Shedding Light on Races of the Spinach Fusarium Wilt Pathogen, Fusarium oxysporum f. sp. spinaciae

Abstract

Two pathogenicity groups of Fusarium oxysporum f. sp. spinaciae, the causal agent of Fusarium wilt of spinach (Spinacia oleracea L.), were described recently based on virulence of isolates on proprietary spinach inbreds. In this study, a wide range in severity of wilt was observed for 68 spinach cultivars inoculated with an isolate of each pathogenicity group, with 22 (32.4%) cultivars displaying differential responses to the isolates. In a second set of trials, seven spinach cultivars were inoculated with five isolates of each pathogenicity group. The cultivars had similar wilt responses to isolates within each group. In both sets of trials, the most severe wilt developed on cultivars inoculated with pathogenicity group 2 isolates when daylength was shorter and light intensity lower. To test whether light intensity exacerbates severity of Fusarium wilt, three spinach cultivars were inoculated with two isolates of each pathogenicity group and grown with or without shading. Shaded plants developed more severe wilt than non-shaded plants. This difference in wilt severity was greatest for plants inoculated with pathogenicity group 2 isolates. We propose naming isolates of pathogenicity groups 1 and 2 as races 1 and 2 of F. oxysporum f. sp. spinaciae, respectively, and recommend the cultivars Kiowa (susceptible to both races) and Magnetic (susceptible to race 2 and highly resistant to race 1) as differentials. Results of this study should help breeders screen spinach germplasm for resistance to both races of F. oxysporum f. sp. spinaciae.

Lessons from 10 years of stakeholder adoption of a soil bioassay for assessing the risk of spinach Fusarium wilt

“…There has also been an increase in awareness of the importance of genetic resistance to Fusarium wilt, including the need for greater resistance in the inbred lines used to produce hybrid seed. To this end, research is in progress at identifying sources of resistance in contemporary spinach cultivars, spinach germplasm collections, and wild spinach populations to aid in breeding for resistance to Fusarium wilt (Batson et al, 2020b; Gyawali et al, 2019).…”

Chlorella vulgaris and Tetradesmus obliquus Protect Spinach (Spinacia oleracea L.) against Fusarium oxysporum

“…Spinach is also susceptible to F. oxysporum and is often used as a model species in phytopathogenic in vivo trials [37]. Due to its high functional and genetic diversity, the strain responsible for fusarium wilt in spinach belongs to forma specialis spinaciae W.C. Snyder & H. N. Hansen [26,28,33,38].…”