A New Greenhouse Method to Assay Soybean Resistance to Brown Stem Rot

Greenhouse, growth chamber, and field experiments were conducted to develop a method to assess resistance of soybeans to Cadophora gregata (Phialophora gregata), causal agent of brown stem rot (BSR). In the new method, C. gregata is introduced at the base of the stems of 2-week-old soybeans, and the presence of the fungus is assessed in the tips of the stems 5 weeks later. To test the effectiveness of the method, two populations of soybeans and 10 checks were inoculated at the stem base and then assayed for fungal colonization of the stem tips, percentage of symptomatic leaflets, and percent internal stem length discolored. The lines also were planted in naturally infested fields to assess for percent internal stem length discolored, and were tested for the presence/absence of a BSR-resistant molecular marker. Greenhouse, field, and molecular marker data were compared. Linear regression analysis suggested that percentage of plants with colonized stem tips explained 41 to 64% of the variability (P \u3c 0.0001) in percent stem length discolored in the field and 58 to 85% of the variability (P \u3c 0.0001) in molecular marker data for BSR resistance. Percent stem length discolored assessed in the greenhouse had the lowest correlation with percent stem length discolored in the field and with the molecular marker. Of three incubation temperatures tested, 22°C was the most conducive for distinguishing resistant/susceptible soybeans using the colonization method

Thin Plate Spline Regression Model Used at Early Stages of Soybean Breeding to Control Field Spatial Variation

Yield variation observed in Soybean (Glycine max) progeny‐row yield trial (PRYT) is the final result of line genotypic merit, field spatial pattern, and experimental error. The spatial variation in field tests could confound the estimates of genetic merits. The objectives of this research were to: i) quantify non‐genetic yield variation in a soybean breeding PRYT; and ii) determine efficiency of the Thin Plate Spline Regression (TPSR) model in adjusting yield because of variation caused by field spatial pattern. The 3rd objective was to evaluate if the use of the TPSR model could improve the selection accuracy of PRYT unreplicated yield tests. Uniformity Study, Early Generation Test, and Confirmation Study were conducted. Our results indicated that large spatial variations in soybean PRYT field could be present as evaluated by the Uniformity Study conducted with two commercial lines. In this experiment, the use of the TPSR proved to be effective in reducing the error variance and the coefficient of variability, with an improvement in relative efficiency (IRE) of 37.9%. In Early Generation Tests, 2565 lines were evaluated within test‐sets along with three checks. The TPSR model also was effective in the Early Generation Tests, the IRE was 40.4%. The correlation coefficients calculated between yield estimates obtained in two-year Early Generation Tests and Confirmation Study improved by 0.21 points compared with results from the non‐TPSR experiments. The results indicated that the use of TPSR model was effective in accounting for some of the spatial variation in field tests

Evaluación agronómica y parámetros genéticos en soya para consumo humano directo en Puerto Rico

