The effect of Puccinia striiformis f. sp. tritici on the levels of water-soluble carbohydrates and the photosynthetic rate in wheat leaves

Abstract

Stripe rust is the most serious wheat disease worldwide. Puccinia striiformis f. sp. tritici (Pst), which is the causal agent of stripe rust, is an obligate biotrophic fungus and must take up nutrients from the host through its haustoria. Recent studies have indicated that sugar is the main nutrient taken up by pathogens from host cells. However, the response of sugars to Pst infection in wheat is not well known. In this study, the levels of water-soluble carbohydrates in Pst-infected wheat leaves were investigated, and the results revealed slight changes for all of the carbohydrates except sucrose. Furthermore, the sucrose levels increased in both the compatible and incompatible systems. The photosynthetic rates of infected leaves were determined and found to be significantly increased during the early stage of Pst infection. In addition, the expression profiles of genes associated with photosynthesis were assayed through real-time PCR, and the trends found were identical to that observed for the photosynthetic rate in Pst-infected wheat leaves. These findings indicate that Pst infection can upregulate genes involved in photosynthesis to promote the photosynthetic rate and ultimately induce sucrose accumulation in infected wheat leaves.