Induction of variability in Vanilla planifolia Andrews through intra/inter specific hybridisation and embryo culture technique
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Date
2005
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Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara
Abstract
The present investigation entitled “Induction of variability in Vanilla planifolia Andrews through intra/interspecific hybridisation and embryo culture technique” was carried out at the Centre for Plant Biotechnology and Molecular Biology (CPBMB), College of Horticulture, Kerala Agricultural University, Vellanikkara during the period from 2003-2005.
Genetic variation in the germplasm of Vanilla planifolia is relatively limited because of the continuous clonal breeding of the existing gene pool. The present work was taken up with the main objectives of enhancing the spectrum of variability in vanilla through intra/interspecific hybridisation and thereby to get desirable recombinants of higher yields, richer vanilla flavour and disease resistant.
The superior clones of V. planifolia (a 82, a 94, a 425, a 428, vv97/84) and V. tahitensis plants maintained at CPBMB were taken as parent plants in the hybridisation programme. Variation in the foliar and stem characters of parent plants was observed which could be manifested in the progeny. Floral morphology and biology of V. planifolia and V. tahitensis plants were studied and variation was observed in flowering season of both species. Pollen fertility was assessed in acetocarmine (1%) stain and was 61 per cent for V. planifolia and 74.69 per cent for V. tahitensis flowers. The viability of pollen was assessed in pollen germination reported by Ravindran (1979) and was 39 and 45.3 per cent for V. planifolia and V. tahitensis pollen grains. There was no significant variation in the pollen fertility and pollen viability percentages of both species. In vivo crossing was done as per the pollination technique of V. planifolia for inter and intraspecific crosses. The pod set percentage varied significantly with genotype. The pod development pattern was similar in both inter/intraspecific hybrid pods. Embryo culture was done as per the protocol reported by Mary et al. (1999) to get hybrid progenies. Seeds from pods of different ages were cultured. The time taken for embryo germination and intensity of embryo germination varied significantly with the maturity and genotype of pods. Seeds from hybrid pods (a 82 x a 94) of 6 weeks maturity germinated early compared to seeds from half mature (14, 18, 20, 22 and 24 weeks) and mature (28 and 36 weeks) pods. The germinated seedlings were multiplied and planted out with the already available protocol.
Variability in the seedling progenies was assessed at monthly intervals for morphological characters. The hybrids obtained from intraspecific crosses a 82 x a 94 and vv 97/84 x a 94 were found vigorous with respect to plant growth. The hybrid progenies from interspecific cross V. t x V. p showed remarkable variation in leaf shapes and four leaf shapes broadly ovate, oblong lanceolate, lanceolate and linear lanceolate were observed in the progenies against narrow lanceolate in V. t parent and oblong-elliptic in V. p parent. Simple and branched stem type were observed in the progenies of interspecific cross (V. t x V. p) and intraspecific crosses (a 82 x a 94 and vv 97/84 x a 94) against normal simple stem in the parents. Single and double aerial roots were produced from single node in the progenies of interspecific cross (V. t x V. p) and intraspecific crosses (a 82 x a 94 and a 425 x a 94) against single root origin in the parent plants. Variation was also observed for number of leaves, plant height, leaf size, leaf colour and internodal length.
Molecular characterisation of selected parents and hybrid progenies was done using RAPD technique. Heirarchical cluster analysis of RAPD data revealed variability between parents and hybrid progenies of intra/interspecific crosses. The variation in the parents and progenies of interspecific cross (V. t x V. p) ranged from 8 - 40 per cent. The intraspecific crosses a 82 x a 94, a 94 x a 82, a 425 x a 94 and vv 97/84 x a 94 showed variation range of 16 - 36 per cent, 4 - 31 per cent, 10 - 34 per cent and 12 - 28 per cent respectively.
The results obtained from morphological and molecular characterisation of parents and progenies confirmed that variability was induced in vanilla through intra/interspecific hybridisation and embryo culture technique.
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