No abstract

Soybean [Glycine max (L.) Merr.] seed composition data are becoming critical for efficient marketing and trade of soybean and soybean products. Previous reports of variation in seed protein and oil across regions within the United States focused on variation associated with state and regional boundaries. We conducted an analysis of an 8‐yr survey of seed protein and oil across US states and regions, including a geostatistical approach to better characterize the continuous variation in seed composition on a regional scale. The objectives were (i) to determine the relative importance of temporal and regional variation, (ii) to explore the extent of spatial variability across years, (iii) to evaluate the temporal stability across regions, and (iv) to explore the negative correlation between protein and oil across regions and years. Our results confirmed previous findings showing higher protein concentration in southern states and regions. However, most of the observed variation occurred at scales below these political boundaries. The geostatistical approach indicated a moderate level of spatial dependency for protein and protein plus oil but low spatial autocorrelation for oil. In all cases, year‐to‐year variation in weather conditions modulated the expression of regional spatial patterns in composition. To fully predict seed composition at a regional scale would require additional information associated with weather and agronomic management.

Soybean [Glycine max (L.) Merr.] produces a high‐quality protein that provides an appropriate balance of amino acids for monogastric animals. It has been reported that the relative abundance of some essential amino acids may be reduced in soybean with high protein concentration. A dilution of essential amino acids in soybean protein would lead to a reduction in the value of that protein to the end user, and undefined variation in amino acid balance of soybean would lead to poorly balanced animal rations. The objective of this work was to determine whether amino acid balance is affected by seed protein concentration and to characterize any putative changes in the relative abundance of each amino acid across a range of soybean protein concentrations. We created a wide range of protein concentrations in soybean seed by imposing managed stress treatments previously shown to lower or raise protein concentration. We found that the amino acid composition of soybean protein was affected by protein concentration. The relative abundance of amino acids that are often limiting for animal growth, such as lysine, methionine, cysteine, tryptophan, and threonine, were reduced with increasing seed protein concentrations, whereas arginine and glutamic acid were increased. However, treatments used in this study uncovered a potential role for the availability and source of reduced C and N to impact the relative abundance of each amino acid independently, highlighting the complexity of this interrelationship.

Deoxynivalenol (DON) levels are not easily predicted from visual disease assessment, and it is thought likely that environmental conditions such as temperature and moisture influence DON accumulation. This field study examined the influence of environmental moisture on DON accumulation in Fusarium-infected wheat (Triticum aestivum). The effect of extended mist irrigation applied from inoculation (at anthesis) until harvest was compared with mist irrigation applied from inoculation until disease assessment (at early dough), as is generally applied in screening nurseries used for germplasm selection and cultivar improvement. DON concentrations were quantified in kernels at early dough, hard dough, kernel hard, and maturity. Kernels from plots with extended mist irrigation generally had lower DON concentrations than those from plots where mist irrigation was not applied following disease assessment. DON concentrations tended to decrease from disease assessment until harvest, regardless of the irrigation treatment. DON concentrations in the cultivars moderately resistant to Fusarium head blight were lower than those in the susceptible cultivar. Environmental moisture is an important factor determining the DON content of Fusarium-infected wheat.

Potato leafhopper [PLH; Empoasca fabae (Harris)] is the most damaging pest of alfalfa (Medicago sativa L.) in midwestern and eastern states. Our objective was to compare alfalfa populations with glandular‐hairs (PLH‐resistant) and susceptible populations for forage yield and quality, PLH damage, and PLH nymph and adult populations. Potato leafhopper‐resistant and susceptible alfalfa populations were planted in New York (NY) plot trials in 1997, 1998, and 1999, and compared seeding year through second production year. When PLH populations exceeded the action threshold for NY, PLH‐resistant populations had lower PLH damage scores (2.3 vs. 3.7), fewer number of nymphs per 10 stems (3.5 vs. 6.2), and fewer adult PLHs per five sweeps (9.1 vs. 18.1) than susceptible populations. However, PLH‐resistant populations yielded more than susceptible populations only in one of four trials. Irrespective of PLH damage level, PLH‐resistant populations had higher crude protein (CP) concentration (203 vs. 194 g kg−1) and matured earlier than susceptible populations. Seeding year trials were severely damaged by PLH. The following year at first harvest, PLH‐resistant populations yielded more than susceptible populations (0.24 Mg ha−1 more in 1997 trial, and 0.61 Mg ha−1 more in 1999 trial), even though PLHs were not causing economic damage. Resistant populations that were not treated with insecticide averaged lower total season yields than insecticide‐treated, PLH‐susceptible populations (0.29 Mg ha−1 less in seeding year, 0.95 Mg ha−1 less in production yrs). Potato leafhopper‐resistant populations provide benefits to growers such as higher CP concentration and less hopperburn, but do not provide complete protection against yield loss from PLH damage.