西瓜枯萎病菌侵染西瓜根茎部的组织病理学观察

Histological observation of watermelon root and stem infected by Fusarium oxysporum f.sp.niveum

为探明西瓜枯萎病菌侵染西瓜根系及茎的过程,本研究选取一株致病力较强的西瓜枯萎病菌FO1022,利用绿色荧光蛋白基因(GFP)标记该菌株,观察病原菌侵染西瓜根茎部的组织学过程。结果表明,用GFP标记的病菌接种感病西瓜品种‘苏蜜1号’,接种后2d,显微观察显示病原菌的分生孢子附着于西瓜根系表皮细胞并萌发,沿细胞间层定殖生长;接种后5d,在西瓜根部维管束导管中观察到大量菌丝和大型分生孢子,在根部表皮细胞上观察到大量厚垣孢子,在茎部部分维管束导管中也观察到少量的菌丝,此时48.6%的幼苗表现萎蔫症状;接种后9d,茎部所有维管束导管都充斥着密集的菌丝体,此时91.7%的幼苗表现枯萎和死亡。与侵染感病品种相比,该菌株在侵染中抗品种和高抗品种时,在侵染时间上要明显滞后。本研究从组织病理学的角度观察并分析了GFP标记的西瓜枯萎病菌侵染西瓜根茎部的过程,为研究西瓜枯萎病菌的致病机理提供参考。

In order to observe the infection process of Fusarium oxysporum f.sp.niveum （FON） in watermelon root and stem,the strain FO1022 with high virulence was selected and the green fluorescent protein was transformed into this pathogen to observe the infection process.The results showed that in the susceptible cultivar ＇ Sumi No.1＇two days after inoculation,conidia of FO1022-GFP were found to attach the watermelon root epidermis and germinated; the preferential colonization sites on the root surface were the grooves along the junctions of adjacent epidermal cells.At day 5 after inoculation,massive hyphae and macroconidia of the fungal pathogen were observed in xylem vessels of the watermelon root,and massive chlamydospores were observed in the root epidermis,while only a few hyphae were observed in xylem vessels of the watermelon stem; at this stage,48.6% of the seedlings appeared to wilt.At day 9 after inoculation,all xylem vessels of the watermelon stem were clogged by massive hyphae,and 91.7% of the seedlings appeared to exsiccate.Compared to the infection process in susceptible cultivar,this pathogen infected more slowly in the moderately-resistant or resistant cultivar.The infection process of FO1022-GFP in watermelon root and stem was observed and analyzed by histopathological observation,which provides a reference for exploring the pathogenic mechanism of this pathogen.