Viruses limit sweetpotato (Ipomoea batatas) production worldwide. Many sweetpotato landraces in East Africa are, however, largely virus-free. Moreover, some plants infected by the prevalent Sweet potato feathery mottle virus (SPFMV) may be able to revert to virus-free status. In this study, we analysed reversion from SPFMV, Sweet potato virus C, Sweet potato mild mottle virus, Sweet potato chlorotic stunt virus (SPCSV) and Sweet potato leaf curl Uganda virus using the indicator plant I. setosa and PCR/reverse-transcriptase PCR. We also investigated environmental factors (temperature and soil nutrients) that may influence reversion from virus infection. We tested reversion in the East African cultivars New Kawogo, NASPOT 1 and NASPOT 11, and the United States cultivars Resisto and Beauregard. Reverted plants were asymptomatic and virus was undetectable in assayed parts of the plant. After graft inoculation, only the East African cultivars mostly reverted at a high rate and from most viruses though cultivar Beauregard fully reverted following sap inoculation with Sweet potato virus C. None of the tested cultivars fully reverted from single or double infections involving SPCSV, and reversion was only observed in co-infections involving potyviruses. Root sprouts derived from SPFMV-reverted plants were also virus free. Reversion generally increased with increasing temperature and by improved soil nutrition. Overall, these results indicate variation in reversion by cultivar and that the natural ability of sweetpotato plants to revert from viruses is malleable, which has implications for both breeding and virus control.

中文翻译：

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影响甘薯病毒感染回复的因素


病毒限制了全球甘薯（Ipomoea batatas）的生产。然而，东非的许多甘薯地方品种基本上不含病毒。此外，一些被流行的甘薯羽状斑驳病毒（SPFMV）感染的植物可能能够恢复到无病毒状态。在本研究中，我们使用指示植物 I. setosa 和 PCR/逆转录酶 PCR 分析了 SPFMV、甘薯病毒 C、甘薯轻度斑驳病毒、甘薯褪绿矮化病毒 (SPCSV) 和甘薯曲叶乌干达病毒的回复情况。我们还研究了可能影响病毒感染逆转的环境因素（温度和土壤养分）。我们在东非品种 New Kawogo、NASPOT 1 和 NASPOT 11 以及美国品种 Resisto 和 Beauregard 中测试了返原情况。恢复的植物没有症状，并且在植物的检测部分中未检测到病毒。嫁接接种后，只有东非品种大部分以较高的速度恢复，并且大多数病毒，但品种 Beauregard 在汁液接种甘薯病毒 C 后完全恢复。没有一个测试品种从涉及 SPCSV 的单次或双重感染完全恢复，并且恢复仅在涉及马铃薯病毒的合并感染中观察到。来自 SPFMV 恢复植物的根芽也不含病毒。回复通常随着温度的升高和土壤营养的改善而增加。总体而言，这些结果表明不同品种的回复存在差异，并且甘薯植物从病毒中回复的自然能力是可塑的，这对育种和病毒控制都有影响。