Genome-wide identification and characterization of NBLRR genes in finger millet (Eleusine coracana L.) and their expression in response to Magnaporthe grisea infection.

BACKGROUND: The nucleotide binding site leucine rich repeat (NBLRR) genes significantly regulate defences against phytopathogens in plants. The genome-wide identification and analysis of NBLRR genes have been performed in several species. However, the detailed evolution, structure, expression of NBLRRs and functional response to Magnaporthe grisea are unknown in finger millet (Eleusine coracana (L.) Gaertn.). RESULTS: The genome-wide scanning of the finger millet genome resulted in 116 NBLRR (EcNBLRRs1-116) encompassing 64 CC-NB-LRR, 47 NB-LRR and 5 CCR-NB-LRR types. The evolutionary studies among the NBLRRs of five Gramineae species, viz., purple false brome (Brachypodium distachyon (L.) P.Beauv.), finger millet (E. coracana), rice (Oryza sativa L.), sorghum (Sorghum bicolor L. (Moench)) and foxtail millet (Setaria italica (L.) P.Beauv.) showed the evolution of NBLRRs in the ancestral lineage of the target species and subsequent divergence through gene-loss events. The purifying selection (Ka/Ks < 1) shaped the expansions of NBLRRs paralogs in finger millet and orthologs among the target Gramineae species. The promoter sequence analysis showed various stress- and phytohormone-responsive cis-acting elements besides growth and development, indicating their potential role in disease defence and regulatory mechanisms. The expression analysis of 22 EcNBLRRs in the genotypes showing contrasting responses to Magnaporthe grisea infection revealed four and five EcNBLRRs in early and late infection stages, respectively. The six of these nine candidate EcNBLRRs proteins, viz., EcNBLRR21, EcNBLRR26, EcNBLRR30, EcNBLRR45, EcNBLRR55 and EcNBLRR76 showed CC, NB and LRR domains, whereas the EcNBLRR23, EcNBLRR32 and EcNBLRR83 showed NB and LRR somains. CONCLUSION: The identification and expression analysis of EcNBLRRs showed the role of EcNBLRR genes in assigning blast resistance in finger millet. These results pave the foundation for in-depth and targeted functional analysis of EcNBLRRs through genome editing and transgenic approaches.

Analysis of genetic diversity and population structure of Magnaporthe grisea, the causal agent of foxtail millet blast using microsatellites.

Foxtail millet blast caused by Magnaporthe grisea is becoming a severe problem in foxtail millet growing regions of India. The genetic diversity and population structure of foxtail millet infecting M. grisea is crucial for developing effective management strategies, such as breeding blast-resistant cultivars. We analyzed thirty-two M. grisea isolates from ten foxtail millet-growing districts in Tamil Nadu, India for genetic diversity using twenty-nine microsatellite or simple sequence repeat (SSR) markers. A total of 103 alleles were identified with a mean of 3.55 alleles/locus. Gene diversity ranged from 0.170 to 0.717, while major allelic frequencies ranged from 0.344 to 0.906. The polymorphism information content (PIC) ranged from 0.155 to 0.680, with a mean value of 0.465. Population structure analysis of the genomic data sets revealed two major populations (SP1 and SP2) with different levels of ancestral admixture among the 32 blast isolates. Phylogenetic analysis classified the isolates into three major clusters. Analysis of molecular variance (AMOVA) showed high genetic variation among individuals and less among populations. Principal Coordinate Analysis (PCoA) revealed 27.16% genetic variation among populations. The present study provides the first report on the genetic diversity and population structure of the foxtail millet-infecting M. grisea population in Tamil Nadu, which could be useful for the development of blast-resistant foxtail millet cultivars.

Design, Synthesis, Structure-Activity Relationship, and Three-Dimensional Quantitative Structure-Activity Relationship of Fusarium Acid Derivatives and Analogues as Potential Fungicides.

