Characterization of Botryosphaeriaceae and Cryphonectriaceae associated with Terminalia SPP. in Africa

Fungal diseases of trees are serious impediments to forest expansion and productivity. While the adverse effects of diseases of non-native plantation forest trees are increasingly recognized in Africa, the health of native trees has been virtually ignored. This is especially acute as many commercially propagated trees are related to native woody plants and recurrent movement of pathogens between native and non-native trees is increasingly being recorded. The genus Terminalia accommodates important indigenous tree species in Africa that provide a variety of valuable wood and non-wood products. Despite the importance of Terminalia spp., very little information has been recorded on their health problems. Research for this dissertation aimed at studying some of the fungal diseases of native and non-native Terminalia species in Africa. Special reference was provided to fungi in the Botryosphaeriaceae, a group of pathogens that infect host plants without always producing clear symptoms. A literature review, presented in Chapter One, highlighted the limited information available on the pathogens and pests associated with these trees. Most disease reports include minimal detail. Often the causal agents had been identified based only on morphology and were not classified to the species level. Studies performed in chapter two compared the assemblages of endophytic species of the Botryosphaeriaceae from T. catappa in Cameroon, South Africa and Madagascar. Five species were identified and two of these are new to science and provided with the names N. batangarum and L. mahajangana. The assemblage of the Botryosphaeriaceae varied from one country to another, however, colonization patterns in the three areas were similar. Greenhouse inoculation trials performed on young T. catappa trees showed variation among isolates tested, with L. pseudotheobromae being the most pathogenic. Chapter three represents the first investigation of the Botryosphaeriaceae on native Terminalia trees in Cameroon and Africa. Morphological and DNA sequence data were used to identify these species as L. theobromae, L. pseudotheobromae, L. parva and E. endophytica. Pathogenicity trials performed on young T. mantaly and T. catappa trees revealed that L. pseudotheobromae was the most virulent species. In chapter four, species of Botryosphaeriaceae on native Terminalia spp. in Southern Africa were studied. Nine species were identified from T. sericea and T. sambesiaca. Seven of these, L. crassispora, L. pseudotheobromae, D. alatafructa, P. olivaceum, N. parvum, N. kwambonambiense and N. vitifusiforme represented previously described species and two, L. cryptotheobromae and N. terminaliae, were described as new. The genetic analyses of populations of L. theobromae and L. pseudotheobromae presented in chapter five showed clear genetic divergence between L. theobromae and L. pseudotheobromae supporting their distinction as separate species. Both L. theobromae and L. pseudotheobromae populations possessed high gene diversity, moderate degrees of genotypic diversity, and high levels of gene flow between isolates from T. cacao and Terminalia spp. Both sexual and asexual modes of reproduction were found. The last chapter of this dissertation presents the description of a new genus in the Cryphonectriaceae, Aurifilum marmelostoma, using a combination of molecular and morphological tools. This fungus is the second genus in this family described from Terminalia spp. Pathogenicity tests conducted to assess its ability to cause disease revealed that the fungus is a possible pathogen of this tree. An extensive number of potentially pathogenic fungi, including five new species were found associated with native and non-native Terminalia spp. in Africa. As some of these fungal species could serve as sources of inoculum onto economically important crops, research presented in this dissertation provides a foundation for understanding health issues affecting Terminalia and related genera in selected regions in Africa. Hopefully, results of this study will serve as valuable tools in forestry management in Africa. CopyrightThesis (PhD)--University of Pretoria, 2010.Plant Production and Soil ScienceUnrestricte

Molecular phylogenetic analyses reveal three new Ceratocystis species and provide evidence for geographic differentiation of the genus in Africa

The emergence of wattle wilt disease on non-native Acacia mearnsii trees in Africa, caused by the indigenous fungus Ceratocystis albifundus, has highlighted a need to better understand the diversity, ecology and distribution of Ceratocystis species in natural African environments. In this study we applied phylogenetic inference to identify and characterize isolates of Ceratocystis collected in a natural savanna ecosystem in South Africa. Three new species were recognized and are described as C. cryptoformis sp. nov. in the C. moniliformis complex, as well as C. thulamelensis sp. nov. and C. zambeziensis sp. nov., both residing in the C. fimbriata complex. Incorporating the new species into global phylogenies of Ceratocystis provided insights into the patterns of evolution and biogeography of this group of fungi. Notably, the African continent was identified as an important centre of diversification of Ceratocystis spp., from which several lineages of these fungi were shown to have radiated.http://link.springer.com/journal/11557hb201

Armillaria root rot threatens Cameroon's Penja pepper (Piper nigrum L.)

