Inheritance of Resistance to Phytophthora Crown Rot in Cucurbita pepo

Abstract

<jats:p><jats:italic>Phytophthora</jats:italic> crown rot, caused by <jats:italic>Phytophthora capsici</jats:italic> Leonian, is a devastating disease in commercial squash (<jats:italic>Cucurbita pepo</jats:italic> L.) production across the United States. Current management practices rely heavily on the use of chemical fungicides, but existence of fungicide-resistant pathogen populations has rendered many chemicals ineffective. Host resistance is the best strategy for managing this disease; however, no commercial cultivars resistant to the pathogen are currently available. Resistance to <jats:italic>Phytophthora</jats:italic> crown rot in PI 181761 (<jats:italic>C. pepo</jats:italic>) is an important genetic resource for squash breeders worldwide; however, the underlying genetic basis of resistance in PI 186761 that would allow designing of sound breeding strategies is currently unknown. The goal of the current study was to determine the inheritance of resistance in breeding line #186761-36P, a resistant selection of PI 181761, using phenotypic data from F<jats:sub>1</jats:sub>, F<jats:sub>2</jats:sub>, and backcross populations derived from a cross between #181761-36P and a susceptible acorn-type cultivar, Table Queen. The results indicated that resistance in #181761-36P is controlled by three dominant genes (R4, R5, and R6). Introgression of these genes into susceptible cultivar groups of <jats:italic>C. pepo</jats:italic> will provide an important tool in the integrated management of <jats:italic>Phytophthora</jats:italic> crown rot.</jats:p>

A Novel QTL for Resistance to Phytophthora Crown Rot in Squash

“…On the contrary, the Table Queen cultivar was highly susceptible as evidenced by a rapid expansion of water-soaked lesions to the cotyledons and subsequent wilting and death. The phenotypic distribution in the F 2:3 population was normal, but skewed towards susceptibility, thus supporting a three-gene model previously described for resistance in #181761-36P [15]. A similar skewed distribution was observed in a C. pepo F 2:3 population derived from a cross between a crown rot resistant breeding line #Pc-NY21 and a susceptible cultivar (#Dunja F 1 ) [10], indicating a similar but independent inheritance pattern in both resistant sources.…”

“…The high resistance to Phytophthora crown rot observed in #181761-36P confirms this accession as a good source for resistance breeding in C. pepo [14,15]. On the contrary, the Table Queen cultivar was highly susceptible as evidenced by a rapid expansion of water-soaked lesions to the cotyledons and subsequent wilting and death.…”

“…Further selection and selfing of PI 181761 yielded a breeding line (designated #181761-36P) fixed for resistance against Phytophthora crown rot. Resistance in #181761-36P is controlled by three dominant genes designated R4, R5 and R6 [15]. Marker-assisted selection (MAS) for Phytophthora crown rot resistance in #181761-36P would greatly expedite breeding and the release of resistant commercial cultivars.…”

Performance and Resistance to Phytophthora Crown and Root Rot in Squash Lines

“…However, the presumed quantitative basis of resistance indicates that the other partially resistant accessions likely possess beneficial alleles that may not be present in the PR lines. The resistant accessions identified by Padley et al (2008) have since been genotyped with simple sequence repeat markers and revealed to be genetically like cultivars representing zucchini and pumpkin morphotypes (Michael et al, 2019). The resistance levels of the PR lines could potentially be improved by the incorporation of additional beneficial alleles from these accessions.…”

A Compost Treatment Acts as a Suppressive Agent in Phytophthora capsici – Cucurbita pepo Pathosystem by Modifying the Rhizosphere Microbiota

“…Chemical control strategies are difficult to adopt, due to the limited number of registered chemicals that are permitted and the scalar harvest system (Gilardi et al, 2015). However, many efforts have been made to find a source of genetic resistance in squash accessions to PHC strains (Michael et al, 2019;Siddique et al, 2019), but this approach is still at its beginning. For these reasons, alternative PHC control agents are being studied and adopted in agriculture.…”