenesis in rose under in vivo and in vitro culture. Induced mutagenesis adopting in vivo method was carried out with three rose cvs. Alliance, Suraga and Folklore belonging to Hybrid Tea group. The cv. Folklore alone was utilized for induced mutagenesis adopting in vitro culture. The budwoods of three selected cultivars were collected at three different stages of growth and exposed to Gamma rays at 20, 30, 40, 50 and 60 Gy, and budded on rooted stock plants and effect of gamma rays on morphological attributes were recorded. In vitro culture conditions were standardized for cv. Folklore. Budwoods were collected at five different growth stages and exposed to gamma rays at 20, 30, 40 and 50 Gy, before culturing. The in vitro variations in terms of culture establishment, shoot proliferation and rooting efficiency were studied. Multiple shoots were also subjected to gamma irradiation to study their in vitro variations. Gamma irradiation of bud woods induced inhibition and reduction in sprouting and survival. Growth retardation exhibited in the form of reduction in plant height and number of branches. The cultivars showwed no significant interaction with different doses of gamma rays for sprouting and survival. The ED50 was estimated as 38Gy. One reddish yellow mutant was isolated from cv. Folklore from 30 Gy treated population and one mutant for increased number of petals from 40 Gy treated population of the same cultivar. In addition, gamma exposure induced variation in size and shape of leaves at 30 and 40 Gy. The treatment of mercuric chloride 0.08 per cent for 12 minutes had the minimum contamination rate for shoot tip and axillary bud explants, and 0.06 per cent for 12 minutes was most effective in the case of internodal segments and leaf disc explants. Axillary buds of 1.0 cm length for enhanced release of axillary bud, internodal segments of 0.5 cm and leaf discs of 1.0 cm with a petiole portion for callus induction were identified as the most suitable explants. Axillary buds excised 4 days after flower opening had the best response in culture establishment. MS basal medium supplemented with BAP 2.5 mg/1+2,4-D 0.5 mg/1 recorded bud break percentage of 80 per cent within 4 days. Early multiple shoot induction and highest number of shoots/culture observed in medium supplemented with kinetin 2.0 mg/1 + GA3 1.0 mg/1. Addition of BAP 2.0 mg/1+ GA3 0.75 mg/1 was the best for getting highest percentage of cultures with multiple shoots. Flower bud initiation was observed in combination of BAP 2.0 MG/1 + GA3 0.5 MG/1. The best medium for in vitro rooting was found to be IAA and NAA 1.0 mg/1 each, along with activated charcoal 500 mg/1. Successful hardening and ex vitro establishment of plantlets were achieved by surface inoculation of germinated spores of mycorrhizae (VAM) in liquid suspension. Highest survival rate of 66.67 per cent was observed by inoculation with Glomus etunicatum against no plants in the untreated lot. Minimum number of days to flowering (105) was taken in plantlets inoculated with G. etunicatum BAP 0.5 mg/1 + NAA 2.0 mg/1 +2, 4-D 0.5 mg/1 was the best combination for callus induction and BAP 0.5 mg/1 + NAA 0.1 mg/1 + ascorbic acid 5 mg/1 had the highest callus proliferation. In vitro rhizogenesis obtained from internodal and leaf calli in MS medium supplemented with BAP 0.5 mg/1 + NAA 2.5 MG/1 + 2, 4-D 0.5 mg/1. Gamma irradiation of axillary buds delayed bud break, reduced percentage of bud break, multiple shoot production and rooting efficiency and also induced morphological variations in leaf and growth pattern. The estimated value for ED50 was 33 Gy under in vitro culture. Exposure of multiple shoots to gamma rays induced several morphological abnormalities and reduced the shoot production and rooting efficiency.