Corynespora Leaf Blight of Cotton in Brazil and Its Management

Abstract

In recent years, Corynespora leaf blight is on the increase in cotton and has become an important disease in the State of Mato Grosso, Brazil. It attacks several plant species including soybean. It is not yet known whether the same strain of this pathogen attacks both the crops. The objectives of the present investigation were to verify the genotypic and phenotypic variation between the isolates attacking cotton and soybean and to verify the sources of resistance in cotton. Differential response of 23 cotton genotypes was studied under glasshouse conditions using mixture of two randomly selected isolates of C. cassiicola of cotton in equal proportion. Genotypic variation among three cotton and two soybean isolates was studied using ERIC/REP-PCR and rDNA molecular techniques. With one exception, all the cotton genotypes tested so far were susceptible to C. cassiicola isolates of both cotton and soybean. Similarly, results of both molecular techniques indicated that the C. cassiicola isolates attacking cotton and soybean belong to the same strain of the pathogen in Brazil. Since Corynespora blight is a newly immerging disease of cotton and soybean in Brazil, integration of crop rotation and the sanitary practices are suggested to manage the disease.