Evaluating common bean dual resistance to root-knot nematode and Fusarium wilt in recombinant inbred lines
Alyx Renato Santos de Freitas, Beatriz Fugolin Biolcati, César Junior Bueno, Guilherme Alexandre Luz da Costa, Maria Lucia Carneiro Vieira, Alisson Fernando Chiorato, Sérgio Augusto Morais Carbonell and Luciana Lasry Bechimol-Reis
Abstract: Common bean yield (Phaseolus vulgaris L.) is severely limited by diseases caused by root-knot nematode (Meloidogyne incognita) and Fusarium oxysporum f. sp. phaseoli (Fop). This study assessed co-infectioneffects by these phytopathogens in 73 F₈ recombinant inbred lines (RILs) derived from the ‘IAC-Tybatã’ × ‘Branquinho’ cross to identify genotypes with dual resistance. Plants received three treatments: control (water), Fop (root immersion in 1.0 × 10⁶ conidia mL⁻¹ suspension), and M. incognita (5,000 eggs/plant) + Fop. Co-infected plants developed significantly more pronounced vascular discoloration compared to plants inoculated with Fop alone. While 76.8% of Fop-inoculated RILs showed mild-to-moderate symptoms, 86.3% of co-infected RILs exhibited moderate-to-severe discoloration. Six RILs (1, 5, 8, 25, 31 and 47) showed dual resistance, displaying mild Fop symptoms and minimal nematode gall formation. The identification of these resistant genotypes is a critical breeding objective for developing common bean cultivars with enhanced protection against these damaging co-occurring pathogens.