Swett Cassandra L, Del Castillo Múnera Johanna, Hellman Elizabeth, Helpio Erin, Gastelum Megan, Lopez Raymundo Elver, Johnson Heather, Oguchi Rino, Hopkins Aimee, Beaulieu Justine, Rodriguez Fernando
Swett Lab, Department of Plant Pathology, University of California, Davis, CA, United States.
Front Plant Sci. 2023 Mar 31;14:1088044. doi: 10.3389/fpls.2023.1088044. eCollection 2023.
Fusarium wilt, caused by f. sp. (Fol), causes losses in tomato production worldwide, with major impacts on Californian tomato processing. Single-gene resistance is the primary management tool, but its efficacy has been compromised following the emergence of two successive resistance-breaking races, which, in California, emerged within 12 years of resistance deployment. Fol race 3-resistant (F3) processing tomato cultivars (containing the resistance gene) were deployed in the state starting in approximately 2009. The emergence of a new resistance-breaking race (which would be called race 4) is imminent, and early detection will be critical to delay the spread while new resistance is sought. The detection of Fol race 4 is challenged by the lack of validated, rapid, and accurate diagnostic tools. In evaluating phenotyping methods, this study found that rapid seedling phenotyping is not reliable and generates false positives for nonpathogens. Longer (10 weeks) mature plant assays are the most reliable, but may not be sufficiently timely. As an additional challenge, based on field and greenhouse studies, Fol race 3 can cause symptoms in resistant F3 cultivars at frequencies greater (30%) than expected for off-types (<2%). We developed a three-F3 cultivar assay to overcome the challenges this posed to differentiating Fol race 3 and Fol race 4. Using the assay, we determined that all putative resistance-breaking cases were Fol race 3; Fol race 4 was not detected in these early survey efforts. These results highlight the need for developing rapid Fol race 4 detection tools and a better understanding of the factors underlying inconsistent gene expression in Fol race 3.
由番茄尖镰孢菌（Fusarium oxysporum f. sp. lycopersici，Fol）引起的枯萎病在全球番茄生产中造成损失，对加利福尼亚州的番茄加工产业产生重大影响。单基因抗性是主要的防治手段，但在相继出现两个能打破抗性的小种后，其效力受到了影响，这两个小种在加利福尼亚州是在抗性品种推广后的12年内出现的。大约从2009年开始，该州开始推广对Fol小种3具有抗性（F3）的加工番茄品种（含有抗性基因）。一种新的能打破抗性的小种（即后来所称的小种4）即将出现，在寻找新抗性的同时，早期检测对于延缓其传播至关重要。由于缺乏经过验证的、快速且准确的诊断工具，Fol小种4的检测面临挑战。在评估表型分析方法时，本研究发现快速的幼苗表型分析不可靠，会对非病原菌产生假阳性结果。较长时间（10周）的成熟植株检测是最可靠的，但可能不够及时。另外一个挑战是，根据田间和温室研究，Fol小种3在抗性F3品种上引起症状的频率（30%）高于预期的异常类型（<2%）。我们开发了一种使用三个F3品种的检测方法，以克服区分Fol小种3和Fol小种4时面临的这些挑战。通过该检测方法，我们确定所有疑似能打破抗性的病例都是Fol小种3；在这些早期调查中未检测到Fol小种4。这些结果凸显了开发快速检测Fol小种4工具的必要性，以及更好地理解Fol小种3中基因表达不一致背后因素的重要性。
