D. R. West

Genomic Regions Associated with Amino Acid Composition in Soybean

Soybean [Glycine max (L.) Merr.] is the single largest source of protein in animal feed. However, few studies have been conducted to evaluate genomic regions controlling amino acid composition in soybean. It is important to study the genetics of amino acid composition to achieve improvements through breeding. The objectives of this study were to determine the ratios between essential to non-essential (E:NE) and essential to total (E:T) amino acids, and to identify genomic regions controlling essential and non-essential amino acid composition in soybean seed. To achieve these objectives, 101 F6-derived recombinant inbred lines (RIL) developed from a cross of N87-984-16 × TN93-99 were used. Ground soybean seed samples were analyzed for amino acids using a near infrared spectroscopy (NIRS) instrument. A significant (p < 0.01) difference among the RIL was found for amino acid composition. Heritability estimates on an entry mean basis ranged from 0.13 for His to 0.67 for Tyr. A total of 94 polymorphic simple sequence repeat (SSR) molecular genetic markers were screened in DNA from progenies. Single factor ANOVA was used to identify candidate quantitative trait loci (QTL), which were then confirmed by QTL Cartographer. At least one QTL for each amino acid was detected in this population. QTL linked to molecular markers Satt143, Satt168, Satt203, Satt274 and Satt495 were associated with most of the amino acids. Phenotypic variation explained by an individual QTL ranged from 9.4 to 45.3%. QTL detected for amino acids in soybean in this experiment are expected to be useful for future breeding programs targeting development of improved soybean amino acid composition for human and animal nutrition.

A Survey for Diclofop-Methyl Resistance in Italian Ryegrass from Tennessee and How To Manage Resistance in Wheat

Abstract Italian ryegrass resistance to diclofop has been documented in several countries, including the United States. The purpose of this research was to screen selected putative resistant populations of Italian ryegrass for resistance to the acetyl-CoA carboxylase (ACCase)–inhibiting herbicides diclofop and pinoxaden and the acetolactate synthase (ALS)–inhibiting herbicides imazamox, pyroxsulam, and mesosulfuron in the greenhouse and to use field experiments to develop herbicide programs for Italian ryegrass control. Resistance to diclofop was confirmed in eight populations from Tennessee. These eight populations did not show cross-resistance to pinoxaden. One additional population (R1) from Union County, North Carolina, was found to be resistant to both diclofop and pinoxaden. The level of resistance to pinoxaden of the R1 population was 15 times that of the susceptible population. No resistance was confirmed to any of the ALS-inhibiting herbicides examined in this research. Field experiments demonstrated PRE Italian ryegrass control with chlorsulfuron (71 to 94%) and flufenacet + metribuzin (84 to 96%). Italian ryegrass control with pendimethalin applied PRE or delayed preemergence (DPRE) was variable (0 to 85%). POST control of Italian ryegrass was acceptable with pinoxaden, mesosulfuron, flufenacet + metribuzin, and chlorsulfuron + flucarbazone (> 80%). Application timing and herbicide treatment had no effect on wheat yield, except for diclofop and pendimethalin treatments, in which uncontrolled Italian ryegrass reduced wheat yield. Nomenclature: Chlorsulfuron; diclofop; flucarbazone; flufenacet; imazamox; mesosulfuron; metribuzin; pendimethalin; pinoxaden; pyroxsulam; Italian ryegrass, Lolium perenne L. ssp. multiflorum Lam. Husnot LOLMU; wheat, Triticum aestivum L.

Utility of Aminocyclopyrachlor for Control of Horsenettle (Solanum carolinense) and Tall Ironweed (Vernonia gigantea) in Cool-Season Grass Pastures

Because horsenettle and tall ironweed are difficult to control in cool-season grass pastures, research was conducted in Tennessee and Kentucky in 2010 and 2011 to examine the efficacy of aminocyclopyrachlor on these weeds. Aminocyclopyrachlor was evaluated at 49 and 98 g ai ha−1 alone and in mixtures with 2,4-D amine at 371 and 742 g ae ha−1. Aminopyralid was also included as a comparison treatment at 88 g ai ha−1. Treatments were applied at three POST timings to horsenettle and two POST timings to tall ironweed. By 1 yr after treatment (YAT) horsenettle was controlled 74% with aminocyclopyrachlor plus 2,4-D applied late POST (LPOST) at 98 + 742 g ha−1. By 1 YAT, tall ironweed was controlled ≥ 93% by aminocyclopyrachlor applied early POST (EPOST) or LPOST, at rates as low as 49 g ha−1. Similar control was achieved with aminopyralid applied LPOST. Both aminocyclopyrachlor and aminopyralid were found to reduce horsenettle and tall ironweed biomass the following year. Moreover, all LPOST applications of aminocyclopyrachlor alone or in mixtures with 2,4-D prevented regrowth of tall ironweed at 1 YAT. Based on these studies, a LPOST herbicide application in August or September when soil moisture is adequate is recommended for control of horsenettle and tall ironweed in cool-season grass pastures. Nomenclature: 2,4-D; aminocyclopyrachlor; aminopyralid; horsenettle, Solanum carolinense L.; tall ironweed, Vernonia gigantea (Walt.) Trel. Porque Solanum carolinense y Vernonia gigantea son difíciles de control en pastos de clima frío, se realizó una investigación en Tennessee y Kentucky, en 2010 y 2011, para examinar la eficacia de aminocyclopyrachlor para el control de estas malezas. Aminocyclopyrachlor fue evaluado a 49 y 98 g ai ha−1 solo y en mezclas con 2,4-D amine a 371 y 742 g ae ha−1. Aminopyralid a 88 g ai ha−1 fue también incluido como tratamiento de comparación. Los tratamientos fueron aplicados en tres momentos POST a S. carolinense y dos momentos POST a V. gigantea. A 1 año después del tratamiento (YAT), S. carolinense fue controlada 74% con aminocyclopyrachlor más 2,4-D aplicados en POST tardío (LPOST) a 98 + 742 g ha−1. A 1 YAT, V. gigantea fue controlada ≥ 93% con aminocyclopyrachlor aplicado en POST temprano (EPOST) o LPOST, a dosis tan bajas como 49 g ha−1. Un control similar fue alcanzado con aminopyralid aplicado LPOST. Se encontró que tanto aminocyclopyrachlor como aminopyralid redujeron la biomasa de S. carolinense y V. gigantea el siguiente año. Además, todas las aplicaciones LPOST de aminocyclopyrachlor solo o en mezclas con 2,4-D previnieron el rebrote de V. gigantea a 1 YAT. Con base en estos estudios, se recomienda una aplicación de herbicida LPOST en Agosto o Septiembre cuando la humedad del suelo es adecuada para el control de S. carolinense y V. gigantea en pastos de clima frío.