Xiujuan Yang

Virulence structure of Magnaporthe oryzae populations from Fujian Province, China

Abstract Rice blast, caused by Magnaporthe oryzae, is one of the most devastating diseases of rice worldwide. The aim of the present study was to elucidate the virulence structure of M. oryzae populations in Fujian Province, China, over the period 2006–2015. For this purpose, 456 M. oryzae isolates collected from diverse cultivars from eight rice cropping regions in Fujian were screened for the presence of 11 known avirulence genes: Avr-Pik, Avr-Pita1, Avr-Pita2, Avr-Pita3, PWL2, Avr1-CO39, ACE1, Avr-Piz-t, Avr-Pia, Avr-Pii and Avr-Pikm, with gene-specific molecular markers. The results showed that Avr-Pik and Avr-Pita3 occurred at the highest frequency (94.5% and 91.7%, respectively), while Avr1-CO39 and Avr-Pii were not detected. Further, the remaining avirulence genes occurred at frequencies ranging from 5.9% to 89.0%. Temporal population dynamics revealed that Avr-Pik was uniformly distributed in all 10 years, at frequencies of more than 87.5%. Spatial distribution analysis showed avirulence genes were present at different frequencies among the geographic regions. In addition, 24 rice monogenic lines of IRRI-Japan with known blast resistance genes were inoculated to assess the virulence of 60 isolates. The results revealed that the resistance gene Pik showed the broadest resistance spectrum to the isolates tested and therefore would be the most useful in rice blast resistance breeding. The resistance genes Pi-z5, Pi-1(1), Pi-kp, Pi-9(t), Pi-ta(1) and Pi-kh also were effective and would therefore also be of value to resistance breeding programmes. The present study provides information that should be useful for the development and deployment of rice blast resistant cultivars in Fujian Province.

A PCR method to detect mating types of Cochliobolus heterostrophus

Abstract A rapid and sensitive polymerase chain reaction (PCR) method was established for detection of mating types of Cochliobolus heterostrophus, the causal agent of southern corn leaf blight (SCLB). Two pairs of mating type-specific primers (ChMAT01-1 for MAT1-1 and ChMAT02-1 for MAT1-2) were designed and tested on DNA extracted from pure cultures, conidial suspensions or naturally infected corn leaf samples with C. heterostrophus. The PCR-based method exhibited specificity in differentiating mating types of C. heterostrophus from the closely related species C. sativus, C. carbonum, C. lunata, C. eragrostidis and Cochliobolus sp., as well as 13 other fungal genera. Specifically, the method was capable of reliably detecting mating types of C. heterostrophus at 0.0001 ng DNA for MAT1-1 or 0.01 ng DNA for MAT1-2 from pure cultures or from 10 conidia or one lesion of C. heterostrophus on inoculated or infected corn leaf samples, even in the presence of as high as 20 ng corn genomic DNA. This PCR assay also successfully detected mating types of C. heterostrophus in naturally infected samples.

First Report of Leaf Spot Caused by Colletotrichum fructicola on Japanese Fatsia (Fatsia japonica) in Fujian Province in China

Fatsia japonica (synonym Aralia japonica Thunb.), which belongs to the family Araliaceae (Lee et al. 2008), is valued in both landscape and interior decoration in South China. In addition, F. japonica has potential medicinal uses (Ye et al. 2014; Yu et al. 2014). In September 2015, leaf spot symptoms were observed on leaves in Fujian Province, China. The disease incidence was between 50%-80% in three commercial nurseries, which had about 15 acres per commercial nursery. Early symptoms appeared as small, slightly sunken, brown spots. With expansion, lesions became tawny in the center, dark brown at the margin and bordered by a tan halo, water-soaked, obvious warts on back and cracks in the centre of the lesions. Ultimately, severely infected leaves wilted and died. Symptomatic leaves were cut into 5- × 5-mm slices, dipped in 75% (v/v) alcohol for 30 s, then in 0.1% (w/v) mercuric chloride solution for 90 s. Samples were then rinsed three times in sterilized water, placed on PDA. Six Colletotrichum-like iso...

First report of leaf spot caused by Cochliobolus eragrostidis on corn (Zea mays L.) in Fujian Province, China

Corn (Zea mays L.) is one of the most important crops in China and the world. Approximately 60,000 ha of corn, especially sweet and waxy corn, are planted yearly in Fujian province (Dai et al. 2016). Leaf spot symptoms were observed on corn beginning in July 2016. The symptoms began as small, water-soaked lesions on young corn leaves, and then became larger, dark brown, necrotic lesions, 1 to 6 mm long. Lesions presented as gray-white in the center with a dark brown halo at the margin (e-Xtra, Fig. 2C). Finally, the most affected leaves became necrotic. To determine the causal agent, a total of 30 corn leaves exhibiting leaf spots were collected from Putian, Xianyou and Xiapu in Fujian Province of China. Small pieces（5 mm × 5 mm）from infected leaves were surface sterilized in 75% (v/v) alcohol for 2 min, and then in 0.1% (w/v) mercuric chloride solution for 90 s. Pieces were rinsed three times in sterilized distilled water, placed on potato dextrose agar (PDA) containing 50 μg•ml-1 rifampicin, and incubat...

Development and application of an allele-specific PCR assay for detecting T409C mutation of cyp51 gene linked with tebuconazole resistance in Villosiclava virens (rice false smut)

Abstract Villosiclava virens is an ascomycete fungus (anamorph: Ustilaginoidea virens) recognized as one of the most economically important pathogens on rice in China that causes false smut disease. In our study, the V. virens cyp51 gene encoding the target protein for fungicide resistant to tebuconazole was cloned. Sequencing showed that fungal mutant strains resistant to tebuconazole harboured the T409C mutation in cyp51. A simple and rapid allele-specific PCR assay was developed to detect the T409C mutation. Among the isolates tested, a unique 391-bp fragment was amplified from resistant mutant strains with primer pair Uv137F1/Uv137DR, whereas no product was amplified from all sensitive isolates. Our study demonstrated that this allele-specific PCR assay is a rapid, simple and reliable method for identification of V. virens mutants resistant to tebuconazole.

Identification of Colletotrichum brevisporum causing anthracnose on passion fruit

Abstract Passion fruit (Passiflora edulis Sims.) has become an important commercial fruit with large-scale cultivation in China. A disease affecting the stems, fruits, leaves and tendrils was observed on passion fruit vines in Sanming, Fujian Province, China, in August 2015. The typical symptoms included lesions of oval to irregular shapes, brown to brownish black in colour, with sunken cavities. Acervuli and dark setae were observed within the lesions. The disease incidence varied from 25 to 60% in different fields. The causative pathogen was identified as Colletotrichum brevisporum on the basis of morphological characteristics and sequence analysis of the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta-tubulin 2 (Tub2) and actin (ACT) genes. Pathogenicity was confirmed by fulfilling Koch’s postulates on plants and detached fruit. To our knowledge, this is the first report of anthracnose disease on passion fruit caused by C. brevisporum worldwide.