Vascular Streak Dieback Research Articles

Parental assigned chromosomes for cultivated cacao provides insights into genetic architecture underlying resistance to vascular streak dieback.

Diseases of Theobroma cacao L. (Malvaceae) disrupt cocoa bean supply and economically impact growers. Vascular streak dieback (VSD), caused by Ceratobasidium theobromae, is a new encounter disease of cacao currently contained to southeast Asia and Melanesia. Resistance to VSD has been tested with large progeny trials in Sulawesi, Indonesia, and in Papua New Guinea with the identification of informative quantitative trait loci (QTLs). Using a VSD susceptible progeny tree (clone 26), derived from a resistant and susceptible parental cross, we assembled the genome to chromosome-level and discriminated alleles inherited from either resistant or susceptible parents. The parentally phased genomes were annotated for all predicted genes and then specifically for resistance genes of the nucleotide-binding site leucine-rich repeat class (NLR). On investigation, we determined the presence of NLR clusters and other potential disease response gene candidates in proximity to informative QTLs. We identified structural variants within NLRs inherited from parentals. We present the first diploid, fully scaffolded, and parentally phased genome resource for T. cacao L. and provide insights into the genetics underlying resistance and susceptibility to VSD.

Application of Bacillus sp Liquid Formula Using Root Infusion Technique To Control VSD (Vascular Streak Dieback) Disease In Cocoa

This study aims to explore the potential of liquid organic waste formula made from Bacillus sp to suppress the severity of vascular streak dieback (VSD) disease in cocoa plants. The research was conducted on smallholder cocoa plantations in Patimbe Village, Palolo Subdistrict, Sigi Regency, Central Sulawesi. The research was arranged in a non-factorial Randomised Group Design (RAK) with 5 treatments and 5 replications. The treatments consisted of control (P0=no formula); coconut water + Bacillus sp (P1); rice washing water + Bacillus sp (P2); tofu water + Bacillus sp (P3); and a combination of coconut water, rice washing water, and tofu water + Bacillus sp (P4). Each experimental unit consisted of 10 cocoa plants infected with VSD disease. The liquid organic waste formula was applied using the root infusion technique in months 1 and 3 at a dose of 250 ml/root. Observations of disease symptoms, disease development, disease severity, and disease suppression efficacy were conducted monthly. The results showed that the combination of organic waste of coconut water, tofu water, and rice washing water with Bacillus sp active ingredient was more effective in suppressing VSD disease than liquid organic waste alone with an effectiveness rate of 81.7%.

Vascular streak dieback: A novel threat to redbud and other woody ornamental production in the United States.

Eastern redbud (Cercis canadensis L.) is a popular and high-value woody ornamental plant native to the eastern and south-central United States of America (U.S.A.). In recent years, redbud production in the Southeastern U.S.A. has been greatly affected by a novel threat: vascular streak dieback (VSD). Infected plants exhibit a common set of symptoms, including leaf scorch, tip dieback, and vascular streaking that creates a marbled pattern in stem cross-section. Based on both conventional diagnosis and molecular identification, it has been found that the fungus Ceratobasidium sp. D.P. Rogers (Csp) is consistently associated with VSD-symptomatic eastern redbuds. However, the causal agent(s) of VSD has not yet been conclusively confirmed. Although eastern redbud has been the most frequently identified host tree, more than 25 other native plant genera have been confirmed to have VSD associated with Csp. The near-obligate nature of this fungus has made it challenging to culture, extract DNA, and conduct further studies to confirm its pathogenicity. This article highlights the emerging challenges of VSD, focusing on the following: 1) the recent history of VSD; 2) the increasing importance of VSD to woody ornamental nursery production in the U.S.A.; 3) the currently available protocols for isolating, culturing, storing, and maintaining the putative causal agent; 4) the rapid molecular detection of Csp; 5) phylogenetic findings on the origin and relatedness of Csp to previously recorded diseases, especially VSD in cacao (Theobroma cacao L.); and 6) preliminary results and observations from fungicide trials and cultivar screening in Tennessee. The article also outlines research needed to comprehensively understand VSD and accelerate the development of effective management strategies.

