Pollen genotype selection for a simply inherited qualitative factor determining resistance to chlorsulfuron in maize

Pollen genotype selection for genes expressed in both the haploid and diplo id phases of the plant life cycle can lead to correlated responses detectab le in the sporophyte. A pollen selection was conducted in two genetic backg rounds of maize (Zen mays L.) for chlorsulfuron resistance, conferred by th e XA17 allele. Plants of two backcross (BC) lines segregating 1 (heterozygo te, resistant) : 1 (homozygote, susceptible) for chlorsulfuron resistance w ere used as pollen donor. Selection treatment was applied during microspore development, and tassels were cut about 10 days before anthesis and placed into a liquid medium with or without 40 mg l(-1) of chlorsulfuron. Pollen was used to fertilize an unrelated susceptible genotype (tester). The resul ting testcrosses (TC) were evaluated in the greenhouse by spraying seedling s with chlorsulfuron at 23 g ha(-1). Non-selected TC progenies derived from heterozygous BC plants showed a proportion of resistant and susceptible pl ants close to the expected 1:1 ratio, while non-selected TC progenies deriv ed from homozygous BC plants showed susceptible plants only. Selected TC pr ogenies derived from heterozygous BC plants showed a frequency of resistant plants ranging from 89% to 100%. BC plants homozygous for the susceptible allele, subjected to selection treatment, gave poor seed set, and no resist ant plants were found in their TC progenies. Resistant TC plants obtained t hrough pollen genotype selection were selfed, and the proportion of resista nt plants was close to 3:1 in all selfed families, in accordance with the h ypothesis that all of them inherited the XA17 allele through selection. In this study, pollen genotype selection was extremely effective, and its effe ct persisted in the second sporophytic generation.