Influence of Endophytic Colonization of Tomato Plants with Two Local Isolates of the Entomopathogenic Fungus Beauveria bassiana by Using Three Different Inoculation Techniques, and Their Effect in Controlling Tomato Leaf Miner Larvae, Tuta absoluta and on plant growth

Abstract

This study was conducted to evaluate the effect of the endophytic colonization of tomato plants with two local isolates of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin, b8 isolate obtained from the pupa of the palm weevil, and b10 isolate, obtained from the soil of a citrus orchard in Latakia Governorate, Syria, and their effect on the growth of tomato plants and in controlling the tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera Gelechiidae) using three different inoculation techniques: foliar spray, stem injection and root dipping. The effects were assessed 15, 30, and 45 days after inoculation. The results obtained showed that the ability of the two isolates (b8 and b10) of the fungus B. bassiana to colonize internally the leaves, stems and roots of tomato plants by using the three inoculation methods. However, the colonization rate (%) of tomato tissues differed according to the method of inoculation, the period after inoculation, and the isolate type. The highest colonization rate recorded by foliar spray technique and reached 100% 15 days after inoculation with the b8 isolate, and 85.19% at 30 days after inoculation with the b10 isolate by the stem injection technique, and 92.59% at 30 days after inoculation with the same isolate by root dipping technique. Leaves were the most colonized part of the plant at all evaluation dates (15, 30 and 45 days after inoculation), and by the three techniques. The inoculation of tomato plants with b8 and b10 isolates of the fungus B. bassiana led to an increase in plant height as well as an increase in wet and dry weight compared with the control plants. The results showed a significant increase in the mortality rates of tomato leaf miner larvae as a result of their feeding on leaves inoculated with the two isolates of the fungus B. bassiana (b8 and b10), and by the three inoculation techniques. The recorded mortality rate of b8 isolate infection was 96.67% and 90% of b10 isolate infection, eight days after inoculation by the foliar spray technique. However, the recorded mortality rate by stem injection and root dipping techniques were relatively lower, 70 and 70% for b8 isolate and 56.67 and 53.33% for b10 isolate, by the two techniques, respectively.

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Keywords:

Endophytic colonization, Tuta absoluta, entomopathogenic fungi, Beauveria bassiana