Identification of simple sequence repeat markers for sweetpotato weevil resistance

Abstract

The development of sweetpotato [Ipomoea batatas (L.) Lam] germplasm with resistance to sweetpotato weevil (SPW) requires an understanding of the biochemical and genetic mechanisms of resistance to optimize crop resistance. The African sweetpotato landrace, 'New Kawogo', was reported to be moderately resistant to two species of SPW, Cylas puncticollis and Cylas brunneus. Resistance has been associated with the presence of hydroxycinnamic acids esters (HCAs), but the underlying genetic basis remains unknown. To determine the genetic basis of this resistance, a bi-parental sweetpotato population from a cross between the moderately resistant, whitefleshed 'New Kawogo' and the highly susceptible, orange-fleshed North American variety 'Beauregard' was evaluated for SPW resistance and genotyped with simple sequence repeat (SSR) markers to identify weevil resistance loci. SPW resistance was measured on the basis of field storage root SPW damage severity and total HCA ester concentrations. Moderate broad sense heritability (H 2 = 0.49) was observed for weevil resistance in the population. Mean genotype SPW severity scores ranged from 1.0 to 9.0 and 25 progeny exhibited transgressive segregation for SPW resistance. Mean genotype total HCA ester concentrations were significantly different (P \ 0.0001). A weak but significant correlation (r = 0.103, P = 0.015) was observed between total HCA ester concentration and SPW severity. A total of five and seven SSR markers were associated with field SPW severity and total HCA ester concentration, respectively. Markers IBS11, IbE5 and IbJ544b showed significant association with both field and HCA-based resistance,

Breeding Progress for Vitamin A, Iron and Zinc Biofortification, Drought Tolerance, and Sweetpotato Virus Disease Resistance in Sweetpotato

“…All programs prioritized high β-carotene content, and beginning in 2014, studies in Mozambique included evaluation of Fe and Zn content. The national agricultural research institutes' breeding programs emphasized development and accelerated release of cultivars (Low et al, 2020), with the national breeding program in Uganda developing specific procedures for breeding for weevil resistance (Yada et al, 2017a), the major pest problem in SSA. In addition, all sub-regional and national programs prioritized selection of clones with high dry matter content, with desired minimum levels varying due to taste differences in different countries.…”

Segregation of Hydroxycinnamic Acid Esters Mediating Sweetpotato Weevil Resistance in Storage Roots of Sweetpotato

“…The high level of genetic diversity observed in the New Kawogo × Beauregard population reported here supports the observation of some progeny exhibiting transgressive segregation for resistance to SPW. Variation in SPW infestation observed in the F 1 population of these two parents was significant and transgressive segregation for SPW resistance was observed in the F 1 sibs ( Yada et al, in press ). The progeny that was more resistant than New Kawogo and others with high HCA esters are new candidates for selection and can be used as sources of genes for future crop improvement ( Figure 4 ).…”

“…The objective of this study was to determine the segregation pattern of resistance to SPW in a bi-parental cross between New Kawogo and Beauregard. Association analyses of SPW resistance and SSR markers was recently reported for this same population ( Yada et al, in press ) and a genetic map based on SNP markers is currently being developed for this population under the Genomic Tools for Sweetpotato Improvement (GT4SP) project (Yencho, unpublished) with the overarching aim of facilitating the identification of quantitative trait loci associated with sweetpotato weevil resistance.…”

Effects of hydroxycinnamic acid esters on sweetpotato weevil feeding and oviposition and interactions with Bacillus thuringiensis proteins

“…Bt proteins and hydroxycinnamic acids both cause mortality in SPW larvae and in combination increased mortality as is expected for an additive effect. We suggest that Bt strains that can be expressed effectively in the root cortex of sweetpotato could enhance resistance mediated by hydroxycinnamic acid esters, and should be explored as a trait that breeders can exploit for biorational pest management of sweetpotato weevils (Otema et al 2017;Yada et al 2017), but future development of multiple component resistance should consider the potential for interactions of different mechanism that reduce efficacy.…”

“…SPW control using conventional pesticides is complicated because sweetpotato roots are subterranean, and the target insect spends the majority of its lifecycle inside roots protected by the soil. Hydroxycinnamic acids esters (hexadecyl and octadecyl-cinnamic acid esters, hexadecylcaffeic acid esters and 5-O-caffeoylquinic acid) are produced naturally by the roots and are biologically active against SPW larvae at ecologically relevant concentrations (Stevenson et al 2009) and have been identified as a breeding trait for improved varieties (Otema et al 2017;Yada et al 2017). These compounds are particularly effective at protecting against oviposition by adults because they occur at the highest concentrations at the root surface where eggs are laid and induce behavioural avoidance after feeding and creating feeding holes in which eggs are laid (Anyanga et al 2013) but are less effective against the larval stage which causes the most damage in the cortex.…”