Penja pepper (Piper nigrum) produced in Cameroon has long been recognized for its exceptional organoleptic quality. The pepper vine is grown using a support tree (Spondias mombin) in Cameroon. A root disease is associated with plant deaths in both plants. The disease symptoms are characterized by collar cracking and gummosis and the disease was tentatively identified as Armillaria root rot. In this work the extent of the problem was characterized by surveying 35 farms in Cameroon. Samples were taken from diseased support trees and pepper vines. Support trees exhibiting typical symptoms were found in approximately one third of the surveyed farms. In these farms, disease incidence and Pepper vine mortality ranged from 1.3 to 50% and 1.2 to 87.7%, respectively. Analysis of the ribosomal internal transcribed spacer region (ITS) locus suggested that the isolates collected from S. mombin and P. nigrum are most likely, which is a first for both hosts, represented by Armillaria camerunensis (Henn.) Volk & Burdsall, a fungus previously associated with declining cacao trees in Cameroon. Given the increasing demand for Penja pepper and the great damaging potential of this root rot, research on management strategies should be prioritized

Armillaria root rot threatens Cameroon’s Penja pepper (Piper nigrum L.)

Penja pepper (Piper nigrum) produced in Cameroon has long been recognized for its exceptional organoleptic quality. The pepper vine is grown using a support tree (Spondias mombin) in Cameroon. A root disease is associated with plant deaths in both plants. The disease symptoms are characterized by collar cracking and gummosis and the disease was tentatively identified as Armillaria root rot. In this work the extent of the problem was characterized by surveying 35 farms in Cameroon. Samples were taken from diseased support trees and pepper vines. Support trees exhibiting typical symptoms were found in approximately one third of the surveyed farms. In these farms, disease incidence and Pepper vine mortality ranged from 1.3 to 50% and 1.2 to 87.7%, respectively. Analysis of the ribosomal internal transcribed spacer region (ITS) locus suggested that the isolates collected from S. mombin and P. nigrum are most likely, which is a first for both hosts, represented by Armillaria camerunensis (Henn.) Volk & Burdsall, a fungus previously associated with declining cacao trees in Cameroon. Given the increasing demand for Penja pepper and the great damaging potential of this root rot, research on management strategies should be prioritized.CIRAD, IRAD, the University of Pretoria and through the “Debt reduction-development contract (C2D) France Cameroon” Poivre de Penja project.https://link.springer.com/journal/40858am2021BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyPlant Production and Soil Scienc

The Botryosphaeriaceae: genera and species known from culture

In this paper we give an account of the genera and species in the Botryosphaeriaceae. We consider morphological characters alone as inadequate to define genera or identify species, given the confusion it has repeatedly introduced in the past, their variation during development, and inevitable overlap as representation grows. Thus it seems likely that all of the older taxa linked to the Botryosphaeriaceae, and for which cultures or DNA sequence data are not available, cannot be linked to the species in this family that are known from culture. Such older taxa will have to be disregarded for future use unless they are epitypified. We therefore focus this paper on the 17 genera that can now be recognised phylogenetically, which concentrates on the species that are presently known from culture. Included is a historical overview of the family, the morphological features that define the genera and species and detailed descriptions of the 17 genera and 110 species. Keys to the genera and species are also provided. Phylogenetic relationships of the genera are given in a multi-locus tree based on combined SSU, ITS, LSU, EF1-α and β-tubulin sequences. The morphological descriptions are supplemented by phylogenetic trees (ITS alone or ITS + EF1-α) for the species in each genus.We would like to thank the curators of the numerous fungaria and Biological Resource Centres cited in this paper, for making specimens and cultures available for examination over the past 15 yr, without which this study would not have been possible. Part of this work was supported by Fundação para a Ciência e a Tecnologia (Portugal) through grant PEst-OE/BIA/UI0457/2011. Artur Alves and Alan Phillips were supported by the programme Ciência 2008, co-funded by the Human Potential Operational Programme (National Strategic Reference Framework 2007–2013) and the European Social Fund (EU).publishe