Isolation, genome analysis and tissue localization of Ceratobasidium theobromae, a new encounter pathogen of cassava in Southeast Asia

In Southeast Asia (SEA) fastidious fungi of the Ceratobasidium genus are associated with proliferation of sprouts and vascular necrosis in cacao and cassava, crops that were introduced from the tropical Americas to this region. Here, we report the isolation and in vitro culture of a Ceratobasidium sp. isolated from cassava with symptoms of witches’ broom disease (CWBD), a devastating disease of this crop in SEA. The genome characterization using a hybrid assembly strategy identifies the fungus as an isolate of the species C. theobromae, the causal agent of vascular streak dieback of cacao in SEA. Both fungi have a genome size > 31 Mb (G+C content 49%), share > 98% nucleotide identity of the Internal Transcribed Spacer (ITS) and > 94% in genes used for species-level identification. Using RNAscope® we traced the pathogen and confirmed its irregular distribution in the xylem and epidermis along the cassava stem, which explains the obtention of healthy planting material from symptom-free parts of a diseased plant. These results are essential for understanding the epidemiology of CWBD, as a basis for disease management including measures to prevent further spread and minimize the risk of introducing C. theobromae via long-distance movement of cassava materials to Africa and the Americas.

Effect of Weather Conditions to Vascular Streak Dieback Disease Severity on Some Cocoa Clones with Different Resistant Levels

Effect of Weather Conditions to Vascular Streak Dieback Disease Severity on Some Cocoa Clones with Different Resistant Levels

Traits of farming practice affecting vascular streak dieback disease on cacao in Central Sulawesi

Traits of farming practice affecting vascular streak dieback disease on cacao in Central Sulawesi

The Role of Leaf Nutrients in Vascular Streak Dieback Disease in Cocoa Plants (Theobroma cacao L.)

Background: Vascular streak dieback (VSD) is an important disease in cocoa and a decrease in nutrient supply is indicated to increase the severity of this disease. This study aimed to analyze the direct and indirect effects of nutrients that play a role in protecting cocoa plants from VSD. Methods: The research location was selected based on criteria such as being a smallholder cocoa plantation area, having 5-10-year-old plants and the presence of VSD disease. A sampling technique for observing disease severity was systematically conducted, with the main sample being farmers’ plantations. Cocoa leaf samples were taken from branches at one-third of the plant height, specifically from the upper canopy (leaves 3-4), which were physiologically mature, healthy and dark green. The variables observed were disease severity and cocoa leaf nutrient contents. The influence of N, P, K, Mg, Ca, Fe, Mn, B, Cu and Zn on VSD severity was analyzed using path analysis. Result: The results showed that disease severity was related to nutrient content in the leaves. The cocoa leaf nutrients that have a direct influence on the increase in VSD disease severity are K, Ca, Mn and Cu, while nutrients N, P, Mg, Fe, B and Zn have a direct influence on reducing VSD disease severity. Nutrients N and P have a significant direct influence, whereas nutrient K has a significant indirect influence through its interaction with nutrients N and P in reducing VSD disease severity.

Effectiveness of Trichoderma spp. secondary metabolites formulation in controlling vascular streak dieback of cacao

