Abstract
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat worldwide. Understanding the survival of Pst during the overwintering period is critical for predicting Pst epidemics in the spring. Real-time quantitative PCR (qPCR) methods quantifying Pst DNA and RNA (cDNA) were developed and compared for the ability to quantify viable Pst in leaf tissues. Both qPCR of DNA and RNA can provide reliable measurement of viable Pst in plant tissues prior to the late sporulation stage for which qPCR of DNA gave a much higher estimate of fungal biomass than qPCR of RNA. The percentage of Pst biomass that was viable in detached and attached leaves under low temperatures decreased over time. Pst survived longer on attached leaves than on detached leaves. The survival of Pst in cultivars with strong winter-hardiness at 0°C and -5°C was greater than those with weak winter-hardiness. However, such differences in Pst survival among cultivars were negligible at -10, -15 and -20°C. Results indicated that Pst mycelia inside green leaves can also be killed by low temperatures rather than through death of green leaves under low temperatures. The relationship of Pst survival in attached leaves with temperature and winter-hardiness was well described by logistic models. Further field evaluation is necessary to assess whether inclusion of other factors such as moisture and snow cover could improve the model performance in predicting Pst overwintering potential, and hence the epidemic in spring.
Highlights
Wheat stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst), is one of the most important diseases of wheat worldwide [1,2]
Previous findings regarding the effect of environmental factors on Puccinia striiformis f. sp. tritici (Pst) overwintering were based field observations, which reflect the overall effects of many external factors on Pst overwintering
The 28S, 18S, 5.8S and 5S RNA were intact on day 0 (Fig 2E), but considerably degraded on day 4 for dead urediniospores (Fig 2F lane 1) with both 28S and 18S almost totally degraded on day 8 (Fig 2G lane 1)
Summary
Wheat stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst), is one of the most important diseases of wheat worldwide [1,2]. Annual cycles of stripe rust on winter wheat can be divided into four stages: oversummering, infection of seedlings in autumn, overwintering, and spring epidemic. Temperature is an important factor influencing Pst development, including its survival during the winter [1,5,6,7,8,9,10,11,12,13,14,15,16]. Wheat-growing regions in China are divided into overwintering and non-overwintering regions for Pst based on winter temperatures [17,20]. Previous findings regarding the effect of environmental factors on Pst overwintering were based field observations, which reflect the overall effects of many external factors on Pst overwintering
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