Search

Three species of Mycosphaerella, namely M. eumusae, M. fijiensis, and M. musicola are involved in the Sigatoka disease complex of bananas. Besides these three primary pathogens, several additional species of Mycosphaerella or their anamorphs have been described from Musa. However, very little is known about these taxa, and for the majority of these species no culture or DNA is available for study. In the present study, we collected a global set of Mycosphaerella strains from banana, and compared them by means of morphology and a multi-gene nucleotide sequence data set. The phylogeny inferred from the ITS region and the combined data set containing partial gene sequences of the actin gene, the small subunit mitochondrial ribosomal DNA and the histone H3 gene revealed a rich diversity of Mycosphaerella species on Musa. Integration of morphological and molecular data sets confirmed more than 20 species of Mycosphaerella (incl. anamorphs) to occur on banana. This study reconfirmed the previously described presence of Cercospora apii, M. citri and M. thailandica, and also identified Mycosphaerella communis, M. lateralis and Passalora loranthi on this host. Moreover, eight new species identified from Musa are described, namely Dissoconium musae, Mycosphaerella mozambica, Pseudocercospora assamensis, P. indonesiana, P. longispora, Stenella musae, S. musicola, and S. queenslandica.

The banana weevil, Cosmopolites sordidus, is the most important insect pest of banana and plantain in the world. Cultural control methods were investigated over 2 years in southern KwaZulu-Natal, South Africa. Harvesting at ground level and dissection of remnants (treatment 1), and covering the base of the mat (entire plant consisting of several meristems) with soil and moving debris to the inter-row (treatment 2), were compared to a positive control that involved treatment of plants with a registered pesticide (treatment 3), and a negative control that involved harvesting at 150 cm from the collar with no soil or sanitation amendments (treatment 4). Yield, weevil damage and pseudostem girth of plants were measured from August to November annually, while adult beetle densities were assessed over 4 weeks in October/November and April. Nematode samples were taken and analysed in October/November every year. Damage parameters included the coefficient of infestation, the percentage coefficient of infestation (PCI) at two intervals, the summed PCI value, the percentage cross-sectional damage of the central cylinder and cortex, and the mean cross-sectional damage percentage. A randomized block design with three replicates was used in the trial. The parameters were similar before the onset of the trial. Fruit yield and plant girth, corrected by nematode densities, were not significantly different in any treatment, nor were the nematodes controlled. Soil cover and recession of remnants was the only effective treatment, significantly reducing the CI, but not the adult density or the other damage parameters. Soil cover showed promise as a cultural control method because it only needs to be applied seasonally and reduced the percentage cross-sectional damage of the central cylinder, the damage parameter most closely related to yield, by 14%.

Radopholus similis is a major pest of East African highland cooking bananas ( Musa spp.) in Uganda. Non-pathogenic Fusarium oxysporum endophytes, isolated from bananas in farmers’ fields, have shown potential to reduce R. similis numbers in tissue culture banana. The mechanism through which endophytes confer resistance to nematodes has previously been demonstrated to involve induced resistance. In this study, the expression of eight defense-related genes in banana was investigated using quantitative real-time reverse transcription PCR. Plants of susceptible (cv. Nabusa, genomic group AAA-EA) and tolerant (cv. Kayinja, genomic group ABB) banana cultivars were inoculated with endophytic F. oxysporum strain V5w2. Gene expression levels were analysed following endophyte inoculation and nematode challenge. Endophyte colonization of roots of the tolerant cultivar induced transient expression of POX and suppressed expression of PR-3 , lectin , PAE , PAL and PIR7A. Catalase and PR-1 activities were up-regulated in the tolerant cultivar 33 days after endophyte colonization of roots, but their expressions were further up-regulated following nematode challenge. Apart from POX and lectin , the other genes analysed were not responsive to endophyte colonization or R. similis challenge in the susceptible cv. Nabusa. This is the first report of endophyte-induced defense-related gene expression in banana.

