Filters
Bacteria associated with the cereal leaf beetle act as the insect’s allies in adapting to protease inhibitors, but impair its development in laboratory condition
Abstract Oulema melanopus [L.] (cereal leaf beetle, CLB) is one of the most serious cereal pests. Plant protease inhibitors (PIs) are known for their insecticidal properties. The role of CLB-associated bacteria in insect adaptation to PIs is not yet known. We investigated the role of CLB-associated bacteria in adaptation to PIs, and whether the reduction of bacteria will affect the CLB development. We found a decrease in proteases activity in insects with a diminished bacterial community compared to those with an intact bacterial community. Thus, the study showed that the CLB-associated bacteria participate in the adaptation of CLB larvae to PIs. On the other hand, regardless of the type of PI used, ultimately a higher survival rates were recorded for larvae with a reduced bacterial community compared to insects with a natural microbiome in laboratory conditions. In such conditions, higher larval survival rates and a higher percentage of larvae reaching the pupal and imago stages were recorded in insects whose bacterial community was reduced. Since the CLB bacterial microbiome showed a negative impact on the development of the insect’s host and its survival in response to PIs in laboratory conditions, it can be concluded that CLB-associated bacteria can be an ally of its insect host, but also an adversary when conditions are not optimal for symbiosis.
Insect Gut Bacteria Promoting the Growth of Tomato Plants (Solanum lycopersicum L.)
We investigated gut bacteria from three insect species for the presence of plant growth properties (PGP). Out of 146 bacterial strains obtained from 20 adult specimens of Scolytidae sp., 50 specimens of Oulema melanopus, and 150 specimens of Diabrotica virgifera, we selected 11 strains displaying the following: PGP, phosphate solubility, production of cellulase, siderophore, lipase, protease, and hydrogen cyanide. The strains were tested for growth promotion ability on tomato (Lycopersicon esculentum) plants. Each strain was tested individually, and all strains were tested together as a bacterial consortium. Tomato fruit yield was compared with the negative control. The plants treated with bacterial consortium showed a significant increase in fruit yield, in both number of fruits (+41%) and weight of fruits (+44%). The second highest yield was obtained for treatment with Serratia liquefaciens Dv032 strain, where the number and weight of yielded fruits increased by 35% and 30%, respectively. All selected 11 strains were obtained from Western Corn Rootworm (WCR), Diabrotica virgifera. The consortium comprised: Ewingella americana, Lactococcus garvieae, L. lactis, Pseudomonas putida, Serratia liquefaciens, and S. plymuthica. To our knowledge, this is the first successful application of D. virgifera gut bacteria for tomato plant growth stimulation that has been described.