Roots Of Pepper Plants Research Articles

Investigations on Nematode Community Dynamics on Pepper Monoculture Vegetations in Otuoke, Bayelsa State, Nigeria

Cultivation of Pepper, a vegetable fruit crop of prominence in Otuoke, is often hampered by parasitic nematode infestation. This negatively affects its economic impact on the rural domestic market. Farmers in Otuoke often ascribe reduced yield to inadequate farming strategy, as they are ignorant of nematode dynamics and resulting damages. This study sought to assay soil and roots of pepper plants for the determination of nematode community dynamics with a view of winging-in rural affordable management option for the agronomical parasites. The soil was collected using a hand trowel and roots were gotten using a knife and the extraction of the parasites was achieved by the use of the modified sieve plate method. The actual assemblage of nematodes was 397 from 11 genera, 205 (51.6%) occurred in farm A and 192 (48.4%) were seen in farm B. Dynamics on nematode diversity and occurrence were seen among species between farms. Meloidogyne species (17.9%) display variable populations between Farms A (19.5%) and B (16.1%). Tylenchorhynchus (11.3%) had a higher number in farm A (14.1%) and unlike in farm B (8.3%). However, Gracilachus (3.0%) and Scutellonema (7.3%)) species were reportedly found in Farm A while Tylenchus (6.5%) Hemicyclophora (5.3%) Pratylenchus (10.1%) and Rotylenchus species (10.1%) were peculiar to farm B. The result suggests that extensive fluctuations in nematode assemblage are possible even in fields with similar characteristics. Nematode occurrence on the root tissue of pepper plants in this study implies danger to quality productivity. Therefore, farmers should adopt poultry filters as manure for the cultivation of crops in the area. Farmers should also adopt exposing agricultural land to direct sunshine for a minimum of three weeks after clearing before tillage. The heat will help inhibit nematode profusion and check population abundance in soil for proper cultivation of crops.

Systemic biochemical changes in pepper (Capsicum annuum L.) against Rhizoctonia solani by kale (Brassica oleracea var. acephala L.) green manure application

BackgroundIn the search for new alternatives to avoid the problems associated with the use of synthetic chemical fungicides in agriculture, the use of green manure (GrM) could help combat fungal diseases of crops, such as those produced by the necrotrophic pathogen Rhizoctonia solani. In the case of the use of Brassica tissues as GrM, it could have an elicitor capacity for systemic plant resistance.ResultsWe used kale leaves as a GrM and applied it to pepper plants infected with R. solani. The application of freeze-dried kale tissues to the roots of pepper plants produced a systemic activation of foliar defences via the salicylic acid (SA) and ethylene (ET) pathways, significantly reducing pathogen damage. In addition, this systemic response led to the accumulation of secondary defence metabolites, such as pipecolic acid, hydroxycoumarin and gluconic acid, in leaves. Remarkably, pepper plants treated with lyophilised kale GrM accumulated glucosinolates when infected with R. solani. We also confirmed that autoclaving removed part of the glucobrassicin (85%) and sinigrin (19%) content of the kale tissues.ConclusionsGrM kale tissues can activate systemic defences in bell pepper against foliar pathogens through SA/ET hormonal pathways, accumulating secondary defence metabolites.

The Influence Micorhyza Arbuscular Indigenous to Growth Pepper Plant (Pipper nigrum L.)

Pepper is a plantation commodity that belongs to the spice category and has an important role in Indonesia's economic growth. Southeast Sulawesi is one of the centers for the development of pepper plants, especially in the South Konawe area. The purpose of this study was to determine the effect of indigenous mycorrhizae on the growth of pepper plants which were carried out in Sindangkasih Village, West Ranomeeto District, South Konawe Regency. Analysis of dry weight and infection of indigenous mycorrhizae on the roots of pepper plants was carried out at the Agrotechnology Laboratory, Faculty of Agriculture, University of Haluoleo Kendari. Data analysis in this study used a single factor Randomized Block Design (RBD) with 4 treatments and 3 replications, so there were 12 trials. The treatment consisted of 4 levels, namely without mycorrhizae (A0), 10 grams of mycorrhizae (A1), 15 grams of mycorrhizae (A2) and 20 grams of mycorrhizae (A3). The results showed that the application of indigenous arbuscular mycorrhizae had an effect on the growth parameters of pepper plants in the form of plant height, number of leaves and number of tendrils, where A3 produced higher plant height, number of leaves and number of tendrils and was significantly different from other treatments. Treatment A2 was not significantly different from treatment A1 but significantly different from treatment A0 (without mycorrhiza). Mycorrhizal inoculation of 20 grams/polybag can cause root infection of pepper plants to increase by 80.00%.

