Whitefly- A Strong Transmitter of Plant Viruses

Abstract

Bemisia tabaci transmit 111 viruses. The silver leaf/sweet potato whitefly prefers 25°C to 30°C for development and rapid generation time while the greenhouse whitefly prefers temperatures of 20°C to 25°C. Eggs hatch in eight to 10 days. Resistance in B- and Q-biotype of B. tabaci appears to be linked to enhanced oxidative detoxification of neonicotinoids. Transmission efficiency from infected weeds to tomato varied from 66.7 to 100 percent, whereas, from tomato to these weeds varied from 58.3 to 83.3 percent. Increased mortality of biotype Q females and immature instars with lower rate of fecundity and progeny size compared to biotype B was recorded in such population when reared in single or mixed cultures. Two genetic types of B. tabaci were distinguished using RAPD-PCR and cytochrome oxidase I (COI) gene sequence comparisons. One type was assigned to biotype B and the other was genetically dissimilar to the populations described elsewhere and was named Ms. This new genetic type forms a distinct group that is sister to two other groups, one to which the B biotype is a member and Q bioype have  similar values of intra population diversity, which were higher than the values shown by populations of biotype B. Epidemics of begomoviruses have been observed in many crops including tomato for which Tomato yellow leaf curl China virus (TYLCCNV) and Tomato yellow leaf curl virus (TYLCV) have been identified as two major disease-causing agents. The replication of geminiviruses induces micro-structural changes in the nucleus of the host cells. The begomovirus vector B.  tabaci is  an  insect species  complex  that  has  geographically  distinct phenotypic and genotypic variants. Criniviruses are limited to phloem and are transmitted in nature in a semipersistent manner by whiteflies. The genus Ipomovirus includes viruses that are transmitted by the whitefly B. tabaci in a semipersistent manner. Virus particles occur in the cytoplasm singly or more often in large aggregates which are sometimes banded. The stem necrosis of soybean is caused by a virus of the Carlavirus and transmitted by the whitefly Bemisia tabaci, also infected beans and identified as Cowpea mild mottle virus. The early symptoms of Tomato torrado virus are necrotic or dead spots, surrounded by a light green or yellow area at the base of the leaflets. The affected areas may fall out, leaving holes (shot holes) in the leaflets. Necrosis and mottling extend to the remainder of the leaves. The article will bring role of whitefly in development of virus diseases in agricultural crops and management strategies could only be achieved when importance of this pest will be eradicated with non-chemical approach.