In research related to fungicides, the development of compounds from natural products with high antifungal activity has attracted considerable attention. Fusaric acid (FA), an alkaloid isolated from the metabolites of Fusarium oxysporum, is an important precursor for developing pharmacologically active herbicides. In our previous work, we reported that FA has a wide range of inhibitory activities against 14 plant pathogenic fungi. In particular, it exhibited excellent antifugal effects on Colletotrichum higginsianum (EC50 = 31.7 µg/mL). Herein, to explore the practical application in the agricultural field, the design and synthesis of three series of FA derivatives and their inhibitory activities against plant pathogenic fungi were examined. Results demonstrated that the optimized FA derivatives had excellent inhibitory activities against C. higginsianum, Helminthosporium (Harpophora maydis), and Pyricularia grisea. In particular, the inhibitory activities were considerably improved when the 5-butyl groups of FA were substituted. The EC50 of C. higginsianum and P. grisea was only 1.2 and 12.0 µg/mL when 5-butylalkyl groups were substituted with 5-([1,1'-biphenyl]-4-yl) and 5-phenyl, respectively. Moreover, the safety index of target compounds, which was obtained from the treatment index of medicines, on rice seeds was evaluated. Finally, 16 leading compounds (H4, H22-H24, H27, H29, H30-H34, H37, H45, H50, H52, and H53) were obtained; they had considerable potential for additional modification and optimization as agricultural fungicides. Moreover, three-dimensional quantitative structure-activity relationship models were developed for obtaining a systematic structure-activity relationship profile to explore the possibility of more potent FA derivatives as novel fungicides.

Bio-Fabrication of ZnONPs from Alkalescent Nucleoside Antibiotic to Control Rice Blast: Impact on Pathogen (Magnaporthe grisea) and Host (Rice).

In the traditional method of the bio-fabrication of zinc oxide nanoparticles (ZnONPs), bacterial strains face metal toxicity and antimicrobial action. In the current study, an alkalescent nucleoside antibiotic was mixed with zinc hexanitrate to fabricate the ZnONPs. An integrated approach of DIAION HP-20 macroporous resin and sephadex LH-20 column chromatography was adopted to separate and purify alkalescent nucleoside AN03 from Streptomyces koyanogensis. Alkalescent nucleoside was confirmed by the Doskochilova solvent system. The bio-fabricated ZnONPs were characterized by using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) analyses. The XRD spectrum and the TEM images confirmed the crystallinity and the spherical shape of the ZnONPs with an average size of 22 nm. FTIR analysis showed the presence of functional groups, which confirmed the bio-fabrication of ZnONPs from alkalescent nucleoside ANO3. In-vitro studies showed that 75 µg/mL of ZnONPs had a strong inhibitory zone (28.39 mm) against the Magnaporthe grisea and significantly suppressed the spore germination. SEM and TEM observations respectively revealed that ZnONPs caused breakage in hyphae and could damage the cells of M. grisea. Greenhouse experiments revealed that the foliar spray of ZnONPs could control the rice blast disease by 98%. Results also revealed that ZnONPs had positive effects on the growth of the rice plant. The present study suggested that ZnONPs could be fabricated from microbe-derived nucleoside antibiotics without facing the problems of metal toxicity and antimicrobial action, thus overcoming the problem of pathogen resistance. This could be a potent biocontrol agent in rice blast disease management.

Novel insights into host specificity of Pyricularia oryzae and Pyricularia grisea in the infection of gramineous plant roots.