Alleviation of arsenic toxicity in pepper plants by aminolevulinic acid and heme through modulating its sequestration and distribution within cell organelles

Aminolevulinic acid (ALA) is essential for chlorophyll and heme synthesis. However, whether heme interacts with ALA to elicit antioxidants in arsenic (As)-exposed plants is still unknown. ALA was applied daily to pepper plants for 3 days prior to beginning As stress (As–S). Then, As–S was initiated for 14 days by employing sodium hydrogen arsenate heptahydrate (0.1 mM AsV). Arsenic treatment decreased photosynthetic pigments (chl a by 38% and chl b by 28%), biomass by 24%, and heme by 47% content, but it elevated contents of malondialdehyde (MDA) by 3.3-fold, hydrogen peroxide (H2O2) by 2.3-fold, glutathione (GSH), methylglyoxal (MG), and phytochelatins (PCs) and electrolyte leakage (EL) by 2.3-fold along with enhanced subcellular As concentration in the pepper plant's roots and leaves. The supplementation of ALA to the As–S-pepper seedlings enhanced the amount of chlorophyll, heme content, and antioxidant enzyme activity as well as plant growth, while it reduced the levels of H2O2, MDA, and EL. ALA boosted GSH and phytochelates (PCs) in the As–S-seedlings by controlling As sequestration and rendering it harmless. The addition of ALA enhanced the amount of As that accumulated in the root vacuoles and reduced the poisonousness of the soluble As in the vacuoles. The ALA treatment facilitated the deposition and fixation of As in the vacuoles and cell walls, thereby reducing the transport of As to other cell organelles. This mechanism may have contributed to the observed decrease in As accumulation in the leaves. The administration of 0.5 mM hemin (H) (a source of heme) significantly enhanced ALA-induced arsenic stress tolerance. Hemopexin (Hx, 0.4 μg L−1), a heme scavenger, was treated with the As–S plants along with ALA and ALA + H to observe if heme was a factor in ALA's increased As–S tolerance. Heme synthesis/accumulation in the pepper plants was reduced by Hx, which counteracted the positive effects of ALA. Supplementation of H along with ALA + Hx reversed the negative effects of Hx, demonstrating that heme is required for ALA-induced seedling As–S tolerance.

Analysis of the response regulatory network of pepper genes under hydrogen peroxide stress.

Hydrogen peroxide (H2O2) is a regulatory component related to plant signal transduction. To better understand the genome-wide gene expression response to H2O2 stress in pepper plants, a regulatory network of H2O2 stress-gene expression in pepper leaves and roots was constructed in the present study. We collected the normal tissues of leaves and roots of pepper plants after 40 days of H2O2 treatment and obtained the RNA-seq data of leaves and roots exposed to H2O2 for 0.5-24 h. By comparing the gene responses of pepper leaves and roots exposed to H2O2 stress for different time periods, we found that the response in roots reached the peak at 3h, whereas the response in leaves reached the peak at 24h after treatment, and the response degree in the roots was higher than that in the leaves. We used all datasets for K-means analysis and network analysis identified the clusters related to stress response and related genes. In addition, CaEBS1, CaRAP2, and CabHLH029 were identified through a co-expression analysis and were found to be strongly related to several reactive oxygen species-scavenging enzyme genes; their homologous genes in Arabidopsis showed important functions in response to hypoxia or iron uptake. This study provides a theoretical basis for determining the dynamic response process of pepper plants to H2O2 stress in leaves and roots, as well as for determining the critical time and the molecular mechanism of H2O2 stress response in leaves and roots. The candidate transcription factors identified in this study can be used as a reference for further experimental verification.

