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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #311926
Title: Characterization of spinach germplasm for resistance against two races of Verticillium dahliae

Author
item Mou, Beiquan
item Klosterman, Steven
item Anchieta, Amy
item Wood, Elisabeth
item SUBBARAO, KRISHNA - University Of California

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2015
Publication Date: 11/23/2015
Citation: Mou, B., Klosterman, S.J., Anchieta, A.G., Wood, E.M., Subbarao, K. 2015. Characterization of spinach germplasm for resistance against two races of Verticillium dahliae. HortScience. 50:1631-1635.

Interpretive Summary: Verticillium dahliae is a soilborne fungal pathogen that causes wilt diseases and devastating losses in many important crops. Verticillium wilt has not presented a problem in California spinach production because the crop is harvested well before the symptoms develop during the post-stem elongation (bolting) stage. However, infested spinach seeds introduce or increase the amount of pathogen in the soil for other rotational crops such as lettuce. This investigation was designed to identify Verticillium wilt-resistant varieties in the USDA spinach germplasm collection against two races of the pathogen: races 1 and 2 of V. dahliae, and to examine seed transmission of the pathogen in different spinach varieties. A total of 277 spinach varieties including nine commercial cultivars were screened against one race 1 and two race 2 isolates from spinach in replicated greenhouse experiments. There was a wide range of variation in reactions among spinach varieties against the pathogen with disease incidence ranging from 0 to 100%. The two race 2 isolates differed in their virulence against spinach varieties. Resistant spinach varieties were identified against both races 1 and 2 pathogen. Some accessions identified as resistant based on disease incidence showed little seed transmission. Variation among plants within varieties was also observed. Nevertheless, the sources of resistance identified in this study are useful for spinach cultivar improvement.

Technical Abstract: Historically, wilt disease caused by V. dahliae has not presented a problem in California spinach production because the crop is harvested well before the symptoms develop during the post-stem elongation (bolting) stage. However, infested spinach seeds introduce or increase inoculum in the soil for rotational crops such as lettuce. This investigation was designed to identify Verticillium wilt-resistant accessions in the USDA spinach germplasm collection against races 1 and 2 of V. dahliae, and to examine seed transmission of the pathogen in different spinach genotypes. In a seed health assay of 392 accessions of the collection, 21(5.4%) were positive for V. dahliae, and 153 (39%) were positive for V. isaacii. A total of 268 accessions plus nine commercial cultivars were screened against one race 1 and two race 2 isolates from spinach in replicated greenhouse experiments. Plants were observed for disease incidence, severity, and seed transmission through plating on NP-10 medium and real-time quantitative polymerase chain reaction (qPCR). There was a wide range of variation in reactions among accessions against V. dahliae with disease incidence ranging from 0 to 100%. The two race 2 isolates differed in their virulence against spinach genotypes. Resistant accessions were identified against both races 1 and 2. Recovery of V. dahliae from seeds plated on NP-10 medium and qPCR results were highly correlated (P = 0.00014). Some accessions identified as resistant based on disease incidence showed little seed transmission. Even though lower wilt incidence and severity generally corresponded with lower seed transmission rates, there were exceptions (r = 0.52). Variation among plants within accessions was also observed. Nevertheless, the sources of resistance identified in this study are useful for spinach cultivar improvement.