DOUBLED-HAPLOID BROCCOLI PRODUCTION USING ANTHER CULTURE - EFFECT OF ANTHER SOURCE AND SEED SET CHARACTERISTICS OF DERIVED LINES

Using anther culture to generate doubled-haploid (DH) homozygous lines for use as parents in F-1 hybrid crosses has become a common practice in breeding broccoli (Brassica oleracea L., Italica Group), During an ther culture and subsequent embryogenesis and plant regeneration, poly ploidization of microspore-derived embryos may not occur or it may occ ur accompanied by a doubling, tripling, quadrupling, octupling, or irr egular polyploidization of the genome, Thus regenerants from the proce ss can be haploids, diploids, triploids, tetraploids, octaploids, or a neuploids. The objectives of this research were to 1) conduct repeat c ycles of broccoli anther culture using a group of F-1 hybrids as anthe r donors and develop populations of regenerants; 2) analyze resulting populations using DNA flow cytometry and determine the influence of F- 1 source on frequency of different ploidy levels among regenerants; an d 3) compare seed set in broccoli inbreds developed in a traditional s elfing program compared to seed set in DH broccoli derived from anther culture, In two cycles (1994 and 1995) of anther culture, anther-deri ved populations of regenerants were developed using the F-1 hybrids 'M arathon', 'Everest', 'High Sierra', and 'Futura' as sources of anthers , In 1994, 'Everest', 'High Sierra', and 'Futura' yielded populations that included 2% to 7% haploids, 53% to 56% diploids, 32% to 38% tetra ploids, and 5% to 6% other types. 'Marathon'-derived regenerants were 5% haploid, 78% diploid, 15% tetraploid, and 2% other, shelving signif icantly more diploids. In 1995, 'Marathon' regenerants again included significantly more diploids and fewer tetraploids than those derived f rom other F-1 sources, confirming that the genotype of the anther sour ce affects the frequency of a particular ploidy level among regenerant s derived from culture. In manual self-pollinations of 1994 regenerant s, only diploids and rare tetraploids set seed., When plants that set no seed were discounted, seed production following manual self pollina tions of 1995 regenerants was not significantly different from that of traditional inbreds derived from the same F-1 sources.