Vascular-streak dieback (VSD) is the main disease of the cacao plant caused by Ceratobasidium theobromae. The VSD disease can potentially reduce cacao yields by up to 45%. VSD control using secondary metabolites of Trichoderma spp. can suppress the disease incidence in the field. The research aimed to study the effectiveness of secondary metabolites of Trichoderma spp. in controlling VSD diseases in field conditions. This research performed in cacao fields owned by a farmer in Rahmat Village, Palolo Subdistrict, Sigi Regency, Central Sulawesi, Indonesia, that were infested by VSD. Treatments were applied using a randomized block design and replicated 5 times with 10 plants of each. The formulations used in the treatment were; liquid of T. virens, liquid of T. amazonicum, powder of T. virens, powder of T. amazonicum, granulates T. virens, granulates T. amazonicum, chemical fungicide (as a comparison), and control. The liquid formula formulated with molasses as carrier material, the granulate formula used zeolite, compost, and peat, whereas the powder formula used lactose. The liquid formula was applied through root infusion, granulated formula was sprinkled around the rooting area, and the powder by spraying on all parts of the plants. The observation was about the infection symptom, disease incidence, and cacao production/yield. The result showed that T. virens and T. amazonicum secondary metabolites can suppress the disease incidence of VSD by 8.61–19.50% and improve cacao production by 12.19-37.01%. The most effective formulation suppressing the disease’s incidence is a liquid formula applied through root infusion.

A sudden and widespread change in symptoms and incidence of vascular streak dieback of cocoa (Theobroma cacao) linked to environmental change in Sulawesi, Indonesia

Unstable new-encounter relationships between plants and pathogens form when organisms are transported between once-isolated biogeographic regions. Ceratobasidium theobromae is a new-encounter pathogen that has plagued the cocoa industry causing vascular streak dieback in Southeast Asia and western Melanesia. The disease underwent a sudden change in symptoms associated with an increase in disease incidence in Indonesia and Malaysia from about 2004. These changes have not been linked to changes in the pathogen or host and this shift could signal an effect of region-wide environmental changes in the responses of cocoa trees to infection. To study the effect of ambient temperature on symptom expression, this study assessed disease symptoms in cocoa trees along altitudinal gradients in Sulawesi, Indonesia. It recorded types of VSD symptoms (necrotic or chlorotic) in clones and local hybrids on managed farms, and in a reciprocal transplant experiment. The results found that consistently across landscapes, in trees of varying inherent susceptibilities to VSD, the incidence of new, necrotic symptoms decreased with altitude and was restricted to lowlands, while the chlorotic symptoms that originally characterised the disease were found throughout the altitudinal range. The new symptom pattern in cocoa appears to be an environmentally driven change in tree responses to the pathogen, possibly related to recent climate warming or elevated atmospheric concentration of CO2 due to widespread burning of forest and peat beds in Indonesia. The increased occurrence of a necrotic response of leaves to invasion by C. theobromae is typical of a hypersensitive response often associated with resistance to invasion by pathogens and could indicate enhanced resistance, although prolonged attachment of diseased leaves allows increased sporulation of the fungus and increased disease incidence.These are the first results to show an altered plant host–fungus pathogen response likely due to climate change, indicating that global warming may cause subtle but ecologically important changes in plant-parasite interactions. New-encounter relationships that are less stable than long-term co-evolved relationships might provide early-warning of ecological changes due to climate change. Determining whether the changed symptoms are a new threat is vital knowledge for farmers' livelihoods in this region.

Putative genes and pathways for Vascular Streak Dieback resistance in cocoa (Theobroma cacao L.) identified through the characterization of linked markers

