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

Research Notes : United States : Is the ms4 male-sterile nrutant partially fertile?

The ms male-sterile mutant is inherited as a recessive allele. Plants homozygous 1or ms4 are male-sterile; heterozygotes are completely male-fertile. Male-sterility in the ms4 system results from the absence of cytokinesis fol-lowing telophase II of microsporogenesis (Delannay and Palmer; 1982)

Research Notes : United States : Seed production by male-sterile soybeans in Missouri

The production of hybrid soybean will require the discovery of F1 heterosis of a magnitude that provides growers the incentive to purchase hybrid seed. The primary barrier to the testing of F1 heterosis is the acquisition of adequate quantities of F1 seed (Nelson and Bernard, 1984). Presently, the most efficient means of obtaining experimental quantities of hybrid seed is through the use of nuclear (genie) male-sterile mutations

A Field-Based Analysis of Genetic Improvement for Grain Yield in Winter Wheat Cultivars Developed in the US Central Plains from 1992 to 2014

Progress in plant breeding programs is the result of creating and selecting new lines with novel allele combinations that perform better than their parents. This year-on-year improvement is known as genetic gain and is a function of genetic diversity, selection accuracy, selection intensity, and selection cycle time. To estimate the gain in wheat (Triticum aestivum L.) breeding in the US Central Plains, lines that were submitted to the collaborative Southern Regional Performance Nursery (SRPN) between 1992 and 2014 were grown in a common nursery for 3 yr at two locations in a single-replicate augmented block design. Moderate to high broad-sense heritability was observed for plant height (H2 = 0.88), heading date (H2 = 0.79), and grain yield (H2 = 0.41). From the common grow-out, genetic gain for yield over the time period was estimated at 1.1% yr−1, whereas individual breeding program genetic gain varied between 0.3 and 1.9% yr−1. Increases in Kansas state on-farm yields during the same period showed a nonsignificant trend of 0.13% yr−1 with large year-to-year variation. These results suggest that although progress is being made in US Central Plains breeding programs, a yield gap remains that could be attributable to genetic progress not being realized in on-farm production

Persistence of rye (Secale cereale L.) chromosome arm 1RS in wheat (Triticum aestivum L.) breeding programs of the Great Plains of North America

Rye (Secale cereale L.) chromosome arm 1RS has been used world-wide by wheat (Triticum aestivum L.) breeding programs as a source of pestand pathogen-resistance genes, and to improve grain yield and stress tolerance. The most common vehicles used to access 1RS are various 1AL.1RS and 1BL.1RS wheat-rye chromosomal translocations. Over the past 25 years, advanced North American wheat breeding lines were evaluated, first by assay of secalin storage proteins, and later by use of DNA marker TSM0120, for the presence of these two translocations. Both methods provide accurate and efficient means of identifying and differentiating 1BL.1RS and 1A.1RS. Both 1Al.1RS and 1BL.1RS wheats were found in all tested years. 1AL.1RS lines were more common in southern Great Plains breeding programs. 1AL.1RS lines were released as cultivars at a frequency identical to that of wild-type breeding lines. In contrast, 1BL.1RS breeding lines were developed by breeding programs throughout the Great Plains, but fewer were released as cultivars. Both 1RS translocation types persist in Great Plains breeding programs. The lower rate of release of 1BL.1RS cultivars no doubt is a consequence of the more drastic effects on breadmaking quality relative to those observed with 1AL.1RS

Occurrence of the Waxy Alleles \u3ci\u3ewxa\u3c/i\u3e and \u3ci\u3ewxb\u3c/i\u3e in Waxy Sorghum Plant Introductions and Their Effect on Starch Thermal Properties

