Evaluation of actinomycete isolates obtained from herbal vermicompost for the biological control of Fusarium wilt of chickpea

A total of 137 actinomycetes cultures, isolated from 25 different herbal vermicomposts, were characterized for their antagonistic potential against Fusarium oxysporum f. sp. ciceri (FOC) by dual-culture assay. Of the isolates, five most promising FOC antagonistic isolates (CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90) were characterized for the production of siderophore, cellulase, protease, hydrocyanic acid (HCN), indole acetic acid (IAA) and antagonistic potential against Rhizoctonia bataticola, which causes dry root rot in chickpea (three strains viz. RB-6, RB-24 and RB-115) and sorghum (one strain). All of the five FOC antagonistic isolates produced siderophore and HCN, four of them (except KAI-90) produced IAA, KAI-32 and KAI-90 produced cellulase and CAI-24 and CAI-127 produced protease. In the dual-culture assay, three of the isolates, CAI-24, KAI-32 and KAI-90, also inhibited all three strains of R. bataticola in chickpea, while two of them (KAI-32 and KAI-90) inhibited the tested strain in sorghum. When the FOC antagonistic isolates were evaluated further for their antagonistic potential in the greenhouse and wilt-sick field conditions on chickpea, 45-76% and 4-19% reduction of disease incidence were observed, respectively compared to the control. The sequences of 16S rDNA gene of the isolates CAI-24, CAI-121, CAI-127, KAI-32 and KAI-90 were matched with Streptomyces tsusimaensis, Streptomyces caviscabies, Streptomyces setonii, Streptomyces africanus and an identified species of Streptomyces, respectively using the BLAST searching. This study indicated that the selected actinomycete isolates have the potential for biological control of Fusarium wilt disease in chickpea.     

Phytophthora blight of Pigeonpea [Cajanus cajan (L.) Millsp.]: An updating review of biology, pathogenicity and disease management

Phytophthora blight (PB), caused by Phytophthora drechsleri f. sp. cajani, is reoccurring as an economically important disease of pigeonpea (Cajanus cajan), especially when excessive rains fall within a short span of time and hot and humid weather persists during the crop season. A few years after the initial reviews of Kannaiyan et al. (1984), the disease was coming to halt. Despite earlier investigations on pathological and physiological characteristics of P. drechsleri f. sp. cajani, the nature of infection process and genetic basis of pathogen variability have not been clearly established. Therefore, information on the biology and survival of the pathogen is needed to devise effective management strategies. Attempts have been made to develop green-house and field screening techniques since three decades ago for identification of host plant resistance. However, only few pigeonpea germplasm and breeding lines belonging to cultivated and wild Cajanus spp. were found tolerant to PB. The recent frequent recurrence of PB epidemics in the major pigeonpea growing areas prioritized the search for higher levels of disease resistance. There is a need to study the biology of the pathogen, epidemiology of the disease and refinement of the resistance screening techniques and develop integrated disease management technology for the disease. In this review, the symptomatology of the disease, biology of pathogen including its variability, epidemiology, sources of resistance, other management options and available information on biochemical and genetic basis of disease resistance have been updated and discussed with the identification of future research priorities.     

Antioxidative activity of protein hydrolysates prepared from alkaline-aided channel catfish protein isolates

Antioxidative activity of hydrolyzed protein prepared from alkali-solubilized catfish protein isolates was studied. The isolates were hydrolyzed to 5, 15, and 30% degree of hydrolysis using the protease enzyme, Protamex. Hydrolyzed protein was separated into hydrolysates and soluble supernatants, and both of these fractions were studied for their metal chelating ability, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), and their ability to inhibit the formation of thiobarbituric acid reactive substances (TBARS) in washed tilapia muscle containing tilapia hemolysate. Both hydrolysates and supernatants were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results showed that DPPH radical scavenging ability and reducing power of catfish protein hydrolysates decreased, whereas the ORAC value, metal chelating ability, and ability to inhibit TBARS increased, with an increase in the degree of hydrolysis. Hydrolysate samples showed higher DPPH radical scavenging ability and Fe(3+) reducing ability, and supernatant samples had higher metal chelating ability. In general, low molecular weight (MW) peptides had high ORAC values and high metal chelating ability, and high MW peptides had a higher reducing power (FRAP) and were more effective in scavenging DPPH radicals. In a washed muscle model system, the ability of catfish protein hydrolysates and their corresponding supernatants to inhibit the formation of TBARS increased with an increase in the degree of hydrolysis.     

