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Bacillus thuringiensis (Bt) represents one of the most economical biopesticides to date. It produces toxins with insecticidal activity against many agricultural pests, including members of the genus Spodoptera. However, Bt tolerance leads to inefficiency in biological control. To overcome this problem, discovering the hidden cause(s) for the evolution of insect tolerance against Bt is of great importance. We hypothesized that changes in the gut microbiota due to the frequent application of Bt is one of those hidden causes. To investigate this hypothesis, we studied the effect of Bt Cry1c application on the Spodoptera littoralis larval gut microbiota in both Bt-susceptible and Bt-tolerant populations. The results revealed changes in the diversity and abundance of gut bacterial composition between the susceptible and tolerant populations. A high abundance of Enterococcaceae was detected in the tolerant population. Interestingly, Cry1c tolerance eliminates the bacterial genera Klebsiella and Serratia from the larval midgut. These changes may confirm the mechanism developed by Spodoptera larvae to counteract Bt Cry1c toxicity. Understanding the B. thuringiensis–gut microbiota interaction may help in improving biocontrol strategies against agricultural pests to overcome the evolution of tolerance. [ABSTRACT FROM AUTHOR]

Genetic diversity of cultivated soybean {Glycine max (L.) Merrill} 2n = 40 is very narrow, although includes diversity for many obvious morphological traits. A field experiment was conducted to study characterize of fifteen soybean genotypes on agro-morphological trait basis and to identify genetic diversity using SDS-PAGE, with resistance to defoliating insects, at Sakha Agricultural Research Station, Kafr ElShiekh, Egypt during 2017 and 2018 seasons,. Morphological description was performed with 10 qualitative and 7 quantitative traits and screening for defoliation by cotton leaf worm in the open field. The results exhibited significant differences among the tested fifteen genotypes for all studied characters. Defoliation of test plants by the cotton leaf worm, in the field screenings system showed that genotypes H14 L8, H1 L10S, H1 L10 and H10 L10 recorded the highest rating values of insect resistant to cotton leaf worm with defoliation rating (0.0 – 0.2), whereas, soybean genotype H5 L21 showed the highest insect susceptible and had defoliation rating (3.8) indicating heavy insect feeding, over both seasons. Genotypes H11 L145 and H14L8 recorded the highest values of seed yield/fad., this attributed to the considerable increase in their number of branches/plant, number of pods/plant, and 100-seed weight, in both seasons. This indicates that such genotypes are the promising ones. The protein identification indicated that the pattern was uniform where each genotype was not affected by year or location. The soybean genotypes were different in their banding pattern and each one is characterized by certain proteins with different molecular weight. Cluster analysis based on qualitative morphological characters showed clear separation of genotypes on the basis of their plant growth habit. [ABSTRACT FROM AUTHOR]

Abstract: The relationship between susceptibility of different peach cultivars (cvs) to the Mediterranean fruit fly (medfly), Ceratitis capitata, and the volatile composition of ripe fruit of each cv has been investigated, since understanding the fruit-insect interaction mechanism is crucial for developing control strategies for such a pest. Volatile compounds were analyzed by SPME–GC–MS in three cvs highly susceptible to medfly attack (Fair Time, Flaminia, Sicilia Piatta), and in two less susceptible cvs (Percoca Romagnola 7 and Doctor Davis). Among the volatile compounds detected, 88 could be identified. The main differences found in the volatile composition of the cvs, concerned the relative abundance of esters. The least susceptible cvs, above all Percoca Romagnola 7, contained the higher amounts of hexenyl, hexyl, 3-methylbutyl, butyl and 2-methylpropyl esters; among these, some C6 derivatives detected, such as (Z)-3-hexenyl acetate, are known to act as priming agents, enhancing plant defence response to insects. Instead, a lower relative content of methyl esters, such as methyl hexanoate and methyl octanoate, known to act as medfly pheromone and attractant respectively, was found in the least susceptible cvs. [Copyright &y& Elsevier]