Department of Plant Pathology, University of Georgia, Tifton, GA 31793, USA.
Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA.
Int J Mol Sci. 2021 Jan 15;22(2):822. doi: 10.3390/ijms22020822.
Fusarium wilt of watermelon, caused by f. sp. (FON), is pathogenic only to watermelon and has become one of the main limiting factors in watermelon production internationally. Detection methods for this pathogen are limited, with few published molecular assays available to differentiate FON from other formae speciales of . FON has four known races that vary in virulence but are difficult and costly to differentiate using traditional inoculation methods and only race 2 can be differentiated molecularly. In this study, genomic and chromosomal comparisons facilitated the development of a conventional polymerase chain reaction (PCR) assay that could differentiate race 3 from races 1 and 2, and by using two other published PCR markers in unison with the new marker, the three races could be differentiated. The new PCR marker, FNR3-F/FNR3-R, amplified a 511 bp region on the "pathogenicity chromosome" of the FON genome that is absent in race 3. FNR3-F/FNR3-R detected genomic DNA down to 2.0 pg/µL. This marker, along with two previously published FON markers, was successfully applied to test over 160 pathogenic FON isolates from Florida, Georgia, and South Carolina. Together, these three FON primer sets worked well for differentiating races 1, 2, and 3 of FON. For each marker, a greater proportion (60 to 90%) of molecular results agreed with the traditional bioassay method of race differentiation compared to those that did not. The new PCR marker should be useful to differentiate FON races and improve Fusarium wilt research.
西瓜枯萎病，由 f. sp. (FON)引起，仅对西瓜具有致病性，已成为国际上西瓜生产的主要限制因素之一。该病原体的检测方法有限，可用的分子检测方法很少，无法将 FON 与其他 专化型区分开来。FON 有四个已知的小种，毒力不同，但使用传统接种方法很难且成本高，只能通过分子方法区分小种 2。在这项研究中，基因组和染色体比较促进了常规聚合酶链反应 (PCR) 检测方法的开发，该方法可将小种 3 与小种 1 和 2 区分开来，并且通过同时使用另外两个已发表的 PCR 标记与新标记，可将三个小种区分开来。新的 PCR 标记 FNR3-F/FNR3-R 扩增了 FON 基因组“致病性染色体”上的一个 511 bp 区域，该区域在小种 3 中不存在。FNR3-F/FNR3-R 检测到基因组 DNA 的下限为 2.0 pg/µL。该标记与两个先前发表的 FON 标记一起，成功应用于测试来自佛罗里达州、佐治亚州和南卡罗来纳州的 160 多个致病 FON 分离物。这三个 FON 引物组一起很好地区分了 FON 的小种 1、2 和 3。对于每个标记，与未使用的方法相比，与传统生物测定方法区分小种的分子结果的比例（60%至 90%）更高。新的 PCR 标记应可用于区分 FON 小种并改进枯萎病研究。
