Phytophthora Palmivora Research Articles

​Control Activity and Antibiotic Gene Detection of Endophytic Bacteria in Suppressing Cocoa Black Pod Disease (Phytophthora palmivora Butl.)

Background: Black pod rot disease of cocoa caused by (Phytophthora palmivora Butl.) is one of the major diseases on cocoa plantations worldwide. Many attempts have been made to prevent or reduce the infection of pathogens, but they have not provided optimum results. This study aims to detect antibiotic genes in endophytic bacteria that can suppress cocoa black pod disease. Methods: Eight endophytic bacteria were isolated from healthy cocoa pods and twigs that showed potentials in suppressing P. palmivora growth in vitro were used in suppressing of black pod rot disease in vivo tests. Antibiotic biosynthesis-related genes from eight endophytic bacterial isolates were confirmed by using PCR method, which includes phenazine-1-carboxylic (PCA), pyrrolnitrin (PRN), phenazine-1-carboxamide acid (PCN), pyoluteorin (PLT) and 2,4-diacetylphloroglucinol (DPAG/Phl). Result: The endophytic bacteria, 4RSI, 5BR B3 and 2RW B2 isolates showed the highest disease suppressing index to black pod rot disease in vivo, i.e., 70.27%, 70.08% and 56.64%. The isolates 5BR B3 and 2RW B2 DNA yielded PCR product by using PCA primers (1400 bp), PRN primers (700 bp) and DAPG primers (1600 bp), while the 5RSI isolate yield PCR product using PRN primers only. Endophytic bacterial isolates 5BRB3 and 2RW B2 provided partial disease suppression to pod rot disease by inhibit pathogen growth and antibiotic compounds production.

Metalaxyl Resistance of Phytophthora palmivora Causing Durian Diseases in Thailand

Thailand is the leading producer and exporter of durians worldwide. Serious diseases in durians include root rot, stem rot, and fruit rot, which are caused by Phytophthora palmivora, P. nicotianae, and Pythium cucurbitacearum, respectively. Thai farmers have applied fungicides for more than 20 years to control rot, but it remains difficult to control. Thus, the monitoring of fungicide-resistance development in pathogens is important for disease management. Pathogens were isolated from naturally infected durians between 2016 and 2017 in southern Thailand. The sequences of the internal transcribed spacer (ITS) and 5.8S regions of rDNA were used for the identification of their species. Seventeen out of twenty isolates were confirmed to be P. palmivora. All the isolates were tested for mycelium-growth sensitivity to metalaxyl, azoxystrobin, and dimethomorph. The results showed that nine isolates were resistant to metalaxyl with the 50% effective concentration (EC50) higher than 100 mg L−1. By contrast, all the isolates were sensitive to both azoxystrobin and dimethomorph, with EC50 < 1 mg L−1. Metalaxyl-resistant isolates were not controlled (−25.6% to 22.2%) by the treatment of the detached leaves of ‘Monthong’ durian with 100 mg L−1 metalaxyl prior to inoculation, but all the metalaxyl-sensitive and moderately metalaxyl-resistant isolates were better controlled (33.0% to 62.6%). These results clearly indicate that metalaxyl-resistant strains are present in the populations of P. palmivora in Thailand.

An Integrated Disease Management of Oil Palms Affected by Bud Rot Results in Shorter Recovery Times

Bud rot is a limiting disease that affects most oil palm crops destroying thousands of hectares in Latin America. Bud rot (BR) is caused by the oomycete Phytophthora palmivora (Butler). Integrated disease management (IDM) technology has been used to control the disease, which slows down the progress of the disease, allowing palm recovery. However, the effect of this technology on the recovery speed of treated palms is not well known. We studied the time taken for palm recovery from BR under the integrated management approach. The study was carried out on 21 oil palm commercial cultivars dura × pisifera (D × P) and O × G hybrids affected by BR in the Colombian oil palm Central Zone. The analysis included different recovery times (RT), the severity degree, time of the year (wet or dry season), number of reinfections, and cultivar. The RT of bud rot-affected palms ranges from 103 to 315 days, with an average of 202.8 days when an IDM is used. RT was lower than that reported in the diseased palms without IDM (540 days). According to the severity degree, the RT lasted 202 days for severity degree 1, 198 days for severity degree 2, and 222 with severity degree 3 and 4. In comparison, there was no significant difference between dry and rainy seasons in RT. Differences between cultivars were found; however, under IDM, all cultivars showed low RT. The IDM has a positive impact in reducing the RT to BR. Low RT has indirect effects minimizing potential yield losses, improving the number of successfully recovered palms, and reducing the risk of disease dissemination.

