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1.
Phytopathology ; 114(1): 102-110, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37432065

RESUMO

Alfalfa Paraphoma root rot (APRR) (Paraphoma radicina) is a recently described alfalfa disease widely distributed in China, first reported in 2020. So far, the resistance levels of 30 alfalfa cultivars to APRR have been characterized; however, the resistance mechanisms among these cultivars remain unknown. In the present study, the alfalfa resistance mechanisms against APRR were investigated by studying the difference of P. radicina infecting susceptible (Gibraltar) and resistant (Magnum II) alfalfa cultivars under the light microscope and scanning electronic microscope. The conidial germination and germ tube growth in the root exudates of different resistant cultivars were also compared. The results revealed that conidial germination, germ tube development, and P. radicina penetration into root tissues of resistant plants were delayed. In susceptible and resistant cultivars, P. radicina infected roots by penetrating epidermal cells and the intercellular space between epidermal cells. During the infection process, germ tubes penetrated the root surface directly or formed appressoria. However, the penetration percentage on the susceptible cultivar was significantly higher than on the resistant cultivar, irrespective of the infection route. Moreover, disintegrated conidia and germ tubes were observed on resistant cultivar roots at 48 h postinoculation. The conidial germination and germ tube growth in root exudates of susceptible cultivars were significantly higher than in resistant cultivars. The current findings implied that the alfalfa resistance mechanism might be related to root exudates. These findings could provide insights into the alfalfa resistance mechanism following P. radicina infection.


Assuntos
Ascomicetos , Medicago sativa , Germinação , Doenças das Plantas
2.
J Fungi (Basel) ; 8(8)2022 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-36012855

RESUMO

Paraphoma radicina is a new pathogen that causes alfalfa paraphoma root rot (APRR), leading to alfalfa production losses. The resistance levels of 30 alfalfa cultivars to APRR have already been characterized. However, the pathogenic mechanism of P. radicina is still unclear. This study aimed to assess the effects of a crude toxin extracted from P. radicina cell-free culture filtrate (CFCF) on susceptible and resistant cultivars of alfalfa. Meanwhile, the crude toxin components were detected using gas chromatography-mass spectrometry (GC-MS) analysis. CFCF cultured in MEB medium for 14 days and crude toxin extracted by ethyl acetate induced significant phytotoxicity caused the average lesion areas of 5.8 and 3.9 mm2, respectively, on alfalfa leaves. The crude toxin exhibited resistance to high temperature, as shown by a lesion area of 3.6 mm2 when treated at 120 °C for 30 min. Different concentrations of the crude toxin in water and MS medium had different effects on susceptible and resistant cultivars. Moreover, the crude toxin affected the plasma membrane, mitochondria, and nuclear membranes of alfalfa root cortical cells. Further, it induced significant phytotoxicity on Sonchus oleraceus L., Capsella bursa-pastoris (Linn.) Medic, and Chenopodium album L. Agropyron cristatum L. (average lesion areas; 11.6, 15.8, 21.4, and 6.2 mm2, respectively), indicating that the crude toxin of P. radicina is a non-host-selective toxin. GC-MS analysis detected four possible active substances in the toxin (3-hydroxypyridine, 5-methylresorcinol, 3-Hydroxypropionic acid, and 4-Hydroxyphenylethanol). Therefore, this study may provide insight into the pathogenic mechanism of P. radicina to alfalfa.

3.
Phytochemistry ; 104: 114-20, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24833033

RESUMO

Six isochromenones (1-6), clearanols F (5) and G (6), one isobenzofuranone (7), and two tetrahydronaphthalene derivatives (8 and radinaphthalenone (9)), were isolated and identified from a culture of the fungus Paraphoma radicina, which was isolated from submerged wood in a freshwater lake. Compounds 5, 6 and 9 were previously unknown. The structures were elucidated using a set of spectroscopic and spectrometric techniques; the absolute configurations of compounds 5 and 6 were determined by comparison of their experimental ECD measurements with values predicted by TDDFT calculations. Compounds 1-9 were evaluated for antimicrobial activity against an array of bacteria and fungi. The inhibitory activity of compound 4 against Staphylococcus aureus biofilm formation was evaluated.


Assuntos
Anti-Infecciosos/isolamento & purificação , Ascomicetos/química , Benzofuranos/isolamento & purificação , Benzopiranos/isolamento & purificação , Tetra-Hidronaftalenos/isolamento & purificação , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Ascomicetos/isolamento & purificação , Bactérias/efeitos dos fármacos , Benzofuranos/química , Benzofuranos/farmacologia , Benzopiranos/química , Benzopiranos/farmacologia , Biofilmes/efeitos dos fármacos , Fermentação , Água Doce , Fungos/efeitos dos fármacos , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Modelos Moleculares , Estrutura Molecular , Staphylococcus aureus/efeitos dos fármacos , Tetra-Hidronaftalenos/química , Tetra-Hidronaftalenos/farmacologia , Madeira/microbiologia
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