Vascular Streak Dieback (VSD) caused by the fungus Ceratobasidium theobromae inflicts heavy yield losses in cocoa. Our previous study has identified and validated five ISSR and one SSR markers co-segregating with resistance and shown that they are efficient to select the resistant lines. In this work, to identify the genes and pathways involved in the resistance mechanisms, the ISSR markers for resistance, generated with UBC811, UBC826 and UBC857, were cloned and sequence characterized. The sequences had shown that the resistance loci lie in the chromosomes III and V. Eight disease resistance related proteins, TCM024428 Ankyrin repeat family protein/BTB/POZ domain-containing protein, TCM024455 Calcium-binding EF-hand family protein, TCM011959 Disease resistance protein, TCM012042 Kinase super family protein isoform 2, TCM012044 Basic helix-loop-helix DNA-binding superfamily protein, TCM014828 NBS-LRR resistance protein, TCM014842 Disease resistance family protein/LRR family, and TCM012034 NB-ARC domain-containing disease resistance protein, have been identified along with their partner defence proteins, domains and biological functions. KEGG analysis revealed tcc04075 plant hormone signal transduction pathway and tcc04626 plant-pathogen interaction pathway, having roles in the VSD resistance mechanism. • Molecular markers linked with VSD resistance in cocoa were cloned and sequenced. • Flanking regions of markers had 175 proteins including 8 resistance proteins. • Hormone signal transduction and pathogen interaction pathways were identified. • Protein partners and interaction patterns of resistance proteins were illustrated. • Domains of resistance protein and their roles in defence were predicted.

TRADITIONAL CULTIVATION TECHNIQUES OF COCOA PLANTS AND THE UTILIZATION TURMERIC EXTRACT BECOME VEGETABLE PESTICIDES FOR MANAGING VASCULAR STREAK DIEBACK (VSD)

The cocoa plant is the main ingredient in the manufacture of chocolate and its de-rivative products. The demand for cocoa derivative products is always high in line with the globalization of food and beverages made from chocolate. Traditional co-coa cultivation techniques are the main priority for farmers and the handling of Vascular Streak dieback (VSD) pests is a top priority for farmers. The purpose of this service is to improve the economy of cocoa farmers in Poli-Polia Village, Poli-Polia District, East Kolaka Regency. The method used is discussion, practice and demonstration material. The results of the shoot grafting technique for cacao seed-lings and the manufacture of organic fertilizers increase the productivity of cocoa plants and the results of turmeric extract can directly deal with VSD diseases that attack cocoa plants. In practice, the method of processing and the efficacy of tur-meric extract is the cause of not developing VSD disease in cocoa plants. On the other hand, cocoa yields can be sold at a high value based on training in harvesting techniques and how to improve the quality of cocoa beans.

Recovery and Improvement of Cocoa Production With the Use of Nutrients from Chitosan-Tonnage Blending Ash

Cocoa is one of the plantation crops that provide a high economic contribution to Central Sulawesi Province in particular and Indonesia in general and be the main income for local farmers. Cocoa is a non-oil and gas export commodity with high demand, therefore the government has determined cocoa as a strategic commodity that needs to be increased in productivity and developed as a source of income for Indonesia and State of Sulawesi. The purpose of this study was to make chitosan-tonnage blending in the composition of 80%-90% and to characterize it and its optimal ratio to restore soil nutrients, so the plants can be resistant to pests and Vascular Streak Dieback (VSD). Furthermore, cocoa fruit were powdered to become as raw material for bispic products. Chitosan come from chitin, with shrimp as raw material, tonnage was cocoa pods which have been hit by black fruit borers. Cocoa plants come from a less productive farmer area of 1 Ha, located in Rantekala Village, Gumbasa District, SigiBiromaru Regency. The results of this study revealed that of the cocoa fruit diameter which is given nutrient elements from chitosan-blending ashesat fruit age ± 6 weeks was 23 cm, compared with the cocoa fruit diameter that only given ZA / NPK fertilizer was 14.5 cm at the age of 7 weeks. The length of the cocoa fruit that was given nutrient elements from chitosan-blending ash blending at ± 6 weeks fruit age was 28 cm, while the cocoa fruit that was given ZA fertilizer only was 21 cm in length at 7 weeks. The production of cocoa beans which were given nutrient elements with chitosan-tonnage blending ashes increased by 60% compared to those that were only given ZA fertilizer. The conclusion from this study was the nutrients from chitosan-tonnage blending ash could be increase the size of the cocoa fruit around 37% for diameters and 27% for lengths greater than those given with ZA fertilizer.

