Pratylenchus Coffeae Research Articles

Cloning of the defense gene PlchiIII and its potential role in the biocontrol of Pratylenchus coffeae nematodes and Meloidogyne incognita eggs in Musa

Abstract A wide range of crops such as bananas and plantains are devastated by plant parasitic nematodes that affect the root system, leading to impaired plant growth and production. In this scenario, the chitinase gene was isolated from the nematode-resistant cultivar of Pisang lilin. The amplified target gene was cloned into pET28a encoding 323 amino acid residues, which shares a high degree of homology with acidic class III chitinase in Musa acuminata, and the product was transformed into E. coli BL21 strain for protein expression. Using affinity chromatography, the recombinant chitinase was purified as a protein of 29 kDa with an optimal activity at pH 7.0. The purified chitinase was capable of degrading the chitin present in the exoskeleton layer of root lesion nematodes (Pratylenchus coffeae) and in the eggshells of root-knot nematodes (Meloidogyne incognita), as well as significantly influencing its development and mortality. Bioassay was performed under in vitro conditions. In root lesion nematodes, 100% mortality was recorded at concentrations of 0.2 µg/mL and 0.15 µg/mL on the 3rd and 5th days, respectively, whereas the egg-hatching rate was inhibited by 100% at concentrations of 0.2 µg/mL and 0.01 µg/mL on the 1st and 5th days, respectively. The results of this study suggest that the PlchiIII gene can be used as a plant-based microbial agent in the biocontrol of nematodes would help in reducing nematode population and increase the yield of banana.

Status of Pratylenchus coffeae in banana-growing areas of Tanzania

Pratylenchus coffeae is among the plant parasitic nematodes contributing to yield losses of banana. To determine the status of P. coffeae, a survey was conducted in banana-growing regions of Tanzania and samples collected. The results indicated that in 2015 there was an increase in total counts of P. coffeae extracted from roots compared to that reported in 1999 in Unguja West, North and South. Moreover, we noted its presence for the first time in mainland Tanzania. Generally, the densities of P. coffeae were high on banana roots collected at 500–1000 m above sea level. This information on the status of P. coffeae is important in planning management of nematodes in Tanzania.

A High-Throughput Molecular Pipeline Reveals the Diversity in Prevalence and Abundance of Pratylenchus and Meloidogyne Species in Coffee Plantations.

Coffee yields are adversely affected by plant-parasitic nematodes and the pathogens are largely underreported because a simple and reliable identification method is not available. We describe a polymerase chain reaction-based approach to rapidly detect and quantify the major Pratylenchus and Meloidogyne nematode species that are capable of parasitizing coffee. The procedure was applied to soil samples obtained from a number of coffee farms in Brazil, Vietnam, and Indonesia to assess the prevalence of these species associated both with coffee (Coffea arabica and C. canephora) and its intercropped species Musa acuminata (banana) and Piper nigrum (black pepper). Pratylenchus coffeae and P. brachyurus were associated with coffee in all three countries but there were distinct profiles of Meloidogyne spp. Meloidogyne incognita, M. exigua, and M. paranaensis were identified in samples from Brazil and M. incognita and M. hapla were detected around the roots of coffee in Vietnam. No Meloidogyne spp. were detected in samples from Indonesia. There was a high abundance of Meloidogyne spp. in soil samples in which Pratylenchus spp. were low or not detected, suggesting that the success of one genus may deter another. Meloidogyne spp. in Vietnam and Pratylenchus spp. in Indonesia were more numerous around intercropped plants than in association with coffee. The data suggest a widespread but differential nematode problem associated with coffee production across the regions studied. The issue is compounded by the current choice of intercrops that support large nematode populations. Wider application of the approach would elucidate the true global scale of the nematode problem and the cost to coffee production. [Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Rational design of biosafe crop resistance to a range of nematodes using RNA interference.

