Pyricularia Blast - a Threat to Wheat Cultivation
Pyricularia Blast - a Threat to Wheat Cultivation
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DOI：
10.17221/3267-cjgpb
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发表时间：
2011-01-01
影响因子：
0.9
通讯作者：
Cubilla, L. E.
中科院分区：
文献类型：
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作者：
Kohli, M. M.;Mehta, Y. R.;Cubilla, L. E.
由稻瘟病菌（Pyricularia grisea）引起的小麦稻瘟病已成为严重制约作物面积和产量增加的因素，特别是在南美洲南锥体地区的热带地区。该病于1985年在巴西巴拉那州首次发现，近年来已成为玻利维亚低洼的圣克鲁斯地区、巴拉圭南部和东南部以及巴西中部和南部的地方病。在阿根廷东北部的夏季种植小麦作物中也观察到严重感染。到目前为止，乌拉圭只出现了零星的感染，特别是在潮湿和温暖的年份。穗感染（经常与镰刀菌头枯病感染混淆）是该疾病最显著的症状，并且能够引起超过40%的产量损失。然而，在严重感染下，感病品种几乎完全丧失产量。小麦稻瘟病主要是穗部病害，但在一定条件下也可对植株的地上部分造成损害。根据脊柱上的感染点，疾病可以部分或全部杀死穗。穗的受感染部分变干而不产生任何可以与健康部分明显区分的谷物。虽然文献中已报道了真菌的毒力多样性，并正在进一步探索中，但宿主物种的遗传抗性更难确定。早些时候，巴西品种，如BH 1146，CNT 8，几个IAC和OCEPAR选择被认为是表现出不同水平的田间抗性，但这在人工接种研究中没有得到证实。然而，其他品种，如BR 18，IPR 85，CD 113，多年来在许多地方表现出中等水平的抗性。最近，几个品种和先进的线来自CIMMYT线，米兰，已被观察到携带高水平的抗稻瘟病整个流行地区。然而，到目前为止，由于病原体的极端变异，这种抗性的遗传基础还不是很清楚。在温室控制条件下对少数分离物表现出完全抗性的品种，在商业化栽培中可能表现出或可能不表现出田间抗性。由于在玻利维亚、巴西和巴拉圭的米兰抗性小麦栽培品种的面积增加，迫切需要将其与其他抗性来源结合，以防止在真菌中选择毒性致病型。除遗传抗性外，避免提早播种和化学防治可减轻病情。在某些情况下，三唑类与嗜球果伞素组合的杀菌剂可以有效地控制抽穗期的病害。即使在小麦稻瘟病综合防治的所有组成部分尚未到位的情况下，它也被视为减少该地区生产损失的一项重要战略。鉴于今后小麦稻瘟病可能对世界小麦种植区构成的威胁，开展更多的研究工作是迫切和必要的。
Wheat blast disease caused by Pyricularia grisea (telemorph Magnaporthe grisea) has become a serious restriction on increasing the area and production of the crop, especially in the tropical parts of the Southern Cone Region of South America. First identified in 1985 in the State of Parana in Brazil, it has become an endemic disease in the low lying Santa Cruz region of Bolivia, south and south-eastern Paraguay, and central and southern Brazil in recent years. Severe infections have also been observed in the summer planted wheat crop in north-eastern Argentina. So far, only sporadic infections have been seen in Uruguay, especially during the wet and warm years. Spike infection (often confused with Fusarium head blight infection) is the most notable symptom of the disease and capable of causing over 40% production losses. However, under severe infection, the loss of production can be almost complete in susceptible varieties. Wheat blast is mainly a spike disease but can also produce lesions on all the above ground parts of the plant under certain conditions. Depending upon the point of the infection on the rachis, the disease can kill the spike partially or fully. The infected portion of the spike dries out without producing any grain which can be visibly distinguished from the healthy portion. While virulence diversity in the fungus has been reported in the literature and is under further exploration, genetic resistance in the host species has been more difficult to identify. Earlier, Brazilian cultivars such as BH 1146, CNT 8, several IAC and OCEPAR selections were credited as demonstrating different levels of field resistance, but this was not confirmed under artificial inoculation studies. However, other cultivars such as BR18, IPR 85, CD 113, have shown moderate levels of resistance over the years in many locations. Recently, several cultivars and advanced lines derived from the CIMMYT line, Milan, have been observed to carry a high level of resistance to blast disease throughout the endemic region. However, to date, the genetic basis of this resistance is not very clear due to extreme variation in the pathogen. Cultivars showing complete resistance against a few isolates under controlled conditions in the glasshouse, may or may not show field resistance in commercial cultivation. Due to an increase of the area under Milan based resistant wheat cultivars in Bolivia, Brazil and Paraguay, it needs to be combined with other sources of resistance urgently to prevent the selection of a virulent pathotype in the fungus. Besides genetic resistance, avoidance of early dates of seeding and chemical control can reduce the disease severity. Fungicides combining triazols with strobilurins can, under some situations, be effective in disease control at the heading stage. Even when all components of integrated disease management of wheat blast are not in place yet, it is seen as an essential strategy to reduce production losses in this region. Given the threat that the blast disease may pose to world wheat growing areas in the future, more research efforts are deemed urgent and necessary.