Role of transient aphid vectors on the temporal spread of Papaya ringspot virus in South India.

摘要

The species composition and dynamics of aphids influencing papaya ringspot virus (PRSV) epidemics was studied at the Indian Institute of Horticultural Research, Bangalore, South India. Papaya seedlings (Hybrid:Surya) were transplanted during September of 2003 and 2004. Aphids were monitored using yellow funnel water traps placed in papaya field and trapped aphids were collected every 24 hours. Papaya ringspot virus incidence was recorded once a week. Based on trap catches, the melon aphid, Aphis gossypii, cowpea aphid, A. craccivora and green peach aphid, Myzus persicae were considered as major aphid species. Aphis gossypii was the predominant species and was recorded throughout the year. Aphid numbers in the trap followed a bimodal distribution with a first peak between March-April and a second peak between December-February. Correspondingly, maximum PRSV infection was noticed during April-May. Maximum temperature, evaporation and sunshine hours had significant, positive correlation to aphid trap catches. But, minimum temperature, relative humidity, wind speed and rainfall had negative correlation. Data were subjected to multiple regression analysis to understand the influence of aphid vectors and weather factors on PRSV infection. An optimized model was developed using stepwise regression to identify the most significant variables. The optimized model: disease incidence (y< sub>3)=-21.087+0.134 TA (total aphids) +0.726 MT (maximum temperature), developed using first years data (2003-04) predicted 74% (R2=0.74) of the PRSV disease incidence. This model was further validated during 2004-05 and explained 66% (R2=0.66) variation in PRSV disease incidence emphasizing the biological validity of the model. The implications of this study in the epidemiology and management of PRSV are discussed.