# Identification of Genomic Regions Associated with Fusarium
## 4 Discussion  
Cowpea is an important legume crop in China. It was among the top six of edible legumes and top 10 of vegetables in terms of consumption. FW is one of the three devastating diseases in cowpea production, and the destruction and yield loss caused by FW increased quickly in recent years. Screening the resistant germplasms is the first step for FW resistance breeding. In China, nearly 5000 cowpea accessions had been collected until now; however, only a small number had been precisely identified for FW resistance. In a previous study, [PERSON] et al. (2015) [10] identified the FW resistance of 99 cowpea accessions and obtained 10 resistant accessions. In the current study, another 99 cowpea accessions were evaluated for FW resistance, and seven resistant accessions were obtained. Taken together, these 17 accessions provide a useful resistant resource for cowpea disease resistance breeding. Through GWAS, 10 SNPs significantly associated with FW resistance were identified in this study. Using similar association mapping analysis, [PERSON] et al. (2015) [10] identified 11 SNPs for LFD and 7 SNPs for VD. However, there were no overlapped SNPs detected in the two studies. This phenomenon may be caused by the FW strain, genotype data and germplasm used in two studies being different. The inoculation strain FW-HZ in this study was isolated from Hangzhou, and the strain used in [PERSON] et al. (2015) was isolated from Lishui. The former was from plain area, and the latter was from mountainous area. The genotype data used in [PERSON] et al. (2015) was the first-generation Illumina cowpea GoldenGate 1536-SNP assay [23], and the genotyping in this study was derived from the second-generation Cowpea iSelect Consortium Array (Illumina, Inc.) with 51,128 SNPs [6]. Moreover, the evaluated germplasms used in the two studies were completely different. Thus, it is not surprising that different results were obtained from these two studies. In addition, [PERSON] et al. [5,9] also identified three FW resistance QTLs, _Fot3-1_, _Fot4-1_, and _Fot4-2_, using QTL mapping. Synteny analysis showed that _Fot4-2_ had a distance of more than 33 Mb from 2_13643 for 2020 VD, and _Fot3-1_ was 4.6 Mb away from 2_21905 for 2020 VD, indicating that they were not the same QTL/gene. FW is a vascular disease caused by _Fusarium oxysporum_[24] which has widely infected many crops, such as cotton, sugarcane, banana, tomato, cucumber and common bean [25]. At present, several FW resistance genes have been cloned in cotton and tomato. _Fov7_, a major FW resistance gene in cotton, encodes a glutamate receptor, and a single nucleotide mutation in this gene leads to the gain or loss of disease resistance [26]. _I, I-2_, and _I-7_ are the typical R genes containing nucleotide binding and leucine-rich repeat domains in tomato, and _I-3_ encodes an S-receptor kinase protein [27]. However, no FW resistance genes have been cloned yet in cowpea. In the current study, a total of 670 predicated genes were identified, and 30 genes were defined as the likely candidates for FW resistance. Of them, _Vigun05g093700_ belongs to the divergent family, and it is known that _PvEG261_[28], one member of this gene family, was considered to have functionality in FW resistance and drought resistance in common bean. _Vigun03g027900_, _Vigun03g087200_, _Vigun03g083600_ and _Vigun04g004600_ belong to the zinc finger family protein, and the zinc finger proteins play key roles in regulating plant defense gene expression and disease responses [29]. For example, _GhZFP1_, which contains two typical zinc finger motifs (C\(\times\)8C\(\times\)5C\(\times\)3H and C\(\times\)5C\(\times\)4C\(\times\)3H), can enhance the salt stress resistance and fungal resistance of transgenic tobacco, and _GhWRTX106-1_, which contains a typical C2 HC zinc finger structure, is thought to play a role in the FW resistance mechanism in cotton [30,31].