Cucumber Roots Research Articles

Bio-efficacy of Biochar's against Fusarium oxysporum f.sp. radicis-cucumerinum inciting Root and Stem Rot Disease of Cucumber in In vitro Condition

To assess in vitro evaluation of bio-efficacy different three biochar's viz., Green house waste (GHW), Eucalyptus wood (EW) and Citrus wood (CW) were evaluated at different three concentrations (each @ 1, 2 and 3%) against F. oxysporum f.sp. radicis-cucumerinum causing root and stem rot of cucumber by using poison food technique. Among the three different biochars, Green house waste (GHW) was found most effective by showing minimum mycelial growth of 50.78, 40.10 and 29.88 mm and 43.58, 55.44 and 66.80% per cent growth inhibition at 1, 2 and 3% concentrations, Whereas, Citrus wood (CW) depicted highest mycelial growth 66.26, 55.88, 44.30 mm with 26.38, 37.91 and 50.78% lowest per cent growth inhibition of the pathogen at same above concentrations, respectively.

In Vitro Antimicrobial Bio-efficacy Assessment of Different Organic Formulations against Root and Stem Rot Disease of Cucumber Incited by Fusarium oxysporum f.sp. radicis-cucumerinum

In vitro evaluation of antimicrobial bio-efficacy of different four organic formulations viz., Neem oil (@ 0.5, 1.0, 1.5% con.), Azadirachtin (@ 0.10, 0.15, 0.20% con.), Bijamrut (@ 5, 10, 15% con.) and Jivamrut (@ 5, 10, 15% con.) were evaluated at different three concentrations against Fusarium oxysporum f.sp. radicis-cucumerinum causing root and stem rot disease of cucumber. Among the four different organic formulations, Azadirachtin was found most effective by showing minimum mycelial growth of 47.48, 31.63 and 21.70 mm and 47.25, 64.86 and 75.89% per cent growth inhibition at 0.10, 0.15 and 0.20% concentrations respectively. The Jivamrut depicted highest mycelial growth 63.88, 55.83, 43.95 mm with 29.03, 37.97 and 51.17% lowest per cent growth inhibition of the pathogen at 5, 10 and 15% concentrations, respectively.

Innovative Approach in Sustainable Agriculture: Harnessing Microalgae Potential via Subcritical Water Extraction

Microalgae can contribute to sustainable agriculture and wastewater treatment. This study investigated Tetradesmus obliquus, grown in piggery wastewater (To-PWW), as a biostimulant/biofertilizer compared to biomass grown in synthetic medium (To-B). Subcritical water extraction was tested for disruption/hydrolysis of wet biomass, at three temperatures (120, 170, and 220 ºC) and two biomass loads (1:10 and 1:80 (g dry biomass/mL water)). Extracts were evaluated for germination, and root formation/expansion. Residues were quantified for nutrient composition to assess their biofertilizer potential and tested for their affinity to oil compounds for bioremediation.The best germination was achieved by To-B extracts at 170 ºC (1:10: 148% at 0.2g/L, 1:80: 145% at 0.5g/L). Only To-PWW extracts at 0.2g/L had a significant germination effect (120 ºC: 120-123% for both loads; 170 ºC: 115% for 1:80). To-PWW extract at 120 ºC and 1:10 significantly affected cucumber and mung bean root formation (224 and 268%, respectively). Most extracts significantly enhanced root expansion, with all To-B extracts at 1:10 showing the best results (139-181%). The residues contained essential nutrients (NPK), indicating their biofertilizer potential, helping decrease synthetic fertilizers demands. To-B residues had high affinity to toluene and diesel but lower to used cooking and car oils. To-PWW showed very low affinity to all oil compounds. Finally, all residues were only able to form stable emulsions with the used car oil. This study fully exploits the use of microalgal biomass in sustainable agriculture, producing biostimulant extracts, and residues for biofertilizer and bioremediation, from a low-cost wastewater source.

