Control of papaya ringspot virus by cross protection and cultivation techniques

Abstract

Papaya ringspot potyvirus (PRSV) is a major limiting factor for economical papaya production in Taiwan. A mild nitrous-induced mutant, HA 6-1, was tested under greenhouse and field conditions to evaluate the potential for control of PRSV. Under the greenhouse conditions, it caused mild or symptomless infection on test plants in the Chenopodiaceae and Cucurbitaceae family and papaya cultivars. Under the greenhouse condition HA 6-1 was tested and illustrated a high degree of protection against the severe PRSV strains of Taiwan. Field trails of cross-protection showed that the protected plants delayed the expression of severe symptoms 1 to 5 months compared with the control. Growing papaya in net-house to protect the vectors transmitting PRSV was extremely effective. The virus incidence was only 0.3% six months after transplanting in a net-house, whereas, 96% of the papaya plants were infected in outside fields. Total yield and quality of papaya fruit harvested in a net house were much higher than that harvested from control. Today, Taiwan annually has more than 1000 ha of papaya growing under net-houses.