Effect of terminal bud clipping on growth and yield of soybean cultivars in the Pacific Northwest

Abstract Soybean [Glycine max (L.) Merr.] is one of the four major staple crops and the world's most important vegetable protein source. Very little information is available on the performance, yield, and cultivars of soybean when choosing a cultivar to grow in Pacific Northwest (PNW). Of the oilseed crops, soybean appears to have the best potential to be grown at a profit (high yields) in PNW when considering the high input costs for irrigated crops. The present study was conducted to determine if terminal bud clipping would increase yields of soybean cultivars under irrigated conditions in 2‐year field experiments. Five soybean cultivars were planted in four‐row plots with rows 0.13 m apart. Plots were replicated four times with two treatments (early clipping and late clipping) and control in a randomized complete block design. Data regarding yield and growth traits were recorded using standard procedure. Soybean yield was significantly influenced by the year of production and terminal bud clipping, whereas cultivars showed no effect. Early and late clipping resulted in a 15% and 18% increase in yields in 2018, whereas late clipping resulted in a 16% yield increase in 2019 compared to control. Terminal bud clipping resulted in shorter plants and reduced lowest pod height, lodging, and maturity compared with the control. Lodging and maturity decreased with late‐maturing cultivars. Finally, results suggest that terminal bud clipping increases soybean yields. Early maturing cultivars (maturity group 0.4) are unsuitable for PNW due to the lowest pod height

Occurrence of Transgenic Feral Alfalfa (Medicago sativa subsp. sativa L.) in Alfalfa Seed Production Areas in the United States.

The potential environmental risks of transgene exposure are not clear for alfalfa (Medicago sativa subsp. sativa), a perennial crop that is cross-pollinated by insects. We gathered data on feral alfalfa in major alfalfa seed-production areas in the western United States to (1) evaluate evidence that feral transgenic plants spread transgenes and (2) determine environmental and agricultural production factors influencing the location of feral alfalfa, especially transgenic plants. Road verges in Fresno, California; Canyon, Idaho; and Walla Walla, Washington were surveyed in 2011 and 2012 for feral plants, and samples were tested for the CP4 EPSPS protein that conveys resistance to glyphosate. Of 4580 sites surveyed, feral plants were observed at 404 sites. Twenty-seven percent of these sites had transgenic plants. The frequency of sites having transgenic feral plants varied among our study areas. Transgenic plants were found in 32.7%, 21.4.7% and 8.3% of feral plant sites in Fresno, Canyon and Walla Walla, respectively. Spatial analysis suggested that feral populations started independently and tended to cluster in seed and hay production areas, places where seed tended to drop. Significant but low spatial auto correlation suggested that in some instances, plants colonized nearby locations. Neighboring feral plants were frequently within pollinator foraging range; however, further research is needed to confirm transgene flow. Locations of feral plant clusters were not well predicted by environmental and production variables. However, the likelihood of seed spillage during production and transport had predictive value in explaining the occurrence of transgenic feral populations. Our study confirms that genetically engineered alfalfa has dispersed into the environment, and suggests that minimizing seed spillage and eradicating feral alfalfa along road sides would be effective strategies to minimize transgene dispersal

Gene flow in commercial alfalfa (Medicago sativa subsp. sativa L.) seed production fields: Distance is the primary but not the sole influence on adventitious presence.

In insect-pollinated crops, gene flow is affected by numerous factors including crop characteristics, mating system, life history, pollinators, and planting management practices. Previous studies have concentrated on the impact of distance between genetically engineered (GE) and conventional fields on adventitious presence (AP) which represents the unwanted presence of a GE gene. Variables other than distance, however, may affect AP. In addition, some AP is often present in the parent seed lots used to establish conventional fields. To identify variables that influence the proportion of AP in conventional alfalfa fields, we performed variable selection regression analyses. Analyses based on a sample-level and a field-level analysis gave similar, though not identical results. For the sample-level model, distance from the GE field explained 66% of the variance in AP, confirming its importance in affecting AP. The area of GE fields within the pollinator foraging range explained an additional 30% of the variation in AP in the model. The density of alfalfa leafcutting bee domiciles influenced AP in both models. To minimize AP in conventional alfalfa seed fields, management practices should focus on optimizing isolation distances while also considering the size of the GE pollen pool within the pollinator foraging range, and the foraging behavior of pollinators

Distribution of roadside feral alfalfa plants in Fresno County, California.

<p>Hot spot analysis showed significant clustering of roadside feral populations (dark purple, dark orange) in alfalfa-seed (purple) and hay-production (orange) areas. Non-clustering populations are also evident (green). Transgenic feral populations (pink) occur in seed- and hay-production areas, as well as along major roads used to transport seed.</p

Distribution of roadside feral alfalfa plants in Walla Walla County, Washington.

<p>Hot spot analysis showed significant clustering of roadside feral populations (dark purple, dark orange) in alfalfa-seed (purple) and hay-production (orange) areas. Non-clustering populations are also evident (green). Transgenic feral populations (pink) were clustered in seed and hay production areas.</p

Distribution of roadside feral alfalfa plants in Canyon County, Idaho.

<p>Hot spot analysis showed significant clustering of roadside feral populations (dark purple, dark orange) in alfalfa-seed (purple) and hay-production (orange) areas. Non-clustering populations are also evident (green). Transgenic feral populations (pink) occur mainly in seed production areas.</p

Number of GE feral population occurrences relative to the distance from historic GE seed fields.

<p>Relationship was significant but inconsistent across counties. In Fresno County, transgenic feral populations occurred more frequently at further distances from the single historic seed field, while in Canyon and Walla Walla counties, transgenic populations occurred closer to historic GE seed fields.</p