In tropical regions of the Western Hemisphere, consumption of high-protein soybean [Glycine max (L.) Merr.] could improve the human diet. It would be necessary however, to develop adapted cultivars of appropriate seed size. The objectives of this study were to estimate heritabitity and phenotypic and genotypic correlations of agronomic traits, and to compare agronomic and reproductive traits of soybeans grown at different planting dates in Puerto Rico. Eighty-nine F4:5  individual plants from the cross of IAC-8 [Maturity Group (MG) IX, not adapted for human consumption, and intermediate seed size] x Kanto-101 (MG IX, large-seeded cultivar developed for human consumption), the parents, and checks were planted in December 1992.  F4:5 lines were evaluated in replicated tests in June and August 1993. Dates of full bloom (R2), of full seed (R6), and of full maturity (R8), plant height, pod width, and 100-seed weight were recorded. On an entry-mean basis, neritability values of all traits were moderately high (0.56) to high (0.96). Phenotypic and genotypic correlations ranged from zero to high (0.96). Rank correlations were moderately high, positive and significant, ranging from 0.41 to 0.79. In general for all traits, genotypes selected in the top 10% in the plantings of June and August, on the basis of entry means, would also have been selected as individual plants in the December planting. These results suggest that in the tropics genotypes may be selected in different planting seasons within the year, initially on the basis of individual plant performance, and later in replicated experiments.En las regiones tropicales del hemisferio occidental, el alto contenido de proteína de la soya [Glycine max (L.) Merrill] puede mejorar la dieta de la población. Para este propósito, sería necesario desarrollar cultivares adaptados a la región y con semillas de tamaño adecuado para consumo humano. Los objetivos del estudio fueron estimar la heredabilidad de algunas características agronómicas, las correlaciones genéticas y fenotípicas entre ellas y la comparación de las características agronómicas y reproductivas de las líneas, sembradas en distintas fechas en Puerto Rico. En diciembre de 1992 se evaluaron 89 plantas individuales F4:5 del cruzamiento de IAC-8 [Grupo de Madurez (GM) IX, no adaptado para consumo humano, con semilla de tamaño mediano] x Kanto-101 (GM III, adaptado para consumo humano, con semilla de tamaño grande), los padres y líneas controles. Las líneasF4:6 se evaluaron en ensayos replicados en junio y agosto de 1993. Las características consideradas fueron fecha de la floración completa (R2), fecha del llenado de las vainas (R6), fecha de la madurez completa (R8), altura de las plantas, ancho de las vainas y peso de 100 semillas. Las heredabilidades expresadas a base del promedio de las líneas fueron de intermedias (0.56) a altas (0.96). Las correlaciones fenotípicas y genotípicas variaron de cero a altas (0.96). Las correlaciones de rango fueron intermedias, positivas y significativas, variando desde 0.41 a 0.79. Para todas las características, los genotipos que fueron seleccionados en el 10% superior durante las siembras de junio y agosto, a base del promedio de las líneas, también fueron seleccionados en diciembre, a base de las medidas en plantas individuales. En el trópico, la selección de genotipos de soya con tamaño de semilla adecuado para consumo humano directo se puede realizar en distintas épocas de siembra durante el mismo año, en plantas individuales en las etapas iniciales del programa y en ensayos replicados posteriormente

Insect-mediated cross-pollination in soybean [Glycine max (L.) Merrill] : I. Agronomic performance

In soybean, manual cross-pollination to produce large quantities of F1 hybrid seed for yield trials is difficult and time-consuming. Conversely, insect-mediated cross-pollination has been shown to produce large quantities of hybrid seed in soybean and could facilitate the identification of heterotic patterns. The objective of our study was: (1) evaluate F1hybrid soybean plants from single crosses for yield and agronomic traits over several environments and (2) compare hybrid performance of the single crosses to lines developed from three-way crosses and backcrosses. In 2003, F1 seed of single-crosses and their parent lines were evaluated in replicated experiments at three locations. Also in 2003, three-way crosses, and BC1F1 seed were produced. In 2004, three-way crosses, BC1F1 crosses, and their parent lines were evaluated at one location. High-parent heterosis (HPH) in single-crosses for grain yield ranged from −41.11% to +11.19%; for protein content from −4.34% to +3.53%, and for oil content from −13.22% to −0.84%. In three-way crosses, HPH for yield ranged from −25.21% to −4.50%, for protein from −2.72% to +1.92%, and for oil from −5.87% to −1.20%. For BC1F1 crosses, HPH for yield ranged from −15.65% to +41.97%, for protein from −2.57% to +1.69%, and for oil from −2.47% to +2.22%. Although positive heterosis levels were observed across all populations tested to determine the economic feasibility it is imperative that more tests of more cross-combinations be evaluated in replicated environments. Extensive research in different environments must be conducted to determine what parental combinations will produce the highest heterosis levels, and to develop criteria for selecting the parents with the best combining ability. This will be important to maximize agronomic performance that can economically justify the use of hybrids in soybean production