Pyricularia oryzae and Pyricularia grisea are pathogens that cause blast disease in various monocots. It has been reported that P. oryzae infects the leaves and roots of rice via different mechanisms. However, it is unclear to what extent the tissue types affect the host specificities of P. oryzae and P. grisea. Here, we evaluated the tissue-specific infection strategies of P. oryzae and P. grisea in various gramineous plants. Generally, mycelial plug inoculation caused root browning but the degree of browning did not simply follow the disease index on leaves. Interestingly, the Triticum and Digitaria pathotypes caused strong root growth inhibition in rice, wheat, and barley. Moreover, the Digitaria pathotype inhibited root branching only in rice. Culture filtrate reproduced these inhibitory effects on root, suggesting that some secreted molecules are responsible for the inhibitions. Observation of root sections revealed that most of the infection hyphae penetrated intercellular spaces and further extended into root cells, regardless of pathotype and host plant. The infection hyphae of Digitaria and Triticum pathotypes tended to localize in the outer layer of rice roots, but not in those of wheat and barley roots. The infection hyphae of the Oryza pathotype were distributed in both the intercellular and intracellular spaces of rice root cells. Pathogenesis-related genes and reactive oxygen species accumulation were induced after root inoculation with all combinations. These results suggest that resistance reactions were induced in the roots of gramineous plants against the infection with Pyricularia isolates but failed to prevent fungal invasion.

Chemoenzymatic total synthesis of nodulones C and D using a naphthol reductase of Magnaporthe grisea.

Herein, the asymmetric and chemoenzymatic synthesis of (R)-nodulone C, cis-nodulone D and related (R)-dihydronaphthalenone is reported. It involves multistep chemical synthesis of putative biosynthetic substrates followed by regio- and stereoselective reduction using a NADPH-dependent tetrahydroxynaphthalene reductase of Magnaporthe grisea to obtain chiral nodulones in a biomimetic fashion.

Multiline aiming at phenotypic stability and rice blast resistance

This study aimed to verify the efficiency of multilines in reducing blast progress and their potential benefits to phenotypic stability in rice. The experiments were conducted in the 2016/17 and 2017/18 agricultural years. A randomized block design was performed with three replications, evaluating 12 lines and a multiline, which consisted of five lines from the Cultivation and Use Value (CUV) test. The multiline presented an estimated grain yield above the average of experiments of around seven bags ha-1 and superior performance in early flowering, justifying the high phenotypic stability for these characters. In this case, the line selection for composing the multiline was favorable and efficient, highlighted by a higher agronomic performance than most lines of the CUV test. The multiline is an adequate strategy to provide higher phenotypic stability and reduce blast progress in the field.

Synthesis and fungicidal activity of novel 2-(2-alkylthio-6-phenylpyrimidin-4-yl)-1H-benzimidazoles.

With the aim of exploring new benzimidazole derivative with high fungicidal activity, a series of novel 2-(2-(alkylthio)-6-phenylpyrimidin-4-yl)-1H-benzimidazoles were designed and synthesized, and their in vitro fungicidal activities were evaluated. Compounds 5a, 5f, 5g, 5h, 5i and 5l exhibited excellent fungicidal activities against Botrytis cinerea, and 5c, 5f, 5h, 5i and 5l displayed notable fungicidal activities against Sclerotinia sclerotiorum. Among them, compound 5i (R1 = fluorine, R2 = benzyl) displayed the best activity towards the two tested fungi. Docking study of 5i with ß-tubulin protein revealed that the NH moiety of benzimidazole ring generated a hydrogen bond with Gln-11 residue, and the fluorine atom of benzene ring formed a hydrogen bond with Tyr-208 residue, respectively; the benzene ring of Tyr-222 and the pyrimidine ring of 5i yielded a π-π interaction. The molecular electrostatic potential analysis elucidated the nitrogen atom of benzimidazole ring, fluorine atom of benzene ring and sulfur atom of thioether moiety were located in the negative potential regions, whereas some hydrogen atoms of benzene, benzimidazole and pyrimidine rings were located in the positive potential regions. This analysis demonstrated the reason why 5i can form hydrogen bonds with amino acid residues of target protein.

Green Synthesis of Silver Nanoparticles by Cytobacillus firmus Isolated from the Stem Bark of Terminalia arjuna and Their Antimicrobial Activity.

