Foliar blight spectrum and genetic variability of Pyrenophora tritici-repentis

Abstract

A survey was conducted for the assessment of foliar blight of wheat in main rice-wheat cropping areas of Punjab province. Foliar samples were collected at the maturity stage of wheat crop from 20 key locations of four districts: Gujranwala, Sheikhupura, Sialkot and Narowal. The foliar fungi were isolated using the blotter method. Prevalence of foliar blight was 100% in the four surveyed districts. From leaf samples, Pyrenophora tritici-repenti isolates were isolated using the standard blotter method. From the survey, it was concluded that foliar blight (tan spot) was a more prevalent fungal disease. It could not be differentiated in the field and it was confirmed in laboratory after the isolation of fungi (P. tritici-repentis). After isolation and identification, the Random Amplified Polymorphic DNA (RAPDs) technique was used for identification and differentiation of P. tritic-repentis isolates. For plant pathogenic fungi, RAPDs analysis has been used to analyse genetic variations or distinguished the P. tritici-repentis isolates. Fifteen strains were studied using a RAPDs analysis with different decamer primers. The molecular fingerprint patterns revealed differences in all the strains of identified P. tritici-repentis and showed genetic variability. In some of the isolates, the amplification profiles of P. tritici-repentis were highly polymorphic among each other, presenting differences. On the other hand, some of the isolates presented amplification profiles quite monomorphic among each other. It indicates RAPDs is a good molecular tool that could be used to characterize the P. tritici-repentis isolates for their genetic characters. From this survey it was concluded that foliar blight was a more prevalent fungal disease and it cannot be distinguished in the field and it was confirmed in the laboratory after the isolation of fungal pathogens. The blotter method is one of the best methods for the isolation of foliar fungal pathogens. After isolation, RAPDs is very quick method for the study of genetic variability.