The Plant-Beneficial Rhizobacterium Bacillus velezensis FZB42 Controls the Soybean Pathogen Phytophthora sojae Due to Bacilysin Production.

Soybean root rot caused by the oomycete Phytophthora sojae is a serious soilborne disease threatening soybean production in China. Bacillus velezensis FZB42 is a model strain for Gram-positive plant growth-promoting rhizobacteria and is able to produce multiple antibiotics. In this study, we demonstrated that B. velezensis FZB42 can efficiently antagonize P. sojae. The underlying mechanism for the inhibition was then investigated. The FZB42 mutants deficient in the synthesis of lipopeptides (bacillomycin D and fengycin), known to have antifungal activities, and polyketides (bacillaene, difficidin, and macrolactin), known to have antibacterial activities, were not impaired in their antagonism toward P. sojae; in contrast, mutants deficient in bacilysin biosynthesis completely lost their antagonistic activities toward P. sojae, indicating that bacilysin was responsible for the activity. Isolated pure bacilysin confirmed this inference. Bacilysin was previously shown to be antagonistic mainly toward prokaryotic bacteria rather than eukaryotes. Here, we found that bacilysin could severely damage the hyphal structures of P. sojae and lead to the loss of its intracellular contents. A device was invented allowing interactions between P. sojae and B. velezensis FZB42 on nutrient agar. In this manner, the effect of FZB42 on P. sojae was studied by transcriptomics. FZB42 significantly inhibited the expression of P. sojae genes related to growth, macromolecule biosynthesis, pathogenicity, and ribosomes. Among them, the genes for pectate lyase were the most significantly downregulated. Additionally, we showed that bacilysin effectively prevents soybean sprouts from being infected by P. sojae and could antagonize diverse Phytophthora species, such as Phytophthora palmivora, P. melonis, P. capsici, P. litchi, and, most importantly, P. infestans. IMPORTANCEPhytophthora spp. are widespread eukaryotic phytopathogens and often extremely harmful. Phytophthora can infect many types of plants important to agriculture and forestry and thus cause large economic losses. Perhaps due to inappropriate recognition of Phytophthora as a common pathogen in history, research on the biological control of Phytophthora is limited. This study shows that B. velezensis FZB42 can antagonize various Phytophthora species and prevent the infection of soybean seedlings by P. sojae. The antibiotic produced by FZB42, bacilysin, which was already known to have antibacterial effectiveness, is responsible for the inhibitory action against Phytophthora. We further showed that some Phytophthora genes and pathways may be targeted in future biocontrol studies. Therefore, our data provide a basis for the development of new tools for the prevention and control of root and stem rot in soybean and other plant diseases caused by Phytophthora.

Direct and cross-pathogenicity of Phytophthora palmivora against cacao, papaya, and peach palm

Direct and cross-pathogenicity of Phytophthora palmivora against cacao, papaya, and peach palm

Structural and Functional Genomics of the Resistance of Cacao to Phytophthora palmivora.

Black pod disease, caused by Phytophthora spp., is one of the main diseases that attack cocoa plantations. This study validated, by association mapping, 29 SSR molecular markers flanking to QTL (Quantitative Trait Loci) associated with Phytophthora palmivora Butler (Butler) (PP) resistance, in three local ancient varieties of the Bahia (Comum, Pará, and Maranhão), varieties that have a high potential in the production of gourmet chocolate. Four SSR loci associated with resistance to PP were detected, two on chromosome 8, explaining 7.43% and 3.72% of the Phenotypic Variation (%PV), one on chromosome 2 explaining 2.71%PV and one on chromosome 3 explaining 1.93%PV. A functional domains-based annotation was carried out, in two Theobroma cacao (CRIOLLO and MATINA) reference genomes, of 20 QTL regions associated with cocoa resistance to the pathogen. It was identified 164 (genome CRIOLLO) and 160 (genome MATINA) candidate genes, hypothetically involved in the recognition and activation of responses in the interaction with the pathogen. Genomic regions rich in genes with Coiled-coils (CC), nucleotide binding sites (NBS) and Leucine-rich repeat (LRR) domains were identified on chromosomes 1, 3, 6, 8, and 10, likewise, regions rich in Receptor-like Kinase domain (RLK) and Ginkbilobin2 (GNK2) domains were identified in chromosomes 4 and 6.

