A Pilot Experiment for Screening Genetic Resistance to Barley Yellow Dwarf Viruses in the Wild Barley Diversity Collection
The barley yellow dwarf viruses (BYDV) contain some of the most economically important viruses infecting cereal crops in the Midwest. BYDV-PAV is the dominant species in Minnesota, and is persistently transmitted through various aphid species, including Rhopalosiphum padi. Virus infection results in yellow, stunted growth and significant yield losses. Genetic resistance remains one of the strongest control strategies for BYDV control. However, the risk of resistance-breaking virus isolates increases over time. The Wild Barley Diversity Collection (WBDC) contains over 300 accessions of wild barley plants that may contain unidentified BYDV resistance genes. The objective of this pilot study was to develop efficient transmission, detection, and phenotyping protocols to screen the full accession in the future. A total of 40 accessions of the WBDC were inoculated with BYDV-PAV utilizing viruliferous R. padi aphids with known resistant and susceptible barley lines for control. Plants grew for four weeks before being phenotyped for disease severity and harvested for RT-qPCR to quantify virus titer. A phenotypic severity scale was created to rate infection on a scale from zero to four. RT-qPCR was found to be a more sensitive and efficient detection method compared to ELISA. Finally, virus titers among the accessions were compared for potential sources of genetic resistance. Additionally, the use of ELISA vs RT-qPCR for virus detection, the effectiveness of aphid transmission, and the use of phenotypic scales versus virus titer for identifying genetic resistance will be discussed.