SummaryDouble‐stranded RNA (dsRNA) molecules targeting two genes have been identified that suppress economically important parasitic nematode species of banana. Proteasomal alpha subunit 4 (pas‐4) and Actin‐4 (act‐4) were identified from a survey of sequence databases and cloned sequences for genes conserved across four pests of banana, Radopholus similis, Pratylenchus coffeae, Meloidogyne incognita and Helicotylenchus multicinctus. These four species were targeted with dsRNAs containing exact 21 nucleotide matches to the conserved regions. Potential off‐target effects were limited by comparison with Caenorhabditis, Drosophila, rat, rice and Arabidopsis genomes. In vitro act‐4 dsRNA treatment of R. similis suppressed target gene expression by 2.3‐fold, nematode locomotion by 66 ± 4% and nematode multiplication on carrot discs by 49 ± 5%. The best transgenic carrot hairy root lines expressing act‐4 or pas‐4 dsRNA reduced transcript message abundance of target genes in R. similis by 7.9‐fold and fourfold and nematode multiplication by 94 ± 2% and 69 ± 3%, respectively. The same act‐4 and pas‐4 lines reduced P. coffeae target transcripts by 1.7‐ and twofold and multiplication by 50 ± 6% and 73 ± 8%. Multiplication of M. incognita on the pas‐4 lines was reduced by 97 ± 1% and 99 ± 1% while target transcript abundance was suppressed 4.9‐ and 5.6‐fold. There was no detectable RNAi effect on nontarget nematodes exposed to dsRNAs targeting parasitic nematodes. This work defines a framework for development of a range of nonprotein defences to provide broad resistance to pests and pathogens of crops.

Does plant richness alter multitrophic soil food web and promote plant-parasitic nematode regulation in banana agroecosystems?

Agroecosystem plant diversification at the field scale has been shown to enhance ecological pest regulation. We explored the effects of plant community composition and soil properties on the soil nematode community, with a particular interest in the regulation of banana plant-parasitic nematodes (PPN). We monitored banana phytometers (Cavendish Grande Naine cultivar) in 85 plots distributed along a plant richness gradient. Plant community composition, soil properties, abundance of bacterivorous, fungivorous and proportion of predaceous soil free-living nematodes, and abundance and damage of PPN (Radopholus similis, Pratylenchus coffeae, Helicotylenchus multicinctus, and Meloidogyne spp.) in phytometer roots were measured. We used structural equation modeling to investigate ecological processes leading to PPN regulation. Low-stratum plant species richness, but not high-stratum, was positively related to microbivore nematode abundances, supposedly because it promoted qualitative diversity of organic inputs and micro-climatic effects supporting more soil microorganisms. Musa genotype and low-stratum plant species richness induced associational susceptibility because of differential susceptibility of Musa genotypes to PPN and because of polyphagia of PPN spreading outside the Musa family, respectively. We found no regulation of PPN by predaceous nematodes, probably because food web complexity prevented trophic cascades from propagating. Ultimately, fungivorous nematode abundance was negatively related to PPN abundance, suggesting apparent competition or increased regulation by antagonistic fungi. Our results suggest that, when facing generalist pests, cropped plant communities should be diversified to promote pest regulation but must be carefully assembled to limit pest susceptibility heterogeneity among crop genotypes and to exclude alternative host plant species.

Hot water immersion of Allium hookeri roots for the control of the plant parasitic nematodes Meloidogyne javanica and Pratylenchus coffeae

Nematodes are important quarantine pests of bulbous plants such as hooker chives. Although control methods such as fumigation, chemical immersion, and heat are often applied, it has proved difficult to disinfect nematodes from plant roots in quarantine. As heat treatment has been successfully useful for the control of nematodes in other agricultural products in quarantine, we investigated the susceptibility and mortality rates of Meloidogyne javanica and Pratylenchus coffeae, which infest hooker chive roots, using a hot water immersion method. Heat damage to the hooker chive roots was noticeable at temperatures over 50°C. Temperatures for the effective time to kill 99% at 1 min (ET99) for M. javanica and P. coffeae juveniles were 49.3°C and 49.1°C, respectively. However, the time to kill 99% of M. javanica eggs at 48°C and 49°C were 27.0 min and 8.3 min, respectively. Using a thermal equilibrium formula, the optimum commercial scale condition, in a 1400-L chamber, for nematode control without associated plant damage was water immersion at 48.2°C for 30 min or at 49.2°C for 13 min with a filling ratio less than 12%. This result can be applicable for the nematode disinfestation of hooker chive roots in plant quarantine.