Inoculum source of Phytophthora palmivora jackfruit seedlings health in response to potting media porosity, sanitation, inoculation, and phosphonate application

Seedling dieback caused by <i>Phytophthora palmivora</i> (Butler) is a significant problem in jackfruit <i>(Artocarpus heterophyllus</i> Lam.) nurseries in Eastern Visayas, Philippines. It has been linked to insufficient knowledge of inoculum sources and possible factors contributing to seedlings’ health. This study was conducted to identify potential sources of <i>Phytophthora</i> inoculum in representative nurseries in Eastern Visayas and evaluate the effect of possible factors that contribute to seedling health. <i>Phytophthora</i> detection was conducted from random samples of potting media, irrigation water, germination beds, and roots of seedlings from representative nurseries supplying seedlings in the region. Detection was done through tissue baiting and the use of a <i>Phytophthora-</i>specific diagnostic kit. The effect of the air-filled porosity (AFP) of potting media, sanitation, pathogen inoculation, and phosphonate on plant growth and seedlings’ health was evaluated. <i>Phytophthora</i> propagules were positively detected in most samples, suggesting that seedlings most likely already harbor the pathogen when distributed to farms in the region. Among the factors, AFP of the potting medium had the most profound effect on seedlings’ growth and health. The tallest plants with the largest stem diameter, highest dry weight biomass, and least disease rating were grown in the most porous medium (21 <i>%</i> AFP) consisting of 20 <i>%</i> garden soil, 20 % carbonized rice hull, 20 % rice hull, 20 % coco coir dust, 10 % sand, and 10 <i>%</i> chicken dung. The benefit of a highly porous medium was, however, seen only when external fertilization was undertaken. Unsterilized media resulted in healthier seedlings compared to sterilized media. Sterilized potting media that were inoculated with the pathogen after sterilization resulted in more severe disease. Sterilized potting media was beneficial for jackfruit seedlings when supplied with adequate nutrients and as long as contamination with the pathogen does not occur. Sterile media, therefore, should be kept away from recontamination with the pathogen otherwise more severe disease may occur. The addition of the plant defense regulator phosphonate showed no effect on the growth and health of seedlings under the trial’s conditions.

A simple method for the extension of shelf life of cultures of Phytophthora species causing black pod disease of cacao (Theobroma cacao L.)

Black pod disease of cacao caused by Phytophthora palmivora and Phytophthora megakarya in Ghana take heavy toll of cacao production in the field. Intensive research has been carried out worldwide on these pathogens. However, viability of the cultures during prolonged storage has remained a major challenge in the research. This paper reports findings of assessment of six storage media viz sterilised distilled water (SDW), sterilised and unsterilized soil suspension (SSS and USS), vegetable 8 juice broth (V8JB), Oat Meal Agar slant under mineral oil (at 4°C) and empty tube. Viability of the cultures was assessed on V8JA and in tetrazolium chloride test. Ability of zoospores of the cultures to infect cacao leaf discs was used to assess growth vigour and pathogenicity. Phytophthora cultures stored in SDW (26 ± 2°C; alternating day light and night) were preserved for 60 days (5 years). Both P. palmivora and P. megakarya performed better on SDW and SSS than on USS due to removal of staling substances in the soil medium by the sterilisation. Vigour of growth and pathogenicity of the stored cultures required re-inoculation of host tissue (cacao pod) in order to maintain potency to continually infect host.

A slicing mechanism facilitates host entry by plant-pathogenic Phytophthora.