Effects of cinnamic acid on the root growth of cucumber (cucumis sativus l.) and figleaf ground (cucurbita ficifolia bouché) seedlings

Effect of cinnamic acid (CA) on growth and endogenous hormone content in the roots of cucumber and figleaf gourd seedlings were studied and explained the reason why figleaf gourd was better in resisting CA stress than cucumber using their seedlings as experimental materials. The effect of CA at different concentrations (0, 0.05, 0.10, 0.15, 0.20 and 0.25 mmol/l) was analysed on primary root elongation, total root elongation, average diameter of total roots, total root volume, and total root tips as well as the effects of 0 and 0.25 mmol/l CA on root growth, root density, root hair growth rate, indole acetic acid (IAA) content and ethylene (ET) production rate. The results showed that CA stress decreased the primary root elongation, total root elongation, total root tips, Grade III root and root hair growth rates of both plants. The inhibiting effect of CA was stronger on cucumber than figleaf gourd. Besides, CA stress increased their average diameters of total roots and root hair densities. The increase in the average diameter of total roots of cucumber was larger than that of figleaf gourd while its increase in root hair density was far lower. Apart from that, 0.25 mmol/l CA stress increased the IAA contents and ET production rates in both kinds of roots. The increase in IAA content in cucumber root was 16% higher than in figleaf gourd. However, the increase in the ET production rate of cucumber root was 51% lower than figleaf gourd root. In conclusion, higher concentration IAA could inhibit root growth. Under CA stress, the increase in the IAA content in figleaf gourd root was lower than that in cucumber root, indicating that CA exerted a weaker inhibiting influence on figleaf gourd. Besides, higher ET production rate contributed to the increase in root hair density. Under CA stress, figleaf gourd root had a higher ET production rate than cucumber root, thus having more root hairs. Bangladesh J. Bot. 53(3): 703-710, 2024 (September) Special

Identification, Characteristics, and Fungicide Efficacy of Seed-Associated Fungi of Saposhnikovia divaricata in Northeast China.

Saposhnikovia divaricata (Trucz.) Schischk. is one of the traditional medicinal herbs in Northeast China, and its roots are used for medicinal purposes. In 2020, a fungus isolated from S. divaricata seeds was observed to cause root rot of seedlings and leaf and stem spot of adult plants in Shuangyashan, Heilongjiang, China. Based on morphological and molecular data, isolates of all fungi were identified as Alternaria alternata. To our knowledge, this is the first report of A. alternata isolated from S. divaricata seeds in China. The carrying rate of S. divaricata seeds from 20 different collection sites reached 100% in 70% of the sites in Hulunbeier area, Inner Mongolia, China. The A. alternata isolate could infect the roots of cucumber, sorghum, mung bean, and maize seedlings and cause root rot. Considering the control of seed-associated fungal diseases, prochloraz 45% EW had the best control effect of 92.6%, followed by flusilazole 400 g liter-1 EC (88.9%) and azoxystrobin + propiconazole 18.7% SE (70.7%) of 15 fungicides. Further field control efficacy showed that 45% prochloraz EW had an 80% control efficacy on the disease at a dose of 0.225 g liter-1. It is recommended that soaking seeds and spraying are the best treatments for controlling seed-associated fungi and leaf spot on S. divaricata caused by A. alternata. Therefore, the aforementioned methods can effectively prevent the occurrence of fungal diseases of S. divaricata and provide a way to reduce reinfestation in the field.

Auxin-Mediated Lateral Root Development in Root Galls of Cucumber under Meloidogyne incognita Stress.

Root-knot nematodes induce the formation of feeding sites within the host roots and the relocation of auxin into galls results in abnormal lateral root growth. Here, we analyzed the changes in cucumber root architecture under Meloidogyne incognita stress and the distribution of auxin in these morphological and molecular root changes. The number of root tips significantly decreased, and regression analysis showed a positive relationship between the size of root galls and the numbers of nematodes in galls compared with the lateral roots on galls, emphasizing the effect of nematode parasitism on root development. Data generated via a promoter-reporter system using the transgenic hairy root system first characterized the auxin distribution during nematode parasitism in cucumber. Using DR5:GUS staining of root galls, we further detected the expression of CsPIN1 and CsAUX1, which regulate polar auxin transport. The results showed that both CsPIN1 and CsAUX1 were induced in galls, and the relative expression of the two genes significantly increased at 21 DAI. The TIBA treatment, which can disrupt polar auxin transport inhibited the numbers of cucumber root tips and total length following increasing concentration gradients. Moreover, the numbers of galls were significantly affected by TIBA treatment, which showed the vital role of auxin during nematode parasitism. Our findings suggest that the transportation of auxin plays an important role during gall formation and induces cucumber lateral root development within nematode feeding sites.

