Studies on the reproductive biology of male-sterile mutants of soybean (Glycine max (L.) Merr.)

The phenotypic effects of three nuclear male-sterile mutants on reproductive biology in soybean (Glycine max (L.) Merr.) were observed by means of light and electron microscopy. The ms2 mutant interrupted microsporogenesis at the tetrad stage. Postmeiotic cytokinesis deliminated tetrads of microspores. Callose dissolution did not occur, and microspores degenerated after depositing primexine and probacullae. Male sterility was associated with, and perhaps induced by, aberrant ontogeny of the tapetal layer;The ms2 mutant also was shown to have a pleiotropic effect on female reproduction. Spontaneous trisomy occurred among progeny at a rate of 2.4%. Aneuploid lines isolated were evaluated for their stability and potential usefulness in the construction of a trisomic series in soybean;The ms4 mutant was shown to inhibit, or render abnormal, developmental processes related to the function of the postmeiotic MMC plasmalemma. The nature of postmeiotic cytokinesis was variable. Frequently, cytokinesis was omitted, or incomplete and/or irregular in orientation. Less often, cytokinesis was normal in orientation, which led to, but did not ensure, the formation of normal pollen. Postmeiotic (PM) cells varied in the degree of pollen wall organization achieved. Pollen-like walls ranged from only random and scattered sporopollenin deposits to stratified walls indistinguishable from normal pollen walls. Plants homozygous for the ms4 allele were able to generate pollen with features identical to those of normal pollen. Thus, the ms4 mutant was considered a partial male-sterile mutant;A spontaneous male-sterile mutant that arose in \u27Wabash\u27 soybean was analyzed both genetically and cytologically. The Wabash male-sterile mutant was shown to be an independent mutation at the ms3 locus. Despite diverse nuclear backgrounds, the Wabash ms3 (Wms3) and the \u27Calland\u27 x \u27Cutler\u27 (original) ms3 were characterized by similar phenotypes. Microspores were generated but produced abnormal walls and were not released from callose. Tapetal cells either degenerated prematurely, or accumulated a refractive material that was thought to be sporopollenin

Crossover Interactions for Grain Yield in Multienvironmental Trials of Winter Wheat

Crossover interactions (COIs) are changes in ranks among cultivars across environments. Breeders are concerned about COIs because their frequency affects how well rankings from one environment predict rankings in another environment. This research was undertaken to determine the frequency and distribution of COIs for grain yield within years in two regional trials of winter wheat (Triticum aestivum L.). The trials were in Nebraska and in the south-central USA (SCUS). Each trial had four environments per year, and results from 1998, 1999, and 2000 were considered. Significance of COI for each pair of lines in each pair of environments within years was determined by a t test with an interaction-wise Type 1 error rate. Grain yield varied significantly across environments in both trials in all years, and in the within-year analyses the line X environment interaction was always highly significant. In the Nebraska trial, the frequency of COIs was less than expected by chance only in one pair of environments in 1 yr. Nonetheless, because estimates suggested the line X environment X year variance was substantially greater than the line X environment variance, this significant occurrence of COIs did not support breeding for local adaptation. In the SCUS trial, a lower frequency of COIs occurred than in the Nebraska trial. In both trials, frequency of COIs in a pair of environments was not closely related to the difference in mean yield between those environments, which raised the usefulness of categorizing environments as low-stress or as high-stress for the purpose of selection