In Uganda, banana (Musa spp.) production is constrained by the burrowing nematode Radopholus similis. Non-pathogenic, endophytic Fusarium oxysporum has been isolated from healthy banana plants, and several strains have shown potential as biological control agents against R. similis. Plant infection by R. similis can be characterised in three steps: host searching, root penetration and reproduction. In this study, we investigated the effects of three endophytic F. oxysporum strains (Eny1.31i, Eny7.11o and V5w2) on root penetration and reproduction of R. similis in tissue culture-derived banana plants. The number of R. similis that penetrated roots of endophyte-inoculated and untreated plants was not influenced by the endophytes in either laboratory or screenhouse experiments. However, R. similis reproduction was reduced by endophytes. Strain V5w2 gave the greatest suppression of R. similis reproduction. The results of this study imply that antagonism of endophytic F. oxysporum against R. similis in banana plants is post-infectional and mediated through disruption of nematode reproduction.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; One of the most serious diseases of banana is fusarium wilt, caused by Fusarium oxysporum f.sp. cubense (Foc). The objectives of this study were to isolate and identify nonpathogenic F. oxysporum strains from soils suppressive to banana wilt, and to determine the diversity of these isolates. More than 100 Fusarium strains were isolated from the rhizosphere of banana plants and identified to species level. Pathogenicity testing was carried out to confirm that these isolates were nonpathogens of banana. A PCR-based RFLP analysis of the intergenic spacer region of the ribosomal RNA operon was used to characterize the nonpathogens. The isolates were also compared with isolates of Foc from South Africa and the known biological control isolate of F. oxysporum, Fo47. The species-specific primers FOF1 and FOR1, in addition to morphological features, were used to confirm the identity of F. oxysporum isolates included in the PCR-RFLP analysis. Twelve different genotypes could be distinguished, identified by a six-letter code allocated to each isolate following digestion with the restriction enzymes HaeIII, HhaI, HinfI, MspI, RsaI and ScrfI. Eleven of these included nonpathogenic F. oxysporum isolates, and these groups could all be distinguished from the genotype that included Foc. Fo47 was included in one of the genotype groups consisting of nonpathogenic F. oxysporum isolates from South Africa.

Radopholus similis is one of the key pests of banana worldwide. In this study, nine endophytic Fusarium oxysporum isolates were screened for the production of secondary metabolites antagonistic to R. similis in culture. Undiluted and diluted culture filtrates were tested against motile stages and eggs of R. similis. All isolates tested demonstrated in vitro antagonistic activity, causing paralysis of R. similis motile stages. The percentage of paralysed nematodes increased with increase in the length of exposure time to culture filtrates. After 24 h exposure in culture filtrates up to 100% of the treated nematodes were paralysed compared to 26.5% in the control treatments. Nematode mortality rates after 24 h exposure in culture filtrates ranged from 76.4% to 100%. Paralysis was reversible at lower filtrate concentrations. Radopholus similis males were more sensitive to culture filtrates than females. Culture filtrates of all isolates demonstrated inhibitory effects on hatching of R. similis eggs. The results demonstrate the potential for using endophytic F. oxysporum as biological control agents against R. similis and for toxic derivatives from their secondary metabolism to be used as potential nematicides.

The banana weevil (Cosmopolites sordidus) is an important pest of bananas (Musaceae: Musa species) in South Africa. Adult trapping methods were compared in field trials using a randomised block design. Pseudostem traps, pitfall traps containing a pheromone (either Cosmolure® (Pheromone A) or Cosmolure+® (Pheromone B)), and unbaited pitfall traps (control), were compared over 5 weeks during all seasons along the Southeast coast of South Africa. Pseudostem traps treated with an insecticide, and rhizome traps, were included as additional treatments in autumn. In summer two treatments were also added: individual suspension of both pheromones above a pitfall trap either in combination with or without a pseudostem trap. The adult beetles were sexed, and the number of internal eggs noted. Pheromone A proved to be the most effective of the different pheromone lures. Grouping of the pheromones resulted in a synergistic response, while combining the pseudostem did not enhance trap efficacy. The different p...

