Survey, Detection, Characterization of Papaya Ringspot Virus from Southern India and Management of Papaya Ringspot Disease

Abstract

Papaya ringspot virus (PRSV) is a significant threat to global papaya cultivation, causing ringspot disease, and it belongs to the species Papaya ringspot virus, genus Potyvirus, and family Potyviridae. This study aimed to assess the occurrence and severity of papaya ringspot disease (PRSD) in major papaya-growing districts of Karnataka, India, from 2019 to 2021. The incidence of disease in the surveyed districts ranged from 50.5 to 100.0 percent, exhibiting typical PRSV symptoms. 74 PRSV infected samples were tested using specific primers in RT-PCR, confirming the presence of the virus. The complete genome sequence of a representative isolate (PRSV-BGK: OL677454) was determined, showing the highest nucleotide identity (nt) (95.8%) with the PRSV-HYD (KP743981) isolate from Telangana, India. It also shared an amino acid (aa) identity (96.5%) with the PRSV-Pune VC (MF405299) isolate from Maharashtra, India. Based on phylogenetic and species demarcation criteria, the PRSV-BGK isolate was considered a variant of the reported species and designated as PRSV-[IN:Kar:Bgk:Pap:21]. Furthermore, recombination analysis revealed four unique recombination breakpoint events in the genomic region, except for the region from HC-Pro to VPg, which is highly conserved. Interestingly, more recombination events were detected within the first 1710 nt, suggesting that the 5’ UTR and P1 regions play an essential role in shaping the PRSV genome. To manage PRSD, a field experiment was conducted over two seasons, testing various treatments, including insecticides, biorationals, and a seaweed extract with micronutrients, alone or in combination. The best treatment involved eight sprays of insecticides and micronutrients at 30-day intervals, resulting in no PRSD incidence up to 180 days after transplanting (DAT). This treatment also exhibited superior growth, yield, and yield parameters, with the highest cost–benefit ratio (1:3.54) and net return. Furthermore, a module comprising 12 sprays of insecticides and micronutrients at 20-day intervals proved to be the most effective in reducing disease incidence and enhancing plant growth, flowering, and fruiting attributes, resulting in a maximized yield of 192.56 t/ha.

Complete genome sequencing and construction of full-length infectious cDNA clone of papaya ringspot virus-HYD isolate and its efficient in planta expression

“…The severity of PRSV infection in papaya orchards is rising alarmingly with time (Premchand et al, 2023). The lack of availability of a significant number of full-length genomic sequences is one of the major drawbacks in viral disease management.…”

Tropical Fruit Virus Resistance in the Era of Next Generation Plant Breeding

“…Delayed implementation of roguing can result in losses of up to 100% in the state of Espírito Santo, the main papaya-growing region of Brazil [39]. Papaya ringspot virus papaya-strain (PRSV-p, a potyvirus) is the etiological agent of the most devastating disease of papaya crop, named ringspot/mosaic disease, since the symptoms constitute the appearance of a mosaic in leaf tissues, and a yellow-circular spot on the fruits [40,41]. During potyviruses infection, the host defense response and innate immune system are activated [42], and specifically to PRSV, a protein interaction between viral coat protein (CP) and papaya identified 23 proteins grouped in four groups, as: transcription factors and cell division; hormones and stress; mitochondrial electron transferase and respiration; and proteasome [43].…”