Comparison of transcriptome and metabolome analysis revealed cold-resistant metabolic pathways in cucumber roots under low-temperature stress in root zone.

Low ground temperature is a major factor limiting overwintering in cucumber cultivation facilities in northern alpine regions. Lower temperatures in the root zone directly affect the physiological function of the root system, which in turn affects the normal physiological activity of plants. However, the importance of the ground temperature in facilities has not attracted sufficient attention. Therefore, this study tested the cucumber variety Jinyou 35 under three root zone temperatures (room temperature, 20-22°C; suboptimal temperature, 13- 15°C; and low temperature, 8-10°C) to investigated possible cold resistance mechanisms in the root of cucumber seedlings through hormone, metabolomics, and transcriptomics analyses. The results showed that cucumber roots were subjected to chilling stress at different temperatures. Hormone analysis indicated that auxin content was highest in the roots. Jasmonic acid and strigolactone participated in the low-temperature stress response. Auxin and jasmonate are key hormones that regulate the response of cucumber roots to low temperatures. Phenolic acid was the most abundant metabolite in cucumber roots under chilling stress. Additionally, triterpenes may play an important role in chilling resistance. Differentially expressed genes and metabolites were significantly enriched in benzoxazinoid biosynthesis in the room temperature vs. suboptimal temperature groups and the room temperature vs. low temperature groups. Most differentially expressed transcription factor genes in AP2/ERF were strongly induced in cucumber roots by both suboptimal and low-temperature stress conditions. These results provide guidance for the cultivation of cucumber in facilities.

Bacillus subtilis B55 degraded the ferulic acid and p-coumaric acid and changed the soil bacterial community in soils.

This study aimed to assess the effects of phenolic acid-degrading bacteria strains on phenolic acid content, plant growth, and soil bacterial community in phenolic acid-treated soils. The strain of interest coded as B55 was isolated from cucumber root litter, and its degradation rates of ferulic acid and p-coumaric acid were 81.92% and 72.41% in Luria-Bertani solution, respectively, and B55 was identified as Bacillus subtilis. B55 had plant growth-promoting attributes, including solubilization of inorganic phosphate and production of siderophore and indole acetic acid. Both ferulic acid and p-coumaric acid significantly restrained an increase in cucumber seedling dry biomass, while the B55 inoculation not only completely counteracted the damage of phenolic acids to cucumber seedlings and decreased the content of ferulic acid and p-coumaric acid in soil, but also promoted cucumber seedlings growth. Amplicon sequencing found that B55 inoculation changed the cucumber rhizosphere bacterial community structure and promoted the enrichment of certain bacteria, such as Pseudomonas, Arthrobacter, Bacillus, Flavobacterium, Streptomyces, and Comamonas. B55 not only promoted cucumber seedling growth, and decreased the content of ferulic acid and p-coumaric acid in soil, but it also increased the relative abundance of beneficial microorganisms in the cucumber rhizosphere.

Wheat cover crop accelerates the decomposition of cucumber root litter by altering the soil microbial community

Cover cropping is a diversifying agricultural practice that can improve soil structure and function by altering the underground litter diversity and soil microbial communities. Here, we tested how a wheat cover crop alters the decomposition of cucumber root litter. A three-year greenhouse litterbag decomposition experiment showed that a wheat cover crop accelerates the decomposition of cucumber root litter. A microcosm litterbag experiment further showed that wheat litter and the soil microbial community could improve cucumber root litter decomposition. Moreover, the wheat cover crop altered the abundances and diversities of soil bacterial and fungal communities, and enriched several putative keystone OTUs, such as Bacillus spp. OTU1837 and Mortierella spp. OTU1236, that were positively related to the mass loss of cucumber root litter. The representative bacterial and fungal strains B186 and M3 were isolated and cultured. In vitro decomposition tests demonstrated that both B186 and M3 had cucumber root litter decomposition activity and a stronger effect was found when they were co-incubated. Overall, a wheat cover crop accelerated cucumber root litter decomposition by altering the soil microbial communities, particularly by stimulating certain putative keystone taxa, which provides a theoretical basis for using cover crops to promote sustainable agricultural development.

