Aceria Tosichella Research Articles

Mixed Infection of Hard Red Winter Wheat with High Plains Virus and Wheat Streak Mosaic Virus from Wheat Curl Mites in Nebraska

A new disease of wheat and corn caused by the High Plains virus (HPV) has been observed in the High Plains region of western United States. HPV is transmitted by the wheat curl mite, Aceria tosichella, which is also the vector of wheat streak mosaic virus (WSMV). In the field it is extremely difficult to visually differentiate plants infected with WSMV from those with HPV. An indirect protein-A sandwich enzyme-linked immunosorbent assay (PAS-ELISA) and Western blot analysis were used to identify WSMV and HPV. Samples of wheat curl mites were collected from arbitrarily chosen sites from commercial wheat plantings in 1995 and 1996 and used to infest caged wheat plants. After 3 weeks, leaf samples were harvested and assayed. Both Western blot analysis and PAS-ELISA were effective at identifying samples positive for WSMV and HPV, both alone and in mixed infections. Western blot results showed that over the 2 years, 65% of the samples were positive for WSMV, 46% were positive for HPV, and mixed infections were found in 40% of the samples. HPV presence was verified with similar results from field collected plant samples. These levels of virus indicate an unexpectedly high incidence of HPV in wheat curl mite populations in Nebraska.

Resistance to Systemic Spread of High Plains Virus and Wheat Streak Mosaic Virus Cosegregates in Two F2 Maize Populations Inoculated with Both Pathogens

High plains virus (HPV) has the potential to cause significant damage in susceptible maize (Zea mays L.) genotypes. The virus is vectored by the wheat curl mite (WCM), Aceria tosichella, Keifer, which also vectors wheat streak mosaic virus (WSMV). We have previously characterized susceptibility of maize inbred lines to double infection of HPV and WSMV. The objective of this study was to characterize the inheritance of resistance to systemic spread of HPV and WSMV in mixed infection. Genetic analysis was done with crosses B73 (resistant) × Wf9 (susceptible) an B73 × W64A (susceptible). Parental, F1, and F2 plants were WCM‐inoculated with HPV and WSMV, and scored for their reactions both visually and by enzymelinked immunosorbent assay. F1 plants were resistant to systemic spread of HPV and WSMV, indicating that resistance is dominant in these lines. Segregation (based on symptomology) in the F2 generation fit a 3:1 resistant:susceptible ratio in both B73 × W64A and B73 × Wf9 (P = 0.34 and 0.11, respectively), consistent with a single chromosome region segregating for resistance to both viruses. The resistant allele was contributed by B73 and was linked to marker bnl6.29 on the short arm of chromosome six. This chromosome region has been shown to control resistance to WSMV (wsm1). Two independent sets of inbred‐backcross‐derived near‐isogenic lines confirmed the effect of this chromosome region. This study reveals the genetic basis of symptomology observed upon mixed infection with HPV and WSMV in these populations. Identification of molecular markers linked to virus resistance genes may enhance inbred line development efforts.

Identification of the Wheat Curl Mite as the Vector of the High Plains Virus of Corn and Wheat

Wheat with virus-like symptoms (extracts containing a 33-kDa protein in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, negative in enzyme-linked immunosorbent assay to wheat streak mosaic virus, and not infectious in a backassay to other wheat) reacted positively to antiserum made against a protein purified from symptomatic corn infected with the High Plains virus (HPV), indicating a serological relationship between the corn and wheat pathogens. The wheat curl mite (WCM, Aceria tosichella Keifer) was identified as the vector of the virus and caused persistent infection of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) in greenhouse experiments. The HPV was recovered in the field from naturally infected wheat where the number of HPV-infected plants decreased with increasing distance from the WCM source in volunteer wheat.

Development of Serological Procedures for Rapid and Reliable Detection of Wheat Streak Mosaic Virus in a Single Wheat Curl Mite.

Wheat streak mosaic virus (WSMV) is transmitted by the wheat curl mite (WCM), Aceria tosichella. Immunofluorescent and dot-immunobinding assays were developed to detect the presence of WSMV in single WCM. Virus-specific immunofluorescent microscopy detected WSMV near the anterior end of viruliferous WCM. With dot-immunobinding assay, WSMV was detected in WCM fed on WSMV-infected wheat (Triticum aestivum) but not in WCM maintained on healthy plants. Both immunofluorescent and dot-immunobinding assays were sufficiently sensitive to detect WSMV in individual WCM, providing a means to determine the percentage of viruliferous WCM in field collections.

Change in Virulence of Wheat Curl Mite Detected on Tam 107 Wheat

Wheat streak mosaic is the most important wheat (Triticum aestivum L.) disease in western Kansas. The wheat cultivar TAM 107 has been resistant to the wheat curl mite (WCM, Aceria tosichella Keifer), which is the vector of wheat streak mosaic virus (WSMV) and as the most popular wheat cultivar in western Kansas has effectively reduced the incidence of the disease. In 1991, several observations indicated that the incidence of WSMV infection in TAM 107 was much heavier than usual. In 1992, a survey of 10 field collections of WCM showed that one collection from TAM 107 was virulent to that cultivar. In 1995, WCM collections from TAM 107 and ‘Karl’ (susceptible to WCM) were made from 14 western Kansas counties and tested for virulence to TAM 107. All collections of WCM obtained from TAM 107 were adapted to TAM 107, and nine of the 14 collections from Karl were adapted to TAM 107. The high incidence of a WCM strain virulent to TAM 107 may explain the increased losses to WSMV recently observed in that cultivar. TAM 107 probably cannot be relied on in the future to provide protection against WSMV in western Kansas. Lines derived from sources of resistance that are effective against WCM virulent to TAM 107 or that are resistant to WSMV are being advanced in wheat breeding programs and should be deployed in the field as soon as possible.

Natural Infection of Pearl Millet and Sorghum by Wheat Streak Mosaic Virus in Kansas

Pearl millet (Pennisetum glaucum) and sorghum (Sorghum bicolor) plants at Hays, Kansas, were observed to have viruslike symptoms. Symptomatic plants were tested by enzyme-linked immunosorbent assay (ELISA) against wheat streak mosaic virus (WSMV), maize dwarf mosaic, sugarcane mosaic virus strain MDMV-B, and johnsongrass mosaic virus. Positive reactions were obtained only with WSMV antisera. Pearl millet and sorghum plants (of genotypes naturally infected in the field) mechanically inoculated in the greenhouse developed symptoms and were positive in ELISA for WSMV. The virus was vectored by wheat curl mites (Aceria tosichella) from pearl millet and sorghum to the host from which it was obtained and to wheat. Mechanical inoculation of several sorghum lines showed that the WSMV isolates differed in ability to infect sorghum, and the type specimen could not infect any of the sorghum lines. These results indicated that WSMV occurring at Hays can infect sorghum and pearl millet, crop plants not reported previously as susceptible to WSMV.