|Ohm, H - PURDUE UNIVERSITY|
Submitted to: International Wheat Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 7, 2005
Publication Date: N/A
Interpretive Summary: Viruses that cause the disease yellow dwarf (YD), including barley yellow dwarf virus (BYDV-PAV) and cereal yellow dwarf virus (CYDV-RPV, previously BYDV-RPV) are serious pathogens of the small cereal grain crops like barley, wheat, oat, and rye in many cereal-growing areas of the world. Although partial resistance and tolerance to YD have been identified in barley, oat and rye, searching for resistance to YD in cultivated wheat, including Triticum aestivum and T. durum, has been largely unsuccessful. Highly effective resistance has been identified in certain species that are related to wheat, including intermediate wheatgrass (Thinopyrum intermedium). Through embryo seed rescue, two lines were developed that had the same Th. intermedium chromosome and conferred a high level of YDV resistance. The resistance, called Bdv3, in field tests in Indiana and throughout the eastern USA, has proven to be extremely effective since 2002. Agronomic performance has been comparable to other elite wheat lines when YDV disease was low and superior when the disease was severe. The identification and use of DNA markers linked to Bdv3 has enhanced the breeding program leading to the release of one germplasm line and two cultivars. In addition to YDV resistance these cultivars also have acceptable soft wheat milling and baking qualities, resistance to Soil borne mosaic virus, and slow powdery mildewing resistance. Studies to begin deciphering the mechanism underlying resistance to CYDV-RPV demonstrated that Bdv3 causes a very significant reduction in the ability of CYDV to move through the phloem, therebye preventing an infection throughout the plant. The germplasm line and cultivars, the associated DNA markers and information regarding the mechanism of this resistance developed through these studies are being used by scientists and small grain breeders worldwide.
Technical Abstract: We have transferred yellow dwarf virus (YDV; BYDV and CYDV) resistance from Thinopyrum intermedium into wheat (Triticum aestivum L.) and have released a wheat germplasm line and two soft winter wheat cultivars with this resistance. YDV symptoms have been negligible or absent in the resistant cultivars in plots since 2002 throughout Indiana and in many tests in eastern USA. Agronomic performance of the resistant cultivars has been comparable to other cultivars when YDV disease was negligible or absent, and increasingly superior to YDV susceptible cultivars with increased severity of the disease. We have noted some pollen sterility in the YDV resistant cultivars under certain stress conditions, such as cool temperatures prior to and during flowering. To further define the length of the alien chromosome segments publicly available STS and SSRs were identified that are linked to the resistance locus. Because of the multiple components involved in the YDV disease complex, selecting for YDV resistance with the molecular markers and maps identified in this study will increase the efficiency of introgressing Th. intermedium chromatin containing YDV resistance into elite wheat germplasm. In addition to the breeding effort, studies examining the mechanism of CYDV resistance showed that resistance is due to an inhibition of virus spread from the intial inolculation site. These studies also demonstrated that this resistance is effective under high aphid infestations.