Study of Novel Endophytic Bacteria for Biocontrol of Black Pepper Root-knot Nematodes in the Central Highlands of Vietnam

Black pepper is an industrial crop with high economic and export value. However, black pepper production in Vietnam has been seriously affected by the root-knot nematodes, Meloidogyne spp. The purpose of this study was to select active endophytic bacteria (EB) for the cost-effective and environmentally friendly management of Meloidogyne sp. Thirty-four EB strains were isolated. Of these, five isolates displayed the highest activity, demonstrating 100% mortality of J2 nematodes. These active EB were identified based on sequencing and phylogenetic analysis of the 16S rRNA gene; notably, all the potential endophytic bacterial strains belong to the genus of Bacillus. In greenhouse tests, Bacillus megaterium DS9 significantly reduced nematodes in the soil and pepper plant roots with great inhibition values of 81.86% and 73.11%, respectively, with the lowest rate of nematodes built up at 0.23. This active antinematodes strain also showed good effect on promoting pepper plant growth. Some enzymatic activities, including chitinase and protease activity related to the biocontrol of Meiloidogyne sp., were also detected. The results investigated in the current study suggested that these selected EB strains may be good candidates for biocontrol agents of Meloidogyne sp., and plant promoting effects. The results also enhanced the novel active antinematode endophytic bacterial communities.

Reclamation of rhizobacteria newly isolated from black pepper plant roots as potential biocontrol agents of root-knot nematodes

Rhizobacteria have been of great interest due to their promising use in biocontrol and promotion of plant growth. The aim of this study was to select active anti-nematode rhizobacteria, enhance their nematicidal activity by optimizing fermentation conditions, and then determine the active components of the fermented product. Among more than 100 isolates, 20 strains showed potent inhibition (81.67–99%) against root-knot nematodes from the genus Meiloidogyne. Almost all of these belong to the genus Bacillus (14 of 20 strains). The six most active strains (with max inhibition of 96.13–98.33%) were RB.DS.05, RB.DL.28, RB.DS.29, RB.DL.31, H11, and CC01; these strains were further investigated for their effect on nematode egg hatching. Of these, Bacillus subtilis RB.DL.28 demonstrated the greatest inhibition (82%). Chitinase and protease were closely associated with the inhibition of egg hatching, while it was newly discovered that natural compounds with thermal stability play a key role in killing J2 nematodes. Based on LC–MS analysis, two major constituents, sulfacetamide and metronidazole-OH, were identified from the filtrates of B. subtilis RB.DL.28. The results from this study suggest that the most active strain, B. subtilis RB.DL.28, and other newly identified rhizobacteria may be good candidates for biocontrol of Meiloidogyne spp. These results expand the catalogue of novel active anti-nematode rhizobacteria communities recently recorded in Vietnam.

Isolation and characterization of endophytic bacteria from roots of Piper nigrum and their activities against Fusarium oxysporum and Meloidogyne incognita

Abstract. Wiratno, Syakir M, Sucipto I, Pradana AP. 2019. Isolation and characterization of endophytic bacteria from roots of Piper nigrum and their activities against Fusarium oxysporum and Meloidogyne incognita. Biodiversitas 20: 682-687. The endophytic bacteria from spices plants have potential as biocontrol agents. Nevertheless, their potential has not been explored. Pepper plant (Piper nigrum L.) is linked with promising endophytic bacteria as biocontrol agents. This study aimed to obtain isolates of endophytic bacteria from root tissues of pepper plant. The isolation of endophytic bacteria was done using surface-sterilization method and using Tryptone Soya Agar (TSA) medium. The result showed that 10 endophytic bacteria were successfully isolated. We found that a total of 9 bacteria were safe for plants and mammals and used for subsequent steps. The selected bacteria showed inhibition activity of Fusarium oxysporum (18.6 to 43.7%). Furthermore, the secondary metabolites of the endophytic bacteria also promoted lethal effects on Meloidogyne incognita (16.6 to 65.8%). The physiological activity also showed that seven isolates were able to produce chitinase, and four (4) isolates were able to produce protease. Additionally, 55.6% of isolates were also able to dissolve phosphorus and fix nitrogen. This study provided fundamental information related to the biocontrol properties of endophytic bacteria isolated from pepper plant roots.

