The newly introduced castor bean whitefly (CBW) Trialeurodes ricini (Misra) has become an important pest which is widely spread all over Egypt. Biochemical studies were conducted to distinguish the different T . ricini biotypes and to determine the biotype economic threshold based on its ability to transmit plant viruses. Forty-five samples of T. ricini adults were collected from castor bean (Ricinus comrnunis) at different geographical locations representing the Egyptian Delta and Nile valley governorates. Esterase banding patterns were investigated to evaluate the extent of variation among the tested populations of the castor bean whitefly. Electrophoresis of homogenates of individual T. ricini females showed that there are five different biotypes (C,-CJ. The predominant biotype (C, type) was found in about 80% of the tested locations. In transmission studies, the polymerase chain reaction (PCR) was used to detect geminiviruses in nucleic acid extracted from the different castor bean whitefly biotypes. PCR revealed that the five biotypes of T . ricini are viruliferous. To evaluate the efficiency of the predominant T . ricini biotype for transmitting the tomato yellow leaf curl virus (TYLCV), acquisition and inoculation access periods were determined. PCR indicated that 50% of whitefly adults collected from castor bean, acquired the virus after 10 h exposure to TYLCV infected tomato. Experimentally, the rate of transmission increased as the inoculation access period was lengthened and reached a maximum after 4 h. The obtained symptomatological results were also confirmed by PCR.
Black cutworm (BCW) is an economically important lepidopteran insect. The control of this insect by a Bt toxin and the understanding of the interaction between the Bt toxin and its receptor molecule were the objectives of this research work. A gene coding for a Vip3A receptor molecule was identified, characterized, and cloned, from the brush border membrane vesicles (BBMV) of the BCW. The nucleotide sequence analysis of the cloned putative Vip3A-receptor gene revealed that the gene was 1.3-kb long and exhibited no homology with any gene in the gene bank. We succeeded in identifying and characterizing most of the Vip3A-receptor gene sequence; and the nucleotide sequence analysis of the cloned putative Vip3A-receptor gene (accession no. KX858809) revealed about 92% of the expected sequence was recovered, which exhibited no homology with any gene in the GenBank.
The effect of ascorbic acid as a food additive, was tested on mulberry silkworm Bombyx mori. The present data show that ascorbic acid at different concentrations (0.25, 0.5, 1 and 2 % ) increased significantly the weights of both larvae and pupae. Fifth instar larvae of B. mori fed on mulberry leaves treated with ascorbic acid produced heavier fresh cocoons. Statistical analysis of data showed that 2 % ascorbic acid produced the heaviest cocoons. It enhanced silk production 29.85 % of the control. In addition, ascorbic acid proved to exhibit a significant effect on the increasing of the fecundity of emerged females.Furthermore, physiological studies have been carried out to explain the above mentioned effects of the vitamin. The tested concentrations of ascorbic acid raised the coefficients of food utilization and growth of mulberry silkworm larvae. Moreover the present study shows that vitaminC as a food additive, affected significantly the CA volume and increased the juvenile hormone level. 0v P in .-% /+O 5 $ -3 J 0 C 3.5
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