Mao W, Lumsden R D, Lewis J A, Hebbar P K
Biocontrol of Plant Diseases Laboratory, USDA-ARS, Beltsville, MD 20705.
Plant Dis. 1998 Mar;82(3):294-299. doi: 10.1094/PDIS.1998.82.3.294.
Bioassays were conducted in a greenhouse at 18°C to determine the effectiveness of a seed treatment used in combination with biocontrol agents for the reduction of corn damping-off caused by species of Pythium and Fusarium. Corn seeds were infiltrated with tap water, drained, air-dried, and then coated with biomass of an antagonistic fungus, Gliocladium virens isolate Gl-3, or an antagonistic bacterium, Burkholderia cepacia isolates Bc-B or Bc-1, or a combination of Gl-3 with each of the bacterial isolates. A nonsterile field soil was infested with a combination of pathogens: Pythium ultimum, P. arrhenomanes, and Fusarium graminearum at 2 inoculum rates (1× and 4×). Pre-infiltration enhanced (P ≤ 0.05) disease control with most treatments at both inoculum rates. Treatments with biocontrol agents alone or in combination, as well as the fungicide captan, effectively reduced the disease at a pathogen inoculum rate of 1×, resulting in greater (P ≤ 0.05) seedling stands, plant height, and fresh weight, and lower (P ≤ 0.05) root rot severity compared with untreated seeds in infested soil. At a pathogen inoculum rate of 4×, stands were lower (P ≤ 0.01) and root-rot severity was higher (P ≤ 0.01) compared to those at 1× for all treatments. Nevertheless, coating seeds with all biocontrol agents (alone or in combination), except with Bc-1 alone, reduced disease (P ≤ 0.05) compared to untreated seeds in infested soil. At both inoculum rates of 1× and 4×, coating seeds with Gl-3 + Bc-B was more effective (P ≤ 0.05) in disease control than any other treatment, resulting in stands, growth rate (plant height and fresh weight), and root rot severity similar to plants from untreated seeds in noninfested soil. In addition, when the exudate from a 2-h infiltration of corn seed was added to the seeds during seed coating, seedling stand was often lower and root rot severity was often higher than those from infiltrated seeds (P ≤ 0.05). These results indicated that the infiltration process removed certain exudates, including nutrients and/or stimulants (not detected in this study) that might be utilized by pathogens to initiate seed infection. A thin-layer chromatography (TLC) profile of the exudates showed the presence of eight amino acids and three major carbohydrates.
在18°C的温室中进行了生物测定，以确定与生物防治剂联合使用的种子处理方法对减少由腐霉菌和镰刀菌引起的玉米猝倒病的有效性。玉米种子用自来水浸润、沥干、风干，然后用拮抗真菌绿粘帚霉Gl-3菌株的生物质、拮抗细菌洋葱伯克霍尔德氏菌Bc-B或Bc-1菌株的生物质，或Gl-3与每种细菌菌株的组合进行包衣。一种未灭菌的田间土壤用病原体组合进行侵染：终极腐霉、瓜果腐霉和禾谷镰刀菌，采用两种接种量（1倍和4倍）。预浸润提高了（P≤0.05）两种接种量下大多数处理的病害防治效果。单独或组合使用生物防治剂以及使用杀菌剂克菌丹的处理，在病原体接种量为1倍时有效地降低了病害，与未处理的侵染土壤中的种子相比，导致更高（P≤0.05）的幼苗株数、株高和鲜重，以及更低（P≤0.05）的根腐病严重程度。在病原体接种量为4倍时，与1倍接种量相比，所有处理的株数更低（P≤0.01），根腐病严重程度更高（P≤0.01）。然而，与未处理的侵染土壤中的种子相比，用所有生物防治剂（单独或组合）包衣种子，除了单独使用Bc-1外，都降低了病害（P≤0.05）。在1倍和4倍接种量下，用Gl-3+Bc-B包衣种子在病害防治方面比任何其他处理更有效（P≤0.05），导致株数、生长速率（株高和鲜重）和根腐病严重程度与未侵染土壤中未处理种子的植株相似。此外，当在种子包衣期间将玉米种子浸润2小时后的渗出液添加到种子中时，幼苗株数通常更低，根腐病严重程度通常高于浸润种子（P≤0.05）。这些结果表明，浸润过程去除了某些渗出物，包括营养物质和/或刺激物（本研究中未检测到），病原体可能利用这些物质引发种子感染。渗出液的薄层色谱（TLC）图谱显示存在8种氨基酸和3种主要碳水化合物。
