Efficient microspore embryogenesis in cauliflower (Brassica oleracea var. botrytis L.) for development of plants with different ploidy level and their use in breeding programme

- For the first time, we are reporting induction of DHs and other ploidy level through microspore embryogenesis in cauliflower and their use in breeding programme.
- The response to cold- pretreatment was genotype specific and need to be optimized for different genotypes.
- Colchicines treatment of 150 mg/l for a period of 36 h was most effective for chromosome doubling of the haploid plants.
- We evaluated the agronomic performance of the plants with higher ploidy level induced via microspore embryogenesis in cauliflower and their possible use in hybrid breeding programme.

Cauliflower (Brassica oleracea var. botrytis L.) is an important vegetable grown throughout the world. In India, wide diversity exists in cauliflower in terms of their adaptation to different temperature and maturity duration. However, there is no report regarding the microspore embryogenesis in different Indian cauliflower. Efficient microspore embryogenesis was optimized in all groups of cauliflowers with selection of genotypes and cold pre-treatments. One model genotype in each group has been identified for their wider application. Among the 30, 13 genotypes responded to microspore embryogenesis. Cold pre-treatment was found to be genotype specific. In late maturity genotype, Kt-119 microspore embryogenesis improved with 24-48 h of cold treatment. Flow cytometry analysis revealed more than 50% of the microspore derived plants as spontaneous diploids thus can be used directly as DH lines. Significant numbers of the microspore derived plants were haploids (15.77%) and tetraploids (17.07%). Colchicines treatment of 150 mg/l for a period of 36 h was most effective for chromosome doubling of the haploid plants with 73.3% of diplodization. Morphological and floral characterization revealed possibility of direct use of tetraploids in breeding programme as inbred line or as a parent to develop F1 hybrids with higher economic yield. The harvest indexes of the tetraploids were at par with the diploid and DH lines with normal male and female fertility. Development of triploid F1 hybrids using tetraploid line could be an alternative to the conventional hybrid breeding of cauliflower because of limited heterosis. Simple sequence repeats were used to genotype the DH and tetraploids generated from a hybrid along with their diploid parental lines. The microsatellite based markers produced only homozygous allele in DH and tetraploid lines.