Prospective Alternate Hosts of an Emerging Polerovirus in Cotton Landscapes in the Southeastern United States

Abstract

The identification of alternate hosts that can act as virus inoculum sources and vector reservoirs in the landscape is critical to understanding virus epidemics. Cotton leafroll dwarf virus (CLRDV) is a serious pathogen in cotton production and is transmitted by the cotton/melon aphid, Aphis gossypii, in a persistent, circulative, and non-propagative manner. CLRDV was first reported in the United States in Alabama in 2017, and thereafter in several cotton-producing states. CLRDV has since established itself in the southeastern United States. The role of alternate hosts in CLRDV establishment is not clear. Fourteen common plant species in the landscape, including crops, weeds, and ornamentals (cotton, hollyhock, marshmallow, country mallow, abutilon, arrowleaf sida, okra, hibiscus, squash, chickpea, evening primrose, henbit, Palmer amaranth, and prickly sida) were tested as potential alternate hosts of CLRDV along with an experimental host (Nicotiana benthamiana) via aphid-mediated transmission assays. CLRDV was detected following inoculation in hibiscus, okra, N. benthamiana, Palmer amaranth, and prickly sida by RT-PCR, but not in the others. CLRDV accumulation determined by RT-qPCR was the highest in N. benthamiana compared with cotton and other hosts. However, aphids feeding on CLRDV-infected prickly sida, hibiscus, and okra alone were able to acquire CLRDV and back-transmit it to non-infected cotton seedlings. Additionally, some of the alternate CLRDV hosts supported aphid development on par with cotton. However, in a few instances, aphid fitness was reduced when compared with cotton. Overall, this study demonstrated that plant hosts in the agricultural landscape can serve as CLRDV inoculum sources and as aphid reservoirs and could possibly play a role in the reoccurring epidemics of CLRDV in the southeastern United States.

Cotton leafroll dwarf disease: An enigmatic viral disease in cotton

“…CLRDV was also detected in 23 weed species growing near cotton fields in Georgia (Sedhain et al, 2021). In greenhouse experiments, CLRDV was detected by reverse transcription (RT)‐PCR following aphid‐mediated transmission in hibiscus ( Hibiscus acetosella ), okra ( Abelmoschus esculentus ), Nicotiana benthamiana , Palmer amaranth ( Amaranth palmeri ), and prickly sida ( Sida spinosa ) (Pandey et al, 2022). Aphids feeding on CLRDV‐infected malvaceous hosts including hibiscus, prickly sida, and okra were able to acquire CLRDV and back‐transmitted it to noninfected cotton seedlings (Pandey et al, 2022).…”

“…In greenhouse experiments, CLRDV was detected by reverse transcription (RT)‐PCR following aphid‐mediated transmission in hibiscus ( Hibiscus acetosella ), okra ( Abelmoschus esculentus ), Nicotiana benthamiana , Palmer amaranth ( Amaranth palmeri ), and prickly sida ( Sida spinosa ) (Pandey et al, 2022). Aphids feeding on CLRDV‐infected malvaceous hosts including hibiscus, prickly sida, and okra were able to acquire CLRDV and back‐transmitted it to noninfected cotton seedlings (Pandey et al, 2022). These volunteer cotton stalks and weed hosts could potentially act as a “green bridge” and as a source of primary inoculum for the next growing season (Bag et al, 2021; Sedhain et al, 2021).…”

“…Another set of degenerate primers targeting ORF3 were designed to detect several polero‐ and luteoviruses from Argentina, Brazil, and India, including CLRDV isolates (Sharman et al, 2015). SYBR Green‐based RT‐quantitative PCR (RT‐qPCR) assays targeting ORF3 were developed for more precise and quick detection (Pandey et al, 2022).…”

Characterizing the vector competence of Aphis gossypii, Myzus persicae and Aphis craccivora (Hemiptera: Aphididae) to transmit cotton leafroll dwarf virus to cotton in the United States

“…The experiment conducted to assess the ability of M. persicae to acquire CLRDV from infected cotton plants was adopted from the experiment conducted by Pandey et al (2022) to assess the virus acquisition by A. gossypii . Nonviruliferous adult aphids were confined to the abaxial surface of leaves at the uppermost one-third of the CLRDV-infected cotton plants using clip cages.…”

“…Five aphids were pooled together into 1 sample, and total RNA was extracted from 6 samples per replicate using the Qiagen RNA mini Kit (Valencia, CA) as per the manufacturer's instructions. Detection of CLRDV by RT-PCR was conducted according to the methods of Pandey et al (2022). The experiment was replicated 3 times for a total of 90 aphids for each M. persicae and A. gossypii .…”