Development of Pratylenchus coffeae in Biochar Applied Soil, Coffee Roots and Its Effect on Plant Growth

Biochar improve physical, chemical and biological properties of soil. It may also be used as botanical pesticides. The experiment was aimed to determine the effect of biochar on population development of parasitic nematode Pratylenchus coffeae. The experiment was carried out in Nematology Laboratory and in a greenhouse of Indonesian Coffee and Cocoa Research Institute (ICCRI), Jember, Indonesia. The experiment was arranged according to completely randomized design with six treatments of biochar concentrations, i.e. 4%; 3%; 2%; 1%; 0.5% and 0% dry weight of soil. Research results revealed that biochar application of 4.0% was effectively killed 74.5% of P. coffeae, while the lowest mortality level of 37.5% at biochar 0.5% treatment. In the greenhouse trial, application of biochar 4.0% was the most effective in suppressing the population of parasitic nematode in coffee seedlings. Application of biochar was also able to increase the growth and biomass of coffee seedlings.

Associations of soil type and previous crop with plant-feeding nematode communities in plantain agrosystems

Understanding the influence of soil properties and cultural practices on the communities of plant-feeding nematodes (PFNs) in agrosystems is a prerequisite for cost-efficient and environment-friendly pest control. Although plantain is a staple food crop in the Caribbean, the relationships between PFN communities and environmental factors are poorly understood in plantain agrosystems. In this study, which was conducted in Martinique (French West Indies), we quantified the PFNs in 301 root samples taken from 53 plantain fields that differed in climate, edaphic conditions, and cultural practices. The physico-chemical properties were also determined for the soil in each field. Coinertia analysis (CI) and General Linear Mixed Models (GLMMS) were used to investigate the relationships between the PFN communities, soil properties, and cultural practices. Four nematode taxa were found in plantain roots: Radopholus similis, Pratylenchus coffeae, Helicotylenchus multicinctus, and Meloidogyne spp. The lesion nematode P. coffeae was the most prominent PFN species, followed by the burrowing nematode R. similis, root-knot nematodes Meloidogyne spp., and the spiral nematode H. multicinctus. P. coffeae was significantly more abundant in ferralsols and nitisols (which have a low organic matter content and a high exchangeable cation content) than in andosols (which have a high organic matter content). Nematode abundances were apparently affected by the previous crops e.g., P. coffeae was slightly more abundant in fields where tuber plants such as sweet potato, yam, or dasheen were the previous crop; R. similis was particularly abundant in fields where banana or plantain was the previous crop; and Meloidogyne spp. were abundant in fields where a market garden was the previous crop. The results of this study will be useful for the design of PFN control methods in plantain.

Nematicidal Effects of 5-Aminolevulinic Acid on Plant-Parasitic Nematodes

Plant-parasitic nematodes are important agricultural pests and often cause serious crop losses. Novel, environmental friendly nematicides are urgently needed because of the harmful effects of some existing nematicides on human health. 5-Aminolevulinic acid (ALA) was reported as a potential biodegradable herbicide, insecticide, or plant-growth promoting agent. Lack of information on ALA against plant-parasitic nematodes prompted this investigation to determine the effects of ALA on Meloidogyne incognita, Heterodera glycines, Pratylenchus coffeae, and Bursaphelenchus xylophilus. A series of in vitro assays and one greenhouse trial were conducted to examine the nematicidal effects of ALA. The results demonstrated that ALA exhibited a strong effect of suppression against the four nematodes tested. ALA also inhibited hatching of M. incognita and H. glycines. Results from the greenhouse experiment indicated that treatment of soil with 6.0 mM ALA significantly reduced the root-gall index (RGI) and egg mass number per root system compared with the uninoculated control (P ≤ 0.05). The metabolism assays indicated that ALA treatment significantly altered the nematode metabolism including the total protein production, malondialdehyde (MDA) content, and oxidase activities. This study suggested that ALA is a promising nematicide against plant-parasitic nematodes.

Evolutionary Expansion of WRKY Gene Family in Banana and Its Expression Profile during the Infection of Root Lesion Nematode, Pratylenchus coffeae.

