生防菌根系定殖竞争作用对西瓜枯萎病发病机理的影响

Effect of antagonistic fungal competition for colonization of roots on pathogenesis of watermelon Fusarium wilt

摘要:

【目的】西瓜枯萎病是由西瓜专化型尖孢镰刀菌(Fusarium oxysporum f. sp. niveum)引起的一种常见的毁灭性土传病害, 对镰刀菌同属非致病性菌株与致病性菌株存在的竞争作用进行研究, 有助于获得新的具有生防效果的菌株, 从而拓宽西瓜枯萎病生物防治的手段。【方法】利用选择性培养基和稀释平板计数法对温室盆栽试验中西瓜根际和非根际土壤及植物组织中非致病性轮枝镰刀菌菌株(Fusarium verticillioides XA)与致病性尖孢镰刀菌(Fusarium oxysporum LD)进行计数, 确定其在西瓜植株根际和组织中的定殖情况。【结果】将从田间西瓜枯萎病发病植株根部分离获得的菌株XA和LD接入健康土壤中, 接种菌株XA既不会引起西瓜枯萎病发病症状, 也不会影响西瓜植株生物量, 但接种菌株LD导致严重发病症状。与单接种LD处理相比较, 双接种(XA+LD)处理地上部鲜重和地上部干重都分别增加了151.2%和110%。XA菌株能成功定殖于西瓜根系, 但在茎基部没有检测到。在接种菌株LD的处理中植物组织和土壤中致病性镰刀菌的数量达到(1.58?4.85)×104 CFU/g。与单接种LD处理相比, 双接种菌株XA和LD处理植物茎基部、根系、根际土壤和土体土壤致病性镰刀菌的数量分别下降63.3%、66.1%、3.3%和24.4%, 根系、根际土壤和土体土壤非致病性镰刀菌的数量增加到(0.35?3.84)×104 CFU/g; 双接种处理对西瓜枯萎病的防效达57.8%。【结论】非致病性轮枝镰刀菌菌株XA可有效降低致病性尖孢镰刀菌LD对西瓜植株的定殖侵染能力, 对西瓜枯萎病具有一定的生防效果。

Abstract:

[Objective] Watermelon Fusarium wilt caused by Fusarium oxysporum f. sp. niveum is a common destructive soil-borne disease. Understanding of the competition between non-pathogenic congeneric Fusarium species and pathogenic Fusarium oxysporum strains has contributed to acquisition of novel bio-control agents and broadening the biological control measures against the plant disease. [Methods] Selective media and dilution plating procedure were used to study colonization of bulk soil, rhizosphere soil and plant tissues of watermelon grown in greenhouse pots by non-pathogenic Fusarium verticillioides XA and pathogenic Fusarium oxysporum LD. [Results] Strains XA and LD were isolated from diseased plant tissues in field. When non-diseased soil was solely inoculated with strain XA or strain LD, inoculation with strain XA had no symptom of wilt and no loss of biomass of watermelon whereas inoculation with strain LD led to heavily symptom of wilt. As compared with the treatment of LD, the treatment of dual inoculation with strains XA and LD increased the fresh weight and dry weight of the aerial part of watermelon plants by 151.2% and 110%, respectively. Strain XA successfully colonized roots but was not found in the basal part of stem of watermelon, while strain LD infected plant tissues and soil with (1.58?4.85)×104 CFU/g. As compared with the treatment of LD inoculation, the dual inoculation with strain XA and strain LD decreased the pathogenic F. oxysporum numbers in the basal part of stem, roots, rhizosphere soil and bulk soil of watermelon by 63.3%, 66.1%, 3.3% and 24.4%, respectively and increased the non-pathogenic F. oxysporum numbers in roots, rhizosphere soil and bulk soil of watermelon to (0.35?3.84)×104 CFU/g; this treatment gained 57.8% of control efficiency against watermelon Fusarium wilt. [Conclusion] The non-pathogenic congeneric strain XA effectively reduced the ability of pathogenic F. oxysporum LD to infect watermelon plants and had certain effectiveness as a biocontrol agent against watermelon Fusarium wilt.