Root-knot nematodes (RKNs) cause severe diseases in peppers annually around the world. In pepper, the Me3 gene provides a heat-stable and broad-spectrum resistance to RKNs. In this study, several simple sequence repeat (SSR) markers and insertion/deletion (InDel) markers were developed to fine map the Me3 gene. Analysis of 2272 individuals (F₂ progenies) revealed that Me3 was located in a 45-kb DNA region between markers SSR784 and SSR339, in which there were three candidate genes. Among them, as a novel nucleotide binding site and leucine rich repeat (NBS-LRR) family gene, the DNA sequence of Capana09g000163 of pepper line 'HDA149' was 6348 bp in length, with a 2802-bp open reading frame encoding 933 amino acids, including NB-ARC and LRR domains. Tobacco transient expression assays demonstrated that expression of Capana09g000163 triggered a hypersensitive response (HR) in Nicotiana benthamiana leaves. Subcellular localization results showed that the Capana09g000163 protein was localized in the cell nucleus. Ectopic expression of Capana09g000163 in Arabidopsis significantly increased resistance against Meloidogyne incognita compared with the wild-type (WT) Arabidopsis. Furthermore, M. incognita was almost unable to develop in transgenic Arabidopsis expressing Capana09g000163. Taken together, we cloned the Me3 gene and verified that it induced resistance against M. incognita with the methods of map-based cloning and transgenic technology, which may be of great significance to pepper breeding for resistance against RKNs.

Continuous cropping in greenhouses can result in root-knot nematode outbreaks resulting from imbalances in the soil nematode community. However, the changes in soil nematode communities in greenhouses with continuous crop production are unclear. We compared soil nematode communities in greenhouses after 2 years (2-yr) and 10 years (10-yr) of continuous crop production by 18S rDNA high-throughput sequencing. Compared with the 2-yr greenhouse, soil in the 10-yr greenhouse showed acidification, nutrient accumulation and salinization. Bacterial-feeding nematodes (BF) were dominant in the 2-yr greenhouse over the whole growing season, but plant-parasitic nematodes (PP) were the dominant group in the 10-yr greenhouse during the late growing season. Meloidogyne gradually became the dominant group and had a relative abundance of 70.9% (maximum) in the 10-yr greenhouse. Rhabditidae, with relative abundance ranging from 99.8% to 26.8%, was the predominant group in the 2-year greenhouse. For β-diversity, hierarchical clustering analysis, unweighted UniFrac principal component analysis (PCA) and principal co-ordinates analysis (PCoA) all revealed that soil nematode communities in the two types of greenhouses were significantly different. Redundancy analysis (RDA) showed that soil nematode communities in the 10-yr greenhouse were related to high soil organic material, total nitrogen, electrical conductivity and disease index of root-knot nematodes. Fisher's exact test and Pearson's correlation coefficients revealed that Meloidogyne contributed to the main differences in soil nematode communities between the two types of greenhouses. Population dynamics of Meloidogyne were divided into dormant phase, low-level increasing phase and exponential phase during the whole season. The soil nematode communities within the 2-yr and 10-yr greenhouses had significant variation and different dynamics. This work contributes to a deeper understanding of changes in the soil nematode community in greenhouses with different continuous cropping duration.