HIGH-FREQUENCIES OF FERTILIZATION AND EMBRYO FORMATION IN HEXAPLOID WHEAT X TRIPSACUM-DACTYLOIDES CROSSES

The Hexaploid wheat variety Fukuho was crossed with Tripsacum dactyloi des (2n = 4x = 72). The total fertilization frequencies for the egg ce ll, polar nuclei, and both, were 58.3%, 26.8% and 58.9% of the 168 ova ries examined. However, the fertilization frequency of single polar nu clei was much lower at only 0.6%. The total frequency of fertilization was higher than that in wheat x maize crosses. A total of 49 hexaploi d wheat varieties, including Hope carrying the dominant genes Kr1 and Kr2, were crossed with T. dactyloides, and most gave embryos. The embr yo formation frequencies ranged from 0.5% to 59.0%. A higher frequency of 32.0% embryo formation was obtained following pollination of the v ariety Hope. In comparison with embryo formation in wheat x maize cros ses the difference of embryo-formation frequencies between the two cro sses was significant. The results of high frequencies of fertilization and embryo formation in wheat x T. dactyloides crosses indicated that the Kr genes are as inactive in wheat x T. dactyloides, as they are i n wheat x maize crosses, and also that the efficiency of fertilization and embryo formation is higher in wheat x T. dactyloides than in what x maize crosses. The potential of wheat x T. dactyloides crosses for wheat haploid production and wheat improvement is discussed.