Negatively Charged Carbon Dots Employed Symplastic and Apoplastic Pathways to Enable Better Plant Delivery than Positively Charged Carbon Dots.

Efficient delivery of nanoparticles (NPs) to plants is important for agricultural application. However, to date, we still lack knowledge about how NPs' charge matters for its translocation pathway, i.e., symplastic and apoplastic pathways, in plants. In this study, we synthesized and used negatively charged citrate sourced carbon dots (C-CDs, -37.97 ± 1.89 mV), Cy5 coated C-CDs (Cy5-C-CDs, -41.90 ± 2.55 mV), positively charged PEI coated carbon dots (P-CDs, +43.03 ± 1.71 mV), and Cy5 coated P-CDs (Cy5-P-CDs, +48.80 ± 1.21 mV) to investigate the role of surface charges and coatings on the employed translocation pathways (symplastic and apoplastic pathways) of charged NPs in plants. Our results showed that, different from the higher fluorescence intensity of P-CDs and Cy5-P-CDs in extracellular than intracellular space, the fluorescence intensity of C-CDs and Cy5-C-CDs was similar between intracellular and extracellular space in cucumber and cotton roots. It suggests that the negatively charged CDs were translocated via both symplastic and apoplastic pathways, but the positively charged CDs were mainly translocated via the apoplastic pathway. Furthermore, our results showed that root applied negatively charged C-CDs demonstrated higher leaf fluorescence than did positively charged P-CDs in both cucumber (8.09 ± 0.99 vs 3.75 ± 0.23) and cotton (7.27 ± 1.06 vs 3.23 ± 0.22), indicating that negatively charged CDs have a higher translocation efficiency from root to leaf than do positively charged CDs. It should be noted that CDs do not affect root cell activities, ROS level, and photosynthetic performance in cucumber and cotton, showing its good biocompatibility. Overall, this study not only figured out that root applied negatively charged CDs employed both symplastic and apoplastic pathways to do the transportation in roots compared with mainly the employment of apoplastic pathway for positively charge CDs, but also found that negatively charge CDs could be more efficiently translocated from root to leaf than positively charged CDs, indicating that imparting negative charge to NPs, at least CDs, matters for its efficient delivery in crops.

Genome-wide association analysis reveal candidate genes and haplotypes related to root weight in cucumber (Cucumis sativus L.).

The plant root system is critical for the absorption of water and nutrients, and have a direct influence on growth and yield. In cucumber, a globally consumed crop, the molecular mechanism of root development remains unclear, and this has implications for developing stress tolerant varieties. This study sought to determine the genetic patterns and related genes of cucumber root weight. A core cucumber germplasms population was used to do the GWAS analysis in three environments. Here, we investigated four root-weight related traits including root fresh weight (RFW), root dry weight (RDW), ratio of root dry weight to root fresh weight (RDFW) and the comprehensive evaluation index, D-value of root weight (DRW) deduced based on the above three traits for the core germplasm of the cucumber global repository. According to the D-value, we identified 21 and 16 accessions with light and heavy-root, respectively. We also found that the East Asian ecotype accessions had significantly heavier root than other three ecotypes. The genome-wide association study (GWAS) for these four traits reveals that 4 of 10 significant loci (gDRW3.1, gDRW3.2, gDRW4.1 and gDRW5.1) were repeatedly detected for at least two traits. Further haplotype and expression analysis for protein-coding genes positioned within these 4 loci between light and heavy-root accessions predicted five candidate genes (i.e., Csa3G132020 and Csa3G132520 both encoding F-box protein PP2-B1 for gDRW3.1, Csa3G629240 encoding a B-cell receptor-associated protein for gDRW3.2, Csa4G499330 encodes a GTP binding protein for gDRW4.1, and Csa5G286040 encodes a proteinase inhibitor for gDRW5.1). We conducted a systematic analysis of the root genetic basis and characteristics of cucumber core germplasms population. We detected four novel loci, which regulate the root weight in cucumber. Our study provides valuable candidate genes and haplotypes for the improvement of root system in cucumber breeding.