Growth promotion and root colonisation in pepper plants by phosphate‐solubilising Chryseobacterium sp. strain ISE14 that suppresses Phytophthora blight

AbstractPreviously, we selected bacterial strain ISE14 through a sequential selection procedure that included radicle, seedling, and in planta assays and field tests. This strain not only suppressed a destructive soilborne disease, Phytophthora blight, caused by Phytophthora capsici but also increased fruit yields of pepper plants in the fields. This study was conducted to identify strain ISE14 by 16S rRNA gene sequence analysis and to characterise biocontrol and plant growth promotion activities of the strain in pepper plants. Strain ISE14, identified as Chryseobacterium sp., significantly reduced disease severity in plants inoculated with Ph. capsici and promoted plant growth (lengths and dry weights of shoots and roots) compared with those in plants treated with Escherichia coli DH5α (negative control) or MgSO4 solution (untreated control). This strain effectively colonised pepper plant roots as assessed by bacterial population analysis and confocal laser scanning microscopy; it enhanced soil microbial activity and biofilm formation, but not the production of indole acetic acid. Strain ISE14 also solubilised organic or inorganic phosphate by production of acid and alkaline phosphatases or reduction in pH, resulting in enhanced pepper plant growth. This strain exhibited similar or greater activity in disease control and plant growth promotion tests compared with positive control strains Paenibacillus polymyxa AC‐1 (biocontrol) and Bacillus vallismortis EXTN‐1 (plant growth). Therefore, Chryseobacterium sp. ISE14 may be a phosphate‐solubilising and plant growth‐promoting rhizobacterium (PGPR) strain that suppresses Phytophthora blight of pepper. To our knowledge, this is the first report of a phosphate‐solubilising PGPR strain of Chryseobacterium sp. that suppresses the pepper disease.

Potensi Seduhan Limbah Baglog Jamur Tiram (Pleurotus ostreatus) dalam Menekan Populasi Radopholus similis dan Meloidogyne spp. pada Tanah Asal Perakaran Tanaman Lada (Piper nigrum L)

Indonesia is one of the largest pepper producing countries in the world. One of the pepper-producing provinces in Indonesia is the Bangka Belitung Islands (Babel). However, the infection of Radopholus similis and Meloidogyne spp. which causes yellow disease becomes one of obstacles in pepper cultivation in Babel. Thus, alternative solution to overcome this yellow disease is by reducing the amount of nematode inoculum of R. similis and Meloidogyne spp. in soil. This study aimed to determine the effectiveness of the infusion of oyster mushrooms baglog waste enriched with molasses to control the population of R. similis and Meloidogyne spp. and to increase the population of rhizobacteria. Infusion of oyster mushrooms baglog waste was mixed with 1% of molasses and was poured into soil obtained from the pepper plant roots. The concentrations used were 10%, 20%, 30% and 50%. Population of phytonematode, rhizobacteria, proteolytic bacteria, and group of fluorescence bacteria were calculated before and 7 days after treatment. Results showed that the populations of R. similis and Meloidogyne spp. in the soil poured with the influsion of oyster mushroom baglog waste decreased by 29.11% (R. similis) and 24.61% (Meloidogyne spp.), compared to the before and control treatments. The suppression of nematode population was found to be the highest in the influsion treatment at concentration of 50%. Overall, treatment of all concentrations succeeded to increase the population of rhizobacteria, proteolytic bacteria, and group of fluorescence bacteria in soil. Moreover, the highest increase was found in soil treated with concentration of 50%. This study provided new information that the infusion application of oyster mushrooms baglog waste enriched with molasses had the potential to increase the population of rhizobacteria and suppress the amount of pathogens R. similis and Meloidogyne spp.

Peran Mikoriza Arbuskula pada Insidensi Penyakit Busuk Pangkal Batang Lada

Stem rot or foot rot disease caused by Phytophthora capsici is known as an important constraint on pepper cultivation. Research was conducted to determine the effect of arbuskula mycorhizal fungi (AMF) on incidence of foot rot disease of pepper seedlings. The experiment was done in the net house and arranged using completed randomized design with 6 treatments, i.e. (1) soil infested by P. capsici (TPC) as negative control treatment, (2) sterilized soil (TS) as positive control treatment, (3) TPC with 5 g of AMF, (4) TPC with 10 g AMF, (5) TPC with 15 g AMF, and (6) TPC with 20 g AMF. Observation involved plant height, number of shoots, disease incidence, the percentage of AMF infection on the roots of pepper plants, and pepper plants dependence on AMF. The results showed that the application of AMF at a dose of 20 g per 10 kg of soil effectively suppressed incidence of foot rot disease and improve plant growth

Hyperspectral imaging for mapping of total nitrogen spatial distribution in pepper plant.

