Vector-virus Relationship for Melanaphis sacchari (zehnt.) (Hemiptera: aphididae) Transmitting Sugarcane Yellow Leaf Luteovirus in Mauritius

Abstract

Sugarcane yellow leaf virus (ScYLV) was reported in Mauritius in 1995. It spreads by vegetative propagation and is transmitted to healthy plants by the aphid, Melanaphis sacchari (Zehnt.) that prevails at a very low density in commercial plantations. The relationships pertaining to the vector and the luteovirus were investigated under laboratory conditions, as an understanding of the acquisition and transmission of the virus by the vector is a prerequisite for further studies on the epidemiology, economic importance and management of the disease at field level. An appropriate aphid rearing technique was developed so as to establish cultures of infected and healthy aphids for the relevant studies. To determine the acquisition time of the virus by aphids, infected plants of the sugarcane variety M 695/69 were infested with non-viruliferous aphids which were sampled daily over four consecutive days and tested by RT–PCR. M. sacchari acquired the virus within 24 h and more precise tests in the insectary, whereby aphids were sampled every 30 min over 6 h, indicated that the virus was acquired after 4.5 h of feeding on infected plants. The time taken for the viruliferous aphids to transmit the virus to disease-free tissue cultured plantlets was determined by allowing infected aphids from the breeding cages to feed on the plantlets for periods of 2, 8, 17 and 28 days. The virus was transmitted to healthy plants within two days. This is the first record of M. sacchari being a vector of ScYLV in Mauritius and the present laboratory data provide basic information for future field experimentation and research work on vector-virus interactions.