Humic acid and grafting as sustainable agronomic practices for increased growth and secondary metabolism in cucumber subjected to salt stress

Salinity stress poses a significant treat to crop yields and product quality worldwide. Application of a humic acid bio stimulant and grafting onto tolerant rootstocks can both be considered sustainable agronomic practices that can effectively ameliorate the negative effects of salinity stress. This study aimed to assess the above mentioned ameliorative effects of both practices on cucumber plants subjected to saline environments. To attain this goal a factorial experiment was carried out in the form of a completely randomized design with three replications. The three factors considered were (a) three different salinity levels (0, 5, and 10 dS m−1 of NaCl), (b) foliar application of humic acid at three levels (0, 100, and 200 mg L−1), and (c) both grafted and ungrafted plants. Vegetative traits including plant height, fresh and dry weight and number of leaf exhibited a significant decrease under increasing salinity stress. However, the application of humic acid at both levels mitigated these effects compared to control plants. The reduction in relative water content (RWC) of the leaf caused by salinity, was compensated by the application of humic acid and grafting. Thus, the highest RWC (86.65%) was observed in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. Electrolyte leakage (EL) increased under salinity stress, but the application of humic acid and grafting improved this trait and the lowest amount of EL (26.95%) was in grafting plants with 0 dS m−1 of NaCl and 20 mg L−1 of humic acid. The highest amount of catalase (0.53 mmol H2O2 g−1 fw min−1) and peroxidase (12.290 mmol H2O2 g−1 fw min−1) enzymes were observed in the treatment of 10 dS m−1 of NaCl and 200 mg L−1 humic acid. The highest amount of total phenol (1.99 mg g−1 FW), total flavonoid (0.486 mg g−1 FW), total soluble carbohydrate (30.80 mg g−1 FW), soluble protein (34.56 mg g−1 FW), proline (3.86 µg g−1 FW) was in grafting plants with 0 dS m−1 of NaCl and 200 mg L−1 of humic acid. Phenolic acids and phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) enzymes increased with increasing salinity and humic acid levels. Contrary to humic acid, salt stress increased the sodium (Na+) and chlorine (Cl−) and decreased the amount of potassium (K+) and calcium (Ca2+) in the root and leaf of ungrafted cucumber. However, the application 200 mg L−1 humic acid appeared to mitigate these effects, thereby suggesting a potential role in moderating physiological processes and improving growth of cucumber plants subjected to salinity stress. According to the obtained results, spraying of humic acid (200 mg L−1) and the use of salt resistant rootstocks are recommended to increase tolerance to salt stress in cucumber. These results, for the first time, clearly demonstrated that fig leaf gourd a new highly salt-tolerant rootstock, enhances salt tolerance and improves yield and quality of grafted cucumber plants by reducing sodium transport to the shoot and increasing the amount of compatible osmolytes.

Isolation and Identification of Cucumber Root Rot-Associated Fungi and Assessment of Their Pathogenicity

Isolation and Identification of Cucumber Root Rot-Associated Fungi and Assessment of Their Pathogenicity

Nitric Oxide Promotes Adventitious Rooting in Cucumber Under Drought Stress Through Regulating Ascorbate Glutathione Cycle and Protein S-Nitrosylation

Nitric Oxide Promotes Adventitious Rooting in Cucumber Under Drought Stress Through Regulating Ascorbate Glutathione Cycle and Protein S-Nitrosylation

The effectiveness of some rhizobacteria on Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 (Nematoda: Meloidogynidae) in cucumber plants