Detection of Sclerotinia sclerotiorum using a monomeric and dimeric single-chain fragment variable (scFv) antibody

Sclerotinia sclerotiorum (Lib.) de Bary is a phytopathogenic fungus capable of causing significant yield losses in numerous crops, including canola, in which the fungus causes sclerotinia stem rot. Immunological detection methods to rapidly determine the presence of S. sclerotiorum on plants may provide growers with a viable diagnostic tool to aid with fungicide use decisions. This paper discusses the generation of a monomeric and dimeric single-chain, variable fragment (scFv) antibody with affinity for S. sclerotiorum using phage display technology. The bacterially expressed and purified scFv is shown to bind S. sclerotiorum with some cross-reactivity with the closely related phytopathogen Botrytis cinerea (Pers.:Fr.). The dimeric scFv displayed improved binding to the fungus as compared to the monomer and could detect the presence of mycelia in inoculated canola petals. To the authors' knowledge, this is the first report of a scFv dimer with affinity for S. sclerotiorum that has the potential for use in the development of a new diagnostic test.     

Antioxidative efficacy of alkali-treated tilapia protein hydrolysates: a comparative study of five enzymes

The antioxidant activities of alkali-treated tilapia protein hydrolysates were determined by their ability to inhibit the formation of lipid hydroperoxides (PV) and thiobarbituric acid reactive substances (TBARS) in a washed muscle model system and by their ability to inhibit DPPH free radicals and chelate ferrous ion in an aqueous solution. Protein isolates were prepared from tilapia white muscle using alkali solubilization at pH 11.0 and reprecipitation at pH 5.5. Protein hydrolysates were prepared by hydrolyzing the isolates using five different enzymes, Cryotin F, Protease A Amano, Protease N Amano, Flavourzyme, and Neutrase, to 7.5, 15, and 25% degrees of hydrolysis (DH). All of the protein hydrolysates significantly (p<0.05) inhibited the development of TBARS and PV. The antioxidant activity of the hydrolysates increased with the DH. Also, the antioxidant activity of the hydrolysates varied significantly (p<0.05) among the different enzymes. The ability of different enzyme-catalyzed protein hydrolysates to scavenge DPPH radicals was not reflected in their ability to inhibit oxidation in a washed tilapia model system. In a washed muscle model system, the hydrolysates prepared using Cryotin F were most effective and the hydrolysates prepared using Flavourzyme and Neutrase were least effective in inhibiting the development of TBARS and PV, whereas in an aqueous solution, hydrolysates prepared using Flavourzyme were most effective in scavenging DPPH radicals and chelating ferrous ions. Enzymatic hydrolysis decreased the size of tilapia protein hydrolysates and, in general, tilapia protein hydrolysates with low molecular weights were better antioxidants than those with high molecular weights.     

Association mapping for seed cotton yield,yield components and fibre quality traits in upland cotton (Gossypium hirsutum L.) genotypes

Association mapping has revolutionized human genetics and is increasingly used in plant genetics. It is an efficient way of determining the genetic basis of complex traits. In cotton so far numerous association mapping studies are available as compared to many other important crops. In our study, mapping was performed using cotton 63K infinium beadchip with 201 germplasm lines. Through fast STRUCTURE analysis, lines were grouped into 12 subgroups and revealed genome sharing among the groups. The critical value (R²) was set to 0.243 as threshold to claim LD between two loci. About 3.13% marker pairs recorded significantly high LD (R² = 1), and 8.19% of marker pairs were in the range of 0.3 to 0.99 R². In MLM, 349 significant marker–trait associations were detected as against 642 in GLM because of effectiveness in eliminating false associations in MLM. A total of 68 markers explained >10% phenotypic variation for yield and fibre quality traits. Phenotypic variation explained by markers was smaller, suggesting that they might be associated with minor QTLs.     

