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The genetic base of soybean [Glycine max (L.) Merr.] cultivars developed for North America is very narrow. This may threaten the ability of breeders to sustain improvement and increase vulnerability of the crop to pests. The objective of this research was to assess the relationship of 18 major ancestors of North American soybean germplasm with 87 plant introductions (PIs) that are potential new sources of genetic variation for soybean breeding programs. Genetic distances (GD) among the 105 genotypes analyzed were calculated from 109 polymorphic DNA fragments amplified with random oligonucleotide primers and simple sequence repeat (SSR) primer pairs. Two hierarchical clustering algorithms were combined with data resampling and multidimensional scaling (MDS) to evaluate relationships among the genotypes. Genetic distances ranged from 0.08 to 0.76, with a mean of 0.52. Genotypes were placed in 11 clusters on the basis of a consensus of the different methods utilized. Co-occurrence values calculated from the resampling iterations showed that the stability of clusters varied. The most stable grouping was among ancestors that corresponded with known relationships based on pedigree and maturity. Several groups of PIs are distinct from the majority of the ancestors. These genotypes may be useful to breeders wanting to utilize genetically diverse introductions in soybean improvement., SOYBEAN BREEDING PROGRAMS in the USA have successfully developed hundreds of improved cultivars through hybridization of elite cultivars and breeding lines that trace back to a small number of original [...]

Global average surface temperature has increased by approximately 0.74 °C over the most recent 100-year period. At a regional level in South Africa, detectable changes in both the rainfall and temperature patterns have occurred in the past 50 years. Climate change has become a reality that can no longer be ignored. Given the relatively long timescales of plant-to-harvest rotations in the commercial production forestry sector in South Africa, and the significant investment implied, climate change has the potential to have substantial impacts on forestry productivity and profitability. Under climate change conditions the climatically optimum areas for specific forest species are hypothesised to shift, with optimum areas changing in extent and location between and within provinces. This paper focuses on the Eucalyptus and Pinus genera. From the ICFR Forestry Productivity Toolbox, climate criteria for three Pinus species plus one hybrid, and four Eucalyptus species plus one hybrid, were used in combination with gridded maps of present mean annual temperature and mean annual rainfall to assess climatically optimum, moderate- and high-risk growth areas, as well as unsuitable growth areas over southern Africa. The temperature and rainfall variables were then perturbed through plausible ranges of projected future climates to determine the potential impacts of climate change on the climatically optimum, moderate and unsuitable growth areas of the Pinus and Eucalyptus families. For both families, rising temperatures may slightly increase the optimum growth area in Mpumalanga and the Eastern Cape, whereas in KwaZulu-Natal the area may reduce. The Pinus species showed less sensitivity to rising temperatures than eucalypts. The two hybrids exhibited less sensitivity than other species of their genera. The hybrid Pinus ExC emerged as least sensitive to increasing temperature. Declining rainfall concomitant with rising temperature will have an especially negative effect on total area of optimal growth. An increase in rainfall will, however, offset all negative impacts of temperature and increase total optimum growth area for both families. [ABSTRACT FROM AUTHOR]

Soybean is an essential protein and oilseed crop, but environmental factors, such as photoperiod and altitude, highly influence its growth. Poor adaptability of soybean cultivars may result in a significant decrease in seed yield due to disruption of flowering or maturity. It is, therefore, vital to select cultivars adapted to specific regions of the world. Global climate change, causing increasing temperature and associated water deficit stress, may further challenge sustainable soybean production worldwide. Therefore, it is necessary to understand genetic responses in soybeans induced by environmental variables. This review highlights previous research showing how several quantitative trait loci (QTLs) activated by photo-thermal responses affected soybean flowering. We discuss cytogenetic stocks, including chromosome segment substitution lines, and their role in introgressing novel genes from wild soybeans. A review of genes showing responses to various environmental variables that affect soybean adaptability is also ensued, with putative functions suggested. These include gene response regulation to temperature and heat stress, identified via genetic mapping, and emerged as tools for developing adapted soybean cultivars. [ABSTRACT FROM AUTHOR]

Early-season vigor is an important morphological determinant of a crop's growth rate and duration. It results from metric parameters, such as light interception and dry matter production, loss, and partitioning. Formulating screening tools to assess early-season vigor by using root and shoot characteristics will be useful for identifying genotypes with superior performance during the juvenile growth stages. A 2-year study was conducted by using a sunlit pot culture set-up to assess genetic variation among 100 rice genotypes for shoot and root traits and several physiological parameters at the seedling growth stage (25-30 days after sowing). Given the absence of a significant year or experimental period × genotype interaction for the traits measured, the 2-year data were combined for each genotype. Individual (IVRI) and cumulative response indexes (CVRI) were estimated for each trait for all genotypes. Genotypes were classified into different categories by using CVRI values and standard errors. The majority of the genotypes exhibited low vigor (43%), followed by genotypes with moderate (33%) and very low (16%) vigor. However, five and three genotypes showed high- and very-high vigor, respectively. The CVRI values varied from a low value of 21.36 for RU1404196 to 36.17 for N-22, the most vigorous genotype. The high-vigor genotypes can be valuable genetic resources for developing new varieties with high early-season vigor as well as for physiological studies on canopy development for optimum light interception and weed competitiveness. The information and methods generated by this study can also be useful in identifying promising rice lines with potentially high vigor in rice breeding programs. [ABSTRACT FROM AUTHOR]