Development of a potato seedling assay to screen for resistance to Verticillium dahliae

Abstract

A seedling assay was developed for Verticillium wilt (VW) resistance in potato to provide efficient and rapid screening to identify resistant clones in segregating populations. The method provides uniform inoculum, which may reduce false negatives and the confounding effect of late maturity in field-grown plants. Seedlings of two cultivated varieties, five wild potato families and five families of complex hybrids were tested for VW symptoms after exposure to fungal suspensions and exudate from liquid cultures. The seedlings of the resistant cultivar and two resistant wild species exhibited fewer symptoms in response to fungal suspensions than the susceptible controls, indicating that seedlings can be scored for VW resistance or tolerance. Furthermore, exposure of seedlings to filter-sterilized exudates lacking the fungus elicited symptoms very similar to treatment with cultures containing VW condia. This result suggests that Vd (Verticillium dahliae Kleb.) liquid culture exudates may contain phytotoxins that can cause visible effects on the growth of certain genotypes. Overall, our results indicate that a greenhouse-based seedling assay can be used effectively to identify resistant or tolerant clones.

Field and Greenhouse Evaluations of Cucurbit Rootstocks to Improve Verticillium Resistance for Grafted Watermelon

“…Although it has been reported that V. dahliae assays performed in greenhouse conditions can be used to predict field performance, results from this study suggest that rootstock reactions to this pathogen in the field may not always be consistent with reactions in the greenhouse. Factors contributing to the observed differences between field and greenhouse studies may include the differing light, water, and temperature levels in the two environments, as well as the presence of additional disease organisms in the field (Bae et al, 2011). In this study, temperatures during the field study were 16°C on average, with 22°C maximum and 11°C minimum, and RH was 81%, whereas in the greenhouse, average temperature was 22 and 21°C in 2014 and 2015, respectively (24°C maximum and 20°C minimum for both years), and RH was 40% and 42%, respectively.…”

“…To identify verticillium wilt-resistant rootstocks, an efficient disease evaluation system is needed. Field assays can be used for this purpose, but they tend to be lengthy and confined to each growing season's constraints (Bae et al, 2011). Greenhouse assays, however, are rapid and can be conducted most times of the year.…”

“…Greenhouse assays, however, are rapid and can be conducted most times of the year. Bae et al (2011) developed a greenhouse assay to screen potato seedlings for verticillium wilt and demonstrated that resistance, tolerance, and susceptibility to this disease can be accurately assessed. The protocol used in the Bae et al, study involved submerging exposed roots into a V. dahliae suspension.…”

Efficiency of breeding olives for resistance to Verticillium wilt

“…As the interaction between progeny and selection methods was not significant, we can confirm that the inoculation method was effective in screening for resistant genotypes regardless of the genitors used. On the other hand, resistance mechanisms working before the entrance of the conidia into the root xylem are also overlooked when using the root dip inoculation method; therefore, an efficient method involving the infection of plants by microsclerotia would be of much interest, as has been developed for other species (Steventon et al, 2002;Bae et al, 2011). However, these methods usually require more time than root dip inoculation to observe symptoms.…”