Visible/near-infrared (Vis/NIR) hyperspectral imaging was employed to determine the spatial distribution of total nitrogen in pepper plant. Hyperspectral images of samples (leaves, stems, and roots of pepper plants) were acquired and their total nitrogen contents (TNCs) were measured using Dumas combustion method. Mean spectra of all samples were extracted from regions of interest (ROIs) in hyperspectral images. Random frog (RF) algorithm was implemented to select important wavelengths which carried effective information for predicting the TNCs in leaf, stem, root, and whole-plant (leaf-stem-root), respectively. Based on full spectra and the selected important wavelengths, the quantitative relationships between spectral data and the corresponding TNCs in organs (leaf, stem, and root) and whole-plant (leaf-stem-root) were separately developed using partial least-squares regression (PLSR). As a result, the PLSR model built by the important wavelengths for predicting TNCs in whole-plant (leaf-stem-root) offered a promising result of correlation coefficient (R) for prediction (RP = 0.876) and root mean square error (RMSE) for prediction (RMSEP = 0.426%). Finally, the TNC of each pixel within ROI of the sample was estimated to generate the spatial distribution map of TNC in pepper plant. The achievements of the research indicated that hyperspectral imaging is promising and presents a powerful potential to determine nitrogen contents spatial distribution in pepper plant.

Root Colonization and Quorum Sensing of the Antagonistic Bacterium Pseudomonas fluorescens 2112 involved in the Red-pepper Rhizosphere

Biofilm formation of multifunctional plant growth promoting rhizobacterium (PGPR), Pseudomonas fluorescens 2112 is necessary for P. fluorescens 2112 to have a positive impact on the rhizosphere of red-pepper. This study investigated whether signal molecules of the quorum sensing AHLs are produced in order to confirm biofilm formative ability. Through the use of Petri dish bioassays a blue circle formed evidence of AHLs. It was confirmed that P. fluorescens 2112 produced six-carbon-chain-long AHLs by TLC bioassay. The bacterial density of P. fluorescens 2112 on the top and bottom of pepper plant roots was estimated as and CFU/g root, respectively. P. fluorescens 2112 exist more with high-density of CFU/g soil at a depth of 1 cm but at a low-density of CFU/g soil at a depth of 5 cm, from the surface of rhizosphere soil. In addition, biofilm formation of P. fluorescens 2112 on the epidermises and the tips of the red-pepper roots were confirmed visually by SEM. Thus, the production of AHLs by P. fluorescens 2112 brings about quorum sensing signaling and the formation of biofilm on the roots which has a positive effect on economically important crops such as red-pepper by additionally producing a variety of antifungal substances and auxin.

Biocontrol Potential of Streptomyces griseus H7602 Against Root Rot Disease (Phytophthora capsici) in Pepper

The root rot of pepper (Capsicum annuum L.) caused by Phytophthora capsici is one of the most important diseases affecting this crop worldwide. This work presents the evaluation of the capacity of Streptomyces griseus H7602 to protect pepper plants against Phytophthora capsici and establishes its role as a biocontrol agent. In this study, we isolated an actinomycete strain H7602 from rhizosphere soil, identified it as Streptomyces griseus by 16S rRNA analysis and demonstrated its antifungal activity against various plant pathogens including P. capsici. H7602 produced lytic emzymes such as chitinase, <TEX>${\beta}$</TEX>-1,3-glucanase, lipase and protease. In addition, crude extract from H7602 also exhibited destructive activity toward P. capsici hyphae. In the pot trial, results showed the protective effect of H7602 against pepper from P. capsici. Application of H7602 culture suspension reduced 47.35% of root mortality and enhanced growth of pepper plants for 56.37% in fresh root and 17.56% g in fresh shoot as compared to control, resulting in greater protection to pepper plants against P. capsici infestation. Additionally, the enzymatic activities, chitinase and <TEX>${\beta}$</TEX>-1,3-glucanase, were higher in rhizosphere soil and roots of pepper plants treated with H7602 than other treated plants. Therefore, our results indicated a clear potential of S. griseus H7602 to be used for biocontrol of root rot disease caused by P. capsici in pepper.

