Studies on crossability barriers in interspecific crosses of pigeonpea [Cajanus cajan (L.) Millspaugh]
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Date
2020-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Interspecific hybridization is a powerful tool of crop improvement programme. It is used for transfer of economically useful traits (yield, abiotic and biotic stress tolerance) in pigeonpea. But, due to presence of fertilization barriers at different stages from pollination to seed set, all interspecific crosses are not successful. The present investigation was carried out at Cytogenetics and Molecular Markers Laboratory and Pulse Breeding Laboratory, Department of Genetics and Plant Breeding and Norman E. Borlaug Crop Research Centre, G.B.P.U.A.&T., Pantnagar during 2018-19 and 2019-2020, with the aim to assess crossability barriers between the cultivated Cajanus cajan (PADT-16 and PUSA-992) and wild species (Cajanus scarabaeoides ICP-15683 and ICP-15703 and Cajanus platycarpus ICP-15663). Crossability and unilateral incongruity was examined by pre-fertilisation parameters like pollen germination, pollen tube growth, and abnormal pollen tubes and these paramters were studied through bright-field and fluroscence microscopy. Molecular diversity among cultivated and wild species was analysed through SSR markers. In hand-selfing and intervarietal crosses mean pollen germination and pollen tube growth was higher than interspecific crosses. Differences in crossability parameters were observed and among the two cultivated varieties, the variety PUSA-992 performed better compared to PADT-16 in interspecific crosses. In cross between C. cajan and C. platycarpus the level of crossability barriers was higher than the cross between C. cajan and C. scarabeoides. In both direct and reciprocal cross between C. cajan and C. scarabeoides pollen tube successfully reached the ovule, however, in cross between C. cajan and C. platycarpus pollen tube failed to reach to ovule when C. platycarpus was used as male, indicated presence of strong pre-fertilisation barriers in cross C. cajan × C. platycarpus. In interspecific crosses involving C. platycarpus as female, low level of reproductive barriers were observed when crossed with C. scarabeoides compared to cross with C. cajan, though pollen tube reached to ovule in both crosses. Pollen tube abnormalities like bursting of tips, emergence of two pollen tubes from a single pollen grain, growth of pollen tube away from stigmatic surface, J-shaped pollen tubes were observed in interspecific crosses. Molecular diversity analysis was carried out using 30 markers, out of which 16 markers showed polymorphism. The genotypes were grouped into two major clusters. The PIC value of primers ranged from 0.48 (CCB10) to 0.96 (ASSR 390). The size of amplified fragments varied from 100bp to 650bp. The value of similarity matrix ranged from 0.26 to 0.83. Maximum diversity was found between cultivated (C. cajan) and wild type (C. platycarpus) (0.13) and closest relationship was found between ICP-15683 and ICP-15703 (0.83).