Morphological, molecular, and pathogenicity characteristics of the native isolates of Metarhizium anisopliae against the tomato leafminer, Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae) in Ethiopia

Abstract

The South American tomato leafminer, Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae), is a newly introduced and a major threat of tomato production in Ethiopia. Laboratory bioassay was conducted to evaluate locally isolated Metarhizium anisopliae (Metsch.) (Sorokin), against larvae of T. absoluta. Twenty-five Metarhizium isolates were isolated from different soil types, using the great wax moth, Galleria mellonella L. baiting method. From these, 13 isolates were prescreened by biological efficiency index model and tested against 2nd and 3rd larval instars of T. absoluta at the concentration of 107 spores ml−1. Sterile water plus Tween 80 (0.1% v/v) was used as a control. Greenhouse reared larvae of T. absoluta were used as experimental organisms. All tested Metarhizium formulations were pathogenic to T. absoluta in all conducted bioassays. Three isolates, AAUM78, AAUM39, and AAUM76, were the most effective and scored 88, 90, and 95% and 90, 93.3, and 95.7% mortality against 2nd and 3rd larval instars of T. absoluta, respectively. The lowest (48.5 and 50%) mortality rate was recorded by isolate AAUM30 against 2nd and 3rd larval instars, respectively, in 7 days post inoculation. However, all isolates showed significant statistical differences with F (24, 50) = 6.825, p < 0.001 and F (23, 15) = 3.97, p < 0.001 of mortality to 2nd and 3rd larval instars, respectively. Molecular analysis categorized these selected isolates under species of M. anisopliae and grouped into 2 different groups. AAUM78 and AAUM39 were recorded LT50 values of 3.93 and 3.5 days at the lowest (104 spore ml−1) concentration and LC50 values of 1.2 × 103 and 2.9 × 103 spore ml−1, respectively. Although AAUM78 and AAUM39 were virulent to the target pest, further field evaluation is required to determine their potential efficacy for T. absoluta control.

Occurrence of Entomopathogenic Fungi from Natural Ecosystems in Phetchabun, Thailand and Their Virulence Against Brown Planthopper

“…behaves as two phases of living: parasitic and saprophytic stages [49] and can be found abundantly in soil from various geographical locations [50,51]. However, differences in their prevalence and distribution are found among cultivated farmland soil, grazing land, and forest soil [52][53][54]. In this study, Metarhizium spp.…”

Isolation, molecular characterization, and virulence assays of entomopathogenic fungi of Oryctes rhinoceros larvae from Asahan origin

“…Conidia are cylindrical to slightly oval, hyaline, and one-celled (Figure 4). Conidiophores can reach a length of 75 μm, stacked -stacked and enclosed by apical conidia measuring 6-9.50 reams x 1.50-3.90 reams, branched, clustered to form a dense, loose mass [14]. Mycelium in Metarhizium has partitions, is colorless, and conidia grow upright.…”

Effects of some bioinsecticides on the tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae)

“…In another study, the application of B. bassiana isolate at a concentration of 2.5 × 10 7 spore lecanii isolates treated at a concentration of 10 7 spore ml −1 on the 1st, 2nd, and 3rd larval instars of T. absoluta were 0.28 × 10 5 -0.11 × 10 5 -3.25 × 10 5 , 0.45 × 10 5 -0.46 × 10 5 -5.47 × 10 5 , and 0.32 × 10 5 -0.27 × 10 5 -3.28 × 10 5 conidia ml −1 . In Ayele et al (2020), when AAUM78, AAUM39, and AAUM76 isolates of M. anisopliae were applied on the 2nd and 3rd larval instars of T. absoluta, mortality rates were 88, 90, and 95 and 90, 93.3, and 95.7%, respectively. However, it was reported that URPE-6 and URPE-19 isolates of M. anisopliae showed very high effects on eggs and larvae of T. absoluta (Pires et al 2010).…”