Abstract
BackgroundThe endophytic capacity of Beauveria bassiana Vuillemin isolates in 2 tomato varieties and their effects on damage and survival of the tomato fruit worm Helicoverpa armigera Hubner larvae were studied. The bioassays consisted of sowing seeds of 2 tomato cultivars soaked for 24 h in B. bassiana conidial suspension at the concentration of 1 × 107 and 1 × 109 conidia/ml for the isolates Bb 115 and Bb 11, respectively. Ten leaf, stem, and root segments were cut and incubated for assessing the endophytic growth of the fungus. Percentage of leaf consumption and pathogenicity of B. bassiana on H. armigera larvae were estimated.Main bodyThe fungus B. bassiana developed endophytically in the 2 tomato varieties and was detected in tomato leaf, stem, and root. However, higher colonization rates were observed in roots than in leaves and stems. The B. bassiana isolate Bb 115 had a greater negative effect on the mean survival times (MSTs) of H. armigera larvae and on leaf consumption for local and improved tomato varieties. In fact, the lowest MSTs were recorded at the concentration of 1 × 109conidia/ml for Bb 115 in 1.5 ± 0.2 days, i.e., 7 days less than the surviving larvae of the control group, which MSTs were 8.4 ± 0.9 days. Consumed leaf areas by larvae averaged (89.17 ± 10.33 mm2) at a fungal concentration of 1 × 109conidia/ml for Bb115. It was the best compared to that of untreated control (820.3 ± 92.77 mm2). The colonization rate of the different plant parts increased with conidia concentration in both tomatoes varieties.ConclusionThis study reported the effect of endophytic colonization of tomato by B. bassiana on the survival of H. armigera larvae and showed that the isolates Bb 115 and Bb 11 could be considered as useful microorganisms for the integrated control of H. armigera.
Highlights
Plant material The local tomato variety “Tounvi” and the improved variety “Padma” were used during the bioassays
Tomato producers are facing a significant pressure from insect pests, the damage caused by the tomato fruit worm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), the major threat to tomato crops throughout the growing season due to its direct damage to the fruits resulting in yield losses ranging from 20 to 60% (Herrero et al 2018)
Endophytic colonization of tomato plants by B. bassiana The endophytic colonization of the tomato organs placed onto Potato Dextrose Agar (PDA) showed a whitish color, characteristic of B. bassiana mycelium
Summary
Methods Plant material The local tomato variety “Tounvi” and the improved variety “Padma” were used during the bioassays. The larvae were placed in plastic containers (6.5 × 19.5 cm) and reared on an artificial diet under controlled conditions (70 ± 5% RH, 26 ± 2 °C, with a photoperiod of L: D 12:12) until pupation (Douro Kpindou et al 2012). The endophytic capacity of Beauveria bassiana Vuillemin isolates in 2 tomato varieties and their effects on damage and survival of the tomato fruit worm Helicoverpa armigera Hubner larvae were studied. Main body: The fungus B. bassiana developed endophytically in the 2 tomato varieties and was detected in tomato leaf, stem, and root. The B. bassiana isolate Bb 115 had a greater negative effect on the mean survival times (MSTs) of H. armigera larvae and on leaf consumption for local and improved tomato varieties. The fungus Beauveria bassiana (Ascomycota: Hypocreales) is one of the most widely used entomopathogens in the biological control of pests through the direct application of conidia suspension (Douro Kpindou et al 2012). Endophytic fungi are important because they produce secondary metabolites with a range of potential uses in the agricultural and the pharmaceutical industry (Selim et al 2012)
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