Stimulation of growth and induction of variability in mangosteen (Garcinia mangostana L.)
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Date
2011
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College of Horticulture, Vellanikkara
Abstract
Mangosteen (Garcinia mangostana L.) is identified as a fruit crop deserving priority attention with a potential for increased acceptability. It is recognized as the ‘queen of tropical fruits’ due to its instant visual and taste appeal and has recently been popularized for its medicinal benefits. It yields profusely and fits very well as a component in the homesteads of Kerala. Almost all trees are female and variability is meagre. Its slow growth and long gestation period limit its commercialization. The present investigation on “Stimulation of growth and induction of variability in mangosteen (Garcinia mangostana L.)” was undertaken in the Department of Pomology and Floriculture, College of Horticulture, during 2006 - 2009 with the objective of developing techniques for accelerating seedling growth in the nursery, reducing gestation period and inducing variability through mutation and polyploidy. The studies on different growing media and growth regulators on seedling growth in the nursery revealed that potting mixture containing vermicompost as organic component was the most superior medium in terms of all the growth and physiological parameters, foliar nutrient content and uptake of nutrients, followed by coir pith, poultry manure and well rotten cow dung. Use of vermicompost medium without any additional growth regulators was sufficient to accelerate seedling growth in the nursery. When coir pith compost, poultry manure or well rotten cow dung was used in the medium, growth regulators had specific effect. Along with coir pith compost, IAA 300 ppm, BA 200 ppm and BA 300 ppm were ideal, while IAA 150 ppm, IBA 150 ppm and BA 300 ppm were superior with poultry manure medium. In normal potting mixture using cow dung, IBA 450 ppm, BA 200 ppm and IBA 300 ppm showed superiority. With the use of suitable media and growth regulators, seedling growth can be accelerated in the nursery and transplanting stage can be attained much earlier. Evaluation of different growth promoting substances in normal potting mixture showed that foliar spray of nutrient solution 3:1:1 (NPK) – 0.50 % (50 ml per plant) and Azospirillum sp. (10 g per plant) applied at fortnightly interval were the superior treatments with respect to all the growth parameters. In two year old grafted plants in the main field, a combination of GA 200 ppm + BA 100 ppm as bud application was the best with respect to majority of growth parameters, followed by GA 100 ppm + BA 100 ppm and GA 100 ppm. These growth regulators can successfully be used in early stages for promoting growth. In five year old juvenile orchard trees also GA and BA combinations, namely, GA 200 ppm + BA 100 ppm, GA 100 ppm + BA 100 ppm and GA 100 ppm + BA 200 ppm were the best treatments in accelerating growth and improving flushing. For the induction of flowering, soil drenching of paclobutrazol 2.0 g a.i. per tree, and bud application of GA 200 ppm + BA 100 ppm and GA 200 ppm + BA 200 ppm were superior and equally effective. For improving yield and yield attributes, paclobutrazol 2.0 g a.i. per tree was the most superior, followed by GA 100 ppm + BA 100 ppm and GA 200 ppm. Incidence of gamboge was minimum in paclobutrazol treatments, compared to GA, BA combinations. Among the various rootstocks tried, mangosteen was most compatible with its own rootstock where as all other rootstocks showed varying degrees of incompatibility. On comparing the growth of softwood grafts with seedlings, the latter showed faster rate of growth. Seedling growth could also be promoted by the use of nurse stocks. Large-scale multiplication of planting materials could be achieved through rooting of softwood cuttings from juvenile shoots of mangosteen. Seeds exposed to 5 Gy to 50 Gy gamma radiation showed wide variation in germination. Beyond 30 Gy, seeds failed to germinate. Seedlings from 30 Gy dose showed stunted growth indicating a possible genetic variation. Irradiation of scions with 5 Gy to 50 Gy had an adverse effect on days required for sprouting of scions, percentage of sprouting and final graft success. All the irradiated scions showed stunted growth even after one year. Two seedlings treated with colchicine at 3.0 and 3.5 per cent in the apical bud showed vigorous growth and distinct variation in growth characteristics. Five mangosteen seedlings with induced variations selected from irradiation and colchicine treatments were subjected to RAPD analysis. Clustering of five variants based on dendrogram separated the genotypes into two groups. Clustering pattern indicated that seed irradiation with 25 Gy and 30 Gy gamma rays and bud application of colchicine 3.5 per cent were effective in inducing variation in genomic DNA of mangosteen.
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