The WRKY family of transcription factors orchestrate the reprogrammed expression of the complex network of defense genes at various biotic and abiotic stresses. Within the last 96 million years, three rounds of Musa polyploidization events had occurred from selective pressure causing duplication of MusaWRKYs with new activities. Here, we identified a total of 153 WRKY transcription factors available from the DH Pahang genome. Based on their phylogenetic relationship, the MusaWRKYs available with complete gene sequence were classified into the seven common WRKY sub-groups. Synteny analyses data revealed paralogous relationships, with 17 MusaWRKY gene pairs originating from the duplication events that had occurred within the Musa lineage. We also found 15 other MusaWRKY gene pairs originating from much older duplication events that had occurred along Arecales and Poales lineage of commelinids. Based on the synonymous and nonsynonymous substitution rates, the fate of duplicated MusaWRKY genes was predicted to have undergone sub-functionalization in which the duplicated gene copies retain a subset of the ancestral gene function. Also, to understand the regulatory roles of MusaWRKY during a biotic stress, Illumina sequencing was performed on resistant and susceptible cultivars during the infection of root lesion nematode, Pratylenchus coffeae. The differential WRKY gene expression analysis in nematode resistant and susceptible cultivars during challenged and unchallenged conditions had distinguished: 1) MusaWRKYs participating in general banana defense mechanism against P.coffeae common to both susceptible and resistant cultivars, 2) MusaWRKYs that may aid in the pathogen survival as suppressors of plant triggered immunity, 3) MusaWRKYs that may aid in the host defense as activators of plant triggered immunity and 4) cultivar specific MusaWRKY regulation. Mainly, MusaWRKY52, -69 and -92 are found to be P.coffeae specific and can act as activators or repressors in a defense pathway. Overall, this preliminary study in Musa provides the basis for understanding the evolution and regulatory mechanism of MusaWRKY during nematode stress.

Potensi Ochrobactrum intermedium - C939A31, Klebsiella oxytoca - C939A32, Bacillus subtilis- I308A32 Asal Tanaman Kopi untuk Mengendalikan Nematoda Luka Akar Pratylenchus coffeae

Infection of root lession nematode, Pratylenchus coffeae , becomes an important factor causing yield loss in coffee production in Indonesia. Biological control of P. coffeae needs to be developed to meet the requirement of environmentally save crop production. The research was conducted to evaluate 3 selected endophytic bacteria isolates, Ochrobactrum intermedium DSQ5, Klebsiella oxytoca NGB-FR 50, and Bacillus subtilis AIMST 10.T18.1, from coffee in controlling P. coffeae . Research methods involved pathogenicity test based on hypersensitive reaction and haemolysis test, and evaluation of their ability to suppress P. coffeae in vitro and in planta . The hypersensitive and haemolysis reactions indicated that these 3 isolates showed negative result both to plant and human. In vitro assays showed that two isolates, K. oxytoca - C939A32 and O. intermedium - C939A3, could suppress P. coffeae populations by 66.7% and 100%. Those results correlated positively with in planta assay’s result.

English

The objective of this study was to evaluate the effect of organic-matter incorporated into the soil on population densities of the causal agents of the dry rot disease of yam, under field conditions. The experiment was performed in a natural infested area with a mixed population of Pratylenchus coffeae and Scutellonema bradys, in Quebrangulo county (Alagoas state, Brazil) in a randomized block design with five treatments and five replicates. The sources of organic matter used as soil amendments were: coconut husk powder, castor bean cake, cattle manure and chicken manure. Non amended soil was used as a control. Nine months after planting, the tubers were harvested. No statistical differences were found among disease incidence, yam production and nematode population densities in the soil. However, the application of chicken manure reduced P. coffeae population in tubers. Key words: Dioscorea spp., Scutellonema bradys, Pratylenchus coffeae, nematode management.

Effectiveness of Endophytic Bacterial Consortium of Coffee Plant on Mortality of Pratylenchus Coffeae in Vitro

Bacteria live in wild in form of a consortium. Use of microbial consortium tends to give better results than single isolate, because the action of enzyme of each type of microbe can complement each other in order to survive. This study aimed to study the effectiveness of bacterial endophytic consortium from coffee plant on plant growth and mortality of parasitic nematodes in coffee. Isolation of bacteria is conducted by growing the crushed roots, stems and leaves of coffee on 20% TSA media, then testing their hemolysis and hypersensitivity reaction. Selected isolates were tested on their effect on the growth of seedling and Pratylenchus coffeae mortality, as well as their chitinolytic, proteolytic, lipolytic, HCN production, dissolution of phosphate (P) and fixation of nitrogen (N2) abilities. The results showed that from 27 isolates of the consortium, 23 isolates showed negative reaction to hypersensitive test and 9 isolates to hemolysis test. The highest mortality rate was shown by K6 isolate (65.8%). The highest growth was shown by K15 and K 21 isolates while the highest root length by K21 isolate. Further analisys showed that 100% of the isolates could hydrolyze proteases, lipid, and produce HCN, while chitinolytic activity was shown by 78% isolates which could fix N2 and 11% of isolates could dissolve phosphate.

