Inactivation of a nuclear polyhedrosis virus on cotton by the substances produced by the cotton leaf surface glands

Abstract

Loss of viability of a nuclear polyhedrosis virus (NPV) of Spodoptera littoralis was shown to occur on cotton leaves but not on cabbage leaves or on semi-synthetic insect diet. The inactivation was rapid, occurred in the dark and required contact between the cotton leaf surface and the polyhedral inclusion bodies (PIBs). It was shown that the products of the cotton leaf glands, which exude a crystalline material onto the leaf surface, could account for the rapid inactivation observed. Inactivation did not involve loss of virus polyhedral inclusion bodies. The use of EDTA or a low pH buffer in the NPV suspension reduced the inactivation which suggested that the loss of activity was due to the presence of calcium and magnesium in the cotton gland exudate.

Horizontal and vertical transmission of wild-type and recombinant Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus

“…In our field experiment (Experiment #5), where we collected L5 larvae from fields treated by wild-type or recombinant HaSNPV variants, vertical transmission rates (12.6% for HaS-NPV-WT and 8.4% for HaSNPV-AaIT) were obviously lower than those observed when we dosed the L3 larvae in the laboratory (30.9% for HaSNPV-WT and 16.7% for HaSNPV-AaIT). This might be due to the lower Table 3 Virus-induced mortality among F1 progeny from paired bollworm adults with either both parents or 1 parent treated with HaSNPV-WT and HaSNPV-AaIT as L3 larvae in the laboratory (Experiment #4) activity of virus persisting in bollworms fed on cotton leaves than on artificial diet, because exudates and secondary chemicals secreted by cotton gland (Elleman and Entwistle, 1985) and free radicals mediated by peroxidase in cotton tissues (Hoover et al, 1998) diminish the virus activity and hence virus transmission. A similar phenomenon as seen for HaSNPV as above has been observed in the Spodoptera exigua-tomato-SeMNPV system (Bianchi et al, 2001).…”

Engineered baculoviruses for pest control

“…Baculoviruses are inactivated by exposure to UV radiation.37,38 To a certain extent, persistence depends on the substrate on which the baculovirus is located, and its form in the environment.39 On cotton, OVs are inactivated more quickly than on any other plant ; estimates of the time period of inactivation are as short as 24 h. This is assumed to be due to the high alkalinity of the cotton leaf surface, which has a pH value of 9É0È9É9 due to the presence of calcium and magnesium salts in the cotton gland exudate.40,41 Loss of viability of Spodoptera littoralis NPV was shown to occur on cotton leaves but not on cabbage leaves or insect diet. 42 It was conÐrmed that the products of cotton gland leaf exudate were the causal factor. Viruses have been shown to retain activity for longer periods in soil than when exposed on foliage.…”

Reduced efficacy of Helicoverpa armigera nucleopolyhedrovirus (HearNPV) on chickpea (Cicer arietinum) and other legume crops, and the role of organic acid exudates on occlusion body inactivation

“…Short post-application persistence of baculoviruses on plants is frequently a consequence of them being inactivated by ultraviolet radiation in sunlight (Shapiro, 1995;Lacey et al, 2008;Grzywacz and Moore, 2017). With specific crops such as cotton and chickpea, the reduced efficacy or short persistence was reported to be because of phytochemicals present in or on crop leaf surfaces (Elleman and Entwistle, 1985;Rabindra et al, 1994;Cory and Hoover, 2006;Williams, 2017). Short post-application persistence of baculoviruses has been reported as a particular problem in chickpea (Cicer arietinum).…”