Optimum Stand Density of Spring Triticale for Grain Yield and Alfalfa Establishment

Triticale (×Triticosecale Wittmack) has potential as a feed crop in the north central United States and could also function as a companion crop for alfalfa (Medicago sativa L.) establishment. The objectives of this research were to assess the suitability of a short-statured spring triticale as a companion crop and determine optimum triticale seeding rates for grain yield and alfalfa establishment. Spring triticale ‘Trimark 37812’ and alfalfa were grown in companion at Ames and Sioux Center, IA during 2004 and 2005. Triticale was seeded at 198, 297, 396, 495, and 594 pure live seeds (PLS) m−2 and alfalfa was seeded at 600 PLS m−2 The grain yield response to changes in stand density was quadratic with maximum yield occurring at 516 plants m−2 A plant density of 325 plants m−2 and a seeding rate of 374 seeds m−2 resulted in maximum profit. The grain yield at the stand density for maximum profit was 4.4 Mg ha−1 Increasing the triticale seeding rate had no effect on alfalfa stand density or dry matter yield. Alfalfa stand densities exceeded the 130 plants m−2threshold required for maximum long-term productivity suggesting the short-statured spring triticale cultivar used in this study was well suited for companion cropping with alfalfa

Harvesting Regimes Affect Brown Midrib Sorghum-Sudangrass and Brown Midrib Pearl Millet Forage Production and Quality

As water levels in the Ogallala Aquifer continue to decline in the Texas High Plains, alternative forage crops that utilize less water must be identified to meet the forage demand of the livestock industry in this region. A two-year (2016 and 2017) study was conducted at West Texas A&M University Nance Ranch near Canyon, TX to evaluate the forage production and quality of brown midrib (BMR) sorghum-sudangrass (SS) (Sorghum bicolor (L.) Moench ssp. Drummondii) and BMR pearl millet (PM) (Pennisetum glaucum (L.) Leeke)) harvested under three regimes (three 30-d, two 45-d, and one 90-d harvests). Sorghum-sudangrass consistently out yielded PM in total DM production in both tested years (yield range 3.96 to 6.28 Mg DM ha−1 vs. 5.38 to 11.19 Mg DM ha−1 in 2016 and 6.00 to 9.87 Mg DM ha−1 vs. 6.53 to 15.51 Mg DM ha−1 in 2017). Water use efficiency was higher in PM compared to SS. The 90-d harvesting regime maximized the water use efficiency and DM production compared to other regimes in both crops; however, some forage quality may be sacrificed. In general, the higher forage quality was achieved in shorter interval harvesting regimes (frequent cuttings). The selection of suitable forage crop and harvesting regime based on this research can be extremely beneficial to the producers of Texas High Plains to meet their individual forage needs and demand

Planting Date and Hybrid Affect Sugarcane Aphid Infestation, Yield, and Water Use Efficiency in Dryland Grain Sorghum

Grain sorghum (Sorghum bicolor L.) is a major dryland crop in the Texas High Plains. Currently, drought and infestation by the sugarcane aphid (SCA, Melanaphis sacchari) are the two major challenges to grain sorghum production in the area. A 2-year field study was conducted to investigate the effect of planting date (PD) and hybrid selection on yield, evapotranspiration (ET), water use efficiency (WUE), and SCA infestation. Five sorghum hybrids (86P20, SP-31A15, AG1201, AG1203, and DKS37-07) were grown on two planting dates (PD1—early May; PD2—late June) under dryland conditions. Insecticides were not used. There were significant differences in grain yield, WUE, evapotranspiration (ET), and SCA population between two PDs and among hybrids. For PD1, SCA infestation occurred after sorghum reached physiological maturity in 2017. Although SCA infestation was observed during late grain filling in 2018, SCA populations were low and did not affect yield. For PD2, SCA was present before anthesis in both years and significantly affected grain yield. Even with heavy SCA infestation in PD2, the grain yield was higher in PD2 than in PD1 due to timely precipitation. Among hybrids, AG1203, 86P20 and DK37-07 performed better with higher yield and less SCA infestation in PD2. Grain yield was more related to seeds per plant than to kernel weight and harvest index

Planting Date and Hybrid Affect Sugarcane Aphid Infestation, Yield, and Water Use Efficiency in Dryland Grain Sorghum

Grain sorghum (Sorghum bicolor L.) is a major dryland crop in the Texas High Plains. Currently, drought and infestation by the sugarcane aphid (SCA, Melanaphis sacchari) are the two major challenges to grain sorghum production in the area. A 2-year field study was conducted to investigate the effect of planting date (PD) and hybrid selection on yield, evapotranspiration (ET), water use efficiency (WUE), and SCA infestation. Five sorghum hybrids (86P20, SP-31A15, AG1201, AG1203, and DKS37-07) were grown on two planting dates (PD1—early May; PD2—late June) under dryland conditions. Insecticides were not used. There were significant differences in grain yield, WUE, evapotranspiration (ET), and SCA population between two PDs and among hybrids. For PD1, SCA infestation occurred after sorghum reached physiological maturity in 2017. Although SCA infestation was observed during late grain filling in 2018, SCA populations were low and did not affect yield. For PD2, SCA was present before anthesis in both years and significantly affected grain yield. Even with heavy SCA infestation in PD2, the grain yield was higher in PD2 than in PD1 due to timely precipitation. Among hybrids, AG1203, 86P20 and DK37-07 performed better with higher yield and less SCA infestation in PD2. Grain yield was more related to seeds per plant than to kernel weight and harvest index

Thermal imaging to evaluate wheat genotypes under dryland conditions

Abstract Thermal imaging has been used to determine canopy temperature and study plant water relationships. The objective of this study was to investigate the potential use of infrared thermal imaging to determine crop canopy temperature (Tc) and evaluate wheat (Triticum aestivum L.) genotypes under drought conditions. Thermal images were acquired at anthesis and grain‐filling stages from 17 genotypes grown under dryland conditions in 2015 and 2016 winter wheat growing season at Bushland, TX. A handheld thermal camera was used to acquire thermal images and the images were processed using customized image processing software. The customized software filters out the background soil from the thermal images and calculates the mean Tc. A significant difference (p < .05) in Tc among genotypes was found during grain filling in 2015 and at anthesis in 2016. Genotypes TAM 111, TAM 114, PlainsGold Byrd, and Jagalene had cooler canopies, and Billings, TAM 304, and TAM 105 had warmer canopies in both years. There was a significant negative correlation between grain yield and Tc measured at anthesis (r =–.48, p < .05) and grain‐filling (r = –.33, p < .05). Infrared thermal imaging showed a promising method to obtain Tc, which can be used to evaluate genotypes for drought tolerance

What is a pathogen? Toward a process view of host-parasite interactions

International audienceUntil quite recently and since the late 19(th) century, medical microbiology has been based on the assumption that some micro-organisms are pathogens and others are not. This binary view is now strongly criticized and is even becoming untenable. We first provide a historical overview of the changing nature of host-parasite interactions, in which we argue that large-scale sequencing not only shows that identifying the roots of pathogenesis is much more complicated than previously thought, but also forces us to reconsider what a pathogen is. To address the challenge of defining a pathogen in post-genomic science, we present and discuss recent results that embrace the microbial genetic diversity (both within- and between-host) and underline the relevance of microbial ecology and evolution. By analyzing and extending earlier work on the concept of pathogen, we propose pathogenicity (or virulence) should be viewed as a dynamical feature of an interaction between a host and microbes