Extracellular compounds produced by fungi associated with Botryosphaeria dieback induce differential defence gene expression patterns and necrosis in Vitis vinifera cv. Chardonnay cells.

Three major grapevine trunk diseases, esca, botryosphaeria dieback and eutypa dieback, pose important economic problems for vineyards worldwide, and currently, no efficient treatment is available to control these diseases. The different fungi associated with grapevine trunk diseases can be isolated in the necrotic wood, but not in the symptomatic leaves. Other factors seem to be responsible for the foliar symptoms and may represent the link between wood and foliar symptoms. One hypothesis is that the extracellular compounds produced by the fungi associated with grapevine trunk diseases are responsible for pathogenicity.In the present work, we used Vitis vinifera cv. Chardonnay cells to test the aggressiveness of total extracellular compounds produced by Diplodia seriata and Neofusicoccum parvum, two causal agents associated with botryosphaeria dieback. Additionally, the toxicity of purified mellein, a characteristic toxin present in the extracellular compounds of Botryosphaeriaceae, was assessed.Our results show that the total extracellular compounds produced by N. parvum induce more necrosis on Chardonnay calli and induce a different defence gene expression pattern than those of D. seriata. Mellein was produced by both fungi in amounts proportional to its aggressiveness. However, when purified mellein was added to the culture medium of calli, only a delayed necrosis and a lower-level expression of defence genes were observed. Extracellular compounds seem to be involved in the pathogenicity of the fungi associated with botryosphaeria dieback. However, the doses of mellein used in this study are 100 times higher than those found in the liquid fungal cultures: therefore, the possible function of this toxin is discussed.

Field evaluation against Aedes aegypti larvae of aluminum-carboxymethylcellulose-encapsulated spore-toxin complex formulation of Bacillus thuringiensis serovar israelensis.

The insecticidal activity after field exposure of an aluminum-carboxymethylcellulose microencapsulated formulation of Bacillus thuringiensis israelensis (Bti) spore-toxin complex, with malachite green as photoprotective agent, was evaluated using third-instar Aedes aegypti (L.) larvae in laboratory bioassays in Veracruz, México. Four insecticide treatments and an untreated control were compared at low and high doses over 96 d of field exposure under full sun or full shade conditions: 1) microencapsulated Bti spore-toxin complex, 2) nonmicroencapsulated Bti spore-toxin complex, 3) a commercial Bti formulation, 4) a commercial formulation of temephos, and 5) an untreated control. The low and high doses corresponded to the LC50 and LC90 concentrations for the Bti insecticides and to 0.5 and 1.0 mg/liter for temephos; the corresponding values for the microencapsulated Bti and commercial Bti, estimated in this study, were 0.061 and 0.14 mg/ml and 0.13 and 0.30 mg/ml, respectively. Overall, the study demonstrated that microencapsulation with aluminum-carboxymethylcellulose improved the activity against Ae. aegypti larvae of B. t. israelensis spore-toxin complex over that of a nonmicroencapsulated spore-toxin complex and that the improvement was particularly important under full sun and high dose. Moreover, insecticidal activity of the microencapsulated B. thuringiensis israelensis spore-toxin complex was superior to that of a commercial B. thuringiensis israelensis formulation and comparable to that of the chemical insecticide temephos. Finally, it was suggested that the microencapsulated B. thuringiensis israelensis formulation should be evaluated for field use in Veracruz because its activity against Ae. aegypti larvae remained high through 31 d and this would allow halving of the current insecticide application frequency.