Transfer of male sterility to cauliflower varieties through inter-generic crosses via embryo rescue technique.
Male sterility described as inability of the plant to produce fertile pollen is widespread in angiosperms and provides one of the most efficient means of directed pollination for the large-scale production of hybrid seeds in crops. Male sterility manifests itself usually in floral development as an incompatibility of nuclear-mitochondrial interaction in alloplasmic lines derived from wide hybridization, which carry nuclear and mitochondrial genomes from different species. CMS may have a spontaneous character or may arise following intra specific, inter specific or inter generic crosses. Maternally inherited cytoplasm male sterility encoded in mitochondrial genes can be utilized more effectively by breeders than Geneic male sterility.
Cauliflower is one of the important cole crops grown throughout the world. Due to the occurrence of self-incompatibility in this crop, cross-pollination is pre-dominant, which ultimately leads to high degree of heterozygosity. Transfer of cytoplasm male sterility in cauliflower varieties would highly beneficial for hybrid seed production technology. Moreover it will reduce time and labour expenditure. In India, in spite of abundant genetic variation in Indian cauliflower, commercial exploitation of heterosis is lagging behind mainly due to the absence economic hybrid seed production technology.
For the transfer of CMS system, different species and genera were used. They are Trachystoma balli, Brassica oxyrrhina, Diplotaxis sifolia, Diplotaxis erucoides, Diplotaxis catholica, Diplotaxis berthaultii and Erucasrum canarience. Crossing of varieties with these species was done and after fifteen days of pollination, the siliqua was taken for the embryo culture. Pretreatment with mercuric chloride and then washing with distilled water was standardized. The siliqua was carefully dissected with the scalpel and embryos were taken out without injuring and placed in simple MS media. After several days the embryo germinates and the plant was placed in the multiplication media. MS + BAP (0.5mg/l) was standardized for the multiplication of shoots and for rooting in MS + IBA (0.5mg/l). The media for different stages were standardized and successful results have been obtained. After rooting, the plant was removed from the media and washed properly so as to remove the agar and finally placed in test tube filled with distilled water. This process was done for the hardening of the plantlets and it is kept for at least one week, with regularly removal of water. Finally it is shifted to pots filled with soil rite in the lab. After a few days, the plantlets were shifted to bigger pots in the field under normal condition. The protocol was successfully standardized
Different stages of embryo rescue technique.
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working in cauliflower for the transfer of male sterility through tissue culture techniques.
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