Search

The fungal pathogen Setosphaeria turcica causes northern corn leaf blight (NCLB) in maize, sorghum, and related grasses. NCLB is a serious fungal foliar disease of cultivated maize that causes devastating yield losses. S. turcica infects maize leaves by means of a specialized cell, the appressorium, but the regulatory mechanisms that underlie appressorium-mediated infection remain largely unknown. Many regulatory pathways and a large number of genes have been described in S. turcica, and many of these genes have been cloned. Characterization of such disease-related genes is important for understanding the biological mechanisms of interaction between pathogen and host and can guide the development of strategies for disease control. There is a significant level of concern regarding the possible dissemination of the S. turcica pathogen to regions where NCLB is not presently prevalent. This scenario is of considerable concern and necessitates immediate research intervention. The present review brings together information on the epidemiology and infection mechanisms of S. turcica. [ABSTRACT FROM AUTHOR]

BACKGROUND: Weeds are one of the critical factors that negatively affect crop yield and quality. Microbial herbicides are a research hotspot for novel herbicides owing to their environmental safety and lack of weed resistance. In the current study, the active ingredients of Serratia marcescens Ha1, a new microbial herbicide, were investigated for their effectiveness against agricultural weeds using bioassay‐guided fractionation. RESULTS: The results revealed that petroleum ether and ethyl acetate extracts of S. marcescens Ha1 had high herbicidal activity. Forty‐nine compounds were identified from the petroleum ether extract, including 2,4‐di‐tert‐butylphenol (DB; C14H22O, 38.82%), ethyl 14‐methyl‐hexadecanoate, 1‐nonadecene, and [1,1′‐biphenyl]‐2,3′‐diol, 3,4′,5,6′‐tetrakis. Of these, DB showed significant inhibitory effects on root and shoot growth in Amaranthus retroflexus, with half‐maximal inhibitory concentration (IC50) values of 389.17 and 832.44 mg L−1, respectively. In addition, 7‐hydroxy‐3‐(2‐methylpropyl)‐2,3,6,7,8,8a‐hexahydropyrrolo[1,2‐a]pyrazine‐1,4‐dione (HPD) was identified as the major active ingredient in the ethyl acetate extract of S. marcescens Ha1 using bioassay‐guided fractionation, with IC50 values of 439.86 and 476.95 mg L−1 against A. retroflexus shoot and root growth, respectively. Scanning electron microscopy indicated that DB and HPD exert destructive effects on A. retroflexus root, and the damage is gradually aggravated with increasing treatment time and concentration. CONCLUSION: The S. marcescens Ha1 extract and its active compounds DB and HPD exhibit significant herbicidal activity, which could be utilized further for the development of microbial herbicides. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Monolepta hieroglyphica (Motschulsky, 1858) has been recently revised as the synonym of M. signata (Oliver, 1808) based on morphological characteristics. M. quadriguttata (Motschulsky, 1860) was synonymized with M. signata over 100 years ago. However, this synonymy has not be confirmed by molecular data. This widely distributed and abundant species shows a high variability in coloration patterns that caused numbers of synonyms. We selected color forms typical for the three nominal taxa for phylogenetic analysis. The phylogenetic, haplotype and genetic differentiation analysis of M. hieroglyphica, M. quadriguttata and M. signata were constructed to determine the relationships between them, and we also found mating behavior between them. They were intermixed together on phylogenetic trees, and M. hieroglyphica and M. quadriguttata had shared haplotype. There was no significant difference among them for genetic distance, and the synonymy of the three names based on external and genital characters can be confirmed by molecular data. [ABSTRACT FROM AUTHOR]

Background: Aphids are significant pests of cash crops and food farm crops. Botanical insecticides are safe for aphid control, especially for organic farming. In this study, Eleocharis dulcis (Burm. f.) Trin. peel extract (EDPE), a new botanical insecticide, was investigated for its active compositions against several agricultural aphids. Results: The results showed that the EDPE had high insecticidal activity against Sitobion avenae Fabricius, Aphis gossypii Glover, Megoura crassicauda Mordvilko, and Acyrthosiphon pisum Harris, with half‐lethal concentration (LC50) values of 95.92, 81.04, 140.31, and 255.73 mg/L after 48 h of treatment. In the pot culture assay, the aphicidal effects of 25% EDPE soluble liquid (SL) at a concentration of 0.016% were 68.98 ± 5.61%, 79.33 ± 8.27%, and 88.82 ± 3.91% after the first, third, and seventh days of treatment, respectively. Nine compounds were identified by bioactivity‐directed fractionation: 4',5'‐dimethoxy‐6,6‐dimethylpyranoisoflavone (1), 3‐methoxy‐4‐hydroxylonchocarpin (2), 4‐hydroxylonchocarpin (3), 4‐methoxylonchocarpin (4), barbigerone (5), lonchocarpusone (6), 6a,12a‐dehydrodeguelin (7), 13‐homo‐13‐oxa‐6a, 12a‐dehydrodeguelin (8) and deguelin (9). Among them, 4‐hydroxylonchocarpin (3) showed the highest aphidicidal activity against M. crassicauda, S. avenae, and A. pisum, with LC50 values of 97.24, 140.63, and 112.31 mg/L, respectively. Conclusion: These data contribute to a better understanding of the aphicidal activity of EDPE and its main component, 4‐hydroxylonchocarpin. This will help to develop new botanical insecticides to contro aphids. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The cyclic adenosine monophosphate (cAMP) signalling pathway plays an important role in the regulation of the development and pathogenicity of filamentous fungi. cAMP‐dependent protein kinase A (PKA) is the conserved element downstream of cAMP, and its diverse mechanisms in multiple filamentous fungi are not well known yet. In the present study, gene knockout mutants of two catalytic subunits of PKA (PKA‐C) in Setosphaeria turcica were created to illustrate the regulatory mechanisms of PKA‐Cs on the development and pathogenicity of S. turcica. As a result, StPkaC2 was proved to be the main contributor of PKA activity in S. turcica. In addition, it was found that both StPkaC1 and StPkaC2 were necessary for conidiation and invasive growth, while only StPkaC2 played a negative role in the regulation of filamentous growth. We reveal that only StPkaC2 could interact with the transcription factor StEfg1, and it inhibited the transcription of StRAB1, a Rab GTPase homologue coding gene in S. turcica, whereas StPkaC1 could specifically interact with a transcriptional regulator StFlo8, which could rescue the transcriptional inhibition of StEfg1 on StRAB1. We also demonstrated that StRAB1 could positively influence the biosynthesis of chitin in hyphae, thus changing the filamentous growth. Our findings clarify that StPkaC2 participates in chitin biosynthesis to modulate mycelium development by targeting the Efg1‐mediated transcription of StRAB1, while StFlo8, interacting with StPkaC1, acts as a negative regulator during this process. [ABSTRACT FROM AUTHOR]