Impact of common sweetpotato viruses on total carotenoids and root yields of an orange-fleshed sweetpotato in Tanzania

Abstract

The growing and consumption of orange-fleshed sweetpotato (OFSP) is considered as a mean to alleviate vitamin A deficiency in sub-Saharan Africa (SSA) region. However, majority of the field-tested OFSP varieties are susceptible to major diseases especially sweetpotato virus disease (SPVD), which is caused by co-infection of sweetpotato chlorotic stunt virus (SPCSV) with sweetpotato feathery mottle virus (SPFMV). A high beta-carotene content but susceptible variety Resisto was used in this study to evaluate the effects of SPVD on total carotenoids content and root yield. Compared with apparently healthy plants, reduction of 43, 16, and 37% of the total carotenoids content in the OFSP variety Resisto were observed in plants infected with SPCSV, SPFMV, and co-infection of both viruses. Storage root fresh weight was significantly ( P < 0.001) reduced due to virus infection with high reduction recorded for SPFMV infection followed by co-infection of SPFMV with SPCSV. The same case was for sweetpotato vine length. However, no major reductions were observed in the vine weights. Co-infection of SPFMV with SPCSV caused more severe symptoms than single infections of the two viruses and each isolate caused distinct disease symptoms on the infected sweetpotato plants. In general, there was no direct correlation between sweetpotato virus disease symptom severity and reduction in total carotenoids. To our knowledge, this is the first report of the negative impact of SPCSV and SPFMV on the total carotenoid accumulation in OFSP varieties. Therefore follow up studies in the area of biochemical analysis should be initiated to gain knowledge on the impacts of SPVD on the biochemical pathways of carotenoid accumulation.