Sources of root-knot nematode (Meloidogyne enterolobii) resistance in sweetpotato genotypes

ABSTRACT The root-knot nematode (RKN) Meloidogyne enterolobii is gaining importance all around the world, including Brazil, damaging sweetpotato genotypes with known resistance to other RKN species, making it challenging to generate new resistant genes. This study aimed to assess the levels of resistance of 10 advanced sweetpotato cultivars to this nematode species. Two experiments were carried out in 2018/2019 and 2021/2022 seasons, under greenhouse conditions in Brasília-DF, Brazil. A completely randomized block design with six replicates of one plant/plot/treatment was used. The gall index (GI) and egg mass index (EMI) in the root system of each plant, the number of eggs and juveniles per gram of root with galls (NERG), and the nematode reproduction factor (RF) were determined. M. enterolobii resistance is present within three of the evaluated clones: BGBD 1399, MD 1609024, and MD 1610036, therefore demonstrating their potential as sources of resistance genes to assist breeding efforts to release cultivars, and help to reduce the impact and spread of this RKN.

摘要 根结线虫（root-knot nematode, RKN）中的象耳豆根结线虫（Meloidogyne enterolobii）在全球范围内的重要性日益凸显，巴西亦不例外。该线虫可侵染对其他根结线虫物种具有已知抗性的甘薯基因型，这给新抗性基因的创制带来了挑战。本研究旨在评估10个参试甘薯栽培品种对该线虫物种的抗性水平。试验于2018/2019及2021/2022季在巴西巴西利亚-DF的温室条件下开展，采用完全随机区组设计，每处理每小区种植1株，设置6次重复。测定指标包括各植株根系的根结指数（gall index, GI）、卵块指数（egg mass index, EMI）、每克带虫根的卵量与幼虫数（number of eggs and juveniles per gram of root with galls, NERG）以及线虫繁殖系数（reproduction factor, RF）。结果表明，供试克隆中有3个（BGBD 1399、MD 1609024及MD 1610036）具备象耳豆根结线虫抗性，证实其可作为抗性基因源，助力抗病品种的选育工作，并有助于减轻该根结线虫的危害与传播范围。