The existence of two waxy alleles, wxa associated with no detectable granule bound starch synthase (GBSS) and wxb associated with apparently inactive GBSS, was recently reported in sorghum [Sorghum bicolor (L.) Moench]. In this paper, the occurrence of the wxa and wxb alleles in the USDA-ARS photoperiod-insensitive sorghum collection was determined, and the effects of the wxa and wxballeles on thermal properties of sorghum starch (gelatinization temperatures and energy requirements) measured by differential scanning calorimetry. Of the 51 purported waxy accessions examined, 14 tested positive for presence of amylose by iodine staining and were considered to be previously misclassified wild type lines. Nine accessions were mixed for presence or absence of amylose. Twenty-four of the 28 accessions confirmed to be waxy by negative iodine staining for amylose had no detectable GBSS using sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (wxa), and four were show to contain GBSS (wxb). Mean gelatinization onset, peak, and end temperatures were significantly lower for wild-type than either of the two waxy genotypes. Mean gelatinization onset temperature was slightly higher for waxy-GBSS+ genotypes than waxy-GBSS− genotypes. Mean gelatinization end temperature was slightly higher for waxy-GBSS− genotypes than waxy-GBSS+ genotypes. Significant genetic variation was observed within genotypic classes, suggesting influence of additional modifier genes affecting sorghum starch structure or micro-environmental effects

Occurrence of the Waxy Alleles \u3ci\u3ewxa\u3c/i\u3e and \u3ci\u3ewxb\u3c/i\u3e in Waxy Sorghum Plant Introductions and Their Effect on Starch Thermal Properties

The existence of two waxy alleles, wxa associated with no detectable granule bound starch synthase (GBSS) and wxb associated with apparently inactive GBSS, was recently reported in sorghum [Sorghum bicolor (L.) Moench]. In this paper, the occurrence of the wxa and wxb alleles in the USDA-ARS photoperiod-insensitive sorghum collection was determined, and the effects of the wxa and wxballeles on thermal properties of sorghum starch (gelatinization temperatures and energy requirements) measured by differential scanning calorimetry. Of the 51 purported waxy accessions examined, 14 tested positive for presence of amylose by iodine staining and were considered to be previously misclassified wild type lines. Nine accessions were mixed for presence or absence of amylose. Twenty-four of the 28 accessions confirmed to be waxy by negative iodine staining for amylose had no detectable GBSS using sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (wxa), and four were show to contain GBSS (wxb). Mean gelatinization onset, peak, and end temperatures were significantly lower for wild-type than either of the two waxy genotypes. Mean gelatinization onset temperature was slightly higher for waxy-GBSS+ genotypes than waxy-GBSS− genotypes. Mean gelatinization end temperature was slightly higher for waxy-GBSS− genotypes than waxy-GBSS+ genotypes. Significant genetic variation was observed within genotypic classes, suggesting influence of additional modifier genes affecting sorghum starch structure or micro-environmental effects

Genomic Analysis and Prediction within a US Public Collaborative Winter Wheat Regional Testing Nursery

The development of inexpensive, whole-genome profiling enables a transition to allele-based breeding using genomic prediction models. These models consider alleles shared between lines to predict phenotypes and select new lines based on estimated breeding values. This approach can leverage highly unbalanced datasets that are common to breeding programs. The Southern Regional Performance Nursery (SRPN) is a public nursery established by the USDA–ARS in 1931 to characterize performance and quality of near-release wheat (Triticum aestivum L.) varieties from breeding programs in the US Central Plains. New entries are submitted annually and can be re-entered only once. The trial is grown at \u3e30 locations each year and lines are evaluated for grain yield, disease resistance, and agronomic traits. Overall genetic gain is measured across years by including common check cultivars for comparison. We have generated whole-genome profiles via genotyping-bysequencing (GBS) for 939 SPRN entries dating back to 1992 to explore the potential use of the nursery as a genomic selection (GS) training population (TP). The GS prediction models across years (average r = 0.33) outperformed year-to-year phenotypic correlation for yield (r = 0.27) for a majority of the years evaluated, suggesting that genomic selection has the potential to outperform low heritability selection on yield in these highly variable environments. We also examined the predictability of programs using both program-specific and whole-set TPs. Generally, the predictability of a program was similar with both approaches. These results suggest that wheat breeding programs can collaboratively leverage the immense datasets that are generated from regional testing networks