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4. Temporal population structure of rubber tree powdery mildew pathogen Erysiphe quercicola in Hainan, China

Author

Xueren Cao, Ying Xiao, Qiaohui Han, Jonathan S. West, and Luo Daquan

Subjects
Erysiphe quercicola, Temporal population structure, Microsatellite marker, Genetics, Plant Science, Horticulture, Agronomy and Crop Science
Abstract

Rubber tree powdery mildew, caused by the obligate pathogen Erysiphe quercicola, is a major threat to rubber tree plantations worldwide. To investigate the temporal changes in the population structure of E. quercicola, diseased samples were collected at three disease epidemic stages (overwinter, early epidemic and late epidemic) from three counties in Hainan, China. Population structure was assessed using 16 polymorphic microsatellite markers. Both permutational multivariate analysis of variance (PERMANOVA) and analysis of molecular variance (AMOVA) indicated that there were significant differences among the population structure of E. quercicola at different epidemic stages. Furthermore, the late epidemic populations had higher genetic diversity than the other two stages. Discriminant analysis of principal components (DAPC) and STRUCTURE analysis showed that E. quercicola samples grouped into four clusters. One of the clusters included only samples from the late epidemic stage, while the other three clusters included samples from all three sample stages. Further analysis confirmed that there were significant (p= 0.001) genetic differences among these four clusters. As the teleomorph stage of E. quercicola has not yet been reported on rubber tree, these findings suggest that the epidemic of rubber tree powdery mildew is not only established by local inoculum sources, but also may be by inoculum drifting from other plantations or through host jumps from other hosts

Published
2023

12. Effects of temperature and leaf age on conidial germination and disease development of powdery mildew on rubber tree.

Author

Cao, Xueren, Xu, Xiangming, Che, Haiyan, West, Jonathan S., and Luo, Daquan

Subjects
LEAF temperature, POWDERY mildew diseases, TEMPERATURE effect, GERMINATION, LEAF development, RUBBER
Abstract

Powdery mildew is an important disease of rubber trees worldwide. To assess the effects of temperature and leaf age on conidial germination and disease development, conidia were inoculated onto rubber tree seedlings with leaves at three phenological stages (copper bronze, colour‐changing, and light green) and then incubated at six constant temperatures (10, 15, 20, 25, 30, and 35°C). Leaf age did not affect conidial germination (p =.296) whilst temperature did (p <.0001), although conidia were able to germinate at all tested temperatures. The estimated optimal temperature for conidial germination was 23.2°C. Leaf age, temperature, and their interactions had significant effects on conidial infection and hypha number (p <.0001). At 10 and 35°C, more than 2 and 4 days were needed for infection to complete, respectively, compared to <2, 1, 0.5, and 0.5 days for 15, 20, 25, and 35°C, respectively. Sporulation and mildew symptoms were only observed on those inoculated leaves of all stages at 20 and 25°C, and at the copper bronze stage only at 15°C. The latent period on the copper bronze leaves at 15°C was longer (9 days) than at 20 and 25°C (4 days). The latent period at 20 and 25°C increased from 4 to 7 days as the leaf development stage increased from copper bronze to light green. Therefore, temperature affected germination and postgermination growth of rubber tree powdery mildew, whereas leaf age primarily affected postgermination growth of the pathogen. [ABSTRACT FROM AUTHOR]

Published
2021
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