STRIPE RUST OF WHEAT: THE RELATIONSHIP BETWEEN DISEASE SEVERITY AND SPORES CONCENTRATION

Wheat is one of the most important cultivated crops in the world. However, wheat is affected by stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Erikss., which is one of the most aggressive rust diseases in wheat. In susceptible cultivars, it can cause severe yield losses and decrease drastically the quality of the grains. The objective of this study is to establish the minimum number of spores required to cause an infestation of stripe rust in a susceptible wheat variety under controlled greenhouse conditions and field environment by rating the disease severity. The susceptible wheat was inoculated with different concentrations (0, 103, 104, 105, 106, and 107 spores /ml) of stripe rust spores and later on, the disease severity was rated. Pathogen-specific primers were designed and tested for the detection of stripe rust spores using PCR and quantification of the pathogen in collected air samples will be developed using qPCR. The prevalence and severity of this disease varies with the geographic locations, host susceptibility, and weather conditions. The ‘Disease Triangle’ concept states that it is essential to have optimum weather conditions, a susceptible host crop, and a virulent pathogen in order to have disease development. If one of these components is absent or is low, disease will not occur or be less severe. Determining the minimum amount of fungal spores necessary to cause an infestation of stripe rust disease is a critical component for predicting potential epidemics.