Influence of Lecanicillium attenuatum on the development and reproduction of the cotton aphid, Aphis gossypii

Abstract

The activity of entomopathogens on insect pests has been investigated for many species but the influence of entomopathogenic fungi on factors other than mortality relating to population increase has not been frequently studied. The influence of Lecanicillium attenuatum CS625 (=Verticillium lecanii CS625) on development and reproduction of cotton aphid (Aphis gossypii) was investigated. A conidia suspension of the isolate was applied onto first instar nymphs. Increased spore concentration did not significantly affect each nymphal stage, total nymphal period, pre-reproductive period and the age of first larviposition. A significant dose effect on reduction of life span, reproductive period and fecundity was observed in 1st and 3rd instars after spore application. When conidia were applied to 1st instars, life span was significantly reduced to 10.8 and 8.4 days at 1 Â 10 4 and 1 Â 10 8 conidia/ml, respectively from 12.2 days in the control. During the life span, total fecundity was 41 ± 7.3, 26 ± 0.8 and 22 ± 5.7 nymphs per female at 1 Â 10 4 , 1 Â 10 6 and 1 Â 10 8 conidia/ml, respectively compared with 51 ± 2.0 nymphs per untreated female. Reproduction period was also significantly shortened with increasing spore concentration. Application of spores to 3rd instars showed a similar trend. However, daily fecundity of individual aphids was not affected by spore dose. It was concluded that the isolate of L. attenuatum is able to affect populations of cotton aphid by reducing life span and total fecundity as well as by killing the aphids directly.

Efficient Photosensitized Splitting of Thymine Dimer by a Covalently Linked Tryptophan in Solvents of High Polarity

“…Remarkably high splitting efficiencies were observed in solvents of high polarity. Interestingly, this solvent effect contrasts strongly with the results [10,15,16] obtained previously with non-flavin-dimer systems, but is in agreement with the results [11,18] obtained with flavin-dimer systems. Furthermore, these results together with data from fluorescence quenching experiments and studies of the effect of pH on splitting of the dimer, some new insights into the intramolecular electron-transfer process in the tryptophan-dimer system were gained.…”

“…The back electron-transfer in low-polar media would become so exothermic as to lie in the Marcus inverted region, which would significantly reduce the rate of the transfer reaction. [10,15,16] The results seem to support previous findings that the photolyase may provide a hydrophobic environment for the substrate (dimer). [8,17] However, an inverse solvent dependence was observed in covalently linked flavin-dimer systems by Carell and coworkers.…”

“…In addition, under excitation with 280 nm light, Trp277, as a substrate binding site, can also directly repair CPD with a relatively high quantum yield (Φ = 0.56) by electron transfer. [8,9] Model systems appeared to be poorly efficient at repairing the lesion by intramolecular electron transfer, for example, Φ = 0.06-0.40 for indole-dimer systems [10] and 0.062-0.016 for flavin-dimer systems [11] in various polar solvents such as water and 1,4-dioxane. This can be explained by the fact that model systems cannot stabilize the chargeseparated species in which the electron is on the acceptor dimer before cleavage.…”

“…In the chromophore-dimer systems, the photosensitized cleavage of the dimer by the attached indole, [10] arylamine [15] or methoxybenzene [16] was strongly solvent-dependent with efficient splitting taking place in solvents of low polarity. This unusual solvent effect can be explained by the fact that fast and unproductive charge recombination by back electron-transfer within the charge-separated species is suppressed in solvents of low polarity.…”

Entomopatojen fungus, Lecanicillium lecanii (Sordariomycetes: Hypocreales)'nin bazı fitofag Hemiptera türlerine etkisi

“…Bu bildirişlerle çalışmamızda elde edilen sonuçlar benzerlik göstermektedir. ) A. gossypii'de ölümlere sebep olması yanı sıra, yaşam süresinde azalmaya sebep olarak da popülâsyonu etkileyebilmektedir (Kim, 2007).…”