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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Root exudates of banana resistant variety ('Nantianhuang') and susceptible variety ('Guijiao No. 6') to Fusarium wilt were collected in vitro by bathing root system to examine the biological effects of root exudates from banana varieties on Fusaiurm oxysporum f. sp. cubense and Bacillus subtilis . We explored the effects of root exudates of different banana varieties on the abundance of soil microorganisms and the growth of F. oxysporum f. sp. cubense and B. subtilis . The results showed that root exudates from resistant variety could significantly reduce the abundance of soil fungi and inhibit the spore germination of F. oxysporum f. sp. cubense . Root exudates from susceptible variety could significantly stimulate mycelia growth and spores germination, whereas root exudates from the tested banana varieties could significantly increase the growth and biofilm formation of B. subtilis . By dealing with the root exudates of resistant and susceptible varieties, the growth rate of mycelia were 11.28 and 12.28 mm·d -1 , and the germination rate of spores were 34.6% and 79.5%, respectively. After culturing for 12 h, the growth rates of B. subtilis (OD 600 ) were 1.27 and 1.14, and the biofilm formation (OD 570 ) were 1.11 and 1.30 after static culturing 72 h, respectively. There were significant differences between the values of resistant and susceptible varieties. The colonization amount of B. subtilis in the rhizosphere of susceptible variety was significantly higher than that of resistant variety. The contents of free amino acids and organic acid in root exudates of the resistant variety were higher than that of susceptible variety. The content ratio of acetic acid and proline in the root exudates of resistant variety were 3.7 times and 2.4 times of that of susceptible variety. In conclusion, root exudates of banana resistant variety could inhibit the growth of F. oxysporum f. sp. cubense. Root exudates from susceptible variety could promote the growth of F. oxysporum f. sp. cubense ,while that from the tested banana varieties could all significantly enhance growth, biofilm formation and colonization ability of B. subtilis .