This work reports an eco-friendly synthesis of silver nanoparticles (AgNPs) using endophytic bacteria, Cytobacillus firmus isolated from the stem bark of Terminalia arjuna. The synthesis of AgNPs was confirmed by visual observation as a change in color of the bacterial solution impregnated with silver. Further, the morphology of the AgNPs, average size, and presence of elemental silver were characterized by UV-Visible spectroscopy, scanning electron microscopy, and dynamic light scattering spectroscopy. The roles of endophytic secondary metabolites in the metal reduction, stabilization, and capping of silver nanoparticles were studied by qualitative FTIR spectral peaks. The antimicrobial ability of AgNPs was evaluated against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and pearl millet blast disease-causing fungi (Magnoporthe grisea). The biosynthesized AgNPs showed good antibacterial and antifungal activities. AgNPs effectively inhibited the bacterial growth in a dose-dependent manner and presented as good antifungal agents towards the growth of Magnoporthe grisea.

Elucidation of genetic relatedness of Magnaporthe grisea, an incitent of pearl millet blast disease by molecular markers associated with virulence of host differential cultivars.

In recent years, blast disease caused by Magnaporthe grisea, an ascomycete fungus is becoming a serious threat to pearl millet crop in India and worldwide. Due to the increase in virulent races of pathogen, blast disease management strategies seemed to be very limited. Hence, unraveling the occurrence of blast isolates across India and understanding their virulence and genetic relatedness using molecular markers are the key objectives of this study. From Farmer's field survey we have evidenced variability in blast pathogen across India by recording 10.6 to 7.9 disease severities. A fair to good variation in cultural and conidial characters were also noticed for 17 field isolates. The identity of 17 isolates was confirmed as Magnaporthe grisea by internal transcribed spacer (ITS) region. Based on 12 host differential virulence reactions, five isolates BgKMg1, BdmMg2, MtgMg11, JprMg16 and JmnMg17 recorded highly susceptible (>5 grade) to nine differentials used in the study. While, host differentials ICMB95444, ICMR06222, ICMR11003, IP21187 and ICMV155 found effective for screening virulence of blast disease. Furthermore, genetic relatedness assessed by ITS, inter simple sequence repeats (ISSR) and simple sequence repeats (SSR) markers produced high degree of polymorphism and was able to distinguish the virulence pattern of 17 isolates that correlated with phenotypic screening. Among markers, clustering of isolates within groups was significantly different with remarkable genetic similarity coefficient and bootstrap values. Overall, these results confirm a significant morphological and genetic variation among 17 isolates, thereby helping to elucidate the virulence of pearl millet blast populations in India that could avoid breakdown of resistance and assist breeding improved pearl millet cultivars.

Further secondary metabolites produced by the fungus Pyricularia grisea isolated from buffelgrass (Cenchrus ciliaris).

The fungal pathogen Pyricularia grisea has been studied to evaluate its production of phytotoxins for the biocontrol of the buffelgrass (Cenchrus ciliaris L.) weed. A first investigation allowed to isolate several new and known phytotoxic metabolites. However, the further investigation on the organic extract obtained from the fungus liquid culture showed the presence of other metabolites possibly contributing to its phytotoxicity. Thus, four known metabolites were isolated and identified by spectroscopic (nuclear magnetic resonance [NMR] and high-resolution electrospray ionization mass spectrometry [HRESIMS]) methods as dihydropyriculol (1), epi-dihydropyriculol (2), 3-methoxy-6,8-dihydroxy-3-methyl-3,4-dihydroisocoumarin (3), and (R)-mevalonolactone (4). The absolute configuration of 1-3 was determined for the first time by a computational analysis of their electronic circular dichroism (ECD) spectra. When the isolated compounds were bioassayed at a concentration of 5 × 10-3 M in a buffelgrass coleoptile and radicle elongation test no toxicity was detected. On the contrary, compounds 1 and 3 showed a significant stimulating effect of radical elongation. Furthermore, the difference in growth stimulation between 1 and its epimer 2 highlights the tight relationship between absolute configuration and biological activity of these fungal metabolites.

Chitosan guar nanoparticle preparation and its in vitro antimicrobial activity towards phytopathogens of rice.

