Abstract
Abstract Potatoes are prone to attack by multiple viruses, which contribute greatly to yield and quality decline depending on the cultivar and the virus involved. This study investigated the effect of co-infection involving Potato virus Y (potyvirus) and Potato leafroll Virus (pelero virus) on productivity of five potato cultivars in Uganda and the nature of virus interaction during co-infection process. Variety response to virus infection by PVY, PLRV and co-infection (PVY + PLRV) varied across different varieties. The plants that were infected with PLRV had leaf rolling, stuntedness, leaf distortion, reduction in leaf size and mottling and light yellow mosaics, and in some cases, purple or red margins were observed, while single infection of PVY induced necrosis, leaf rugosity, crinkling, stunting, interveinal necrosis, blotching of the margins, leaf distortion and mottling. When the two viruses were combined during co-infection with PVY + PLRV, the symptoms were characterized by bright blotching and necrotic leaf margins with purpling of the leaf tips and leaf margins, stuntedness and leaf distortions. The virus disease severity was higher under mixed infected plants than single infected plants. The high disease severity culminated in a significant effect on yield, marketable tuber number per plant, plant growth height and plant vigor, which were different across the varieties. Co-infection involving PVY and PLRV caused a reduction in the marketable yield of 95.2% (Kinigi), 94% (Victoria), 89.5 (Rwagume), 45.3% (Royal) and 23.7% (Sifra). Single infection by PLRV caused a reduction in a marketable yield in Victoria (91.8%), Kinigi (84.8%), Rwagume (73.3%), Royal (47.2%) and Sifra 22.1%, while PVY caused a marketable yield reduction in Victoria (87.2%), Rwagume (85.9.7%), Kinigi (85.1%), Royal (37.4%) and Sifra (14.1%). The effects associated with the co-infection of PVY and PLRV were lower than the combined value of the single infections, suggesting that the two viruses were interacting to affect the potato productivity. The high yield loss suggested that effective resistance strategy targeting PVY, PLRV and their combination was required to save the potato industry in Uganda.
Highlights
The occurrence of more than one virus species in a single plant is very common in many potato fields causing significant yield losses (Zhang et al 2001)
The results showed that co-infections of PVY + PLRV were associated with higher disease severity values compared to single infection
The results showed that co-infection of PVY + PLRV was associated with higher disease severity that culminated significant (P < 0.05) effects on plant growth and disease development based on relative area under the disease progress curve (rAUDPC) values
Summary
The occurrence of more than one virus species in a single plant is very common in many potato fields causing significant yield losses (Zhang et al 2001). There are more than 40 viruses that infect potatoes in the fields (Jeffries 1998), and based on the distribution, pathogenic variability and yield loss, PVY and PLRV are the most important viruses (Palukaitis 2012). Survey studies conducted in potato fields in the neighboring countries of Kenya and Tanzania have reported that potato plants are co-infected with two or more viruses (Valkonen 2015; Okeyo 2017). Most of the potato varieties grown by farmers in Uganda are very susceptible to viruses (KAZARDI 2016) and are likely to be infected with several viruses. During the co-infection process, interactions may occur between viruses within the host cell and such viral interactions may be antagonistic, synergistic or neutral (Moreno and López-Moya 2019). Antagonism usually occurs when the co-infecting viruses are related, resulting in interference, whereas in neutral
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