Biocontrol Potential of Endophytic Bacteria Against Cereal Cyst Nematode, Heterodera avenae

Abstract

The effects of five endophytic bacterial strains, namely Pantoea sp., Pseudomonas stutzeri, Klebsiella sp., Brevundimonas diminuta, and Bacillus cereus were tested as plant growth promoters and biocontrol agents against cereal cyst nematode Heterodera avenae under laboratory and greenhouse conditions. The main PGP-properties, namely the production of IAA, HCN and ammonia as well as the ability to solubilize-P were examined under in vitro conditions. Additionally, greenhouse experiment were performed in two seasons (2021/2022 and 2022/2023) at Ismailia Agricultural Research Station to evaluate the effectiveness of endophytic strains as a biocontrol agents against cereal cyst nematode. According to the laboratory experiment, all of the tested endophytic bacteria were apparently able to trigger PGP-properties. However, B. cereus followed by Ps. stutzeri and Brev. diminuta appears to be superior to the other endophytic strains in the production of IAA, HCN, and ammonia as well as the ability to solubilize phosphate. While, Klebsiella sp. strains displayed the lowest capacity in this concern. Results of greenhouse experiment revealed that all treatments induced a  ignificant (P≤0.05) decline in H. avenae population, compared to the control. A percentages reduction in number of H. avanae white female cysts, were observed in treated roots after 60 days of nematode inoculation with all strains compared with control treatment. Treatment B. cereus recorded (91.5 and 93%) and Ps. stutzeri (84.4, and 87%) in both seasons, respectively. However, an increased number of white female cyst development was observed in the control treatment in both tested seasons. The same results were observed in the reduction of the reproduction factor. Also, the results showed that all inoculation treatments significantly increased plant growth and yield parameters of wheat over control treatment. This trend was true in both growing seasons. Among bio-agents, the maximum increase in 100 grain weight 104% (2021/22), and 96% (2022/23) were recorded with B. cereus, followed by Ps. stutzeri 91% (2021/22), and 78% (2022/23). Almost a similar trend was observed for the root, and shoot dry weights and wheat yield characters. The data acquired demonstrated a considerable increase in shoot N, P, and K content at all bacterial inoculation treatments, along with comparable growth characteristics outcomes for wheat plants.