Brome mosaic virus detected in Kansas wheat co-infected with other common wheat viruses.

Wheat breeders are developing new virus-resistant varieties; however, it is assumed that only a few viruses or well-known viruses are present in the field. New sequencing technology is allowing for better determination of natural field virus populations. For three years, 2019-2021, Kansas wheat field surveys were conducted to determine the constituents of natural field virus populations using nanopore sequencing. During analysis, brome mosaic virus (BMV) was identified for the first time in Kansas but was in association with other wheat viruses. Brome mosaic virus was identified from 29 out of 47 different Kansas counties sampled and 44% of the total samples. BMV was found co-infected with wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) in 27.8% of the samples, with WSMV only (13.9%) and co-infected with WSMV + TriMV + High Plains wheat mosaic emaravirus (HPWMoV) (13.9%). RNA genomes of Kansas BMV isolates had 99.4 to 100% nucleotide and amino acid sequence identity, respectively, to each other. RNA2a possessed relatively high divergence (π = 0.01) compared to RNA1a and RNA3a (π = 0.004). Coding regions of all BMV RNAs were considered negative for purifying selection pressure as nonsynonymous and synonymous nucleotide ratio was less than one (dNs/dS >1). The identification of BMV in Kansas virus populations adds another layer of complexity to plant breeding. This work provides information to improve tools to aid in monitoring, detecting, and determining the variation within BMV.

Temperature and Alternative Hosts Influence Aceria tosichella Infestation and Wheat Streak Mosaic Virus Infection.

Wheat streak mosaic, caused by Wheat streak mosaic virus (WSMV; family Potyviridae), is the most important and common viral disease of wheat (Triticum aestivum L.) in the Great Plains of North America. WSMV is transmitted by the wheat curl mite (WCM; Aceria tosichella). We evaluated how mean daily temperatures, cumulative growing degree-days, day of the year, and surrounding alternative host identity affected WCM infestation and WSMV infection of wheat from late summer through early autumn in Montana, United States. Cumulative growing degree-days, warm mean daily temperatures (i.e., >10°C), and surrounding alternative hosts interacted to alter risk of WCM infestation and WSMV infection. Wheat surrounded by Bromus tectorum L. and preharvest volunteer wheat had WCM infestation and WSMV infection rates of 88% in years when the mean daily temperature was 15°C in October, compared with 23% when surrounded by bare ground, and <1% when the temperature was 0°C regardless of surrounding alternative host. Mean daily temperatures in the cereal-growing regions of Montana during autumn are marginally conducive to WCM population growth and movement. As the region continues to warm, the period of WCM movement will become longer, potentially increasing the frequency of WSMV outbreaks.

Dietary effects on body weight of predatory mites (Acari, Phytoseiidae).

Pollen is offered as alternative or supplementary food for predacious mites; however, it may vary in its nutritional value. Body weight appears a representative parameter to describe food quality. Thus, we assessed the body weight for adults of the generalist mites Amblyseius swirskii, Amblydromalus limonicus, and Neoseiulus cucumeris reared on 22, 12, and 6 pollen species, respectively. In addition, A. swirskii and A. limonicus was reared on codling moth eggs. In all mite species, female body weight was higher than that of males, ranging between 4.33 and 8.18 µg for A. swirskii, 2.56-6.53 µg for A. limonicus, and 4.66-5.92 µg for N. cucumeris. Male body weight ranged between 1.78 and 3.28 µg, 1.37-3.06 µg, and 2.73-3.03 µg, respectively. Nutritional quality of pollen was neither consistent among the mite species nor among sex, revealing superior quality of Quercus macranthera pollen for females of A. swirskii and Tulipa gesneriana pollen for males, Alnus incana pollen for females of A. limonicus and Aesculus hippocastanum pollen for males, and Ae. hippocastanum pollen for both sexes of N. cucumeris. The results are discussed against the background of known or putative pollen chemistry and mite's nutritional physiology.