Fine Mapping Of The Root-knot Nematode Resistance Gene Me1 In Pepper(Capsicum Annuum L.)

Root-knot nematode is a serious disease which is harmful for plant normal growth and causes production failures in pepper. Developing resistant varieties is an effective way to control root-knot nematode. Conventional breeding cycle is a long term while molecule marker-assisted selection can speed up the breeding process. At present, it has been reported at least 9 root-knot nematode resistant genes in pepper and Me1 is a durable and broad-spectrum resistant gene known located on chromosome 9. In this paper, we used disease-resistant variety DH330(Me1), disease-susceptive variety 0516 and their BC1 population as the experimental materials to construct a fine map of Me1, candidate genes were indicated as foundation for Me1 gene cloning, revealing its resistant mechanism. Molecular marker-assisted selection will be useful to develop new nematode resistant varieties cultivation. The main results were as follows:1. South root-knot nematode(M.incognita) was used to identify resistance of BC1 population with 1583 individuals. Resistant and susceptible individuals segregated with the ratio 1.04:1, which is consistent with the theory of dominant gene 1:1 ratio(2=0.495<3.84).2. Compared root-knot nematode resistant genes positioning genetic map with CM334 genome physical map, we choosed 77 pairs of KASPar primers to screen and 4 pairs of primers have polymorphism between population; linkage analysis showed markers K77 and K32 were closest to gene Me1, genetic distance were 7.68 cM and 19.04 cM respectively, realizing the primary mapping for gene Me1.3. By SSR Hunter software, we searched for simple repeat sequence located between the marker K77 and marker K32 with CM334 and Zunla genome information. In this two genomes, dinucleotide AT/TA with the frequencies of 28.5% and 81.1% respectively; trinucleotide AAC/CCA/TGT/TTG with the frequencies of 19.0% and 44.7%. We developed 233 SSR markers, six of which showed polymorphism between population. Combined with BC1 population resistance identification phenotypetarget gene was localized between SSR marker 24-20 and ZY6-13 within 210 Kb interval(physical interval 250.08 to 250.09Mb) and the genetic distances were 1.83 and 0.75 cM respectively.4. With bioinformatics, we obtained gene annotation in CM334 genome in genetic mapping interval. According to sequence information, polymorphic fragment and site were found through fragments amplification and sequencing. Designed primers which mapped Me1 between markers 16880-1 and 16830-H. The genetic distances between two markers and Me1 were 1.44 cM and 0.63 cM. Referring to CM334 genome information, there were 4 genes in this 130 Kb physical interval. It can be further explored in following research.