Sustainable production of banana, plantain and enset in Africa is crucial to secure food and provide income to millions of people. These crops, however, are severely threatened by diseases, pests and environmental constraints. Most bananas in Africa are produced by small-scale farmers who often do not have the financial resources for sustained production by means of the application of chemical fertilisers, fungicides and pesticides. Biotechnology can provide a means whereby plants can be improved for sustainable cultivation. Applications of biotechnology include tissue culture technology, development of molecular markers, and genetic transformation. Biotechnology, however, should not be used in isolation to solve the problems in banana and plantain production in Africa, but should be incorporated into integrated disease and pest management programmes. South Africa has the infrastructure and capacity to play an important role in the training of scientists, research on production constraints, and implementation of biotechnological advances for the rest of Africa.

Fusarium oxysporum f. sp. cubense (Foc) is one of the most important threats to global banana production. Strategies to control the pathogen are lacking, with plant resistance offering the only long-term solution, if sources of resistance are available. Prevention of introduction of Foc into disease-free areas thus remains a key strategy to continue sustainable banana production. In recent years, strains of Foc affecting Cavendish bananas have destroyed plantations in a number of countries in Asia and in the Middle East, and one African country. One vegetative compatibility group (VCG), 01213/16, is considered the major threat to bananas in tropical and subtropical climatic conditions. However, other genetically related VCGs, such as 0121, may potentially jeopardize banana cultures if they were introduced into disease-free areas. To prevent the introduction of these VCGs into disease-free Cavendish banana-growing countries, a real-time PCR test was developed to accurately detect both VCGs. A previously described putative virulence gene was used to develop a specific combination of hydrolysis probe/primers for the detection of tropical Foc race 4 strains. The real-time PCR parameters were optimized by following a statistical approach relying on orthogonal arrays and the Taguchi method in an attempt to enhance sensitivity and ensure high specificity of the assay. This study also assessed critical performance criteria, such as repeatability, reproducibility, robustness, and specificity, with a large including set of 136 F. oxysporum isolates, including 73 Foc pathogenic strains representing 24 VCGs. The validation data demonstrated that the new assay could be used for regulatory testing applications on banana plant material and can contribute to preventing the introduction and spread of Foc strains affecting Cavendish bananas in the tropics.

Stem lesions in sunflower caused by Albugo tragopogonis (Pers.) S.F. Gray developed individually from primary infections and did not result from a systemic infection. Cell division and callose formation were not observed, but weak lignin deposition occurred in infected tissues. Hyphae occurred intercellularly in stems in the cortex, cambium, vascular rays, and pith. In petioles parenchymatous tissue was heavily colonized in contrast to lightly colonized collenchymatous hypodermis. The middle lamellae of cells in infected tissue were dissolved, and cells degenerated and eventually collapsed. Stem infections lead to deterioration of tissue integrity, weakening of stems, and finally to lodging of stems (breaking over).Key words: Albugo tragopogonis, Helianthus annuus, histopathology, stem lodging.

The genotypic diversity in a South African population of Fusarium subglutinans f.sp. pini (F.s. pini) was determined, based on the number of vegetative compatibility groups (VCGs). Isolates of F.s. pini from South Africa (69), California (five) and Florida (19) were included in the study. The nit1 (or nit3) and NitM mutants were selected as chlorate resistant sectors and paired on minimal medium. The South African isolates of F.s. pini were assigned to 23 different VCGs. No heterokaryons formed between isolates from South Africa, California and Florida. The high degree of genotypic diversity in the South African population of F.s. pini is probably due to some level of sexual reproduction in the population.

