Search Results (8)

Uromyces fabae, the causal agent of broad bean rust, is a major cause of yield losses in North and East Africa, China, and Australia. It has also served as an important model species for research on rust fungi. Early EST sequencing in U. fabae showed that viruses might be present in this species; however, no follow-up investigations were conducted. In order to identify these viruses, we performed purification of dsRNA followed by Illumina sequencing. We also used ultracentrifugation followed by negative staining electron microscopy to visualize virus particles. We identified 20 viral sequences, which we termed Ufvss. A phylogenetic analysis was performed that grouped Ufvss into totiviruses, polymycoviruses, and virgaviruse; three sequences could not be included in the phylogeny. We also found isometric particles. Our findings contribute to the knowledge of mycoviral diversity in rust fungi and point to the importance of further investigation of these viruses. Full article

The development of new anti-ureolytic compounds is of great interest due to the newly discovered role of urease inhibitors in crop protection. Purine degradation and the generation of ammonium by urease are required for the full virulence of biotrophic and hemibiotrophic fungal plant pathogens. Accordingly, chemicals displaying urease inhibitor activity may be used as a novel class of fungicides. Several urease inhibitors belonging to different chemical classes are known, and some compounds have been developed as urea fertilizer additives. We tested whether the natural urease inhibitors p-benzoquinone (p-HQ) and hydroquinone (HQ), as well as the synthetic inhibitors isopropoxy carbonyl phosphoric acid amide (iCPAA), benzyloxy carbonyl phosphoric acid amide (bCPAA), and dipropyl-hexamino-1,3 diphosphazenium chloride (DDC), prevent or delay plant infection caused by pathogens differing in lifestyles and host plants. p-BQ, HQ, and DCC not only protected maize from infection by the hemibiotroph C. graminicola, but also inhibited the infection process of biotrophs such as the wheat powdery mildew fungus Blumeria graminis f. sp. tritici and the broad bean rust fungus Uromyces viciae-fabae. Interestingly, the natural quinone-based compounds even reduced the symptom severity of the necrotrophic fungi, i.e., the grey mold pathogen B. cinerea and the Southern Leaf Spot fungus C. heterostrophus, to some extent. The urease inhibitors p-BQ, HQ, and DCC interfered with appressorial penetration and confirmed the appropriateness of urease inhibitors as novel fungicidal agents. Full article

Uromyces viciae-fabae is a highly specific biotrophic fungus that causes faba bean rust, one of the major diseases affecting this crop. We have assessed the feasibility of using intercropping (faba bean mixed with either pea, wheat or barley) or mixtures of susceptible and resistant cultivars to control rust both under field and controlled conditions. The results of four field intercropping experiments showed a significant reduction in rust severity on faba bean when intercropped with barley (average 22% reduction) but not with the other combinations. This reduction was also confirmed in studies under controlled conditions. The barrier effect of barley appears as the main mechanism explaining rust suppression. Additional experiments under controlled conditions showed that intercropping with barley did not influence the N content of faba bean and that different levels of N nutrition had no impact on rust severity in any case. The cultivar mixture field experiments showed that rust severity in the susceptible cultivar decreased as the proportion of the resistant cultivar in the mixture increased. The importance of the barrier effect of the resistant cultivars was determined in an experiment under controlled conditions. It can be concluded that crop diversification offers great potential to reduce rust in faba bean. Full article

Lentil rust is a major disease worldwide caused by Uromyces viciae-fabae. In this study, we screened a large germplasm collection of cultivated lentils (Lens culinaris ssp. culinaris) and its wild relatives, both in adult plants in the field with a local rust isolate during 2 seasons and in seedlings under controlled conditions with four fungal isolates of worldwide origin. The main results from our study were the following: (1) a significant number of accessions with resistance based on hypersensitive reaction (reduced Infection Type (IT)) were identified in cultivated lentil and in L. ervoides, L. nigricans and L.c. orientalis. The IT scores showed a clear isolate-specific response suggesting race-specificity, so each fungal isolate might be considered a different race. Resistance was identified against all isolates what might be the basis to develop a standard differential set that should be a priority for rust definition and monitoring. (2) Interestingly, although at lower frequency than in L. ervoides and L. nigricans, the hypersensitive response was also observed within cultivated lentil, with accession 1561 (L.c. culinaris) displaying resistance to the four isolates making this accession a valuable ready-to-use resource for lentil resistance breeding. Resistance to all other rust isolates was also available within L.c. culinaris in an isolate-specific manner. Accession 1308 (L. ervoides) showed resistance against all isolates tested, as well as a reduced number of accessions belonging to other wild Lens species. (3) In addition, our screenings allowed the identification of several accessions with partial resistance (reduced Disease Severity (DS) despite high IT). Adult Plant Resistance resulting in reduced severity in adult plants in the field, despite high susceptibility in seedlings, was more frequently identified in L.c. culinaris, but also in L. nigricans and L.c. orientalis. Full article

