Abstract
Soybean rust caused by Phakopsora pachyrhizi Syd. is a potential disease causing severe losses in yield and oil quality of soybean [Glycine max (L.) Merr.]. The physiological variability studies were carried out for 25 isolates collected from different growing environment of Karnataka, India during Kharif 2010-2012. Morphological and cultural characters of 25 isolates were studied under identical condition. Among 25 isolates, the maximum uredospore size was found in Ugarkhurd isolate (90.93×70.05 μm). The differential JS-335 reacted to the maximum of eight isolates, and isolate Rayanal produced both RB and TAN reaction on most of the differentials. In the clustering of different isolates into pathotypes, the cluster analysis indicated the expression of eight isolates on differential JS-335 and there was no expression of all the isolates on differential PI-459024B. In cluster-II, nine isolates expressed on PI-200492, while one isolate expressed on JS-335. In cluster-III, 23 isolates expressed on PI-459024B and 12 isolates expressed on PI-200492. Hence, this study described the three pathotypes that causes soybean rust in India namely, Cluster I-Reddish Brown (RB) lesion producing pathotypes, Cluster II - TAN lesion producing pathotypes and Cluster III - Mixed or RB + TAN producing pathotypes. This information could further be used for identification of race pattern in Karnataka and other major rust prone areas of India.
Highlights
Soybean [Glycine max (L.) Merr.] is a widespread crop in the world and ranks first among the oilseed crops
Asian soybean rust caused by Phakopsora pachyrhizi Syd. is the potential disease that causes severe losses in yield and oil quality of soybean
In Taiwan in 1983, 50 single-urediniospore isolates of P. pachyrhizi inoculated onto the five soybean entries namely, plant introduction (PI) 462312 (Ankur), TK-5, TN 4, PI 200492 (Komata), and PI 230971, were differentiated into three physiological races based upon specific reaction patterns of Reddish Brown (RB) and tan colour (TAN) lesions (Yeh, 1983)
Summary
Soybean [Glycine max (L.) Merr.] is a widespread crop in the world and ranks first among the oilseed crops. In Taiwan in 1983, 50 single-urediniospore isolates of P. pachyrhizi inoculated onto the five soybean entries namely, plant introduction (PI) 462312 (Ankur), TK-5, TN 4, PI 200492 (Komata), and PI 230971, were differentiated into three physiological races based upon specific reaction patterns of RB and TAN lesions (Yeh, 1983). In Japan, 18 P. pachyrhizi races were differentiated using 11 soybean entries based upon reaction type and the number of uredinia produced per lesion (Yamaoka et al, 2002).
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