Dehydrin-Like Proteins in Soybean Seeds in Response to Drought Stress during Seed Filling

There is no information on accumulation of dehydrin proteins during seed development and maturation of soybean [Glycine max (L.) Merr.] in response to drought stress. Our objective was to study accumulation of dehydrin-like proteins in developing soybean seeds in response to drought stress. A greenhouse experiment and a field experiment were conducted. In the greenhouse experiment, three treatments were imposed on soybean plants after beginning of linear seed filling (R5): well-watered (WW), gradual stress (GS) imposed before severe stress, and sudden severe stress (SS). In the field treatments were irrigation (I) and nonirrigation (NI) (rainfed) conditions imposed from R5 to R8 (mature seeds). Greenhouse results indicated dehydrin-like proteins (28 and 32 kDa) were detected 18 d after R5 (R5.8) in developing seeds from drought-stressed plants but not in seeds from the well-watered plants. In the mature seeds, dehydrin-like proteins (28, 32, and 34 kDa) were detected in seeds from drought-stressed plants as well as the well-watered plants. In the field, dehydrin-like proteins accumulated similarly under irrigation and nonirrigation conditions, with the first detection for dehydrins (28 and 32 kDa) at 22 d after R5 (R6). Accumulation of dehydrin-like proteins was maximal in seeds harvested at 43 d after R5 (seed physiological maturity)

Título en español

The genetic variability for seed composition between high and low protein soybean (Glycine max (L.) Merr.) parents was evaluated. Wells and Woodworth were the low-protein cultivars, and PI 153.269 and Pando were plant introductions with high protein content. Wells was crossed to PI 153.269 and two back crosses to Wells were obtained. Woodworth was crossed to Pando, and two backcrosses were made to Woodworth.  F2-, BC1F1-, and BC2F1-derived lines and the parents were evaluated in two environments. Protein and oil percentages were measured by infrared analysis. No line from either set of crosses had protein concentrations as high as those of the high-protein donor parent. The F2-derived line with the highest protein from the cross Wells x PI 153.269 had 48.0%, whereas PI 153.279 had 49.4%. In the Woodworth x Pando cross, the best F2-derived line had 46.0%, whereas Pando had 49.2%. Mean protein percentage and genetic variance of the populations decreased with each backcross. Broad sense heritabilities on an entry mean basis ranged from 0.76 to 0.89. Discussed here are the implications of these findings in relationship to a breeding method tor protein improvement.Se evaluó la variabilidad genética de semillas de soja (Glycine max (L.) Mer.) obtenidas de cruces entre padres con alto contenido (PI 153.269, Pando) y bajo contenido en proteína (Wells, 'Woodworth'). Wells se cruzó con PI 153.269 y se lograron dos generaciones de retrocruces con Wells. Woodworth se cruzó con Pando y también se obtuvieron dos generaciones de retrocruces con Woodworth. Los padres y las líneas derivadas de las generaciones  F2, BC1F1, y BC2F1 se evaluaron en dos ambientes. Se determinó el contenido de proteína y aceite mediante el uso de rayos infrarrojos. En ninguno de los dos cruces se encontraron líneas con contenido proteínico tan alto como el de los padres donantes. En el cruce entre Wells x PI 153.269, la línea derivada F2 más rica en proteína tuvo un contenido de 48.0%, mientras que el padre donante tuvo 49.4%. En el cruce entre Woodworth X Pando, la línea derivada F2 con mayor riqueza de proteína tuvo 46.0%, mientras que Pando tuvo 49.2%. Las varianzas genéticas y las medias de contenido de proteína de las poblaciones fueron disminuyendo con cada generación de retrocruce. Las heredabilidades en sentido amplio de contenido de proteína, expresadas a base de las líneas incluidas en el experimento, tuvieron un rango de 0.76 a 0.89. Se discuten las implicaciones que estos resultados sugieren para la utilización de un método de hibridación encauzado a mejorar la riqueza en proteína de la soja