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Identification of Races and Mating Types of C ochliobolus carbonum from Corn in the Y unnan P rovince in C hina

2013; Wiley; Volume: 162; Issue: 5 Linguagem: Inglês

10.1111/jph.12194

1439-0434

Canhua Lu, Yixin Wu, Honhing Ho, Zichao Mao, Yueqiu He,

Plant and Fungal Interactions Research

Abstract Northern corn leaf spot, a foliar disease caused by C ochliobolus carbonum , has become prevalent in southwestern C hina, especially in the Y unnan P rovince. Races and mating types were identified for 169 isolates collected from 13 prefectures of Y unnan by artificial inoculation using six hybrid corns as differential hosts and by crossing with three standard mating strains: CC 092 ( MAT1‐2 ), CC 120 ( MAT1‐1 ) and CC 026 ( MAT1‐1 ). Results showed the existence of three races: CCR 1 (one isolate), CCR 2 (43 isolates) and CCR 3 (125 isolates). Most isolates were moderately or weakly virulent with only five being highly virulent. CCR 3 was widely distributed and significantly more virulent than CCR 2 that coexisted with CCR 3 in many locations. On S ach's nutrient agar, 20.71% of the Y unnan isolates self‐mated, forming sterile perithecia. Fully developed perithecia could be formed between isolates of different geographic origins, but only 15.98% strains mated successfully with CC 092 and 5.33% formed mature perithecia with 4–6 ascospores per asus. Similar results were obtained in crossing with CC 026 or CC 120. Mating could also occur between CCR 3 and CCR 2. Both mating types were found in Y unnan with 84 MAT1‐1 strains (one CCR 1, 10 CCR 2 and 73 CCR 3) and 85 MAT1‐2 strains (33 CCR 2 and 52 CCR 3) and they coexisted in most areas. To identify the mating type rapidly, three specific primers were successfully developed and employed to amplify the mating‐type genes, with stable patterns of 1627 and 876 bp fragments obtained from MAT1‐1 and MAT1‐2 isolates, respectively. The ratio between MAT1‐1 and MAT1‐2 was 1 : 1, indicating that the mating‐type genes segregated randomly in the field naturally.