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

Microarray analysis of iron deficiency chlorosis in near-isogenic soybean lines

BACKGROUND: Iron is one of fourteen mineral elements required for proper plant growth and development of soybean (Glycine max L. Merr.). Soybeans grown on calcareous soils, which are prevalent in the upper Midwest of the United States, often exhibit symptoms indicative of iron deficiency chlorosis (IDC). Yield loss has a positive linear correlation with increasing severity of chlorotic symptoms. As soybean is an important agronomic crop, it is essential to understand the genetics and physiology of traits affecting plant yield. Soybean cultivars vary greatly in their ability to respond successfully to iron deficiency stress. Microarray analyses permit the identification of genes and physiological processes involved in soybean's response to iron stress. RESULTS: RNA isolated from the roots of two near isogenic lines, which differ in iron efficiency, PI 548533 (Clark; iron efficient) and PI 547430 (IsoClark; iron inefficient), were compared on a spotted microarray slide containing 9,728 cDNAs from root specific EST libraries. A comparison of RNA transcripts isolated from plants grown under iron limiting hydroponic conditions for two weeks revealed 43 genes as differentially expressed. A single linkage clustering analysis of these 43 genes showed 57% of them possessed high sequence similarity to known stress induced genes. A control experiment comparing plants grown under adequate iron hydroponic conditions showed no differences in gene expression between the two near isogenic lines. Expression levels of a subset of the differentially expressed genes were also compared by real time reverse transcriptase PCR (RT-PCR). The RT-PCR experiments confirmed differential expression between the iron efficient and iron inefficient plants for 9 of 10 randomly chosen genes examined. To gain further insight into the iron physiological status of the plants, the root iron reductase activity was measured in both iron efficient and inefficient genotypes for plants grown under iron sufficient and iron limited conditions. Iron inefficient plants failed to respond to decreased iron availability with increased activity of Fe reductase. CONCLUSION: These experiments have identified genes involved in the soybean iron deficiency chlorosis response under iron deficient conditions. Single linkage cluster analysis suggests iron limited soybeans mount a general stress response as well as a specialized iron deficiency stress response. Root membrane bound reductase capacity is often correlated with iron efficiency. Under iron-limited conditions, the iron efficient plant had high root bound membrane reductase capacity while the iron inefficient plants reductase levels remained low, further limiting iron uptake through the root. Many of the genes up-regulated in the iron inefficient NIL are involved in known stress induced pathways. The most striking response of the iron inefficient genotype to iron deficiency stress was the induction of a profusion of signaling and regulatory genes, presumably in an attempt to establish and maintain cellular homeostasis. Genes were up-regulated that point toward an increased transport of molecules through membranes. Genes associated with reactive oxidative species and an ROS-defensive enzyme were also induced. The up-regulation of genes involved in DNA repair and RNA stability reflect the inhospitable cellular environment resulting from iron deficiency stress. Other genes were induced that are involved in protein and lipid catabolism; perhaps as an effort to maintain carbon flow and scavenge energy. The under-expression of a key glycolitic gene may result in the iron-inefficient genotype being energetically challenged to maintain a stable cellular environment. These experiments have identified candidate genes and processes for further experimentation to increase our understanding of soybeans' response to iron deficiency stress

Título en español

The harvest of immature seeds was investigated as a means of enhancing rapid generation advance in soybean [Glycine max (L.) Merr.] breeding programs. One objective of the study was to determine field emergence of immature seeds harvested from genotypes adapted to temperate climates when grown in tropical environments. A second objective was to compare pod color and the ratio of seed width (SW) to pod width (PW) and SW to pod thickness (PT) as indicators of the time to harvest immature viable seed. Two cultivars were planted in three environments in the Iowa State University Soybean Nursery at the Isabela Research Center of the University of Puerto Rico. Harvest of seeds began 24 days after flowering (DAF) and continued at weekly intervals until 59 DAF. Two harvest procedures were compared: removing pods from plants, and pulling plants without detaching the pods. Field emergence, pod color, PW, PT, and SW were measured for each harvest procedure, harvest date, cultivar, and environment. There were no significant differences between harvest procedures for average field emergence. Significant differences were observed among environments, cultivars, and harvest dates. The harvest of immature seed 31 DAF resulted in adequate field emergence. The most rapid method of selecting pods with immature viable seeds was to harvest pods that had begun to turn yellow. Pod yellowing occurred about 38 DAF of cultivars.Se investigó la cosecha de semillas inmaturas de soja [Glycine max (L.) Merr.] como una forma de acelerar el avance de generaciones en programas de fitomejoramiento. Un objetivo del experimento fue determinar la emergencia en el campo de semillas inmaturas cosechadas de genotipos adaptados a climas templados cuando éstos se siembran en ambientes tropicales. El segundo objectivo fue comparar el color de la vaina y la relación del ancho de la semilla (SW) con el ancho de la vaina (PW) y SW al grosor de la vaina (PT) como indicadores de cuándo cosechar semillas inmaturas viables. Se sembraron dos cultivares en tres ambientes en la lowa State University Soybean Nursery localizada en el Centro de Investigaciones y Desarrollo Agrícola de Isabela de la Universidad de Puerto Rico. Se comenzó a cosechar semillas 24 días después de la floración (DAF) y se continuó a intervalos semanales hasta los 59 DAF. Se usaron dos procedimientos para cosechar; en uno las vainas se arrancaron de las plantas y en el otro se cosecharon las plantas con vainas.  Para cada procedimiento, fecha de cosecha, cultivar y ambiente se midieron la emergencia en el campo, PT, SW y AV, y se observó el color de las vainas. No se detectaron diferencias significativas en la emergencia en el campo entre los dos procedimientos para cosechar. Se observaron diferencias significativas en la emergencia en el campo de las semillas cosechadas entre los distintos ambientes, cultivares y fechas de cosecha. La emergencia en el campo observada con semillas cosechadas 31 DAF fue adecuada. El método mas rápido de seleccionar vainas con semillas inmaturas viables fue el de cosechar vainas que ya habían comenzado a amarillear. El cambio de color de las vainas, de verde a amarillo, ocurrió aproximadamente a los 38 DAF

Quantitative Trait Loci (QTL) that Underlie SCN Resistance in Soybean [\u3ci\u3eGlycine max\u3c/i\u3e (L.) Merr.] PI438489B by ‘Hamilton’ Recombinant Inbred Line (RIL) Population

Soybean cyst nematode caused by Heterodera glycines Ichinohe is the most devastating pest in soybean [Glycine max (L.) Merr.]. Resistance to SCN is complex, polygenic, race and cultivar specific, and it is controlled by several quantitative trait loci (QTL). Our objective was to identify and map QTL for SCN resistance to races 3 (HG Type 0) and 5 (HG Type 2.5.7) using a high density SNP-based genetic linkage map based on the PI438489B by ‘Hamilton’ (PIxH, n=50) recombinant inbred line population. The PI438489B by Hamilton map contained 648 SNPs distributed on 31 LGs with coverage of 1,524.7 cM and an average distance of 2.35 cM between two markers (Kassem et al., 2011). Using interval mapping (IM) and composite interval mapping (CIM), eight QTL were identified for SCN resistance to races 3 and 5 on 7 different soybean chromosomes. Four QTL for resistance to SCN race 3 were identified and mapped on chromosomes 7, 13, 15, and 16. Similarly, four QTL for resistance to SCN race 5 were identified and mapped on chromosomes 5, 8, and 11. The QTL identified here will be highly beneficial in breeding programs to develop cultivars with resistance to both SCN races 3 and 5

Reactions of soybean differentials carrying <i>Rps1a</i>, <i>1b</i>, <i>1c</i>, <i>1d</i>, <i>1k</i>, <i>2</i>, <i>3a</i>, <i>3b</i>, <i>3c</i>, <i>4</i>, <i>5</i>, <i>6</i>, <i>7</i>, and <i>8</i> genes to <i>Phytophthora sojae</i> isolates.

<p>Reactions of soybean differentials carrying <i>Rps1a</i>, <i>1b</i>, <i>1c</i>, <i>1d</i>, <i>1k</i>, <i>2</i>, <i>3a</i>, <i>3b</i>, <i>3c</i>, <i>4</i>, <i>5</i>, <i>6</i>, <i>7</i>, and <i>8</i> genes to <i>Phytophthora sojae</i> isolates.</p