TEMPERATURE SENSITIVITY AND EFFICACY OF WHEAT STREAK MOSAIC-VIRUS RESISTANCE DERIVED FROM AGROPYRON INTERMEDIUM

Agronomically promising wheat (Triticum aestivum) Lines are now available that have the short arm of chromosome 4Ai-2 from Agropyron intermedium translocated onto the long arm of wheat chromosome 4D. This translocation confers a high level of resistance to wheat streak mosaic virus (WSMV). In growth chamber tests, we demonstrated that, when the translocation is present, the resistance is effective at 20 but not at 25 degrees C. Lines with the entire Ai-2 chromosome remained symptom-free at both temperatures. In field tests, both naturally infested and mechanically inoculated lines carrying the 4Ai2-S translocation were WSMV symptom free, and grain yields, test weights, and plant height were not reduced by WSMV. The grain yields of WSMV-susceptible cultivars were reduced by 21 to 45% in the same test. Although the WSMV resistance carried on the translocation is high-temperature sensitive, it was effective in the field and continues to be a very promising source for the development of WSMV-resistant cultivars.