Kastelein P, Köhl J, Gerlagh M, Goossen-van de Geijn H M
Plant Research International B.V., P.O. Box 16, 6700 AA Wageningen, The Netherlands.
Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet. 2002;67(2):257-67.
Since 1994 the importance of tan spot of wheat has increased in the wheat growing areas of the Netherlands. The purpose of the present study was to determine inoculum sources of this disease caused by Pyrenophora tritici-repentis. Both in 1999 and 2000, the incidence of tan spot was assessed in 40 commercial fields of winter wheat scattered over the main wheat growing areas of the Netherlands. Adjoining fields were checked for presence of stubble or crops with straw covers and the surrounding vegetation was searched for grasses with leaf spots. Straw and affected leaves of wheat and grasses were examined for P. tritici-repentis. In greenhouse experiments the pathogenicity of isolates from alternative hosts was compared with that of isolates from wheat. The possible development of P. tritici-repentis perithecia on straw of crops other than wheat was explored for barley, oat, rye grass and rape grown in fields nearby a tan spot affected wheat field. Furthermore, dispersal of tan spot was studied in a field trial in which winter wheat was sown leeward to stubble of above-mentioned severely tan spot affected wheat crop. During the surveys three cases were found of wheat crops adjoining fields with P. tritici-repentis infested stubble or straw covers. It was only after flowering that the first symptoms of tan spot appeared in the three commercial wheat crops. Couch grass (Elymus repens) was often found as host of P. tritici-repentis. In the surroundings of more then half of the wheat crops affected by tan spot this weed was also infected. Pyrenophora tritici-repentis isolates from couch grass were found to be as pathogenic to wheat as isolates from wheat to both wheat and couch grass. The observations on straw of barley, oat, rye grass, rape and wheat revealed P. tritici-repentis perithecia only on wheat straw. In the field trial with wheat sown leeward to P. tritici-repentis infested stubble, first symptoms of tan spot appeared on wheat during April and May when the release of ascospores was at a maximum. Disease severity gradually decreased with increasing distance from the side adjoining the stubble. The results of this study indicate that straw covers and stubble from tan spot diseased wheat crops and cough grass are inoculum sources of P. tritici-repentis.
自1994年以来，小麦条斑病在荷兰小麦种植区的重要性日益增加。本研究的目的是确定由小麦根腐离蠕孢引起的这种病害的接种源。在1999年和2000年，对分布在荷兰主要小麦种植区的40个冬小麦商业田块进行了条斑病发病率评估。检查相邻田块是否有残茬或有秸秆覆盖的作物，并在周围植被中寻找有叶斑的禾本科植物。对小麦和禾本科植物的秸秆及受影响叶片进行了小麦根腐离蠕孢检测。在温室试验中，比较了来自替代寄主的分离株与来自小麦的分离株的致病性。在一个条斑病发病小麦田附近种植的大麦、燕麦、黑麦草和油菜上，探索了小麦根腐离蠕孢在除小麦以外的作物秸秆上产生子囊壳的可能性。此外，在一项田间试验中研究了条斑病的传播情况，试验中将冬小麦播种在上述条斑病严重发病小麦作物残茬的下风向。在调查过程中，发现了3例小麦作物毗邻受小麦根腐离蠕孢侵染的残茬或秸秆覆盖物的田块。这3个商业小麦作物都是在开花后才出现条斑病的最初症状。狗尾草（偃麦草）常被发现是小麦根腐离蠕孢的寄主。在受条斑病影响的小麦作物中，超过一半的作物周围的这种杂草也受到了感染。从狗尾草中分离出的小麦根腐离蠕孢分离株对小麦的致病性与从小麦中分离出的分离株对小麦和狗尾草的致病性相同。对大麦、燕麦、黑麦草、油菜和小麦秸秆的观察表明，仅在小麦秸秆上发现了小麦根腐离蠕孢子囊壳。在将小麦播种在受小麦根腐离蠕孢侵染的残茬下风向的田间试验中，条斑病的最初症状于4月和5月出现在小麦上，此时子囊孢子的释放量最大。病害严重程度随着与毗邻残茬一侧距离的增加而逐渐降低。本研究结果表明，条斑病发病小麦作物的秸秆覆盖物和残茬以及狗尾草是小麦根腐离蠕孢的接种源。