The pathogenic potential of endophytic Botryosphaeriaceous fungi on Terminalia species in Cameroon

In Cameroon, native Terminalia spp. represent an important component of the forestry industry, but limited information is available regarding the fungal pathogens that affect them. The Botryosphaeriaceae are endophytic fungi and latent pathogens that can result in wood stain, cankers, die-back and death of trees, particularly when trees are under stress. The aim of this study was, therefore, to identify and characterize the Botryosphaeriaceae occurring as endophytes of Terminalia spp. in Cameroon, as part of a larger project to identify potential pathogens of these trees in the country. Samples were collected from three Terminalia spp. in the Central, Southern and Eastern Regions and the resultant Botryosphaeriaceae were identified using morphology and DNA sequence comparisons for the ITS and tef 1-α gene regions. Furthermore, inoculation trials were conducted to consider the relative pathogenicity of the isolates collected. The majority of isolates (88%) represented species of Lasiodiplodia, including L. pseudotheobromae, L. theobromae and L. parva. The remaining isolates were identified as Endomelanconiopsis endophytica. Pathogenicity trials on young T. mantaly and T. catappa trees revealed that L. pseudotheobromae was the most pathogenic species followed by L. theobromae.DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB), University of Pretori

Botryosphaeriaceae associated with Terminalia catappa in Cameroon, South Africa and Madagascar

Species in the Botryosphaeriaceae represent some of the most important fungal pathogens of woody plants. Although these fungi have been relatively well studied on economically important crops, hardly anything is known regarding their taxonomy or ecology on native or non-commercial tree species. The aim of this study was to compare the diversity and distribution of the Botryosphaeriaceae on Terminalia catappa, a tropical tree of Asian origin planted as an ornamental in Cameroon, Madagascar and South Africa. A total of 83 trees were sampled, yielding 79 Botryosphaeriaceae isolates. Isolates were initially grouped based on morphology of cultures and conidia. Representatives of the different morphological groups were then further characterised using sequence data for the ITS, tef 1-alpha, rpb2, BOTF15 and beta-tubulin gene regions. Five species of the Botryosphaeriaceae were identified, including Neofusicoccum parvum, N. batangarum sp. nov., Lasiodiplodia pseudotheobromae, L. theobromae and L. mahajangana sp. nov. Lasiodiplodia pseudotheobromae and L. theobromae, were the most commonly isolated species (62%), and were found at all the sites. Neofusicoccum parvum and N. batangarum were found in South Africa and Cameroon, respectively, whereas L. mahajangana was found only in Madagascar. Greenhouse inoculation trials performed on young T. catappa trees showed variation among isolates tested, with L. pseudotheobromae being the most pathogenic. The Botryosphaeriaceae infecting T. catappa appear to be dominated by generalist species that also occur on various other hosts in tropical and sub-tropical climates.Members of the Tree Protection Co-operative Programme (TPCP), National Research Foundation (NRF), THRIP initiative of the Department of Trade and Industry (DTI

Aurifilum, a new fungal genus in the Cryphonectriaceae from Terminalia species in Cameroon