English

The potential of Fulan (2,5-dimethoxytetrahydrofuran), a synthetic nematicide applied at 10 g /stand and two plant bed types; ridging and mounding to manage plant parasitic nematodes and increase the yield of yam was investigated at Ejura during 2011 and 2012 at three levels of N-P205-K50 (NPK). The factorial experiment was mounted on randomized complete block design and replicated three times. Ridged bed type + the highest level of fertilizer applied (60, 60, 80 kg/ha N-P205-K20) + Fulan application interacted positively (P < 0.05) resulting in significant yields (32 and 30%) over the control treatments in mound and ridged bed types, respectively. The same treatment resulted in the highest marketable weight of yam which was 61% over ridged bed type + fertilizer applied at 60, 60, 80 kg/ha N-P205-K20 without Fulan application. Cracks were significantly low in Fulan treated tubers. The outstanding reduction in cracks was recorded in mound + F4 + Fulan which were 92% less than mound bed type only (control) tubers. Additionally, Fulan application suppressed nematode densities. The remarkable suppression in Meloidogyne incognita and Pratylenchus coffeae occurred in ridged bed type + fertilizer applied at 45, 45, 60 kg/ha N-P205-K20 + Fulan treatment which was 93% over mound bed type without fertilizer and Fulan application and 97% over mound bed type + fertilizer applied at 60, 60, 80 kg/ha N-P205-K20 without Fulan application, respectively. Ridged bed type appeared to be the better plant bed type alternative since the highest yield and nematode suppression were recorded in that option; besides, ridging presents drudgery saving intervention which farmers could exploit. Key words: Dioscorea species, drudgery saving intervention, Fulan, plant bed type.

Identification of Ramie Genes in Response to Pratylenchus coffeae Infection Challenge by Digital Gene Expression Analysis.

Root lesion disease, caused by Pratylenchus coffeae, seriously impairs the growth and yield of ramie, an important natural fiber crop. The ramie defense mechanism against P. coffeae infection is poorly understood, which hinders efforts to improve resistance via breeding programs. In this study, the transcriptome of the resistant ramie cultivar Qingdaye was characterized using Illumina sequence technology. About 46.3 million clean pair end (PE) reads were generated and assembled into 40,826 unigenes with a mean length of 830 bp. Digital gene expression (DGE) analysis was performed on both the control roots (CK) and P. coffeae-challenged roots (CH), and the differentially expressed genes (DEGs) were identified. Approximately 10.16 and 8.07 million cDNA reads in the CK and CH cDNA libraries were sequenced, respectively. A total of 137 genes exhibited different transcript abundances between the two libraries. Among them, the expressions of 117 and 20 DEGs were up- and down-regulated in P. coffeae-challenged ramie, respectively. The expression patterns of 15 candidate genes determined by qRT-PCR confirmed the results of DGE analysis. Time-course expression profiles of eight defense-related genes in susceptible and resistant ramie cultivars were different after P. coffeae inoculation. The differential expression of protease inhibitors, pathogenesis-related proteins (PRs), and transcription factors in resistant and susceptible ramie during P. coffeae infection indicated that cystatin likely plays an important role in nematode resistance.

