Induced chemical mutagenesis in Rose under in vitro culture

Abstract

The present investigation entitled “Induced chemical mutagenesis in rose (Rosa chinensis) under in vitro culture” was carried out in the Tissue Culture Laboratory attached to the Horticultural Department, College of Agriculture, Vellayani during 1989-90. The main objectives of the experiment were to standardize a suitable culture medium for the growth and development of axillary buds and to standardize a successful method of chemical mutagenesis in rose under in vitro culture using the most potent chemical mutagen, ethyl methane sulphonate. The standardization of hormone levels in the culture medium (ms) was done at three stages of explant development viz. culture establishment, axillary bud proliferation and in vitro rooting. Surface sterilization of axillary buds were standardized by using mercuric chloride selecting out three concentrations 0.06, 0.08 and 0.1 per cent and 3 periods of treatment 5, 10 and 15 minutes. The axillary buds used were of 4 maturity stages ie. Axillary buds at the time of flower harvest and 2, 4 and 6 days after flower harvest. The various concentrations of ethyl methane sulphonate tested include 0.125, 0.25, 0.375 and 0.5 per cent. Two methods of mutagen treatments were tried ie. direct treatment and cotton swab method. In the direct treatment the axillary buds were subjected to EMS treatment at different periods treating the buds at the time of culturing, 2 days after culturing, 4 days after culturing and 6 days after culturing. In the cotton swab method buds were treated with EMS in the plant itself at various stages ie. at the time of flower harvest and 2,4 and 6 days after flower harvest. Surface sterilization of axillary buds was found to be most successful with mercuric chloride at 0.08 per cent for 15 minutes of the various levels of hormonal combinations tested BAP 2 mg/1 +2.4-D 1 mg/1 was found to be the best for culture establishment and BAP 2 mg /1 +GA 1mg/1 for shoot proliferation. Maximum rooting was obtained in full strength MS medium supplemented with IAA 2 mg/1 of the two methods of mutagen treatments tried direct treatment of axillary buds with EMS was not found to be effective as the buds turned brown and no further development occurred. In the cotton swab method, lower concentrations of EMS (0.125 and 0.25 per cent) gave a better performance based on days taken for bud take multiple shoot production and rooting percentage. A decrease in survival percentage was noted with increase in mutagen concentration. Higher concentration of EMS (0.375 and 0.5 per cent) curbed multiple shoot production in buds excised at the time of flower harvest and delayed multiple shoot production in other stages. The percentage cultures showing rooting and the number of roots/shoot also decreased with increase in concentration of EMS. Increase in maturity of buds also delayed multiple shoot production and decreased rooting percentage of the 4 stages of buds used for in vitro culture, buds excised at the time of flower harvest was found to be the best. But mutagen treatment retarded their performance. For mutagen treatment buds excised 4 days after flower harvest was found to be best followed by buds excised 2 days after flower harvest. Buds excised 6 days after flower harvest showed a poor performance in the normal and treated populations. The experiment clearly demonstrated that induced mutagenesis in rose can be successfully done adopting in vitro culture techniques.