Magnaporthe oryzae conidia on basal wheat leaves as a potential source of wheat blast inoculum
Magnaporthe oryzae conidia on basal wheat leaves as a potential source of wheat blast inoculum
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DOI：
10.1111/ppa.12414
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发表时间：
2015-12-01
期刊：
影响因子：
2.7
通讯作者：
Valent, B.
中科院分区：
文献类型：
--
作者：
Cruz, C. D.;Kiyuna, J.;Valent, B.
由稻瘟病菌引起的小麦稻瘟病在南美几个国家的暴发年份给小麦造成了重大损失。尽管在一些小麦品种上有小麦稻瘟病的报道，但在受严重影响的商业田中，来自叶片的接种剂的重要性仍存在争议。一般认为，小麦穗瘟发生之前，通常不会发生叶部病变和/或叶片上的产孢量。本研究的目的是(I)确定小麦稻瘟病在基生叶上的发生情况，(Ii)估计在这些叶片上产生的分生孢子的数量，以及(Iii)确定当前的杀菌剂使用方法对小麦基生叶上孢子化病斑产生的接种物的影响。在三叶期接种表明，某些品种和菌株组合对老小麦叶片的危害比年轻展开叶片更严重。在最适培养条件下，米曲霉在少量小麦基叶上可产生数万至数十万个分生孢子。在最适产孢量条件下，高感品种每克干基叶平均产孢量为166.9万个。在温室和田间条件下，叶片上分生孢子的产生与穗的出苗一致。当在自然流行条件下进行田间研究时，叶面喷洒杀菌剂与不喷洒对照相比，基叶上的稻瘟病菌分生孢子数量减少了62-77%。如果基生叶上的分生孢子有助于小麦穗瘟的发育，那么及早使用叶面杀菌剂可能会减少接种量。
Wheat blast caused by Magnaporthe oryzae Triticum causes significant losses on wheat during outbreak years in several South American countries. Despite reports of wheat blast leaf lesions on some wheat cultivars, the importance of inoculum originating from leaves in severely affected commercial fields is disputed. It is generally considered that leaf lesions and/or sporulation on leaves do not usually appear before the occurrence of spike blast in wheat. The purpose of this study was to (i) determine the occurrence of wheat blast on basal leaves, (ii) estimate the number of conidia produced on these leaves, and (iii) determine the impact of current fungicide application practices on inoculum produced from sporulating lesions on basal wheat leaves. Inoculations at the three-leaf stage showed that certain cultivar and isolate combinations caused more disease on old wheat leaves than young expanding leaves. Under optimum conditions, M. oryzae had the potential to produce tens to hundreds of thousands of conidia on small amounts of wheat basal leaves. A mean of 1 669 000 conidia were produced on 1 g dry basal leaves of a highly susceptible cultivar under optimum conditions for sporulation. Conidia production on leaves coincided with spike emergence under both greenhouse and field conditions. When field studies were conducted under natural epidemic conditions, foliar fungicide applications reduced the amount of M. oryzae conidia on basal leaves by 62-77% compared to non-sprayed controls. An earlier application of foliar fungicides might reduce inoculum if conidia from basal leaves contribute to wheat spike blast development.