Leonard K J, Martinelli J A
U.S. Department of Agriculture, Agricultural Research Service, Cereal Disease Laboratory, University of Minnesota, St. Paul 55108.
Faculade de Agronomia, UFRGS, C. P. 776, 90012-970 Porto Alegre, RS, Brazil.
Plant Dis. 2005 Aug;89(8):802-808. doi: 10.1094/PD-89-0802.
Race-specific resistance to crown rust, the most important disease of oat (Avena sativa) in Bra-zil, often fails within a few years of use in Brazilian cultivars. Virulence of 144 isolates of Puccinia coronata from cultivated oat in Brazil in 1997 to 1999 and 36 isolates from Uruguay in 1994-95 and 1998 was tested on a set of 27 oat crown rust differentials lines, each with a different Pc gene for race-specific resistance. Frequencies of virulence and mean virulence complexity were compared among these five collections from Brazil and Uruguay as well as with mean virulence complexity for a collection of 17 isolates from cultivated oat in western Siberia in Russia. Virulence-avirulence for each of the 27 Pc genes was polymorphic in both Brazil and Uruguay. Virulence frequencies were similar for collections from Brazil in 1998 and 1999 and for the collection from Uruguay from 1998, but there were large differences between the 1997 collection and the 1998 and 1999 collections from Brazil. Mean virulence complexity in both Brazil and Uruguay was greater than reported in the United States and much greater than in the Russian collection of P. coronata. A large number of races of P. coronata were found, with no more than five isolates of any race found in a single year in Brazil or Uruguay. The high virulence complexity and great diversity of virulence polymorphisms in Brazil and Uruguay make it unlikely that race-specific resistance can be effective there even though the South American populations of P. coronata are apparently entirely asexual.
对冠锈病的品种特异性抗性是巴西燕麦( Avena sativa )最重要的病害,在巴西品种中使用几年后常常失效。1997年至1999年对巴西种植燕麦的144个冠柄锈菌分离株以及1994 - 1995年和1998年来自乌拉圭的36个分离株的毒性,在一组27个燕麦冠锈病鉴别系上进行了测试,每个鉴别系都具有不同的用于品种特异性抗性的Pc基因。比较了来自巴西和乌拉圭的这五个菌系集合之间的毒性频率和平均毒性复杂性,以及与俄罗斯西西伯利亚种植燕麦的17个分离株集合的平均毒性复杂性。27个Pc基因中每个基因的毒性 - 无毒性状在巴西和乌拉圭都是多态的。1998年和1999年来自巴西的菌系集合以及1998年来自乌拉圭的菌系集合的毒性频率相似,但1997年的集合与1998年和1999年来自巴西的集合之间存在很大差异。巴西和乌拉圭的平均毒性复杂性均高于美国报道的水平,并远高于俄罗斯冠柄锈菌的集合。发现了大量的冠柄锈菌小种,在巴西或乌拉圭的任何一年中,单个小种的分离株不超过五个。巴西和乌拉圭的高毒性复杂性和毒性多态性的高度多样性使得即使南美冠柄锈菌群体显然完全是无性的,品种特异性抗性在那里也不太可能有效。