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First Report of Poplar Leaf Rust Caused by Melampsora medusae on Populus mexicana in the United States
... So far, there are few reports on the factors affecting the size of urediniospores, so a larger sample size and more specific analysis of samples from more regions are needed. The measurements of urediniospores of M. Medusae were smaller than those in New South Wales, Australia(Walker et al., 2010) and Florida, USA(Loyd and Smith, 2018).Zheng et al. (2019) identified M. Medusa on P. deltoides cv.' Zhonghua hongye', P. szechuanica, P. simonii and P. yunnanensi in Shaanxi and Sichuan, China, in February 2019, which was similar to the survey time of this study, indicating that the transmission speed was fast and there was a trend of continuous transmission. M. Medusae was first discovered on P. deltoides in Shishou (SS) and Sihong (SH), which has important guiding significance for the quarantine of M. Medusae in China. ...
... In addition, Melampsora medusae f. sp. caused rust disease in P. trichocharpa in the Pacific Northwest (Newcombe, 1998), while leaf rust attributed to M. medusae is considered one of the most yield-limiting diseases in poplar plantations globally (Gortari et al., 2018;Loyd and Smith, 2018). In addition, leaf spot disease on Euphrates poplar (P. ...
Eleven soil samples were collected from different plantations at the Forestry Model Base, Northeast Forestry University, China (45°43'10″N, 126°37'15″E), and 122 Trichoderma strains (T1-T122) were isolated. Nine Trichoderma species were identified based on morphological and molecular classification methods. The diversity of woody fungi was analyzed based on the type and quantity of Trichoderma spp. in the soil samples isolated from each plantation. Subdominant T. pseudoharzianum T17 (TpsT17) was screened and its biocontrol potential against Fusarium oxysporum CFCC86068 (Fox68) and growth promotion of Populus davidiana × P. alba var. pyramidalis (PdPap) seedlings were investigated. Compared with PdPap + Fox68 treatment, PdPap + TpsT17 + Fox68 treatment had an obvious antagonistic effect on Fox68 based on the status of roots and stomata of the poplar seedlings. In addition, pretreatment with TpsT17 increased catalase activity 14-fold and decreased hydrogen peroxide and malondialdehyde concentrations 2.57- and 7-fold, respectively, in the PdPap + TpsT17 + Fox68 treatment compared with the PdPap + Fox68 treatment. The transcription levels of PR1, JAZ6751, MYC2, MP, and JAR1 in PdPap + TpsT17+Fox68-treated plants were upregulated 5.75-, 5.63-, 14.88-, 8.24-, and 10.45-fold, respectively, at 3 d, while LAX2 exhibited little change in comparison with the level in PdPap + Fox-treated plants. TpsT17 was detected in the roots and stems of PdPap + TpsT17- and PdPap + TpsT17+Fox68-treated PdPap 28 d after inoculation, which demonstrated the endogenous capacity of TpsT17.
Four new species of rust fungi are described (Puccinia ibrae, Uredo clavo, U. crusa, and U. tuitei) and five others are reduced to synonymy (Uredo macella, U. nigropuncta, U. panamensis, Uromyces cissampelidis, and U. rzedowskii). Among the 35 new host and geographic range extensions are the first North American records of Aecidium opuntiae, P. duthiae, P. mutisiae, P. puta, and U. occultus. Olivea petitiae, formerly known only from one Puerto Rican specimen, is now reported from 13 locations in six Caribbean nations. Uromyces sabineae, formerly known only from one Puerto Rican specimen, is now reported on four new host taxa from five locations in three Caribbean nations. Spermogonia and uredinoid aecia are described for the first time for Ravenelia pithecolobii, and the first systemic aecia are reported for P. dietelii.
We have designed two taxon-selective primers for the internal transcribed spacer (ITS) region in the nuclear ribosomal repeat unit. These primers, ITS1-F and ITS4-B, were intended to be specific to fungi and basidiomycetes, respectively. We have tested the specificity of these primers against 13 species of ascomycetes, 14 of basidiomycetes, and 15 of plants. Our results showed that ITS4-B, when paired with either a ‘universal’ primer ITS1 or the fungal-specific primer ITS1-F, efficiently amplified DNA from all basidiomycetes and discriminated against ascomycete DNAs. The results with plants were not as clearcut. The ITS1-F/ITS4-B primer pair produced a small amount of PCR product for certain plant species, but the quantity was in most cases less than that produced by the ‘universal’ ITS primers. However, under conditions where both plant and fungal DNAs were present, the fungal DNA was amplified to the apparent exclusion of plant DNA. ITS1-F/ITS4-B preferential amplification was shown to be particularly useful for detection and analysis of the basidiomycete component in ectomycorrhizae and in rust-infected tissues. These primers can be used to study the structure of ectomycorrhizal communities or the distribution of rusts on alternate hosts.
An outbreak of poplar rust on ‘resistant cultivars’ in Northland in March 1991 was investigated and a new interspecific hybrid rust identified. The rust is thought to have arisen in Australia by hybridization between Melampsora medusae and M. larici-populina in a mixed infection on poplar foliage. The hybrid exhibited various morphological, physiological and ultrastructural features of both parents and accordingly is named Melampsora medusae-populina sp. nov. The rust failed to overwinter via Larix decidua or on poplars in New Zealand but is probably persisting on poplars in Australia.