Partial resistance to yellow rust in introduced winter wheat germplasm at the north of Pakistan

Thirty-seven winter wheat lines introduced from Oklahoma State University, along with local check were studied to assess their partial resistance level, at Hazara Agricultural Research Station (HARS), Abbottabad. Pathotypes of Puccinia striiformis West. tritici (Pst) prevalent at the site were found virulent on all of the introduced winter wheat lines. Partial resistance level was assessed through final rust severity ( FRS), area under rust progress curve (AURPC) and coefficient of infection (CI). A considerably high disease pressure was observed with a maximum FRS up to 95% recorded for line F5-34. Six lines were having FRS value more than 70%, while remaining 24 lines along with local check were having FRS value less than 70%. Seventeen lines were having higher AURPC values while remaining 21 lines were having AURPC values ranging from 300 to 1100, marked to be partially resistant. Based on CI value, four lines (F-5-64, F-5-71, F-5-15 and OK00611W) were marked as highly partially resistant, having CI value up to 20; F-5-4, F-5-21, F-5-69, F-5-78, F-5-103, F-5-122, F-5-141, OK99212, OK00608W, Intrada and Ghaznavi, with CI value 21-40, were marked as moderately resistant; and F-5-5, F-5-9, F-55-38, F-5-70, F-5-83, F-5-99, F-5-110, F-5-139, OK95616-56, OK98G508W, OK00421, OK00514 and OK00618W, with CI value 41-60, were designated to have low level of partial resistance. Line OK00611W performed better, producing maximum grain yield with an increase of 2736 kg ha(-1) over the local check as well as having better level of partial resistance. Cluster analysis of the OSU introduced winter wheat lines revealed four major groups/cluster, based on partial resistance parameters and grain yield. Considerable diversity was observed for level of partial resistance of these introduced winter wheat breeding lines, which may be advanced further for manipulation in breeding or inheritance studies.