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

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