Phytophthora species, classified as oomycetes, are among the most destructive plant pathogens worldwide and pose a substantial threat to food security. Plant pathogens have developed various methods to breach the cuticle and walls of plant cells. For example, plant-pathogenic fungi use a 'brute-force' approach by producing a specialized and fortified invasion organ to generate invasive pressures. Unlike in fungi, the biomechanics of host invasion in oomycetes remains poorly understood. Here, using a combination of surface-deformation imaging, molecular-fracture sensors and modelling, we find that Phytophthora infestans, Phytophthora palmivora and Phytophthora capsici slice through the plant surface to gain entry into host tissues. To distinguish this mode of entry from the brute-force approach of fungi that use appressoria, we name this oomycete entry without appressorium formation 'naifu' invasion. Naifu invasion relies on polarized, non-concentric, force generation onto the surface at an oblique angle, which concentrates stresses at the site of invasion to enable surface breaching. Measurements of surface deformations during invasion of artificial substrates reveal a polarized mechanical geometry that we describe using a mathematical model. We confirm that the same mode of entry is used on real hosts. Naifu invasion uses actin-mediated polarity, surface adherence and turgor generation to enable Phytophthora to invade hosts without requiring specialized organs or vast turgor generation.

Microbial community occupying cocoa branch and petiole with vascular streak dieback disease symptoms

Vascular Streak Dieback (VSD) disease caused by Ceratobasidium theobromae is the most severe emerging cocoa disease in Southeast Asia. Once the tree is infected, tree defoliation will occur as leaf senescence followed by leaf falls. VSD to have associated with endophytes. However, a fundamental question is whether a similar microbe inhabiting vascular tissue of branch and petiole is entire or patchy? The aim of research was to track and quantify microbial diversity associated with VSD symptoms occupying branches and petiole throughout the stem in different clones. The study focused on VSD symptoms expressing in local (Sulawesi 02), susceptible (RCC 70), and resistant (MCC 02) clones to VSD disease. Sample collection was conducted in Lili Riaja, Soppeng District. The 30 cm-branch with the attached petiole of interest was cut into small pieces 1 cm and transferred into water agar medium before submersion into 2.5% NaOCl for 3 minutes, 70% alcohol for 2 minutes and sterilized water for 1 minute. Morphological characterization followed by microscope check was determined to microbial genera. Eight different fungal communities occupying branch and/or petiole consisted of Cladosporium sp., Fusarium sp., Colletotrichum sp., Penicillium sp., Aspergillus sp., Moniliophthora sp., Lasiodiplodia sp., Curvularia sp. and one Oomycete Phytophthora palmivora. Among occupants in branch and petiole, Fusarium sp. and Colletotrichum sp. were the most frequent. Only one Oomycete Phytophthora palmivora occupying clone samples was found. The most diverse microbes were found to associate with Sulawesi 02 and RCC 70 clones, while fewer microbes were detected with MCC 02 clone.

Observations on the Potential of an Endophytic Fungus Associated with Cacao Leaves against Phytophthora palmivora

A study was conducted to test the pathogenicity of an endophytic fungus associated with asymptomatic cacao leaves, to determine its identity through cultural, morphological and molecular characterization, and to evaluate itsantagonistic ability vs. Phytophthora palmivora causing cacao black pod rot disease. Experiments were carried out under laboratory and shade house conditions. Homogeneity of variances and normal data distribution were determined using Bartlett’s and Shapiro–Wilk tests, respectively. Inoculation of the endophyte in healthy cacao seedlings and pods at 5 × 105 to 1 × 106 conidia per mL by spraying resulted in asymptomatic infections. The endophyte was recovered from artificially inoculated tissues 14 and 26 days after inoculation (DAI) (UF18 seedlings), and at 10 (K9 seedlings) and 14 DAI from cacao pods. The endophyte was identified as Colletotrichum siamense based on its cultural, morphological and molecular characteristics. In vitroanti-pathogen assays showed that C. siamense had the potential to limit pathogen growth by antibiosis. At 3, 5 and 7 days after incubation period (DAIP), growth of the pathogen in co-cultivation with the endophyte measured 60.0, 70.0 and 71.0 mm, respectively, which wasconsiderably lower than the growth of the pathogen alone.

