Feasibility of selection for quantitative traits among haploid tobacco sporophytes.
Witherspoon W.D. Jr. | Wernsman E.A. Jr.
The ability to produce large haploid populations, a significant correlation of performance between haploids and double haploids (DH) of the same genotypes, and the capacity to double the chromosomes of selected individuals are basic requirements for mass selection among haploid sporophytes. Nine burley tobacco (Nicotiana tabacum L.) genotypes were pollinated with N. africana Merxm. and Buttler pollen; resulting seeds were sown in the greenhouse and at two seedling dates in the field. Number of haploid plants recovered per 1000 seed from field and greenhouse seedlings were not different, but higher numbers of aneuploid hybrids were produced in the greenhouse. An estimated mean of 0.75 haploid plants per capsule seeded was obtained from the field plant beds. Haploid and diploid plants of nine genotypes were grown in six replications of a split-plot design in two environments. The performance of the nine genotypes for green and cured leaf yields, total alkaloid and reducing sugar concentrations, plant height, and leaf number per plant was highly correlated between the two ploidy levels. Environmental effects on the haploid plants, and genotype X environment interactions did not mask variability among genotypes in the haploid condition. The highest yielding and the lowest yielding genotypes occupied similar positions of rank in the ploidy conditions. Mass selection for quantitative traits among tobacco haploids followed by chromosome doubling of selected individuals should be a means of developing DH populations whose mean performance would be superior to that of a random DH population.
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