Detection and elimination of sweetpotato viruses

Abstract

In sub-Saharan Africa, sweetpotato (Impomoea batatas L.) production is greatly constrained by sweetpotato virus disease (SPVD) complex. This study was conducted to assess the incidence of viruses in healthy-looking sweetpotato in Uganda and to optimise modern technologies for virus diagnosis. A collection of healthy-looking sweetpotato vines from central Uganda were serologically assayed for sweetpotato viruses and the positive samples were confirmed by RT-PCR. A multiplex RT-PCR assay was optimised for simultaneous detection of Sweet potato chlorotic stunt virus (SPCSV), Sweet potato feathery mottle virus (SPFMV) and Sweet potato mild mottle virus (SPMMV). The use of in vitro thermotherapy was also investigated as a means of eliminating sweetpotato viruses. Four viruses namely SPCSV, SPFMV, SPMMV and SPCFV were detected mostly as single infections in the healthy looking plants. SPCSV (70. 6%) recorded highest incidence followed by co-infection of SPFMV and SPCSV (8.3%). Based on shoot survival and effectiveness of virus elimination, the best results were obtained by exposing plantlets to daily temperature regime of 32 RÉSUMÉEn Afrique sub saharienne, la production de la patate douce (Impomoea batatas L.) est grandement affectée par un complexe de maladies de virus (SPVD). Cette étude était conduite pour évaluer l'incidence maladie des virus sur des boutures apparemment saines de la patate douce en Ouganda et optimiser les technologies pour diagnostic de virus. Des boutures apparemment saines de patate douce collectées au centre de l'Ouganda étaient sérologiquement testées et les échantillons infectés étaient confirmés par RT-PCR. Un essai multiplexe RT-PCR était optimisé pour la detection simultanée du virus du rabougrissement chlorotique de la patate douce (SPCSV), le virus de la marbrure duveteuse de la patate (SPSMV) et le virus de marbrure modérée de la patate douce (SPMMV). L'usage de la thermothérapie in vitro était aussi testé comme moyen d'élimination des virus de la patate. Quatre virus dont SPCSV, SPFMV, SPMMV et SPCFV étaient detectés surtout comme seules infections des plantes apparemment saines. Le SPCSV (70. 6%) avait présenté une incidence élevée, suivi de SPFMV et SPCSV dont le niveau d'infection était le même (8.3%). Basé sur la survie des pousses et l'efficacité de l'élimination de virus, les meilleurs résultats étaient obtenus en exposant les plantules à un regime de température de 32 o C pendant 8 heures sous obscurité et 36 o C pendant 16 heures sous lumière durant quatre semaines. La culture du bout du méristème combinée à la thermothérapie a perimis l'élimination de SPFMV et SPMMV dans 77 % des plants qui étaient au départ infectés avec des virus respectifs. Par ailleurs, l'élimination de SPCSV avait échoué.

Virus Movement from Infected Sweetpotato Vines to Roots and Reversion on Root Sprouts

“…Lack of reversion by SPCSV-infected plants was also observed under field conditions (Adikini et al, 2016), which makes SPCSV a limiting factor in cleaning sweetpotato planting material; although in some cultivars, infected plants can easily be identified visually by symptoms. This agrees with the work of Rukarwa et al (2010), who did not obtain any virus-cleaned material from plants infected with SPCSV when subjected to meristem tip culture and thermotherapy.…”

“…This result agrees with that of Gasura et al (2009), that cultivars with the ability to recover were common in the high-SPVD pressure zones in central and western regions of Uganda. Also, the reversion of most Ugandan cultivars from SPFMV infection makes it easier to clean infected plants through meristem tip culture and thermotherapy (Rukarwa et al, 2010). On the other hand, no cultivar reverted from SPCSV, although there was reduction in virus titer by the fifth month after sprouting.…”

Screening for sweet potato (Ipomoea batatas L.) leaf curl virus (SPLCV) and its elimination using thermotherapy-meristem tip culture technique

“…Even though 52.4 % of sweet potato plants infected with the virus were cleaned through thermotherapymeristem tip culture, it is of great significance when the effect of virus on yield is considered. Rukarwa et al (2010) also reported that 77 % of virus-infected plants in Central Uganda were eliminated through meristem tip culture coupled with thermotherapy of 32 O C for four weeks, and this compares favourably with the result in this work.…”

PCR diagnosis and in vitro sanitation of the papaya MSXJ hybrid with ringspot virus disease

“…These results showed a greater scope than those exhibited in patchouli (Pogostemon cablin) (Noveriza et al, 2012) in which therapy did not eliminate the virus in any of the time treatments (10, 20, and 30 min) even when higher temperatures (50, 55, and 60 °C) than those of thermotherapy in the MSXJ hybrid were used. When these treatments are compared with those of Rukarwa et al (2010) using conventional thermotherapy (32 °C for 8 h in darkness and/or at 36 °C for 16 h light for 4 wk), it is possible to verify that they did not completely eliminate SPCSV even when thermotherapy was combined with meristem cultivation. Similarly, Bota et al (2014), in their experiment to obtain virus-free Vitis vinifera L. tissues, determined the low effectiveness of thermotherapy (20%) using a thermal chamber at 37.5/34.0 ºC (day/night) for 40 d.…”