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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. [ABSTRACT FROM AUTHOR]

Verticillium wilt is a major disease of olive (Olea europaea) orchards worldwide. To control the disease, use of a reliable method for pre-planting screening of new planting stocks for infection by V. dahliae is essential. In this study, 20 symptomatic and asymptomatic olive trees, sampled from Zahak region of Sistan in Iran, were analyzed with real-time and nested PCR for in planta detection of V. dahliae. We could confirm the presence of V. dahliae in 12 out of 20 (60%) sampled trees using real-time PCR, whereas nested PCR produced amplicons for all tested symptomatic and asymptomatic samples (100% of tested trees), indicating that nested PCR was more efficient method than real-time PCR for in planta detection of V. dahliae. We used the designed nested PCR to determine also the pathotype of V. dahliae using Vdf2/Vdr2 primer set at the second round, which could produce the 297-bp amplicon for all tested samples infected with non-defoliating pathotype of V. dahliae. We showed that although the Verticillium wilt is spread in the olive cultivation areas in Zahak region of Sistan, nested PCR can be deployed for the timely detection and thereby prevention of the further spread of V. dahliae in the olive cultivation areas. • Verticillium wilt disease has been spread in olive plantations in Zahak region of Sistan. • Nested PCR is more efficient than real-time PCR for in planta detection of V. dahliae. • Nested PCR is a robust method for in planta detection of V. dahliae not only in symptomatic but also in asymptomatic trees. [ABSTRACT FROM AUTHOR]

The article investigates an outbreak of a wilt like disease of alfalfa (lucerne) in the Markazi Province of Iran. Symptoms during early growth stages typically consisted of V-shaped orange-pinkish necrotic areas on the leaflets. On severely affected shoots of more mature plants, leaflets were usually desiccated and twisted, forming spirals. These symptoms are very similar to those reported for verticillium wilt in alfalfa sterilized stem tissue onto water agar. The fungus was confirmed as the causal agent of the disease by inoculating Lucerne plants by root dipping into conidial suspensions. This is the first reported occurrence of verticillium wilt disease of alfalfa in Iran, or indeed anywhere in continental Asia. This particular wilt can be a severe disease in alfalfa and, should it become widespread in Iran, it could cause significant crop loss.