Native Terminalia spp. in West Africa provide a popular source of construction timber as well as medical, spiritual and social benefits to rural populations. Very little is, however, known regarding the diseases that affect these trees. During an investigation into possible diseases of Terminalia spp. in Cameroon, orange to yellow fungal fruiting structures, resembling those of fungi in the Cryphonectriaceae, were commonly observed on the bark of native Terminalia ivorensis, and on dead branches of non-native Terminalia mantaly. In this study the fungus was identified based on morphological features as well as DNA sequence data (ITS and β-tubulin) and its pathogenicity was tested on T. mantaly seedlings. Our results showed that isolates of this fungus represent a previously undescribed genus in the Cryphonectriaceae, which we describe as Aurifilum marmelostoma gen. et sp. nov. Pathogenicity tests revealed that A. marmelostoma is pathogenic on T. mantaly. These tests, and the association of A. marmelostoma with disease symptoms on T. ivorensis, suggest that the fungus is a pathogen of this important tree.DST/NRF Centre of Excellence in Tree Health Biotechnology (CTHB), University of Pretoria, Institute of Agricultural Research for Development (IRAD), International Institute of Tropical Agriculture (IITA), Yaoundé Urban Council in Cameroo

Composition of arbuscular mycorrhizal fungi associated with cassava (Manihot esculenta Crantz) cultivars as influenced by chemical fertilization and tillage in Cameroon

Objectives: Arbuscular mycorrhizal fungi (AMF) form root symbiotic relationships with higher plants, but their abundance and symbiotic effectiveness may be influenced by agricultural practices. This study investigated the effect of N-K fertilization and tillage on soil’s AMF composition and root colonization of some selected cassava varieties in Eastern and Southern Cameroon.Methodology and results: Three cassava varieties were grown in Eastern Cameroon in tilled and non-tilled plots. In Southern Cameroon, five varieties were grown in non-tilled plots, with half of them receiving NPK (10-10-20) fertilization. Collected soil and root samples were analyzed to quantify and describe the AMF communities. AMF root colonization was 35% regardless to the variety and farming system in Eastern region, while it reached 45% in Southern Cameroon. Root colonization varied among varieties within and between locations. Fertilized plots displayed lesser microbial density than non-fertilized plots and the tillage highly reduced the root colonization as well as the density of spores.Conclusions and application of findings: In Eastern and Southern parts of Cameroon, the identified AMF communities in a symbiotic relationship with cassava were ascribed to the three genera Glomus, Gigaspora and Acaulospora. Among these three genera, Glomus was predominant in all the sites; indicating its wide geographical distribution in Cameroon and affinity with cassava. Species of the genus Glomus may therefore be used during mycorrhizal inoculations of cassava. However, AMF root colonization varies in relation to the variety type and the environment; with the southern region of Cameroon showing the higher colonization levels. This study revealed that to obtain higher AMF spores densities in soil and maximize root colonization, cultivation systems with a lesser soil disturbance and fertilization is recommendable in cassava cultivation.Keywords: Arbuscular mycorrhiza funji (AMF), Cameroon, Cassava cultivation, Chemical fertilization, Tillag

DIVERSITY AND DYNAMICS OF RHIZOBIAL POPULATIONS IN ACIDIC SOILS WITH ALUMINUM AND MANGANESE TOXICITIES IN FOREST ZONES

Soil acidity in the humid forest zones of Cameroon is one of the major constraints to agricultural productivity. This study was carried out to assess the rhizobial communities of two acidic soils; with aluminum toxicity (Nkoemvone) and manganese toxicity (Nkolbisson) for their potential to improve soil fertility in Cameroon. These two soils were used to inoculate to the host plants cowpea and siratro. At harvest, 120 rhizobacterial isolates were extracted from the nodules of these two hosts and subjected to morphological characterization. Twenty isolates per site were selected and analyzed for their 16S rDNA genetic profile following restrictions with endonucleases of PCR products and electrophoresis. The restriction patterns of the 16S rDNA of the 40 isolates showed 12 different profiles. Eight occurred in both types of soils, where as 4 were specific to the manganese-toxic-acidic soil. While the Al toxicity reduced the nodulation and growth of both plants, the Mn toxicity mostly affect the cowpea. This study ascertained the distribution of rhizobia based on soil characteristics. Further molecular analyses would allow the identification of the isolates recovered as well as their phylogenetical relationships