Biochemical characteristics of cover crop litter affect the soil food web, organic matter decomposition, and regulation of plant-parasitic nematodes in a banana field soil

Suppression of plant-parasitic nematodes and decomposition of organic matter are important soil food web functions. The availability and nature of carbon substrates in soil drive the structure, dynamics, and activities of soil food webs and may alter the way they function in the ecosystem. In this study, we assessed the effects on nematode communities of incorporating litter from three cover crops with contrasting biochemical characteristics into soil taken from a banana field. The litter type influenced nematode taxa and functional guilds during the 90-day assay. The cellulose- and hemicellulose-rich litters of Crotalaria zanzibarica and Paspalum notatum induced similar nematode successions, causing bacterivorous and fungivorous nematode populations to increase early in the study period and promoting a fungal decomposition pathway at the end of the trial. These two litters were the most effective at decreasing the soil’s nematode infective potential with regard to major banana plant-parasitic nematodes, such as Pratylenchus coffeae, Helicotylenchus multicinctus, and Rotylenchulus reniformis. C. zanzibarica showed good potential as a green manure plant, as it increased the soil mineral nitrogen content during the 45 days following incorporation of litter. By contrast, litter from Acacia auriculiformis, which had high lignin content, induced immobilization of soil nitrogen and did not significantly increase microbivorous nematodes before day 45. This treatment failed to reduce the soil’s nematode infective potential for H. multicinctus and R. reniformis populations. Our study also showed that the dynamics of nitrogen mineralisation in soil were related to the C:N ratio of litters but not to the decomposition pathway. The biochemical characteristics of litters appear to be critical drivers of nematode ecological successions and decomposition pathways following plant litter amendments to soil taken from a banana field.

Population of Pratylenchus coffeae (Z.) and growth of Arabica coffee seedling inoculated by Pseudomonas diminuta L. and Bacillus subtilis (C.).

AbstractPratylenchus coffeae is a parasitic nematoda that infected the roots of some plants, one of them is coffee. The Infection of Pratylenchus coffeae cause root tissue damage that led to root lession and make root become rotten, it will interfere the ability of roots to absorb water and nutrients in the soil which resulted in the growth of plants. At the moment, control of Pratylenchus coffeae are following integrated pests management (IPM) program, which integrated between the use of coffee resistant clone and application of biological agents. Research on biological control was conducted more intensive, at the moment; due to it is friendlier save against environment and cheaper then using chemical nematicides. The research was conducted to know the effects of Micorrhiza Helper Bacteria (MHB),Pseudomonas diminuta and Bacillus subtilis in suppressing the population of P. coffeaeas well as their effect on growth of coffee seedling. Coffee arabica (Coffea arabica L.) seedling one moth old were used in the experiment. The experiment prepared with eight treatments and five replications, as follows: A (Pseudomonas diminuta with density of 108 cfu / ml), B (Pseudomonas diminuta with density of 2x108 cfu / ml), C (Bacillus subtilis with density of 108 cfu / ml ), D (Bacillus subtilis with density 2x108 cfu / ml), E (Carbofuran nematicide 5 g formulation / pot), F (Pseudomonas diminuta and Bacillus subtilis with each density of 108 cfu / ml), K- (Nematoda inoculation but without bacteria and nematicide), K+ (coffee seedling without any additional treatment). The experiment was conducted for sixteen weeks or about four months. The results of the experiment showed that application of MHB could suppress population of P. coffeae and increase coffee seedling growth significantly. Inoculation of B. subtilis at 108 cfu per seedling suppressed significantly nematoda population of 71.3% compared with untreated seedling but inoculated with nematoda. It was not significant different with carbofuran treatment which could suppress nematoda population by 89.7%. The same result also occur on the treatment of P. diminuta at density level 2.108 cfu/seedling, which could suppress nematoda population by 64.2%. Seedling growth were treated with MHB also significantly increase compared with seedling without treatment and inoculation of nematodas, especially on the treatment of B.subtilis at density level 108 cfu and P.diminuta at density level of 108 cfu, with increasing level of 35.4% and 34.2 %, respectively.Keywords: MHB (Mycorrhiza Helper Bacteria), Arabica coffee (Coffea arabica L.), Pratylenchus coffeae, Bacillus subtilis, Pseudomonas diminuta.

Genome-wide analysis and differential expression of chitinases in banana against root lesion nematode (Pratylenchus coffeae) and eumusa leaf spot (Mycosphaerella eumusae) pathogens.