Uromyces viciae-fabae Pers. de-Bary is an important fungal pathogen causing rust in peas (Pisum sativum L.). It is reported in mild to severe forms from different parts of the world where the pea is grown. Host specificity has been indicated in this pathogen in the field but has not yet been established under controlled conditions. The uredinial states of U. viciae-fabae are infective under temperate and tropical conditions. Aeciospores are infective in the Indian subcontinent. The genetics of rust resistance was reported qualitatively. However, non-hypersensitive resistance responses and more recent studies emphasized the quantitative nature of pea rust resistance. Partial resistance/slow rusting had been described as a durable resistance in peas. Such resistance is of the pre-haustorial type and expressed as longer incubation and latent period, poor infection efficiency, a smaller number of aecial cups/pustules, and lower units of AUDPC (Area Under Disease Progress Curve). Screening techniques dealing with slow rusting should consider growth stages and environment, as both have a significant influence on the disease scores. Our knowledge about the genetics of rust resistance is increasing, and now molecular markers linked with gene/QTLs (Quantitative Trait Loci) of rust resistance have been identified in peas. The mapping efforts conducted in peas came out with some potent markers associated with rust resistance, but they must be validated under multi-location trails before use in the marker-assisted selection of rust resistance in pea breeding programs. Full article

The understanding of the genetic diversity of germplasm of any crop is necessary for genetic improvement. Pea (Pisum sativum L.) is a very important legume crop that provides protein and several essential vitamins, carbohydrates, and minerals. The genetic diversity and population structure of pea germplasm consisted of 115 entries of Australian accessions and 4 entries of Indian varieties used as checks with varying responses and severities of rust, which were analysed using 31 polymorphic SSR (Simple Sequence Repeats) markers. The combination of the markers revealed that 78 alleles were present at 32 loci. It was also observed that each marker had three alleles with an average PIC (Polymorphic Information Content) value of 0.272. The population structure analysis showed the genetic differentiation of the entries. The model-based population structure grouped the entries into three sub-populations of SP1, SP2, and SP3 having 37, 35, and 32 entries, respectively with 15 entries as admixtures. AMOVA (Analysis of Molecular Variance) disclosed that there was 56% variation among the individuals and 20% within the population. A mean fixation index (Fst) of 0.240 among the pea entries exhibited relatively significant variation in population. This study provides basic information to select parental lines for developing rust resistant varieties to meet the ultimate goal of sustainable agriculture. Full article

The field pea has both semi-leafless (SL) and leafed (L) types. Mixing these two types together might improve yield by optimizing pea solar radiation interception, reducing lodging, and decreasing disease. However, an optimum mixing ratio has not yet been established, since previous studies mixed two leaf types from two separate varieties. This study used four near-isogenic pairs of pea genotypes differing only in leaf type to determine the optimal mixing ratio for yield and agronomic traits. Two leaf types were mixed at seeding in five mixing ratios: 0:100, 50:50, 67:33, 83:17, and 100:0 SL/L. With precise UAV quantification of canopy height (r² = 0.88, RMSE = 2.6 cm), the results showed that a ratio of over 67% semi-leafless pea had a 10% greater lodging resistance when compared to the leafed monoculture. For mycosphaerella blight and Uromyce viciae-fabae rust diseases, the 83:17 mixture decreased disease severity by 4% when compared with the leafed monoculture. Regression analysis of yield estimated that the 86:14 ratio provided an 11% increase to the leafed monoculture, but there was no increase compared with the semi-leafless monoculture. Mixing the two types in a high semi-leafless ratio can reduce leafed lodging and prevent yield loss but does not increase the overall yield over the semi-leafless monoculture. Full article

Faba bean is gaining attention in Australia as a rotation grain legume where most of the country’s produce is exported. Rust, caused by Uromyces viciae-fabae, is a major constraint to Faba bean production in eastern Australia and its chemical control results in increased cost of production. The deployment of diverse sources of resistance in new cultivars underpins economic and eco-friendly control of rust diseases of crops. A selection from cultivar Doza (Doza#12034) and a European accession Ac1655 exhibited seedling rust resistance against U. viciae-fabae pathotype 24–40. Doza#12034 and Ac1655 were crossed with a susceptible genotype Fiord and recombinant inbred line (RIL) F₆ populations were generated. Rust tests on Fiord/Doza#12034 and Fiord/Ac1655 F₄ and F₆ populations demonstrated monogenic inheritance of resistance in both crosses and the underlying resistance loci were named Uvf-2 and Uvf-3, respectively. Genetic mapping of both RIL populations located Uvf-2 and Uvf-3 in chromosomes III and V, respectively. The SNPs that showed linkage with Uvf-2 and Uvf-3 were converted into kompititive allele specific PCR (KASP) assays. Markers KASP_Vf_0703 and KASP_C250539 flanked Uvf-2 at 4.9 cM and 2.9 cM distances, whereas Uvf-3 was flanked by KASP_Ac×F165 (2.5 cM) and KASP_vf_1090 (10.1 cM). Markers KASP_Vf_0703 and KASP_Ac×F165 can be used for marker-assisted selection of Uvf-2 and Uvf-3, respectively, after confirming parental polymorphisms. Full article