The aim of the present study was to prepare chitosan guar nanoparticle (CGNP) with high antimicrobial activity to use as a bioprotectant against rice phytopathogens. Nanoparticles were prepared using sodium tripolyphosphate by the ionic gelation method. The physico-chemical properties of nanoparticles were characterized through DLS, FTIR, TEM, SEM, AFM and XRD. The application of CGNP to rice seeds stimulated seed germination and seedling growth. CGNP showed growth inhibition towards rice pathogens P. grisea and X. oryzae under in-vitro condition. Excised rice leaves treated with CGNP and challenged with P. grisea showed no blast disease symptom whereas control leaves showed very high blast disease symptom. The results of this study indicate that CGNP can be used as an antimicrobial agent to control blast, blight disease of rice.

Blast Fungal Genomes Show Frequent Chromosomal Changes, Gene Gains and Losses, and Effector Gene Turnover.

Pyricularia is a fungal genus comprising several pathogenic species causing the blast disease in monocots. Pyricularia oryzae, the best-known species, infects rice, wheat, finger millet, and other crops. As past comparative and population genomics studies mainly focused on isolates of P. oryzae, the genomes of the other Pyricularia species have not been well explored. In this study, we obtained a chromosomal-level genome assembly of the finger millet isolate P. oryzae MZ5-1-6 and also highly contiguous assemblies of Pyricularia sp. LS, P. grisea, and P. pennisetigena. The differences in the genomic content of repetitive DNA sequences could largely explain the variation in genome size among these new genomes. Moreover, we found extensive gene gains and losses and structural changes among Pyricularia genomes, including a large interchromosomal translocation. We searched for homologs of known blast effectors across fungal taxa and found that most avirulence effectors are specific to Pyricularia, whereas many other effectors share homologs with distant fungal taxa. In particular, we discovered a novel effector family with metalloprotease activity, distinct from the well-known AVR-Pita family. We predicted 751 gene families containing putative effectors in 7 Pyricularia genomes and found that 60 of them showed differential expression in the P. oryzae MZ5-1-6 transcriptomes obtained under experimental conditions mimicking the pathogen infection process. In summary, this study increased our understanding of the structural, functional, and evolutionary genomics of the blast pathogen and identified new potential effector genes, providing useful data for developing crops with durable resistance.

Wheat blast: from its origins in South America to its emergence as a global threat.

Wheat blast was first reported in Brazil in 1985. It spread rapidly across the wheat cropping areas of Brazil to become the most important biotic constraint on wheat production in the region. The alarming appearance of wheat blast in Bangladesh in 2016 greatly increased the urgency to understand this disease, including its causes and consequences. Here, we summarize the current state of knowledge of wheat blast and aim to identify the most important gaps in our understanding of the disease. We also propose a research agenda that aims to improve the management of wheat blast and limit its threat to global wheat production.

Application of Copper-Chitosan Nanoparticles Stimulate Growth and Induce Resistance in Finger Millet (Eleusine coracana Gaertn.) Plants against Blast Disease.

Copper-chitosan nanoparticle (CuChNp) was synthesized and used to study its effect on finger millet plant as a model plant system. Our objective was to explore the efficacy of CuChNp application to control blast disease of finger millet. CuChNp was applied to finger millet either as a foliar spray or as a combined application (involving seed coat and foliar spray). Both the application methods enhanced growth profile of finger millet plants and increased yield. The increased yield was nearly 89% in combined application method. Treated finger millet plants challenged with Pyricularia grisea showed suppression of blast disease development when compared to control. Nearly 75% protection was observed in the combined application of CuChNp to finger millet plants. In CuChNp treated finger millet plants, a significant increase in defense enzymes was observed, which was detected both qualitatively and quantitatively. The suppression of blast disease correlates well with increased defense enzymes in CuChNp treated finger millet plants.

Preparation, Characterization and Antifungal Properties of Chitosan-Silver Nanoparticles Synergize Fungicide Against Pyricularia oryzae.