Host-pathogen interaction of root-knot nematode Meloidogyne incognita on pepper in the southeast of Spain

The feeder roots of pepper plants (cv. California Wonder) in Campo de Cartagena (southeast Spain) were found to be severely infected by Meloidogyne incognita. Morphometric traits, differential host test and DNA analysis based on PCR were used to characterize the nematode. Naturally and artificially infected pepper plants showed severe yellowing and stunting, with heavily deformed and damaged root systems. Root galls were spherical and commonly contained more than one female and egg masses with eggs. Typical giant cells with a granular cytoplasm and many hypertrophied nuclei were observed in histological preparations. The relationship between initial nematode population density (Pi) and pepper plant growth was tested in greenhouse experiments with inoculum levels that varied from 0 to 64 eggs and second-stage juveniles (J2) ml−1 soil. A Seinhorst model was fitted to plant height and top fresh weight data of inoculated and non-inoculated plants. The tolerance limit with respect to plant height and fresh top weight of pepper to M. incognita was estimated as 0.85 eggs and J2 ml−1 soil. The minimum relative values (m) for plant height and top fresh weight were 0.15 and 0.16, respectively, at Pi ≥ 64 eggs and J2 ml−1 soil. The maximum nematode reproduction rate (Pf/Pi) was 315.4 at an initial population density (Pi) of 4 eggs and J2 ml−1 soil. The obtained results could be used as a base to establish field experiments that allow strategies to prevent surpassing the threshold of nematodes in fields that are infested.

고추역병 생물적방제 근권세균의 선발 및 근권정착 능력 연구

하남성지역의 고추역병 발병포장 건전한 고추뿌리와 근권토양에서 세균 507균주를 분리하였는데, 그중에서 고추역병균에 길항효과가 우수한 G28-6, G28-5, I7-6과 H14-1균주를 선발하였다. In vitro에서 선발된 균주들은 고추역병균의 균사생장, 유주자낭과 유주자 형성, 그리고 피낭포자의 발아를 현저하게 억제하였고, Pot시험에서 선발된 균주 모두 70% 이상의 방제효과를 나타냈고, 포트시험에서 방제효과가 우수하였던 G28-6균주는 고추역병 자연발생 비닐하우스에서 79.4%의 방제가를 보여 공시된 화학농약 80% Mancozeb 보다 훨씬 높은 방제효과를 보였다. 뿐만 아니라 선발된 4균주 모두 in vitro에서 우수한 근권정착능력을 보였다. 고추역병 방제에 우수한 길항세균으로 선발된 G28-6균주의 16S rRNA gene 염기서열분석과 그의 형태적, 생리적 특성들을 Bergey's manual of Systematic Bacteriology를 기준으로 비교하여 Pseudomonas aurantiaca로 동정하였다. Four promising biocontrol agents against Phytophthora capsici were selected from 507 bacterial isolates collected from rhizosphere soils and roots of pepper plants. In vitro experiment, these four biocontrol agents inhibited mycelial growth, germination of cystospores, and formation of zoosporangia and zoospores of Phytophthora capsici. In the pot experiment, the four biocontrol agents showed control efficiency higher than 70%. In greenhouse experiment, the isolates G28-6 gave the control value of 79.4%. These four biocontrol agents successfully colonized in the population density beyond 105 cfu/g on roots of pepper in vitro. The isolates G28-6 was identified as Pseudomonas aurantiaca, based on its cultural, morphological, and biochemical characterization and 16S rRNA gene sequence analysis.

Influence of pulsed electric field on growths of soil bacteria and pepper plant

DC 20 volt of electricity was charged to the electrodes placed around hot pepper plants to induce electrical redox reaction. Anode and cathode were periodically exchanged at intervals of 30 seconds to develop a pulsed electric field (PEF), by which the ORP of the soil around the pepper plant roots were fluctuated from 17 to −13 volts. Mean viable cell number of the intrinsic bacteria in five different positions was variable from 77,000 to 396,000 around electrodes and 339,000 to 680,000 around plants in the PEF, and 538,000 to 927,000 around plants in the conventional field. The mean viable cell number of the extrinsic bacteria (R. solanacearum) in five different positions was variable from 15,000 to 47,000 around electrode and 152,000 to 374,000 around plant in the PEF, and 294,000 to 607,000 around plants in the conventional field. Mean 3.93 and 5.67 of hot pepper plants were infected with bacterial wilt every two days by passive and active infection, respectively, in the conventional field. Mean 1.25 and 2.5 of hot pepper plants were infected with bacterial wilt every two days by passive and active infection, respectively, in the PEF. Mean sprouting number of seeds in the PEF and conventional field and was 45.0 and 48.2, respectively. Mean dry weight of hot pepper plants was 3.15 g and 2.51 g in the PEF and conventional field, respectively. The TGGE band pattern in the PEF was not very different in comparison with that in the conventional field (B and D) based on the band number, which corresponds to the bacterial diversity. This study suggests that the PEF would be functioning as an environmental factor to inhibit bacterial growth rather than to be a physical agent to destroy bacterial cells.

