Evaluation and Selection of Watermelon Germplasm for the Breeding of Fusarium Wilt and Root-Knot Nematode Resistant Rootstock

Watermelons are grafted to prevent soil-borne diseases such as Fusarium wilt (FW) and increase their resistance to abiotic stress.Root-knot nematodes (RKN) are a contributing factor to economic loss in several cucurbits, including watermelon.Growing resistance varieties is an effective way to reduce the damage caused by soil-borne diseases.Resistance evaluation was performed on 50 watermelon lines to select rootstocks resistant to FW and RKN.Fusarium oxysporum f. sp.niveum race 2 was inoculated into 10-day-old seedlings using a root dipping method, and resistance was evaluated for four weeks.The 37-day-old watermelon seedlings were inoculated with Meloidogyne incognita and evaluated 60 days later.Three lines (IT199860, PI296341-6, and PI532811) were resistant to FW race 2, while one line (PI494527) was moderately resistant.Three lines (PI296341-5, PI457916-2, and PI457916-5) were RKN resistant.The PI296341-6 line was selected for its resistance to FW and moderate resistance to RKN.These findings imply that the identified resistant lines can be used in rootstock breeding programs against FW and/or RKN.