In this study, the possibilities of using 3 specific rhizobacteria isolates for the control of Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 (Nematoda: Meloidogynidae) in cucumber plants of Beith alpha cultivar were investigated in 2023. The variables of the climate chamber experiment were seedling and seed treatments of the specific bacterial isolates and the QST713 (Serenade®) commercial isolate, nematode (1500 J2/pot) and non-nematode treatments, as well as positive and negative control treatments. As a result of the study, when the rate of root galling on cucumber roots was determined according to the Zeck scale, the most successful treatment in decreasing root galling was the seedling treatment of KD29 isolate (2.64), while the highest rate of root galling was observed in the positive control (6.27). When the bacterial treatments were compared with the positive control, it was observed that all bacterial treatments had a decreasing effect on the number of egg mass. When the effects of the treatments on the reproduction rate of the J2 population were analyzed, it was found that seedling treatments of isolate KD238 (0.69) and commercial isolate QST713 (0.86) had a decreasing effect on the J2 reproduction rate in the soil. As a result of the laboratory experiment, it was determined that KD157, KD238 and KD29 isolates had 42.25, 33.98 and 27.77% mortality effect on J2s after 96 hours, respectively. However, especially considering the decrease in the J2 population in the soil, the amount of root growth and the decrease in the number of egg mass, these bacteria stimulate the induced systemic resistance (ISR).

Research on the function of CsMYB36 based on an effective hair root transformation system

ABSTRACT The hairy root induction system was used to efficiently investigate gene expression and function in plant root. Cucumber is a significant vegetable crop worldwide, with shallow roots, few lateral roots, and weak root systems, resulting in low nutrient absorption and utilization efficiency. Identifying essential genes related to root development and nutrient absorption is an effective way to improve the growth and development of cucumbers. However, genetic mechanisms underlying cucumber root development have not been explored. Here, we report a novel, rapid, effective hairy root transformation system. Compared to the in vitro cotyledon transformation method, this method shortened the time needed to obtain transgenic roots by 13 days. Furthermore, we combined this root transformation method with CRISPR/Cas9 technology and validated our system by exploring the expression and function of CsMYB36, a pivotal gene associated with root development and nutrient uptake. The hairy root transformation system established in this study provides a powerful method for rapidly identifying essential genes related to root development in cucumber and other horticultural crop species. This advancement holds promise for expediting research on root biology and molecular breeding strategies, contributing to the broader understanding and improvements crop growth and development.

Recruitment of beneficial cucumber rhizosphere microbes mediated by amino acid secretion induced by biocontrol Bacillus subtilis isolate 1JN2.

At present, the use of beneficial microorganisms to control cucumber Fusarium wilt is a widely used method, and the rhizosphere microecological reset is one of the mechanisms involved. However, how biocontrol strains reshape cucumber rhizosphere microecology remains to be further studied. The composition changes of cucumber root exudates induced by biocontrol strain 1JN2, the microbial ecology of cucumber rhizosphere and the colonization ability of biocontrol strain 1JN2 in cucumber rhizosphere were analyzed through UHPLC-MS/MS analysis, Illumina high-throughput sequencing and SEM, respectively. First, cucumber plants treated with biocontrol Bacillus 1JN2 reduced the disease severity of Fusarium wilt by 60%. Significant changes in cucumber root exudates were found after 1JN2 inoculation and the contents of four amino acids including glutamine, tryptophan, glycine and glutamic acid were significantly increased. Second, It was found that the bacterial diversity in the rhizosphere of cucumber was significantly increased in both the strain treatment group and the amino acid mixture treatment group, The number of Bacillus was the largest in all dominant populations, exceeded 20% in all treatment groups. The bacteria of Hydrogenispora and Vicinamibacteria were significantly increased after treatment. Overall, the results demonstrated that amino acid substances in cucumber root exudates induced by biocontrol strain 1JN2 can shift the cucumber root microenvironment and prevent the occurrence of Fusarium wilt disease.

Effect of Cucumber Continuous Monocropping on Traditional Chinese Medicine Residue through Analysis of Physicochemical Characteristics and Microbial Diversity

