Identification and Evaluation of Major Potato Cultivars Resistance to Globodera rostochiensis and Detection of Their H1 Resistance Gene Marker
[Objective]Potato cyst nematodes(PCN),including Globodera rostochiensis and G.pallida,are damaging soilbome quarantine parasitic pests on potatoes.The G rostochiensis has now distributed in seven counties of Yunnan,Guizhou,and Sichuan provinces in China,and several seed potato bases are threatened by the spread of G.rostochiensis.This study aimed to identify the resistance level of major potato cultivars to G.rostochiensis,clarify the presence of a known H1 resistance gene,and to provide a reference for screening and promoting resistant cultivars for controlling G.rostochiensis.[Method]For bioassay,15 major potato cultivars from the southwest mixed-cropping zone were inoculated with G.rostochiensis populations in an isolation greenhouse.The number of cysts per plant was counted and relative susceptibility was calculated,and finally the resistance of the cultivars was ranked according to a standard scoring notation.For H1 resistance gene identification,two molecular markers 57R and TG689,linked to the H1 for resistance to G.rostochiensis Ro1 pathotype,were used to identify 15 cultivars of the bioassay,with the BCH marker for amplification of the beta carotene hydroxylase gene as a control.For the field trial,a comparison of resistant and susceptible potato cultivars was conducted in a naturally infested field in 2020 and 2021 in Zhaotong,Yunnan Province.To estimate the initial(Pi)and final(Pf)populations of G.rostochiensis,soil sample was taken before planting and after harvested,and the reproduction factor(Pf/Pi)was calculated.The height of above-ground part of the plant at budding and initial flowering stages and the total yields at harvesting stage were measured.[Result]Among the 15 major potato cultivars,five cultivars(Yunshu 505,Xuanshu 5,Huishu 15,Huishu 19,and Yunshu 304)are highly resistant.It's hard for G.rostochiensis to reproduce on these cultivars.Two cultivars(Lishu 6 and Xuanshu 6)are moderately susceptible.Eight cultivars are highly susceptible,especially the Pf/Pi of Hui-2,Lishu 15 and Xuanshu 8 was higher than that of the susceptible control Huishu 16(Pf/Pi=17.15).Additionally,the results of the two H1 gene-linked molecular markers were generally consistent,five cultivars(Yunshu 505,Xuanshu 5,Huishu 15,Yunshu 304,and Xuanshu 6)contain the H1.G.rostochiensis reproduction factor differed significantly on resistant and susceptible cultivars in the field.The average Pf/Pi values of highly resistant cultivars(with resistance score 9)were＜1 in 2021(0.04-0.12)and 2022(0.05-0.14),indicating that nematode population densities decreased after planting of highly resistant cultivars.On the contrary,the average Pf/Pi values of the highly susceptible cultivars were＞1.00 in 2021(1.18-2.75)and 2022(1.76-3.24),indicating an increase in nematode populations in the field after planting of highly susceptible cultivars.There were significant differences between cultivars in plant height and yield(P＜0.05).The mean height of the five highly resistant cultivars was significantly higher than that of the eight highly susceptible cultivars in the two years.The cultivars Xuanshu 5,Huishu 15 and Huishu 19 had the highest yields of 51.67-56.48 and 33.28-40.57 t.hm-2 in two years,while Hui-2 had the lowest yields.[Conclusion]The resistant cultivars in the southwest mixed-cropping zone show excellent resistance to G.rostochiensis,mainly carrying the H1,and can reduce G.rostochiensis population densities in the field.High yields are produced by the resistant cultivars Xuanshu 5,Huishu 15,and Huishu 19,while Yunshu 304 is utilized as a processing potato for zinc-rich crisps.More focused identification of resistance levels of local cultivars based on G.rostochiensis incidence is urgently required.
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