Natural variation in Portuguese common bean germplasm reveals new sources of resistance against Fusarium oxysporum f. sp. phaseoli and resistance-associated candidate genes

Authors: LEITAO, SUSANA - Universidade Nova De Lisboa; MALOSETTI, MARCOS - Wageningen University And Research Center; Song, Qijian; EEUWIJK, FRED - Wageningen University And Research Center; RUBIALES, DIEGO - Institute For Sustainable Agriculture; PATTO, MARIA - Universidade Nova De Lisboa

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2019
Publication Date: 1/28/2020
Citation: Leitao, S., Malosetti, M., Song, Q., Eeuwijk, F., Rubiales, D., Patto, M. 2020. Natural variation in Portuguese common bean germplasm reveals new sources of resistance against Fusarium oxysporum f. sp. phaseoli and resistance-associated candidate genes. Phytopathology. 110(3):663-647.

Interpretive Summary: Fusarium wilt is among the most important fungal diseases affecting common bean production throughout the world. This pathogen penetrates through root tips or wounds and grows in the plant's vascular system. In susceptible plants, the disease may lead to vessel clogging, internal stem discoloration, a rapid yellowing of foliage, followed by defoliation and ultimately plant death. The existing resistance provides only moderate or incomplete levels of protection to the highly virulent race 6 in common bean. Portuguese common bean germplasm is a mixture of Mesoamerican and Andean pools and may have novel resistance gene combinations; however, little is known about the response of the Portuguese germplasm against the disease. In this study, we evaluated a set of diverse Portuguese common bean types for resistance to fusarium wilt race 6 and mapped the presence of genes using DNA signatures. The study lead to the discovery of beans with new resistance genes and DNA signature markers associated with those genes. The results will help scientists and plant breeders at government institutions, universities, and private companies to develop new cultivars of beans with superior resistance to fusarium wilt.

Technical Abstract: Common bean (Phaseolus vulgaris L.) is one of the most consumed legume crops in the world and fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. phaseoli (Fop), is one of the major diseases affecting its production. Portugal has preserved common bean germplasm with an admixed genetic background that may have novel resistance combinations between the original Andean and Mesoamerican gene pools. In order to identify new sources of fusarium wilt resistance and detect resistance-associated SNPs, we explored, for the first time, a diverse collection of the underused Portuguese common bean germplasm via genome-wide association analysis. The collection was evaluated for fusarium wilt resistance under growth chamber conditions, using the highly virulent Fop strain, FOP-SP1 race 6. Fourteen of the 162 Portuguese accessions evaluated were completely resistant and 71 were incomplete resistant. The same collection was genotyped with Illumina BARCBean6K_3BeadChip and DArTseq arrays and SNP-resistance associations were tested using a mixed linear model accounting for the genetic relatedness among accessions. Association mapping identified nine SNPs associated with resistance on chromosomes Pv04, PV05, Pv07, and Pv08, indicating that fusarium wilt resistance is under oligogenic control. Putative candidate genes related to phytoalexins biosynthesis, hypersensitive response and plant primary metabolism were identified. The results highlight the importance of exploring underused germplasm for new sources of resistance and provide new genomic targets for the development of functional markers to support selection in future disease resistance breeding programs.