New strawberry breeding lines with low susceptibility to Phytophthora crown and root rot in Huelva, Spain

Phytophthora crown and root rot of strawberries is caused by Phytophthora cactorum and it is one of the main diseases of the crop in Huelva province (southwestern Spain). Breeding programs for resistance to this disease are in progress in Spain. In a previous work, the different susceptibility of the most important strawberry cultivars used and previous breeding lines was observed. In the present work, three cultivars and two breeding lines were included in assays of susceptibility with artificial inoculation. Eighteen plants of each cultivar were inoculated with a root bath in a suspension with P. cactorum propagules. After inoculation, plants were cultivated in a growth chamber in a randomized design with three repetitions of six plants each. The assays were conducted three times from September to October in 2017, 2018 and 2019. Results showed four susceptibility groups: 'Florida Fortuna' was the most susceptible cultivar, followed by 'Rábida FNM'. 'Rociera FNM' and the breeding line A14 presented moderate susceptibility. A14-205P was the lowest susceptible breeding line but significantly similar to A14. A14-205P had 46.5% less disease severity than the most susceptible cultivar in the average of three years. Therefore, the use of these breeding lines is an efficient and sustainable resource to control this disease.