First report of Phytophthora palmivora (E. J. Butler) E. J. Butler, 1919 causing fruit rot in Areca triandra Roxb. ex Buch.-Ham. from India

First report of Phytophthora palmivora (E. J. Butler) E. J. Butler, 1919 causing fruit rot in Areca triandra Roxb. ex Buch.-Ham. from India

Selection of cocoa clones for resistance to Phytophthora palmivora by artificial inoculation and natural infection in the field

Selection of cocoa clones for resistance to Phytophthora palmivora by artificial inoculation and natural infection in the field

Antifungal effect of zinc oxide nanoparticles against disease in durian caused by Phytophthora palmivora

Antifungal effect of zinc oxide nanoparticles against disease in durian caused by <i>Phytophthora palmivora</i>

Synthesis and charcterization of Cu-doped TiO2 (Cu/TiO2) nanoparticle as antifungal phytophthora palmivora

Preparation of Cu-doped TiO2 nanoparticles (Cu/TiO2) as antifungal Phytophthorapalmivorahas been carried out. In this study, we did a synthesis of Cu/TiO2 nanoparticles by the sol-gel method and determine the performance of the modification of Cu/TiO2 nanoparticles as antifungal agents P. palmivora. The stages of this research include synthesis of Cu/TiO2 nanoparticles using the sol-gel method, characterization of Cu/TiO2 nanoparticles using UV-Vis DRS and characterization of Cu/TiO2 nanoparticles using SEM-EDX, and P. palmivora antifungal activity test. TiO2 is known to be used as an antifungal agent and to increase photocatalyticactivity, TiO2 is doped with Cu metal ions to be active in visible light. The results showed that Cu/TiO2 has a band gap energy of 3.12 eV. Based on the results of SEM-EDX analysis of TiO2-Cu nanoparticles confirmed the presence of elements Cu (2.16%), Ti (28.74%) and O (69.10%) with morphological shapes such as irregular spheres. Cu/TiO2 nanoparticles have a strong ability at concentrations of 0.05% and 2.5% in inhibiting the growth of the fungus P. palmivora. Percent inhibition respectively 60.41% and 75% and at concentrations>3% have activities that can kill P. palmivora fungus.

Endophytic fungi as potential biocontrol agents of Phytophthora palmivora in the cocoa plant

Abstract. Simamora AV, Hahuly MV, Henuk JBD. 2021. Endophytic fungi as potential biocontrol agents of Phytophthora palmivora in the cocoa plant. Biodiversitas 22: 2601-2609. In Indonesia, the cocoa tree is one of the essential cultivation crops for farmers. Despite the importance of cocoa cultivation in Indonesia's economy, the productivity of this crop has declined. Cocoa black pod disease caused by Phytophthora palmivora (Butl.) is one of the most severe diseases affecting this crop worldwide, with average annual losses above 40%. Instead of using manufactured chemicals, biological control is an effective and eco-friendly alternative control measure against plant pathogens. This work aimed to assess the potential of endophytic fungi isolated from healthy cocoa pods to control Phytophthora palmivora in vitro and in vivo. Endophytic fungal isolates were classified based on the morphological characteristics of their cultures and reproductive structures. All isolates found were tested to inhibit P. palmivora in the dual culture method, and the best 10 isolates were continued for detached pod assay. Then, the best five isolates (Aspergillus4, Aspergillus5, Aspergillus6, Fusarium6, Ramichloridium sp.) were evaluated for their capability to reduce P. palmivora in cocoa seedlings and in the field plants. Aspergillus, Fusarium, and Ramichloridium showed maximum activity against P. palmivora in dual culture, pod, and seedling assays. Nevertheless, when all these five isolates were applied in the field, they did not suppress the disease development.

Phytophthora palmivora Causing Disease on Theobroma cacao in Hawaii

Commercial production of cacao in Hawaii has doubled in the past 10 years, and farmers are receiving premium prices for their beans from the expanding local confectionery industry. Black pod, caused by Phytophthora spp., is the only major cacao disease that has been reported in Hawaii but distribution and molecular identification are lacking. To determine the species of Phytophthora affecting Theobroma cacao, a sampling trip was conducted on Hawaii Island and Oahu. Ten isolates of Phytophthora palmivora were obtained from diseased cacao on Hawaii Island, but none from Oahu, despite the presence of symptomatic pods. No other Phytophthora species were found. Laboratory studies showed that all isolates produced lesions on unwounded cacao pods, but they differed in terms of their temperature–growth responses. Fungicide sensitives for a subset of isolates (n = 4) were determined using media amended with a range of fungicide concentrations. The Hawaiian isolates of P. palmivora were more sensitive to mefenoxam, chlorothalonil, and fosetyl-Al, than isolates from Ghana (n = 2) and Mexico (n = 1). This study identifies P. palmivora as a causal agent of black pod in Hawaii based on molecular data and provides valuable preliminary information on fungicide resistance and temperature response that can be used to improve disease management.