Severity and changed symptoms of vascular streak dieback caused by Ceratobasidium theobromae in several cocoa (Theobroma cacao) clones in Sulawesi, Indonesia

Severity and changed symptoms of vascular streak dieback caused by Ceratobasidium theobromae in several cocoa (Theobroma cacao) clones in Sulawesi, Indonesia

Flush characteristics of several cocoa genotypes different in resistant to vascular streak dieback

Vascular streak dieback (VSD) is one of the main diseases on cocoa that can cause a decrease in production and even death on susceptible plants. The use of selection criteria is very important in the selection process at the seedling phase, young plants and even mature plants in order to support the breeding process of resistant varieties. The aim of the study was to determine the characteristics of flush including flush color, stomata characters and duration of flush color change to green or towards mature leaves as one of the selection indicators for VSD resistance in cocoa. The research was conducted at Kaliwining Experimental Station, Indonesian Coffee and Cocoa Research Institute, Jember, Indonesia. Study of flush color and stomata characters was conducted using a randomized complete block design consisting of four cocoa genotypes with different levels of resistance, classified as resistant to VSD disease (Sulawesi 1, PNT 16) and as susceptible (BCL and BL 50). Each clone was repeated three times and each replication consisted of three plant samples. Flush color duration study was carried out on six cocoa genotypes as treatments, three genotypes with resistant to VSD (PNT 16, Scavina 12, Sulawesi 1) and three genotypes as susceptible to VSD (BL 50, BCL, Criollo 22). Each treatment was repeated three times and each replication consisted of three plant samples. The results showed that the resistant genotypes showed a tendency to have lower chlorophyll and anthocyanin content than the susceptible ones. The stomata character in the resistant genotypes was not different than the susceptible ones, however, the resistant genotype showed that the stomata density at flush tended to be lower. The duration of flush color change to mature leaves (green) in resistant genotypes was significantly faster than susceptible genotypes.

Field screening of elite Cacao (Theobroma Cacao L.) clones to vascular streak dieback (VSD) disease as the selection criteria for planting materials

The field screening for VSD disease infection in four elite cocoa clones (KKM22, KKM4, PBC230, and MCBC1) was conducted after two years of transplanting. This study aimed to determine the efficient selection criteria for planting material of cocoa-based on the intensity of VSD disease and new shoot regeneration characteristics such as number, length, and diameter of new shoots after removal of the infected VSD twigs. Around half population (60%) of the trees were infected by the disease but the infection was minor and observed only on the leaf and twigs of 150 mm in length along the jorquette branches. The MCBC1 clone with a disease severity score of 1.82 is classified under the VSD disease resistance clone whereas other clones with a score averaging 2.21 are grouped under the moderately resistance clone. The cultural practice via pruning of all infected twigs (150 mm) was efficient to control the disease from spreading. One month after pruning, the MCBC1 from disease resistance clone had the lengthiest (62.3 mm) and thickest diameter (15.6 mm) of the new shoot compared with other clones. This study indicates the need for the screening of VSD disease in cocoa plantations so that the disease can be managed and controlled at the early stage of infection. This study also reported the first finding on using new shoot regeneration after pruning for the selection criterion of cocoa planting material in the future breeding programme.

In vitro growth induction of Ceratobasidium theobromae, the causal agent of cacao Vascular Streak Dieback disease

Vascular Streak Dieback (VSD) disease, caused by Ceratobasidium theobromae, has devastated cacao plants in Indonesia and other countries. However, there is limited information on the biology of the fungus, including mass propagation method. This study aimed to find a technique in inducing the growth of C. theobromae as inoculum sources. The stages of research were sampling the plant cacao tissue infected by C. theobromae; induction of mycelia growth on infected cacao tissue using coconut water, glucose, and sucrose; and confirmation C. theobromae by morphology, pathogenicity test on cacao seedling, and genetic. We found characteristic symptoms of VSD disease in cocoa plantations marked by chlorosis in cocoa leaves and blackening of the node on the leaf petiole. The growth induction of C. theobromae could be performed using a 2% glucose solution. The hyaline hyphae, perpendicular branching of hyphae, and a dolipare septate were shown in the hyphae structure. Pathogenicity test of mycelia C. theobromae from infected plant tissue showed typical symptoms of VSD. Genetic confirmation by PCR method successfully amplified specific target DNA of C. theobromae resulted in ± 550 bp amplicon. The result could be performed to propagate C. theobromae inoculum for various purposes in studying VSD disease.