Knowledge on structure and conserved domain of Musa chitinase isoforms and their responses to various biotic stresses will give a lead to select the suitable chitinase isoform for developing biotic stress-resistant genotypes. Hence, in this study, chitinase sequences available in the Musa genome hub were analyzed for their gene structure, conserved domain, as well as intron and exon regions. To identify the Musa chitinase isoforms involved in Pratylenchus coffeae (root lesion nematode) and Mycosphaerella eumusae (eumusa leaf spot) resistant mechanisms, differential gene expression analysis was carried out in P. coffeae- and M. eumusae-challenged resistant and susceptible banana genotypes. This study revealed that more number of chitinase isoforms (CIs) were responses upon eumusa leaf spot stress than nematode stress. The nematode challenge studies revealed that class II chitinase (GSMUA_Achr9G16770_001) was significantly overexpressed with 6.75-fold (with high fragments per kilobase of exon per million fragments mapped (FPKM)) in resistant genotype (Karthobiumtham-ABB) than susceptible (Nendran-AAB) genotype, whereas when M. eumusae was challenge inoculated, two class III CIs (GSMUA_Achr9G25580_001 and GSMUA_Achr8G27880_001) were overexpressed in resistant genotype (Manoranjitham-AAA) than the susceptible genotype (Grand Naine-AAA). However, none of the CIs were found to be commonly overexpressed under both stress conditions. This study reiterated that the chitinase genes are responding differently to different biotic stresses in their respective resistant genotypes.

Suppressive effects of palisade grass (Brachiaria brizantha) on Pratylenchus coffeae

The suppressive effects of palisade grass (Brachiaria brizantha) cv. MG5 on Pratylenchus coffeae were tested in pot and seedling tray experiments and under field conditions. In pot tests, four isolates of P. coffeae were tested by inoculating 500 mixed life stages of each isolate on 5- or 7-week-old palisade grass plants. The nematode number in palisade grass was significantly lower than in susceptible cucumber in all isolates and below 20% of the inoculated level 69-86 days after inoculation. In seedling tray tests, the number of eggs and adults + juveniles in palisade grass roots was examined 5-25 days after inoculation (dai) of 200 mixed life stages of an isolate of P. coffeae to a 3-week-old seedling. The number of adults + juveniles in palisade grass roots was not statistically different from sorghum and black oat 5 and 10 dai, while the number of eggs and adults + juveniles was significantly lower than these two plants 20 and 25 dai. In field plot tests, palisade grass was cultivated for approximately 4 months in 2011 and 2012. The P. coffeae density after palisade grass cultivation was significantly lower than that after bare fallow in 2011, whereas the nematode density was not significantly different between these two treatments in 2012. Rates of lesions on sweet potatoes cultivated after growing palisade grass were significantly lower than those after growing sorghum or guinea grass, but not significantly different from that after fallow. These results indicated that the cultivation of palisade grass cv. MG5 has a nematode suppressive effect that is comparable to fallow treatments.

The plant parasite Pratylenchus coffeae carries a minimal nematode genome

Here we report the genome sequence of the lesion nematode, Pratylenchus coffeae, a significant pest of banana and other staple crops in tropical and sub-tropical regions worldwide. Initial analysis of the 19.67 Mb genome reveals 6712 protein encoding genes, the smallest number found in a metazoan, although sufficient to make a nematode. Significantly, no developmental or physiological pathways are obviously missing when compared to the model free-living nematode Caenorhabditis elegans, which possesses approximately 21 000 genes. The highly streamlined P. coffeae genome may reveal a remarkable functional plasticity in nematode genomes and may also indicate evolutionary routes to increased specialisation in other nematode genera. In addition, the P. coffeae genome may begin to reveal the core set of genes necessary to make a multicellular animal. Nematodes exhibit striking diversity in the niches they occupy, and the sequence of P. coffeae is a tool to begin to unravel the mechanisms that enable the extraordinary success of this phylum as both free-living and parasitic forms. Unlike the sedentary endoparasitic root-knot nematodes (Meloidogyne spp.), P. coffeae is a root-lesion nematode that does not establish a feeding site within the root. Because the P. coffeae nematode genome encodes fewer than half the number of genes found in the genomes of root-knot nematodes, comparative analysis to determine genes P. coffeae does not carry may help to define development of more sophisticated forms of nematode-plant interactions. The P. coffeae genome sequence may help to define timelines related to evolution of parasitism amongst nematodes. The genome of P. coffeae is a significant new tool to understand not only nematode evolution but animal biology in general.