Early-Stage Phenotyping of Sweet Potato Virus Disease Caused by Sweet Potato Chlorotic Stunt Virus and Sweet Potato Virus C to Support Breeding

Abstract

Sweet potato virus disease (SPVD) is a global constraint to sweetpotato (Ipomoea batatas) production, especially under intensive cultivation in the humid tropics such as East Africa. The objectives of this study were to develop a precision SPVD phenotyping protocol, to find new SPVD-resistant genotypes, and to standardize the first stages of screening for SPVD resistance. The first part of the protocol was based on ELISA results for sweet potato chlorotic stunt virus (SPCSV) and sweet potato virus C (SPVC) with adjustments to a negative control (uninfected clone ‘Tanzania’) and was performed on a pre-breeding population (VZ08) comprising 455 clones and 27 check clones graft-inoculated under screenhouse conditions. The second part included field studies with 52 selected clones for SPCSV resistance from VZ08 and eight checks. In screenhouse conditions, the resistant and susceptible check clones performed as expected, 63 clones from VZ08 exhibited lower relative absorbance values for SPCSV and SPVC than inoculated check Tanzania. Field experiments confirmed SPVD resistance of several clones selected by relative absorbance values (nine resistant clones in two locations, i.e. 17.3% of the screenhouse selection), supporting the reliability of our method for SPVD-resistance selection. Two clones were promising, exhibiting high storage root yields of 28.7–34.9 t ha−1 and SPVD resistance, based on the proposed selection procedure. This modified serological analysis for SPVD-resistance phenotyping might lead to more efficient development of resistant varieties by reducing costs and time at early stages, and provide solid data for marker assisted selection with a quantitative tool for classifying resistance.

High-throughput characterization and phenotyping of resistance and tolerance to virus infection in sweetpotato

“…Ejumula was not among the high yielding varieties under San Ramon conditions, even when uninfected, so even if it's yield reduction might not be much after infection, breeders would have considered it susceptible if it yielded less than their check varieties, even if it is clearly not as susceptible as varieties grown in areas with low virus pressure such as ‘Beauregard’ ( McGregor et al, 2009 ) and ‘Benjamin’. Genotype VZ08.328, considered moderately resistant by breeders ( David et al., 2023 ) manifested as Tolerant in our experiment ( Figs. 4 and 6 ).…”

“…ELISA is mostly used for detection and/or quantification of sweetpotato viruses due to its robustness, low cost, and ease of use ( Karjeija et al., 2000b ; David et al., 2023 ). However, due to the presence of inhibitors and often low virus concentrations in sweetpotato, ELISA lacks the sensitivity needed to detect and quantify viruses for practical use and needs complementary assays for confirmation, most commonly involving grafting onto indicator plants and/or PCR ( Moyer & Salazar, 1989 ).…”

Feasibility of Detecting Sweet Potato (Ipomoea batatas) Virus Disease from High-Resolution Imagery in the Field Using a Deep Learning Framework

“…Previous studies have primarily focused on laboratory-based and traditional methods for detecting sweet potato virus diseases. For example, Huang et al [48] utilized NCM-ELISA and RT-qPCR to identify plants infected with SPFMV and SPCSV viruses, while David et al [6] visually evaluated sweet potato virus symptoms using a scale ranging from 1 (no symptoms) to 5 (very severe symptoms). However, these methods have limitations.…”

“…SPVD can lead to more than an 85% reduction in tuber yield compared to the mild symptoms caused by individual viral infections [5]. Currently, the most effective measure to manage SPVD in farmer fields is the use of clean planting material [6]. Genetic resistance against SPVD is not yet available.…”