Effects of Mixed Pathotypes of Didymella rabiei on the Development of Ascochyta Blight on Chickpea

Ascochyta blight (Didymella rabiei) is an economically important disease on chickpea in Syria and other parts of the world. Studies were conducted under plastic-house and field conditions to determine the effects of mixed infection of D. rabiei pathotypes on disease development on different chickpea genotypes. The plastic-house results showed that under mixed-genotype infections, disease severity caused by two-genotype mixtures (1+2, 1+3, 1+4, 2+3, 3+4) was not significantly different from the average level of disease caused by the most virulent pathotype in each mixture. Co-infection by Pathotypes-1+2, resulted in higher disease severity compared to Pathotype-2 alone. Co-infection by the four Pathotypes mixture, resulted in lower disease severity compared to Pathotype-4 alone. ILC-194 was the most susceptible genotype, followed by Ghab-1, while ICC-12004 was the most resistant genotype. In field experiments, all disease parameters and percent yield reduction were higher when chickpea genotypes were infected with a mixture of Pathotype-1 and 2 compared to individual inoculations with the two pathotypes. Chickpea variety mixtures did not reduce parameters of disease epidemics. To develop disease epidemics under field conditions, it is better to mix Pathotype-1 and 2 compared with individual inoculations. Further studies are required to learn how pathotype mixtures affect disease epidemics in chickpea-Ascochyta pathosystem.