Identification Of Resistance And Gene Analysis Of Main And New Wheat Varieties To Fusarium Crown Rot In Huang-Huai Wheat Region

Fusarium crown rot(FCR)is a serious soil-borne disease in wheat production.Despite being present in all major wheat-growing regions globally,FCR was first reported in the Huanghuai wheat region in 2012,and has been increasing year by year.Current efforts to prevent and control FCR rely primarily on chemical agents,but the effect is not ideal,and their use poses environmental risks.Planting disease-resistant varieties is a safe,effective,and eco-friendly approach to controlling FCR.Unfortunately,there is a shortage of FCR-resistant wheat varieties in the Huang-Huai wheat area,the main wheat-producing region in China,which hinders disease control through variety resistance.Urgently identifying and promoting FCR-resistant varieties in the affected areas is essential.During the 2020-2021 and 2021-2022 wheat production seasons,we assessed the FCR resistance of 397 wheat varieties selected and promoted in the Huanghuai wheat region.We inoculated the virulent strain WZ-8A of F.pseudograminearum,the dominant pathogen of FCR,in indoor pot experiments and field disease beds to identify high FCR resistance wheat varieties.From the 260 wheat varieties tested in 2020-2021,two wheat varieties showed high resistance to FCR,accounting for 0.77% of the total varieties tested,while the main resistance varieties accounted for 6.15% among the 16 varieties identified.In contrast,50 varieties were susceptible,and 192 were highly susceptible,making up 19.23% and 73.85% of the tested varieties,respectively.No immune species were found.Similarly,among the 137 wheat varieties collected in 2021-2022,only 6 medium-resistant varieties were identified,accounting for 4.38%,while 38 and 95 varieties were susceptible and highly susceptible,respectively,representing 27.74% and 69.34% of the tested varieties.No immune or highly resistant varieties were found.Field disease nursery investigation during the growing stage(filling stage)revealed that 5 high-resistance varieties,accounting for 1.92%,and 39 varieties with medium resistance,accounting for 15%,were identified from the 260 wheat varieties tested in 2020-2021.Conversely,85 varieties were susceptible,accounting for 32.69%,while 131 were highly susceptible,accounting for 50.38%.No immune species were found.Among the newly collected 137 wheat varieties in 2021-2022,20 medium-resistant varieties were identified,accounting for 14.60%,while 57 and 60 were susceptible and highly susceptible,representing 41.61% and 43.80% of the tested varieties,respectively.No immune or highly resistant varieties were found.We further screened 44 wheat varieties with moderate or above resistance identified in the field disease nursery in 2020-2021 in the field disease nursery.We used the highly susceptible variety Aikang58 as the control and identified 32 wheat varieties with moderate resistance,9 with susceptibility,and 3 with high susceptibility.Our findings suggest that the Huanghuai region lacks immune and highly resistant wheat varieties,and most of the identified varieties are susceptible or highly susceptible.A recent report suggests that Ta Cwi may act as a positive regulator for FCR resistance in wheat.We identified the carrying status of this resistance gene in 80 varieties with resistance above the test performance and 3 control varieties with high susceptibility.The results of PCR testing showed that all 83 varieties contained the Ta Cwi gene,indicating that Ta Cwi is not a specific resistance gene for FCR disease.Since both F.pseudograminearum and F.graminearum are part of the Fusarium spp.and can cause FCR and Fusarium Head Blight,we investigated the presence of main resistance genes Fhb1 and Fhb7 in the 80 moderately resistant varieties and three highly susceptible control varieties.Results showed that only Chanmai 218 carried both Fhb1 and Fhb7 genes,while 11 varieties like Xumai 2023,Kaimai 18,and Zhongmai 99 carried only the Fhb1 gene.Microfluorescence observation revealed that when F.pseudograminearum infected the base of the stem of wheat 218,the hyphae’s expansion in the cells was hindered.Compared with the susceptible variety Aikang58,the mycelial branches in the cells of F.pseudograminearum were significantly increased.