Texas A&M AgriLife Research Center, Beaumont, TX 77713, U.S.A.
Regional Agricultural Research Station, Maruteru, Acharya N. G. Ranga Agricultural University, Andhra Pradesh 534 122, India.
Plant Dis. 2021 Apr;105(4):1034-1041. doi: 10.1094/PDIS-07-20-1596-RE. Epub 2021 Mar 3.
Farmers rely heavily on the use of strobilurin fungicides to manage sheath blight (ShB) caused by AG1-IA, the most important disease in rice in the southern United States. Greenhouse and field studies were conducted to evaluate the potential use of plant growth-promoting rhizobacteria (PGPRs) in combination with a reduced rate of azoxystrobin application as a strategy to improve the current fungicide-reliant management. Of the nine antagonistic PGPR strains screened in the greenhouse, strain MBI600 provided the most significant and consistent suppression of ShB. Efficacy of strain MBI600 was further evaluated at the concentrations of 0, 10, 10, 10, and 10 CFU/ml alone or in combinations with 0, 17, 33, 50, 67, 83, and 100% of the recommended application rate (0.16 kg a.i./ha) of azoxystrobin. Strain MBI600 applied at 10,10, and 10 CFU/ml alone was effective in reducing ShB severity. Combinations of this strain at these rates with ≥33% of the recommended application rate of azoxystrobin further reduced ShB severity. A dose-response model defining the relationships between strain MBI600, azoxystrobin, and ShB severity was established. Estimates of the effective concentrations (EC and EC) of strain MBI600 when applied in combination with 50% of the recommended application rate of azoxystrobin were 10 and 10 CFU/ml, respectively. A field trial was conducted over 4 years to verify the efficacy of their combinations. Strain MBI600 alone, when applied at 10 CFU/ml at the boot stage, reduced ShB severity but did not significantly increase grain yields each year. Combination of strain MBI600 with azoxystrobin at half of the recommended application rate improved efficacy of strain MBI600, reducing ShB severity to a level comparable to that of azoxystrobin applied at the full rate in all 4 years. The combined treatment also increased grain yield by 14 to 19%, comparable to the fungicide applied at the full rate in 3 of 4 years. Combined use of PGPR strain MBI600 with a reduced rate of azoxystrobin application can be a viable management option for control of ShB while allowing producers to use less fungicide on rice.
农民严重依赖使用苯并咪唑类杀菌剂来防治稻瘟病（ShB），这是美国南部最重要的水稻病害。本研究通过温室和田间试验评估了将植物促生菌（PGPR）与减少肟菌酯施用量相结合作为一种改善当前依赖杀菌剂管理的策略的潜力。在温室中筛选的 9 种拮抗菌株中，MBI600 菌株对 ShB 的抑制作用最为显著和一致。进一步评估了 MBI600 菌株在单独使用或与推荐施用量（0.16 kg a.i./ha）的 0、17、33、50、67、83 和 100%肟菌酯组合使用时，在 0、10、10、10 和 10 CFU/ml 浓度下的功效。MBI600 菌株单独以 10、10 和 10 CFU/ml 的浓度使用时可有效降低 ShB 严重度。这些浓度的菌株与肟菌酯推荐施用量的≥33%组合使用进一步降低了 ShB 严重度。建立了定义 MBI600 菌株、肟菌酯和 ShB 严重度之间关系的剂量反应模型。当与肟菌酯推荐施用量的 50%组合使用时，MBI600 菌株的有效浓度（EC 和 EC）估计值分别为 10 和 10 CFU/ml。进行了为期 4 年的田间试验以验证其组合的功效。MBI600 菌株单独使用时，在 boot 期以 10 CFU/ml 的浓度使用可降低 ShB 严重度，但每年均未显著增加粒产量。MBI600 菌株与肟菌酯以推荐施用量的一半组合使用可提高 MBI600 菌株的功效，使 ShB 严重度降低至与推荐施用量下的肟菌酯相当的水平，在所有 4 年中均如此。联合处理还使粒产量增加了 14%至 19%，与 4 年中有 3 年中推荐施用量下的杀菌剂相当。PGPR 菌株 MBI600 与减少肟菌酯施用量联合使用可以作为控制 ShB 的可行管理选项，同时允许生产者在水稻上使用更少的杀菌剂。
