Rice blast is the major disease that threatens rice production in Fujian. Investigation of the variation of avrirulence genes (AVRs) in the field population of rice blast fungus could facilitate the release and rotation of the resistance varieties, and subsequently prevent the burst of rice blast disease caused by the loss of rice blast resistance. We firstly investigated the pathogenicity and genetic variation of a field population consisting of 113 Magnaporthe oryzae monoconidial strains isolated from three different major rice planting regions in Fujian province. For pathogenicity and virulence assays of the strains, spray inoculation was performed using 24 monogenic lines carrying 24 different major blast resistance genes. The results showed that the pathogenicity frequency of strains isolated from Jianyang, Ninghua and Shanghang were ranged from 12.50% to 95.83%, 29.17% to 100% and 4.55% to 86.36%, respectively. All strains showed strong pathogenicity toward the monogenic lines carrying Piks、Pib、Pi3 and Pi12, while strains isolated from Jianyang and Ninghua also showed strong pathogenicigy toward the monogenic lines carrying other 12 resistance genes, including Pia, Pii, Piz, Pita, Pit, Pish, Pi5, Pi7, Pi19, Pi20, Pita2 and Pi11. To investigate the genetic variation of AVR genes in the above strains, we performed genotyping of 8 AVR genes: Avr-Pia, Avr-Pib, Avr-Pik, Avr-Piz-t, Avr-Pii, Avr-Pi9, Avr-Pi54, and Avr-Co39. As expected, Avr-Co39 was absent in all the strains, indicating that all the strains collected in the three regions of Fujian province did not carry the AVR gene. The frequency of Avr-Pib in the 113 strains was also very low (37.17%). However, the ratio was much higher than that of the functional Avr-Pib (4.32%), indicating some loss-of-function mutations of Avr-Pib in the Fujian field population. We compared the sequence of selected AVR genes amplified from some field isolates to the reference sequences, and found variation in the promoter region of Avr-Pib, as well as Avr-Pik and Avr-Piz-t. Besides, we also found mutations in the coding region of Avr-Pik and Avr-Pita amplified from some of the Fujian field isolates. Our results suggested that rice cultivars carrying Pi1, Piz5, Pi9, Pik, Pikh and Pikm still could be used in Fujian Province.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |