POLYHAPLOID PRODUCTION IN THE TRITICEAE - WHEAT X TRIPSACUM CROSSES

Wheat, Triticum aestivum L., haploid production relies heavily on its crosses with bulbous barley, Hordeum bulbosum L., and on anther cultur e, procedures influenced by genotypic specificity. Wheat x maize, Zea mays L., crosses are devoid of this constraint. In this study eastern gamagrass [Tripsacum dactyloides (L.)L.] is utilized. Cross success is anticipated to extend (i) the range of species available for Triticea e haploid production, and (ii) the crossing cycle duration. Intergener ic crosses of T. aestivum (2n = 6x = 42; AABBDD), T. tuurgidum L. (2n = 4x = 28; AABB), and T. turgidum x Aegilops squarrosa L. (T. tauschii ) synthetic hexaploids (2n = 6x = 42; AABBDD) with Tr. dactyloides (2n = 2x = 36) as the pollen donor resulted in progenies that were polyha ploids of the Triticeae parents, presumably due to elimination of the Tr. dactyloides chromosomes during early em development. Embryo recove ry frequencies were 20.6% for T. aestivum cultivars, 26.8% for T. turg idum cultivars and 23.5% for the synthetic hexaploids. Plant regenerat ion ranged between 66.7 to 78.5% over the three maternal crossing grou ps. As with maize, polyhaploid production in the Triticeae with Tripsa cum is dependent upon a post-pollination treatment with 2,4-D (2,4-dic hlorophenoxyacetic acid) to promote embryo development and shows no st rong genotypic specificity. Limited meiotic analyses for the T. aestiv um cultivars and synthetic hexaploids gave metaphase I associations ch aracteristic of nonallosyndetic chromosomal pairing. Pollinations with Tripsacum, together with maize pollinations offer an extended crossin g cycle and in addition extend the range of alien species for producin g polyhaploids in the Triticeae.