Nematicidal Activity of Plant Extracts Against the Root-Knot Nematode, Meloidogyne incognita

Nematicidal activity of extracts from plants was assayed against Meloidogyne incognita. In laboratory assays extracts from tobacco (Nicotiana tabacum L), clove (Syzygium aromaticum L), betelvine (Piper betle L), and sweet flag (Acorus calamus L) were most effective in killing the nematode, with an EC50 that was 5-10 times lower than the EC50 of the synthetic pesticides chlorpyrifos, carbosulfan and deltamethrin. The shapes of the dead nematodes differed in a char- acteristic way, and groups of pesticides and plant extracts could clearly be distinguished based on this phenomenon, which may be an indicator for the modes of action of the tested pesticides. In a greenhouse bioassay clove bud and betelvine were tested as mulch. Experiments revealed that the total number of live nematodes on roots of pepper plants treated with mulch of the clove bud was 7% of that of the controls and did not differ significantly from that of plants treated with the recommended synthetic pesticide carbofuran. The application of clove buds as a botanical pesticide for future use against nematodes is highly promising since clove is the 6 th major plant grown on Bangka Island, and the market value of clove has decreased sharply over the last years.

New Evidence About the Relationship Between Water Channel Activity and Calcium in Salinity-stressed Pepper Plants

This study, of how Ca2+ availability (intracellular, extracellular or linked to the membrane) influences the functionality of aquaporins of pepper (Capsicum annuum L.) plants grown under salinity stress, was carried out in plants treated with NaCl (50 mM), CaCl2 (10 mM), and CaCl2 (10 mM) + NaCl (50 mM). For this, water transport through the plasma membrane of isolated protoplasts, and the involvement of aquaporins and calcium (extracellular, intracellular and linked to the membrane) has been determined. After these treatments, it could be seen that the calcium concentration was reduced in the apoplast, in the cells and on the plasma membrane of roots of pepper plants grown under saline conditions; these concentrations were increased or restored when extra calcium was added to the nutrient solution. Protoplasts extracted from plants grown under Ca2+ starvation showed no aquaporin functionality. However, for the protoplasts to which calcium was added, an increase of aquaporin functionality of the plasma membrane was observed [osmotic water permeability (Pf) inhibition after Hg addition]. Interestingly, when verapamil (a Ca2+ channel blocker) was added, no functionality was observed, even when Ca2+ was added with verapamil. Therefore, calcium seems to be involved in plasma membrane aquaporin regulation via a chain of processes within the cell but not by alteration of the stability of the plasma membrane.

Comparison of mild extraction procedures for determination of arsenic compounds in different parts of pepper plants (Capsicum annum, L.)

AbstractEight extraction agents (water, methanol–water mixtures in various ratios, methanol, a 20 mmol l−1 ammonium phosphate buffer, and a methanol–phosphate buffer) were tested for the extraction of arsenic compounds from fruits, stems + leaves, and roots of pepper plants grown on soil containing 17.2 mg kg−1 of total arsenic. The arsenic compounds in the extracts were determined using high‐performance liquid chromatography–hydride generation inductively coupled plasma mass spectrometry. Whereas pure water was the most effective extraction agent for fruits (87 ± 3.3% extraction yield) and roots (96 ± 0.6% extraction yield), the 20 mM ammonium phosphate buffer at pH 6 extracted about 50% of the arsenic from stems + leaves. Decreasing extractability of the arsenic compounds was observed with increasing methanol concentrations for all parts of the pepper plant. In pepper fruits, arsenic(III), arsenic(V), and dimethylarsinic acid (DMA) were present (25%, 37%, and 39% respectively of the extractable arsenic). Arsenic(V) was the major compound in stems + leaves and roots (63% and 53% respectively), followed by arsenic(III) representing 33% and 42% respectively, and small amounts (not exceeding 5%) of DMA and methylarsonic acid were also detected. Hence, for a quantitative extraction of arsenic compounds from different plant tissues the extractant has to be optimized individually. Copyright © 2005 John Wiley &amp; Sons, Ltd.