Rice (Oryza sativa L.) is one of the major staple food crops of nearly two-third of the world's population. However, rice blast caused by fungus Pyricularia oryzae is generally considered the most serious disease of cultivated rice worldwide due to its extensive distribution and destructiveness under favourable climatic conditions. In this report, the combination between chitosan (CS) and silver (Ag), Ag@CS, was introduced for antifungal activity against Pyricularia oryzae extracted from blast-infected leaves. In detail, Ag@CS nanoparticles (NPs) were first synthesized and further mixed with Trihexad 700 WP (Tri), Ag@CS-Tri, against the fungus by agar diffusion method. The prepared Ag@CS-Tri NPs were characterized by Fourier transform infrared (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). In aqueous condition, Ag@CS-Tri NPs were successfully prepared and existed as spherical NPs with particle size of 17.26 ± 0.89 nm, which is an ideal size for their uptake into plant cells, indicating that the size of their parentally Ag@CS NPs is small enough to combine Tri, and their diameter is large enough to effectively penetrate the cellular membrane and kill fungi. More importantly, the antifungal property of Ag@CS-Tri NPs was significantly increased with inhibition zone around 25 nm compared with only around 12 nm of Ag@CS at the same concentration of Ag (2 ppm) and CS (4000 ppm). These results demonstrated that the synergistic effect of Tri and Ag@CS NPs can be a potential candidate with high antifungal activity for the use of antibiotics in agriculture.

Reaction of wheat plants and alternative hosts to Magnaporthe oryzae / Reação de plantas de trigo e hospedeiros alternativos a Magnaporthe oryzae

Blast disease, caused by the fungus Magnaporthe oryzae, has a major impact on wheat farming. The study of plant responses to pathogens has improved the management of this disease. Moreover, it is important to identify potential host plants in the crops' vicinity and to understand reactions caused by plant-pathogen interactions. The objective of this study was to assess the histopathology of wheat plants, Digitaria insularis and Digitaria sanguinalis inoculated with M. oryzae isolates obtained either rice or wheat plants. Thirty-three days after sowing, greenhouse-grown plants of all three species were inoculated with each M. oryzae isolate. The observed effects (48 hours after inoculation) differed depending on the particular interaction between each pathogen isolate-plant species pair. For instance, wheat and D. sanguinalis had the weakest defensive response against spore germination, production of melanized appressoria, and appressorial penetration, with average values above 87, 90, and 43%, respectively, for these events in these plants. Furthermore, germination and appressoria melanization were more aggressive in the rice isolate than in the wheat isolate. Additionally, evidence for a defensive response (such as cell death) was observed in wheat plants inoculated with rice isolates. However, such a response was absent in plants inoculated using wheat isolates, presumably because pathogen recognition failed.(AU)

A brusone é uma doença causada pelo fungo Magnaporthe oryzae e de grande impacto para a triticultura. O estudo das respostas da planta aos patógenos tem auxiliado no manejo das doenças, e a identificação das plantas hospedeiras nas proximidades da lavoura é importante, assim como conhecer as reações de interação com o patógeno. O objetivo deste estudo foi determinar os eventos histológicos de plantas de trigo Digitaria insularis e Digitaria sanguinalis inoculadas com isolados de M. oryzae de plantas de arroz e trigo. Aos 33 dias da semeadura, as plantas cultivadas em estufa foram inoculadas com dois isolados de M. oryzae. O efeito observado nas plantas, 48 horas após a inoculação, mostrou interações diferentes para cada isolado do patógeno e entre as espécies de plantas. As plantas de trigo e D. sanguinalis foram os materiais com menores respostas de defesa à germinação, de produção de apressórios melanizados e penetração do apressório, com valores acima de 87, 90 e 43%, respectivamente. Entre os isolados do patógeno, o mais agressivo para germinação e produção de apressório melanizado foi o proveniente de plantas de arroz. A resposta de defesa da planta, como a morte celular, foi observada nas plantas de trigo inoculadas com isolado proveniente de plantas de arroz, enquanto não houve resposta de defesa da planta quando inoculada com isolado obtido de plantas de trigo, provavelmente por não ocorrer o reconhecimento do patógeno.(AU)

Pyriculins A and B, two monosubstituted hex-4-ene-2,3-diols and other phytotoxic metabolites produced by Pyricularia grisea isolated from buffelgrass (Cenchrus ciliaris).

