Aphid-mediated transmission of cotton leafroll dwarf virus to and from alternate hosts

The identification of alternate hosts that can act as a reservoir of virus in a region is important to understand the virus epidemics. Cotton leafroll dwarf virus (CLRDV) is transmitted by the cotton/melon aphid, Aphis gossypii (Glover) (Hemiptera; Aphididae) in a persistent, circulative, and non-propagative manner. CLRDV is a positive-sense single stranded RNA virus with a genome size of 5.8kb with seven open reading frames, and it belongs to the family Solemoviridae and the genus Polerovirus. CLRDV was reported in the United States first in Alabama in 2018 and later from seven other cotton-producing states including Georgia. Ten plant species (hollyhock, marshmallow, country mallow, abutilon, prickly sida, okra, hibiscus, squash, benthamiana, and chickpea) were evaluated as possible alternate hosts of CLRDV via aphid-mediated inoculation (@100 viruliferous aphids per plant for a 72h of IAP). CLRDV was detected following aphid-mediated inoculation in hibiscus, okra, and benthamiana by reverse transcription polymerase chain reaction. CLRDV accumulation was maximum in benthamiana compared to cotton and other alternate hosts. However, aphids when feeding only on infected hibiscus and okra were able to acquire virus and back-transmit to non-infected cotton. Additionally, cotton aphids can survive well in these alternate hosts with higher intrinsic rate of increase in cotton and hibiscus compared to okra. The alternate host/s of CLRDV and/or the cotton aphid could function as CLRDV inoculum sources. Overall, our results emphasize the role of alternate hosts in CLRDV epidemics in the southeastern United States cotton pathosystem.