Intra-and inter-ploid cross compatibility and trisomic production in asparagus (Asparagus officinalis L.)

Performance of intra- and inter-ploid crosses among diploid, triploid and tetraploid, frequency of trisomics and optimal cross combination to produce trisomics are discussed in this study. In intra-ploid crosses, 2x X 2x showed the highest values of fruit set and fertilization rate. On the contrary, the lowest values of fruit set and fertilization rate were recognized in 3x X 3x crosses. Although 4x X 4x crosses showed relatively high fruit set, the fertilization rate was much lower than that of 2x X 2x. In inter-ploid crosses, 2x X 3x showed higher fruit set and produced more seeds than 3x X 2x, in spite of low pollen germinability in triploids. In 2x X 4x and 4x X 2x, although there were large differences in fruit set, only a few perfect seeds were obtained in both crosses. By the ploidy estimation with flow cytometry, progenies from only the crosses between diploid and triploid were presumed to be near diploid in inter-ploid crosses. The number of chromosomes of them ranged from 18 to 23, and trisomic plants (2n=2x+1=21) occurred at the highest frequency (40%) in 2x X 3x. These results indicate that 2x X 3x cross is the most efficient method to produce high number of trisomics in asparagus.