Improvements of soil quality and cocoa productivity with agricultural waste biochar

National cocoa production has been decreasing, which was in 2017 down to 600,000 tons/year, only a third quarter of national need. The decline is due to a decrease in national cocoa production caused by lower productivity in smallholder cocoa. In 2003, the productivity was 1,100 kg/ha/year and in 2017 was only 820 kg/ha/year. The low productivity is caused by pod rot disease, pod borer, and vascular streak dieback (VSD). Not only that, soil degradation was also found to be a contributing factor. Compost or manure have been used as ameliorants, but they should be in high volume and have a short-term effect (3-4 months), easily decomposed, and produce CO2 that damages the ozone layers. A more suitable solution is using biochar which is more resistant to decomposition (hundreds of years), can hold CO2, water, and nutrients from being washed away by erosion. In addition, biochar does not require Cocoa farming generate organic waste that can be processed into biochar, such as cocoa pods, cocoa or shade trees from pruning. The biomass produced can reach up to 8-18 tons/year and is adequate to improve the soil fertility in cocoa plantations.

Role of Cocoa Clones and Endophyte Fungi in controlling VSD Disease in the Field

The fungus Ceratobasidium theobromae is the cause of vascular streak dieback (VSD) in cocoa. VSD disease can cause death in susceptible clones by more than 59%. The use of resistant cocoa clones and endophytic fungi can be an alternative for VSD disease control. The research objective was to evaluate cocoa clones and endophytic fungi to control VSD in the field. The experimental design used was a randomized block design with a factorial pattern. The first factor was cocoa clones, which consisted of clones 45 (K1) and 25 (K2), and the second factor was several types of endophytic fungi. The results showed an interaction between cacao clones and endophytic fungi isolates on the height and number of cocoa leaves. The two cacao clones tested could be naturally infected by C. theobromae without endophytic fungi, with disease incidence of VSD 5, 21% in K1, and 5.75% in K2. The two cocoa clones treated with endophytic fungi, i.e., Paecilomyces sp. EP1, Paecilomyces sp. EP2 and Paecilomyces sp. EP1 + Trichoderma sp.) did not show symptoms of VSD until 20 weeks after planting.

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.

Potency of secondary metabolites of Trichoderma asperellum and Pseudomonas fluorescens in the growth of cocoa plants affected by vascular streak dieback

Abstract. Simamora M, Basyuni M, Lisnawita. 2021. Potency of secondary metabolites of Trichoderma asperellum and Pseudomonas fluorescens in the growth of cocoa plants affected by vascular streak dieback. Biodiversitas 22: 2542-2547. Vascular streak dieback (VSD) is the main disease in cocoa caused by Oncobasidium theobromae. Using secondary metabolites of Trichoderma asperellum and Pseudomonas fluorescens is one of the methods to control disease in cocoa plants. The aim of this research is to evaluate the potency of secondary metabolites of T. asperellum and P. fluorescens to control VSD and study its effect on the growth of cocoa plants. The study used a non-factorial, completely randomized design (CRD) with eight treatments and four replications. The secondary metabolites were applied every week for ten times. The results showed that the secondary metabolites of T. asperellum and P. fluorescens were effective in controlling VSD. The combination of organic fertilizer and secondary metabolite of P. fluorescens and T. asperellum as found to be the best treatment to increase cocoa growth and the number of shoots increased by 43.58 shoots