Genetic effects and temperature during the reproductive period for unsaturated fatty acids in soybean [Glycine max (L.) Merr.] seed oil affect oil composition. Increasing oleic and reducing linolenic acids are desirable to improve oil for food and other uses. The objective of this study was to access the environmental effect on fatty acids of seed oil for seventeen soybean genotypes with normal and modified fatty acid profiles. Stability coefficients (b values) were calculated from the regression of fatty acid level on average temperature over the final 30 d of the reproductive period across 10 environments. Mid-oleic acid genotypes were generally less stable for oleic acid content than genotypes with reduced oleic acid. Significant differences, however, were found for oleic acid stability among mid-oleic acid genotypes. Midoleic acid lines N98-4445A and N97-3363-4 were the most unstable among the 17 genotypes with stability coefficients of 3.28 and 2.53, respectively. However, the higher oleic acid line M23 was relatively stable in oleic acid with a stability coefficient of 0.13 over environments. IA 3017 at 10 g kg 21 was the most stable in linolenic acid content across environments while progressively higher linolenic acid genotypes were less stable. Soybean lines similar to M23 and IA 3017 will be essential to develop increased oleic acid and reduced linolenic acid cultivars to ensure consistent production of soybean oil with the desired fatty acid levels.

The European corn borer (ECB), Ostrinia nubilalis (Hübner), is an important pest of temperate maize (Zea mays L.). Damage to the stalk could be minimized by breeding for resistant genotypes but selection is hindered by a laborious phenotypic assay. Knowledge of the position of quantitative trait loci (QTL) conferring resistance to ECB tunneling could greatly simplify selection for this trait. This study was conducted to map QTL for resistance to ECB tunneling, plant height, and anthesis. Recombinant inbred lines of the maize single‐cross population B73×B52, were grown at two locations in Iowa in 1997 and 1998. Genotypic and phenotypic data were obtained from each line to perform the QTL analysis. Nine QTL were detected for ECB tunneling, and they were associated with 59% of the genetic variation. Genetic effects for decreased tunneling were derived from the resistant parent, B52, at six QTL. One digenic interaction was detected between QTL for ECB tunneling. Eight and 10 QTL were detected for anthesis and plant height, respectively. ECB tunneling was not significantly correlated with either trait. Several QTL for ECB tunneling reported herein, QTL for ECB tunneling in other maize populations, and QTL for resistance to leaf damage by insect pests of tropical maize are located at similar positions of the maize genetic map.

Palmitic acid is the major saturated fatty acid found in soybean [Glycine max (L.) Merr.] oil, accounting for approximately 11% of the seed oil content. Reducing the palmitic acid levels of the oil is desirable because of the negative health effects specifically associated with this fatty acid. One of the genetic loci known to reduce the seed palmitate content in soybean is fapnc. Previous studies indicated that fapnc is associated with a deletion in a gene (designated FATB) encoding 16:0‐ACP thioesterase activity. In this report, we isolated full length cDNAs of three of the four unique FATB genes expressed in soybean and show that the isoform designated GmFATB1a represents the specific gene deleted in lines possessing the fapnc locus. Allele specific primers corresponding to GmFATB1a were used to genotype plants from two F4‐derived populations that were segregating for fapnc The GmFATB1a‐specific markers were effective in accounting for 62 to 70% of the genotypic variation in palmitate content in the two populations studied. Because the markers developed in this study are 100% linked to the locus of interest, they should be particularly useful in marker‐assisted selection programs designed to lower the palmitic acid levels of soybean oil.

Plant cell walls of forage provide a major source of energy for ruminant animals. Digestion of cell walls is limited by the presence of lignin, therefore the improving the digestibility of forages by reducing lignin content is a major goal in forage crop breeding programs. A recombinant inbred line maize population was used to map quantitative trait loci (QTL) for neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) of leaf-sheath and stalk tissues. All traits were positively genetically correlated. The larger genetic correlations were between NDF and ADF in sheaths (r = 0.84), NDF and ADF (r = 0.96), ADF and ADL (r = 0.83), and NDF and ADL (r = 0.76) in stalks. Twelve QTL were detected for NDF and 11 QTL for ADF in leaf-sheaths. Eight QTL detected for both traits were defined by the same or linked marker loci. Eight QTL were associated with leaf-sheath ADL. Eleven QTL were detected for NDF and ADF, and 12 QTL for ADL in stalks. Nine of eleven QTL detected for both NDF and ADF in stalks coincided in their genomic position. A high proportion of QTL detected for these traits had the same parental effects and genomic locations, suggesting that it is only necessary to select on one fiber component (NDF or ADF) to improve digestibility. Favorable correlated responses of unselected fiber components are expected due to coincident genomic locations of QTL and the high genetic correlation between fiber components. Several QTL detected in this study coincided in their positions with putative cellulose synthase genes from maize.

Soybean [Glycine max (L.) Merr.] produces 29.4% of the world's edible vegetable oil. An important determinant of the nutritional value and the oxidative stability of soybean oil is the oleic acid content. Elevation of the oleate content levels leads to the improvement of soybean oil quality. However, our knowledge of the genetic factors underlying oleate variation in soybean seeds remains incomplete, hampering the use of marker‐assisted selection in soybean breeding programs. We used a whole‐genome scan approach to identify oleate quantitative trait loci (QTLs) in a soybean population segregating for oleic acid content and a cognate segregating population to confirm oleate QTL. A novel oleate QTL with moderate effects was revealed on linkage group F in the proximity of the simple sequence repeat marker sat_309, which was confirmed in both populations across all environments tested. Furthermore, this study verified the existence of an oleate QTL with moderate effects in the proximity of FAD2‐1B isoform on linkage group I, which interacted epistatically with the oleate QTL on linkage group F. Oleate QTLs with moderate effects were also detected on linkage groups A2 and N only in one of the populations under study. Minor QTLs on linkage groups E, L, A1, and D2 confirmed previous mapping studies for oleate content in soybean.