Medicago truncatula quantitative resistance to a new strain of Verticillium alfalfae from Iran revealed by a genome-wide association study

Amir Hossein Fartash; Cécile Ben; Mélanie Mazurier; Asa Ebrahimi; Mojtaba Ghalandar; Laurent Gentzbittel; Martina Rickauer

doi:10.3389/fpls.2023.1125551

Medicago truncatula quantitative resistance to a new strain of Verticillium alfalfae from Iran revealed by a genome-wide association study

Front Plant Sci. 2023 Apr 14:14:1125551. doi: 10.3389/fpls.2023.1125551. eCollection 2023.

Authors

Amir Hossein Fartash¹, Cécile Ben^{1

2}, Mélanie Mazurier¹, Asa Ebrahimi³, Mojtaba Ghalandar⁴, Laurent Gentzbittel^{1

2}, Martina Rickauer¹

Affiliations

¹ Laboratoire écologie fonctionnelle et environnement, Université de Toulouse, Centre National de Recherche Scientifique, Toulouse Institut National Polytechnique, Université Toulouse 3 - Paul Sabatier (UPS), Toulouse, France.
² Project Center for Agro Technologies, Skolkovo Institute of Science and Technology, Moscow, Russia.
³ Department of Plant Breeding and Biotechnology, Science and Research Branch, Islamic Azad University, Tehran, Iran.
⁴ Plant Protection Department, Markazi Agricultural and Natural Resources Research and Education Center, Arak, Iran.

Abstract

Verticillium wilt is a major threat to many crops, among them alfalfa (Medicago sativa). The model plant Medicago truncatula, a close relative of alfalfa was used to study the genetic control of resistance towards a new Verticillium alfalfae isolate. The accidental introduction of pathogen strains through global trade is a threat to crop production and such new strains might also be better adapted to global warming. Isolates of V. alfalfae were obtained from alfalfa fields in Iran and characterized. The Iranian isolate AF1 was used in a genome-wide association study (GWAS) involving 242 accessions from the Mediterranean region. Root inoculations were performed with conidia at 25°C and symptoms were scored regularly. Maximum Symptom Score and Area under Disease Progess Curve were computed as phenotypic traits to be used in GWAS and for comparison to a previous study with French isolate V31.2 at 20°C. This comparison showed high correlation with a shift to higher susceptibility, and similar geographical distribution of resistant and susceptible accessions to AF1 at 25°C, with resistant accessions mainly in the western part. GWAS revealed 30 significant SNPs linked to resistance towards isolate AF1. None of them were common to the previous study with isolate V31.2 at 20°C. To confirm these loci, the expression of nine underlying genes was studied. All genes were induced in roots following inoculation, in susceptible and resistant plants. However, in resistant plants induction was higher and lasted longer. Taken together, the use of a new pathogen strain and a shift in temperature revealed a completely different genetic control compared to a previous study that demonstrated the existence of two major QTLs. These results can be useful for Medicago breeding programs to obtain varieties better adapted to future conditions.

Keywords: alfalfa; biotic stress; fungal pathogen; gene expression; global warming; legume; quantitative disease resistance; vascular wilt.

Grants and funding

This work has been supported with project PHC Gundishapur N˚ 38423VK through funding field trips to Iran. AF was supported by the Iranian NanoBioTechnologist laboratory (INBTCo.), Tehran, Iran with a PhD grant.