Effects of combined application of vermicompost and mineral fertilizer on the growth of Allium cepa L. and soil fertility

The promotion of organic farming involves curtailing extensive use of mineral fertilizers. The present study was aimed to compare the effects of vermicompost (10 Mg ha^–1), commercial mineral fertilizer (NPK—100:80:80), and their combination on (1) the growth of a major cash crop “onion” (Allium cepa L.) and (2) the changes that may have occurred in the amended soil. The experiment was a randomized complete block design with four replications during the crop‐growing season of 2008/09. Results showed significantly higher plant growth in the combined/mix treatment of vermicompost and NPK, as measured by the vegetative growth of bulbs, number and length of tillers per bulb, and fresh weight of bulbs and by the biochemical characteristics of the onion tillers/leaves (total chlorophyll, caretenoids, protein, and total sugar contents). Comparison of the mixed treatment as compared to the control showed increases in bulb size (54%), total number of bulbs per bed (52%), and fresh weight of all bulbs (198%). The chemical properties and enzyme activity of the amended soil also improved significantly in the combined treatment as compared to the application of vermicompost or the mineral fertilizer alone. Total organic C, microbial biomass C, and sulfate content were significantly higher in the mix treatment, with increases of 60%, 127%, and 126%, respectively, as compared to those of the chemical‐fertilizer‐alone treatment. Similarly, β‐glucosidase, alkaline phosphatase, and dehydrogenase were significantly higher by 145%, 91%, 71%, respectively, in the mix treatment as compared to those of fertilizer‐alone application. This study indicates that application of a combination of mineral fertilizer and vermicompost in the field can positively influence the biological properties and fertility of soils, and support better plant growth, when compared to the application of mineral fertilizer or vermicompost alone. The study suggests that this combined application can reduce the quantity and cost of mineral‐fertilizers application for bulbous‐crop cultivation by 50%, while also sustaining soil biological activity of tropical and subtropical soils.     

Integrated management of late leaf spot and rust diseases of groundnut (Arachis hypogaea L.) with Prosopis juliflora leaf extract and chlorothalonil

Abstract

Late leaf spot (LLS, Phaeoisariopsis personata) and rust (Puccinia arachidis) are the two major biotic constraints of groundnut (Arachis hypogaea L.) of global importance. To identify economic and eco-friendly disease management options, we evaluated extracts of 38 plant spp. of 23 families, for their antifungal activity. Aqueous leaf extracts (20%, w/v) of Prosopis juliflora and Lycopersicon esculentum completely inhibited the in vitro germination of P. personata and P. arachidis, and extracts of Achras sapota, Cyamposis tetragonolobus, Piper betle and Tagetus patula were inhibitory by >95%. In the greenhouse, the severity of LLS and rust corresponded with the time interval between the foliar application of leaf extract and fungal inoculum. Extract of P. juliflora (2%, w/v) in simultaneous application reduced the lesion frequency of LLS and rust by ～75%, and 35.7% and 50.7% in a prophylactic spray of 96 h before the pathogen inoculation. The extract had no effect on the phenolic content of groundnut leaves both during LLS and rust infections. In the field, P. juliflora extract applied four times at 15-day intervals, was effective against LLS and rust up to 95 days after sowing (d.a.s.). Foliar application of P. juliflora extract at 45, 75 and 90 d.a.s. and chlorothalonil at 60 d.a.s. effectively reduced foliar diseases severity and increased the pod yields by 81–98%. This study identified P. juliflora extract as a significant component for the integrated management of groundnut foliar diseases.     

Experimental investigation of mechanical behavior of Jute-Flax based glass fiber reinforced composite

Present technological development and innovation needs a better class of material that meets all the practical applications along with its environmental friendly nature and economical value. Hybrid natural fiber composites, a sector of natural composites meets these requirements. This paper deals with fabrication, mechanical characterization of a hybrid (Jute+Flax+GFRP) composite and also the comparison of it with the (Jute+GFRP) based composite. These composites are fabricated using hand lay-up technique. The arrangement of hybrid composite is such that a layer of vertically laid flax fiber is flanked between layers of horizontally laid jute fiber. Epoxy resin alongside with HY951 hardener is used as the binding agent throughout the layer. Glass fiber laminates are used on both sides for improving the surface finish and surface hardness. The volumetric fraction is such that one third of total volume is occupied by Jute and Flax fibers. Test results shows that the hybrid natural composite has excellent properties under tensile, flexural loading. At last failure morphology analysis is done using Scanning Electron Microscope (SEM) and the internal structure of the broken specimen is discussed.