Wheat stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is an important airborne disease worldwide. Pst inoculum strength in southern Henan in winter or early spring is important for spring epidemics in the main autumn-sown wheat-growing regions of China. However, there is limited knowledge about the source and time of initial infection on winter wheat in southern Henan. The first occurrence of wheat stripe rust in southern Henan was recorded annually from 2011 to 2022, from which we used the backward trajectory approach to infer the likely source of Pst inoculum responsible for the initial disease occurrence. The results suggested that the Pst inoculum responsible for initial rust established in the winter in southern Henan originated from the Gansu Pst oversummering area in China, whereas it originated from the adjacent winter Pst sporulation regions in southern Shaanxi and northwestern Hubei if Pst symptoms were first observed in early spring in southern Henan. Another possible Pst source is southern Hubei where Pst can also sporulate in the winter. Thus, early Pst development in winter in the main wheat production region in China (Henan) is likely to be caused by Pst inoculum spread from the oversummering inocula or Pst epidemics in autumn seedlings in Gansu.
Vascular wilt of lettuce is caused by strains of the Fusarium oxysporum species complex. According to their biological activity, these strains are members of the forma specialis lactucae (FOL). The aim of this study was to characterize strains of Fusarium oxysporum isolated from lettuce in Italy and other countries, belonging to the four currently known races. Strains were analyzed based on pathogenicity on different hosts and a combined phylogenetic analysis of rpb2, tef-1α, cmdA and tub2 genes. For uncharacterized strains, the race was determined through pathogenicity test with a set of differential lettuce cultivars for races 1 and 4. To assess the host range, pathogenicity tests were performed on five species: lettuce (Lactuca sativa), lamb's lettuce (Valerianella locusta), spinach (Spinacia oleracea), wild rocket (Diplotaxis tenuifolia) and cultivated rocket (Eruca sativa). Most FOL strains were pathogenic on lettuce with different levels of disease severity; in particular, FOL races 3 and 4 showed the highest level of virulence on lettuce. FOL races 3 and 4 were pathogenic both on lettuce and lamb's lettuce, whereas races 1 and 2 only on lettuce. Furthermore, this study identified the first occurrence of FOL race 4 in Italy to 2016, as the strain FOL 1/16 was assigned to race 4. Results of multigene phylogenetic analysis showed that FOL races 1 and 4 cluster with the species F. curvatum, strains of race 2 with F. curvatum and F. odoratissimum and strains of race 3 with F. cugenangense. Phylogenetically, race 4 is very close to race 1, but it showed more similarities to race 3 for host range and virulence. This study shows for the first time a broader host range for the races 3 and 4 of FOL. The results demonstrate that phylogenetic analysis permits the separation of some races of FOL, but phylogenetic classification alone is insufficient for conclusive separation of races, therefore it should be accompanied by biological assays based on pathogenicity.
Bacterial canker of tomato, caused by the pathogenic Gram-positive bacterium Clavibacter michiganensis, represents a serious threat to tomato growers worldwide. Diverse approaches have been reported to control this infectious and aggressive bacterium. Current control strategy mostly relies on the application of copper-based products, and to some extent mancozeb and streptomycin, which are leading to growing concerns about resistance promotion, phytotoxicity effect and environmental pollution. In this paper, we present a comprehensive overview on ecofriendly management strategies to control this phytopathogen. New technologies, including the application of biological and non-biological inducers integrated with conventional preventive measures, represent a new approach in plant protection to develop a sustainable strategy to fight this devastating disease.
Turkish fir (Abies bornmuelleriana) has been evaluated as a Phytophthora Root Rot (PRR)-resistant alternative to other PRR-susceptible Abies Christmas tree species. Though Turkish fir survival under heavy PRR disease pressure exceeds that of other host species, previous research has suggested that there may be variability in resistance owing to pedigree, ambient environment, and Phytophthora species. To assess differences in PRR survival in the field, 36 open-pollinated families of Turkish fir were challenged with a mixture of five species of Phytophthora under conditions conducive for disease. Seedlings were grown from seed that was gathered during a provenance collection effort from three provinces in Turkey. At the collection locations in each province, mother trees were located along an altitudinal gradient. The goals for this study included determining Turkish fir resistance in comparison to susceptible fir spp., evaluating phenotype among Turkish fir families, assessing if differences in phenotypes could be attributable to source location or elevation, determining if source province or elevation influenced mortality, and comparing recovery of the five Phytophthora spp. used as inoculum. Turkish fir was demonstrated to be more resistant than noble fir (A. procera) or Fraser fir (A. fraseri) under the experimental conditions. Among the 36 Turkish fir families, six families had a significantly lower probability of PRR mortality compared to all other families; half of these families were from the Karabük province. Similarly, the Karabük province had the lowest overall mortality when family mortality proportions were totaled and compared among provinces. Evaluation of mortality among families from higher elevation sites within a province showed reduced mortality in comparison to mid and lower elevation sites, with variation among seed sources from different provinces. Among the five species of Phytophthora bulked for inoculum, P. cryptogea was the predominant species recovered from dead seedlings in both years. Results suggest that Turkish fir may be a viable PRR-resistant option for utilization in the Christmas tree industry despite some variability in phenotype among family.