Abstract
The root-knot nematode Meloidogyne graminicola is a serious pest in rice affecting production in many rice growing areas. Natural host resistance is an attractive control strategy because the speed of the parasite’s life cycle and the broad host range it attacks make other control measures challenging. Although resistance has been found in the domesticated African rice Oryza glaberrima and the wild rice species O. longistaminata, the introgression of resistance genes to Asian rice O. sativa is challenging. Resistance due to a major gene in O. sativa would greatly aid breeding. Recently two accessions resistant to M. graminicola have been identified in a screen of 332 diverse O. sativa cultivars. In this study, these two resistant cultivars, LD 24 (an indica from Sri Lanka) and Khao Pahk Maw (an aus from Thailand), were crossed with a moderately susceptible cultivar, Vialone Nano (a temperate japonica from Italy). Approximately 175 F2 progeny of both populations were screened for susceptibility to M. graminicola infection. Between 20 and 23 individuals with highest and lowest galls per plants were pooled to make susceptible and resistant bulks which were sequenced to conduct bulked segregant analysis using the QTL-seq method. This revealed a nematode resistance locus from 23 Mbp to the bottom of rice chromosome 11 in both crosses suggesting a rare introgression of the same locus is responsible for resistance in both cultivars. While this information can be used in marker-assisted breeding, analysis of available SNP data revealed candidate loci and genes worthy of further investigation for gene identification.
Highlights
Rice (Oryza sativa) is an essential food crop hosting various pests and diseases including plant-parasitic nematodes which pose a threat to production
The main objective of this current study was to use the QTL-seq method to test the hypothesis that these two resistant cultivars which are themselves genetically quite different, harbour the same allele for resistance, and identify loci and candidate genes for conferring resistance to M. graminicola with the long-term goal of improving nematode resistance in cultivated rice, O. sativa
For the other population (VN 9 KPM) Vialone Nano was crossed with the resistant aus rice cultivar Khao Pahk Maw (KPM) from Thailand
Summary
Rice (Oryza sativa) is an essential food crop hosting various pests and diseases including plant-parasitic nematodes which pose a threat to production. With over 41,000 species of plant-parasitic nematodes described (Decraemer and Hunt 2006), they pose a great threat to world agriculture. It has been estimated that plant nematodes alone can cause damage of around USD80 billion per year world-wide (Nicol et al 2011). Within the genus Meloidogyne, the rice root-knot nematode (M. graminicola) (Golden and Birchfield 1965) is considered a serious threat to rice production (Plowright and Bridge 1990). The second stage juveniles (J2s) are the only infective stage of these nematodes and they invade rice roots near the root tip (Bridge et al 2005). The infection causes the development of hook-like galls inside which the nematodes complete their life cycle (Mantelin et al 2017)
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