Pyricularia grisea has been identified as a foliar pathogen on buffelgrass (Cenchrus ciliaris) in North America and was studied as a potential source of phytotoxins for buffelgrass control. Two monosubstituted hex-4-ene-2,3-diols, named pyriculins A and B, were isolated from its culture filtrate organic extract together with (10S,11S)-(-)-epipyriculol, trans-3,4-dihydro-3,4,8-trihydroxy-1(2H)-napthalenone, and (4S)-(+)-isosclerone. Pyriculins A and B were characterized by spectroscopic (essentially nuclear magnetic resonance [NMR], High-resolution electrospray ionization mass spectrometry [HRESIMS]) and chemical methods such as (4E)-1-(4-hydroxy-1,3-dihydroisobenzofuran-1-yl)hex-4-ene-2,3-diols. The relative and absolute configuration of these compounds was determined by a combination of spectroscopic (NMR, electronic circular dichroism [ECD]) and computational tools. When bioassayed in a buffelgrass coleoptile and radicle elongation test, (10S,11S)-(-)-epipyriculol proved to be the most toxic compound. Seed germination was much reduced and slowed with respect to the control and radicles failed to elongate. All five compounds delayed germination, but only (10S,11S)-(-)-epipyriculol was able to prevent radicle development of buffelgrass seedlings. It had no effect on coleoptile elongation, while the other four compounds caused significantly increased coleoptile development relative to the control.

Bioactivity and structure-activity relationship of cinnamic acid esters and their derivatives as potential antifungal agents for plant protection.

A series of cinnamic acid esters and their derivatives were synthesized and evaluated for antifungal activities in vitro against four plant pathogenic fungi by using the mycelium growth rate method. Structure-activity relationship was derived also. Almost all of the compounds showed some inhibition activity on each of the fungi at 0.5 mM. Eight compounds showed the higher average activity with average EC50 values of 17.4-28.6 µg/mL for the fungi than kresoxim-methyl, a commercial fungicide standard, and ten compounds were much more active than commercial fungicide standards carbendazim against P. grisea or kresoxim-methyl against both P. grisea and Valsa mali. Compounds C1 and C2 showed the higher activity with average EC50 values of 17.4 and 18.5 µg/mL and great potential for development of new plant antifungal agents. The structure-activity relationship analysis showed that both the substitution pattern of the phenyl ring and the alkyl group in the alcohol moiety significantly influences the activity. There exists complexly comprehensive effect between the substituents on the phenyl ring and the alkyl group in the alcohol moiety on the activity. Thus, cinnamic acid esters showed great potential the development of new antifungal agents for plant protection due to high activity, natural compounds or natural compound framework, simple structure, easy preparation, low-cost and environmentally friendly.

Design, synthesis and fungicidal activity of novel 2-substituted aminocycloalkylsulfonamides.

A series of novel 2-substituted aminocycloalkylsulfonamides were designed and synthesized by highly selective N-alkylation reaction, whose structures were characterized by 1H NMR, 13C NMR and HRMS. Among them, the configuration of compounds III12 and III20 were confirmed by X-ray single crystal diffraction. Bioassays demonstrated that the title compounds had considerable effects on different strains of Botrytis cinerea and Pyricularia grisea. Comparing with positive control procymidone (EC50=10.31mg/L), compounds III28, III29, III30 and III31 showed excellent fungicidal activity against a strain of B. cinerea (CY-09), with EC50 values of 3.17, 3.04, 2.54 and 1.99mg/L respectively. Their in vivo fungicidal activities were also better than the positive controls cyprodinil, procymidone, boscalid and carbendazim in pot experiments. Moreover, the fungicidal activity of III28 (EC50=4.62mg/L) against P. grisea was also better than that of the positive control isoprothiolane (EC50=6.11mg/L). Compound III28 would be great promise as a hit compound for further study based on the structure-activity relationship.