Fusarium subglutinans has been associated with many hosts. Some isolates of the fungus are responsible for pitch canker disease of pines. A South African population of F. subglutinans from pine seedlings was characterized by comparing it to isolates from various hosts, pine and non-pine. A total of 26 isolates representing six different hosts were selected for the study. Cultural and morphological characteristics were studied. Virulence of isolates was tested on 1-yr-old Pinus patula seedlings. Sexual compatibility of isolates of F. subglutinans with B- and E-tester strains, and crossings of pine isolates in all possible combinations, were performed. Pine isolates were also compared with pitch canker and non-pine isolates using random amplified polymorphic DNAs (RAPDs). All isolates were morphologically characteristic of F. subglutinans, but differed somewhat in cultural features. Only isolates from pine were pathogenic to P. patula seedlings. Virtually no isolates were sexually compatible with the fertile tester strains. An exception was isolate MRC 115 from maize. Some pine isolates (MRC 6211 and MRC 6217) were, however, sexually compatible with South African (MRC 6213) and pitch canker (MRC 6229) isolates. Cluster patterns constructed from RAPD profiles revealed that isolates clustered according to host. South African isolates from pine were related to the pitch canker isolates from other areas, and were similar to non-pine isolates only in morphology. Virulence, genetic analyses and composite RAPD data suggest that pine isolates originate from the same gene pool, and probably represent a distinct new biological species.

1. Agro-ecological Intensification of Farming Systems in the East and Central African Highlands Bernard Vanlauwe, Guy Blomme and Piet van Asten 2. Agricultural Intensification and the Food Security Challenge in Sub-Saharan Africa Brian A. Keating, Peter S. Carberry and John dixon 3. The Agro-ecological Solution?! Food Security and Poverty Reduction in Sub-Saharan Africa, with an Emphasis on the East African Highlands Henk Breman Theme 1: Systems Components 4. CIALCA Interventions for Productivity Increase of Cropping System Components in the African Great Lakes Zone Pieter Pypers et al. 5. Exploring the Scope of Fertilizer Use in the East African Region Lydia Wairegi and Piet van Asten 6. The 4R Nutrient Stewardship in the Context of Smallholder Agriculture in Africa Shamie Zingore and Adrian Johnston 7. Mitigating the Impact of Biotic Constraints to Build Resilient Banana Systems in Central and Eastern Africa Rony Swennen et al. 8. Challenges for the Improvement of Seed Systems for Vegetatively Propagated Crops in Eastern Africa Julian Smith, Daniel Coyne and Elmar Schulte-Geldermann Theme 2: System Integration 9. CIALCA's Efforts on Integrating Farming System Components and Exploring Related Trade-offs Piet van Asten et al. 10. Towards Ecologically Intensive Smallholder Farming Systems: Design, Scales and Trade-offs Evaluation Pablo Tittonell 11. Using the 'Livestock Ladder' as a Means for Poor Crop-livestock Farmers to Exit Poverty in Sud-Kivu Province, Eastern DR Congo Brigitte L. Maass et al. 12. N2Africa: Putting Nitrogen Fixation to Work for Smallholder Farmers in Africa Ken E. Giller et al. 13. Integrating Climate Change Adaptation and Mitigation in East African Coffee Ecosystems Henk van Rikxoort et al. Theme 3: Drivers for Adoption 14. Agricultural Technology Diffusion and Adoption in Banana and Legume Based Systems of Central Africa Emily Ouma et al. 15. Supply and Demand Drivers of the Sustainable Intensification of Farming Systems through Grain Legumes in Central, Eastern and Southern Africa Joseph Rusike et al. 16. Assessing and Improving the Nutritional Diversity of Cropping Systems Roseline Remans et al. 17. Disseminating Agroforestry Innovations in Cameroon: Are Relay Organizations Effective? Ann Degrande et al. 18. Participatory Re-introduction of Vicia Faba Beans in Resource-poor Farming Systems: Adoption of a Farmer-led Initiative Erik Karltun et al. Theme 4: Communicating and Disseminating Complex Knowledge 19. Walking the Impact Pathway: CIALCA's Efforts to Mobilize Agricultural Knowledge for the African Great Lakes Region Boudy van Schagen et al. 20. Scalability and Farmer Heterogeneity: Implications for Research on Sustainable Intensification John Lynam 21. Integrated Agricultural Research for Development (IAR4D): An Approach to Enhance the Livelihoods of Smallholder Farmers in the Lake Kivu Region Robin Buruchara et al. 22. Communication Channels Used in Dissemination of Soil Fertility Management Practices in the Central Highlands of Kenya Sarah W. Kimaru-Muchai et al. 23. Targeting Farmers' Priorities for Effective Agricultural Intensification in the Humid Highlands of Eastern Africa Jeremias Mowo et al. Index

