Virulence, Molecular Diversity, and Mating Type of Curvularia lunata in China

Abstract

Curvularia leaf spot (CuLS), caused by Curvularia lunata, is a devasting foliar disease in the maize-growing regions of China. Resistant varieties were widely planted in these regions in response to CuLS. However, over time, C. lunata has gradually adapted to the selective pressure and, in recent years, the incidence of CuLS has increased. To assess the correlation between virulence and genetic diversity, a total of 111 isolates was collected from 15 maize-growing regions located in nine provinces in China. These isolates were evaluated for virulence on maize using nine differential hosts: Shen135, CN165, Mo17, Luyuan92, 78599, Ye478, B73, E28, and Huangzaosi. To evaluate the genetic diversity, 657 polymorphic amplified fragment length polymorphism markers were generated. Results showed that the isolates could be grouped into three pathotypes according to the phenotypic expression of the differential inbred lines. Isolates were clustered into two genetic diversity groups and further divided into subgroups. However, the correlation between virulence and genetic diversity grouping was low. Also, there was a low correlation observed between pathotype and geographic distribution. The ratio of mating type I to mating type II for all isolates was close to 3:4.

Curvularia lunata and Curvularia Leaf Spot of Maize in China

“…Moreover, comparative transcriptome analysis of low-virulence and high-virulence C. lunata strains revealed that host pressure increased pathogen virulence by increasing the pathogen’s biosynthesis of toxins and melanin. , To prevent disease re-epidemics in maize-growing areas, more attention should be given to the dynamic changes of strains with varied virulence. The combination of different molecular approaches and biochemical methods could be applied to monitor pathogenic variation. , Additionally, C. lunata can produce many virulence factors, but the synthesis mechanisms of these factors, such as toxin and melanin, are still not clear. Therefore, further exploration of the precursors, intermediates, and node genes involved in virulence factor synthesis is required to propose corresponding effective methods to control C. lunata infection.…”

“…Biochemical and molecular identification techniques have also been utilized to differentiate the virulence of C. lunata isolates. Isozymes, random amplified polymorphic DNA (RAPD), universally primed PCR (UP-PCR), internal simple sequence repeat (ISSR), and amplified fragment length polymorphism (AFLP) methods have also been tested to analyze the genetic variability among C. lunata strains. ,,,,− The classifications using one method or a combination of two or more methods were found to correlate with the classifications achieved using the differential host system method. Thus, biochemical and molecular identification methods have been used to assist the differential host system method in classifying the virulence of C. lunata .…”

“…After this outbreak, the cultivation of CLS-resistant varieties sprung up in various regions, , which decreased the disease prevalence and intensity, and as a result the CLS became not a serious problem in maize production. In the past decade (2010–2019), according to the reports by Zhang et al, and Chang et al and surveys by local base stations, some provinces in China, such as Anhui, Henan, Shandong, Hebei, and Liaoning, have higher disease severity indexes in maize that caused large leaf spots and wilting to occur in almost all maize growing areas of provinces, indicating a rerising threat of CLS occurrence to maize production. Although the severity of CLS varies significantly between provinces and among localities of the same province, it is still an important maize disease in China (Figure ).…”

ClNOX1/ClNOXR‐mediated MAPK and cAMP‐PKA signalling pathways and ROS metabolism are involved in Curvularia lunata sexual reproduction and host infection

“…Virulence on maize leaves was scored with a disease index (Zhang et al ., 2019). After the investigation of disease index, the lesion number was statistically analysed and the length and width of at least 50 lesions were measured.…”

The key iron assimilation genesClFTR1,ClNPS6were crucial for virulence ofCurvularia lunatavia initiating its appressorium formation and virulence factors

“…Supplemental lighting was used at 25–50 klux (325–650 μE m −2 s −1 ) with 14 h light and 10 h night. Disease severity was evaluated as described (Zhang et al ., 2019). The length and width of brown infected areas were measured as the lesions size at the indicated time using Image J software.…”