The use of traditional Chinese medicine (TCM) residue as a crop culture substrate has unique advantages in alleviating the obstacles associated with continuous monocropping, such as increasing production, improving quality and alleviating pests and diseases. However, the effect of TCM residue application on substrates in continuous monocropping practices has not been determined. In this study, the cucumber variety “Jinyou No. 10” was used as the material, and fermented TCM residue, vermiculite and perlite were used as organic substrates (3:1:1). The cucumbers were cultivated on substrates for different durations of continuous monocropping, which were the first cropping cycle (A1), second cropping cycle (A2), third cropping cycle (A3) and fourth cropping cycle (A4). The control (A0) was the substrate sample without any crop planted in it. After the cucumbers were harvested, substrate samples (areas around the cucumber roots) were collected. The physiochemical properties of the cultivated substrates were determined, and the microbial community structures were analyzed through 16S rRNA and ITS sequencing. The physiochemical indices of the substrates with different durations of continuous monocropping (A1–A4) were significantly different than those of the control (A0) substrate. Moreover, the continuous cropping of cucumber had greater effects on fungal communities than on bacterial communities. Bacterial community structure analysis revealed a greater proportion of important bacterial taxa (Proteobacteria, Chloroflexi, and Nitrospirae) in the continuous monocropping substrates than in the A0 substrate. For the fungal community, Ascomycota accounted for the largest percentage of the fungal community in all the samples. The diversity of the microbial community was found to be influenced primarily by electrical conductivity, organic matter content, pH and total potassium content according to the correlation analysis of physicochemical properties and relative abundance of the microbial community. Our study would provide a basis for addressing persistent challenges in continuous cropping and for obtaining the utmost benefit from using TCM organic residue waste.

Identification and characterizations of a few species of Fusarium infecting cucumber in greenhouse conditions

One of the most problematic and devastating diseases affecting cucumber production is Fusarium wilt (Cucumis sativus L.). The present study aimed to characterize Fusarium species isolated from three different regions of cucumber fields in Babylon province, Iraq and identify them based on morphological features and phylogenetic analyses. This study showed the presence of Fusarium incarnatum, F. solani and F. oxysporum in cucumber roots. Fusarium species were phylogenetically analyzed based on internal transcribed spacer (ITS) regions. All Fusarium isolates were pathogenic to cucumber cultivars but varied significantly in their growth and pathogenicity toward cucumber seeds during the experiment. F. solani-2 was greater in growth and pathogenicity than all other Fusarium species. In contrast, F. solani-1 was the lowest. The data obtained from morphological and molecular studies sufficiently supported each other, and the phylogenetic trees based on ITS were distinguished. Closely related species and distinctly separated all morphological taxa. These findings are reported for the first time for the cucumber plant in Babylon province. All these ITS sequences showed homologous to those of Fusarium species isolates in the GenBank database with a similarity percentage of 99%. To the best of present knowledge, this is the first molecular record of F. incarnatum on the cucumber plants in Iraq. The study concluded that F. incarnatum was reported for the first time in Iraq and worldwide as a causal agent of wilt disease in cucumber plants. The three species of Fusarium have different pathogenic abilities, highlighting their disease incidence, growth, and pathogenicity.

Influence of Bacillus subtilis strain Z-14 on microbial ecology of cucumber rhizospheric vermiculite infested with fusarium oxysporum f. sp. cucumerinum

Fusarium oxysporum (FO) is a typical soil-borne pathogenic fungus, and the cucumber wilt disease caused by F. oxysporum f. sp. cucumerinum (FOC) seriously affects crop yield and quality. Vermiculite is increasingly being used as a culture substrate; nevertheless, studies exploring the effectiveness and mechanisms of biocontrol bacteria in this substrate are limited. In this study, vermiculite was used as a culture substrate to investigate the control effect of Bacillus subtilis strain Z-14 on cucumber wilt and the rhizospheric microecology, focusing on colonization ability, soil microbial diversity, and rhizosphere metabolome. Pot experiments showed that Z-14 effectively colonized the cucumber roots, achieving a controlled efficacy of 61.32% for wilt disease. It significantly increased the abundance of Bacillus and the expression of NRPS and PKS genes, while reducing the abundance of FO in the rhizosphere. Microbial diversity sequencing showed that Z-14 reduced the richness and diversity of the rhizosphere bacterial community, increased the richness and diversity of the fungal community, and alleviated the effect of FO on the community structure of the cucumber rhizosphere. The metabolomics analysis revealed that Z-14 affected ABC transporters, amino acid synthesis, and the biosynthesis of plant secondary metabolites. Additionally, Z-14 increased the contents of phenylacetic acid, capsidol, and quinolinic acid, all of which were related to the antagonistic activity in the rhizosphere. Z-14 exhibited a significant control effect on cucumber wilt and influenced the microflora and metabolites in rhizospheric vermiculite, providing a theoretical basis for further understanding the control effect and mechanism of cucumber wilt in different culture substrates.