Current status of plant pathogens of agricultural importance for Colombia. A review

Plant disease still plays a major role in limiting agricultural production worldwide. Pathogens and pests reduce crop yield and can cause large reductions in crop quality. Colombia is no exception as it contends with many devastating pathogens that present a major threat to the country’s agricultural sector. This review is important because it highlights four of the more damaging pathogens that affect the economics of important crops in Colombia - Xanthomonas phaseoli pv. manihotis (Xpm), Fusarium oxysporum f. sp. cubense (Foc), Phytophthora palmivora, and Hemileia vastatrix. This paper was based on an extensive literature search for plant diseases in Colombia in databases such as PubMed and Google Scholar. Moreover, this search was complemented with research on crop production in the country in databases made available by the Food and Agriculture Organization of the United Nations (FAO). The four pathogens reviewed in this paper were chosen not only because of their current devastating effects on Colombia’s agricultural production but also because of their potential to cause further damage in the near future. Understanding the current situation of these crop pathogens in Colombia is imperative for state directives aimed at developing informed and efficient control strategies.

The Study of the Kinetics of Metalaxyl Accumulation and Dissipation in Durian (Durio zibethinus L.) Leaf Using High-Performance Liquid Chromatography (HPLC) Technique.

Metalaxyl is an effective approach to control Phytophthora palmivora infection in durian plantation. However, inappropriate metalaxyl usage may increase production cost, pathogen with fungicide resistance, and environmental toxicity. This study established and validated a simple and reproducible procedure to measure metalaxyl concentration in the durian leaf using HPLC. Linearity of the detection ranged from 1–100 µg/mL. The limits of detection (LOD) and quantification (LOQ) were 0.27 and 0.91 µg/mL, respectively. The extraction method gave recovery rates ranging from 88% to 103%. Durian seedlings were treated with 4 g/L metalaxyl either by foliar spray or soil drench. The highest metalaxyl accumulation in durian leaf was found between 6–24 h after treatment and persisted above its effective concentration at least 60 days after foliar application. The dissipation pattern fit to a first-order kinetics equation showed a half-life of 16.50 days. Soil drenching led to eight times higher metalaxyl concentrations in plants than foliar spraying and caused plant death within 15 days after application. These results suggest that foliar spraying of 4 g/L metalaxyl or soil drenching at a lower concentration every two months is sufficient in controlling P. palmivora infection in durian seedlings.

Genotype–environment interactions shape leaf functional traits of cacao in agroforests

The outbreak of frosty (Moniliophthora roreri) and black pod (Phytophthora palmivora) in Central American cacao agroforests throughout the 1980s led to the breeding of Theobroma cacao clones resistant to these diseases. However, while clonal disease resistance has been well-documented, clonal adaptability to contrasting pedoclimates remains less understood. Plant functional responses to environmental constraints can be assessed by evaluating intraspecific trait variation (ITV), but trait-based approaches have rarely been implemented in genotype assessments. The objective of our study was to determine cacao clone ITV in contrasting environments. Here, we used bivariate, multivariate, and functional trait space analyses to quantify ITV in nine leaf functional traits, among six disease-resistant cacao clones, growing in two clonal gardens with distinct environmental characteristics (a “mild dry season” with near-optimal cacao growing conditions and a “harsh dry season” site with sub-optimal conditions). All leaf traits varied among the six clones, though trait differences among clones differed depending on the site: physiological trait differences among clones were larger at the “mild dry season” site, chemical trait differences were wider at the “harsh dry season” site, and morphological trait differences among clones were similar at both sites. Multivariate and hypervolume trait space analyses revealed greater site influence on trait values of the least productive clones, while the most productive clones were characterized by higher specific leaf area, independent of the site. To our knowledge, our paper is among the first to show evidence that functional traits provide new insights into genotype × environment interactions and clonal selection in agroforestry systems and support in favor of applying functional trait-based research to plant breeding paradigms.