Plant parasitic nematodes cause significant crop damage globally. Currently, many nematicides have been banned or are being phased out in Europe and other parts of the world because of environmental and human health concerns. Therefore, we need to focus on sustainable and alternative methods of nematode control to protect crops. Plant roots contain and release a wide range of bioactive secondary metabolites, many of which are known defense compounds. Hence, profound understanding of the root mediated interactions between plants and plant parasitic nematodes may contribute to efficient control and management of pest nematodes. In this review, we have compiled literature that documents effects of root metabolites on plant parasitic nematodes. These chemical compounds act as either nematode attractants, repellents, hatching stimulants or inhibitors. We have summarized the few studies that describe how root metabolites regulate the expression of nematode genes. As non-herbivorous nematodes contribute to decomposition, nutrient mineralization, microbial community structuring and control of herbivorous insect larvae, we also review the impact of plant metabolites on these nontarget organisms.1 study on effect of both plant and specific metabolites detected in root exudates of the plant, 2 study on effect of plant, 3 study on effect of synthetic compound on nematodes, NA indicate not applicable.

Phyllanthus emblica L. belonging to the family Euphorbiaceae is a common medicinal plant in Bangladesh. In order to evaluate the phytoconstituents and bioactivity of various parts of P. emblica, both the wild type (i.e., small) and cultivated (i.e., big) fruits were collected from the local market of Bangladesh and six ethanolic extracts were prepared from various parts of the collected fruits for this current study. A comparative analysis of the phytochemical compositions and various bioactivities especially antibacterial, antifungal, and antioxidant activity of the six ethanolic extracts were accomplished. The qualitative phytochemical analysis of plant extracts revealed the presence of large amounts of proteins, carbohydrates, phenolic compounds, glycosides, alkaloids, coumarins, flavonoids, tannins, saponins and resins etc. The maximum antioxidant activity was observed for wild type P. emblica seed extracts and the minimum activity was observed for cultivated flesh extracts. Moreover, among the samples the wild type P. emblica extracts have excellent amount of total phenol contents and the highest free radical scavenging activity. It is also found that P. emblica samples were active against both gram-positive (i.e., B. subtilis) and gram-negative (i.e., E. coli, and S. typhi) bacteria. The highest antibacterial activity was achieved in the wild type P. emblica seed extracts against both pathogenic (S. typhi) and non-pathogenic bacterial strains (E. coli, and B. subtilis). These samples showed almost no activity against Fusarium sp. fungus.

Although the effects of plant secondary metabolites on plant defense have been studied for decades, the exact roles of secondary metabolites in shaping plant-associated microbial and nematode communities remain elusive. We evaluated the effects of benzoxazinoids (BXs), a group of secondary metabolites present in several cereals, on root-associated nematodes. We employed 18S rRNA metabarcoding to compare maize root-associated nematode communities in a bx1 knock-out maize line impaired in BX synthesis and in its parental wild type (WT). Both genotype and plant age affected nematode community composition in the roots, and the effects of BXs on nematode communities were higher in the roots compared to the rhizosphere. Differential abundance analysis and quantitative PCR showed that the root lesion nematode Pratylenchus neglectus was enriched in the bx1 mutant line, while another root lesion nematode Pratylenchus crenatus was reduced. Correlation analysis showed that BX contents in maize roots mostly correlated negatively with the relative abundance of nematode reads. However, positive correlations between BXs and nematode taxa, including several plant parasitic nematodes, were also identified. Our detailed nematode community analysis suggested differential and selective effects of BXs on soil nematodes depending on both the nematode species and BX compound.

Entomopathogenic fungus-Aschersonia sp.was found in the potted plants in the experimental sites of the Department of Zoology, Jahangirnagar University, Bangladesh. Using tissue planting technique, fungus colony was recovered on PDA. Morphology characterization based on mycelium, conidia, colony features as well as sequencing of rDNA of isolated fungus resulted as Aschersonia sp. Vegetative growth of the fungus on different fungal culture media, temperature, pH, and the light were conducted. The optimum temperature, pH and light regimes for mycelial growth were recorded at 20°C, pH 7, alternate light and dark condition. The suitable mycelial growth of the fungus was obtained on potato sucrose agar, Richard agar, carrot agar media over ten different culture media studied. To the best of our knowledge, the occurrence of Aschersonia sp. in Bangladesh is a new record.

The experiment was carried out to survey for incidence and prevalence of purple blotch disease which ranged from 30.49 to 51.76 percent. Isolation, identification of pathogen and determination of pathogenicity were conducted as well; In-vitro evaluation of some botanical extracts, some commercial fungicides and some antagonistic microorganisms against Alternaria porri were performed. At 5 percent concentration of Adhatoda vasica extract showed the maximum of 91.11% inhibition of mycelial growth of A. porri followed by 60 % and 55.33% of inhibition due to Azadirachta indica and Ocimum sanctum extract respectively. At 10 percent concentration showed similar patterns of mycelial inhibition. The antagonistic effects of four biocontrol agents viz., Trichoderma viride, T. koningii, T. harzianum, Bacillus sp. on mycelia growth of A. porri were studied and maximum reduction in colony growth of A. porri was observed due to T.viride. All the concentrations (0.1g/100 ml; 0.2g/100 ml; 0.3g/100 ml) of Bavistin DF and Companion applied fully inhibited the growth of A. porri.

Background: Aerobic rice fields are frequently infested by pathogenic oomycetes (Pythium spp.) and the rice rootknot nematode Meloidogyne graminicola. Here, the interaction between Pythium arrhenomanes and Meloidogyne graminicola was studied in rice roots of two aerobic rice varieties. In different experimental set-ups and infection regimes, plant growth, rice yield, Pythium colonization, as well as establishment, development and reproduction of M. graminicola were studied.

Experiments were carried out to find out the bio-efficacy of four Trichoderma species, viz. Trichoderma harzianum, T.koningii, T.viride (green strain), T.viride (yellow strain) against canker pathogen Lasiodiplodia theobromae. Bioassay of antagonist against test pathogens conducted by dual culture techniques at different temperatures; volatile, non volatile and naturally untreated metabolites of isolates were examined. T. koningii and T.viride (yellow strain) exhibited maximum inhibition in controlling the pathogens. Fungicides, viz. Bavistin and Dithane M-45 used where Bavistin found little effective but Dithane M-45 showed no effects on pathogen. Trichoderma viride showed better performance to control Lasiodiplodia theobromae than commercial fungicides used during present investigation.

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