BACKGROUND: Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of banana. Toxins produced by Foc have been proposed to play an important role during the pathogenic process. The objectives of this study were to investigate the contamination of banana with toxins produced by Foc, and to elucidate their role in pathogenesis. METHODOLOGY/PRINCIPAL FINDINGS: Twenty isolates of Foc representing races 1 and 4 were isolated from diseased bananas in five Chinese provinces. Two toxins were consistently associated with Foc, fusaric acid (FA) and beauvericin (BEA). Cytotoxicity of the two toxins on banana protoplast was determined using the Alamar Blue assay. The virulence of 20 Foc isolates was further tested by inoculating tissue culture banana plantlets, and the contents of toxins determined in banana roots, pseudostems and leaves. Virulence of Foc isolates correlated well with toxin deposition in the host plant. To determine the natural occurrence of the two toxins in banana plants with Fusarium wilt symptoms, samples were collected before harvest from the pseudostems, fruit and leaves from 10 Pisang Awak 'Guangfen #1' and 10 Cavendish 'Brazilian' plants. Fusaric acid and BEA were detected in all the tissues, including the fruits. CONCLUSIONS/SIGNFICANCE: The current study provides the first investigation of toxins produced by Foc in banana. The toxins produced by Foc, and their levels of contamination of banana fruits, however, were too low to be of concern to human and animal health. Rather, these toxins appear to contribute to the pathogenicity of the fungus during infection of banana plants.

Fusarium oxysporum f. sp. cubense (Foc) causes Fusarium wilt, a lethal disease that results in devastating economic losses to banana production worldwide. The pathogen originates from Asia where it evolved with its host, the wild banana plant Musa acuminata. Foc consists of three races, eight lineages and 24 Vegetative Compatibility Groups (VCGs). Most damage is caused by Foc tropical race 4 (TR4), which occurs exclusively in Asia. China is the biggest producer of Cavendish bananas (AAA) in the world, with plantations covering approximately 372.4677×103 hectares constituting up 90% of banana production, with the rest made up of Pisang Awak (ABB) and Dajiao or Plantain (AAB) bananas. In this study, 80 Foc isolates from six production areas were collected from diseased banana cultivars in China. These isolates were all single-spored and characterized to lineage level using five restriction enzymes while VCG identity was determined by generating nit-mutants, and pairing these mutants with a VCG tester set for Foc. To determine the occurrence of Foc TR4 in China, all isolates were screened with a newly developed Foc TR4-specific primer set. All the Foc isolates were also inoculated on Cavendish, Pisang Awak and Dajiao bananas for pathogenicity testing. Our results showed that Foc in China was highly diverse, as five of the eight lineages and 11 of the 24 known VCGs could be determined. The Foc TR4-specific primer set was highly specific for detecting VCG 01213/16, and could be used in diversity studies to rapidly identify this VCG complex. The majority of the isolates from China were identified as Foc TR4 (VCG 01213/16), and this VCG was found in four of the five production areas. Species of Fusarium other than F. oxysporum were non-pathogenic to banana. The selection of Foc-resistant banana clones, and the development of appropriate disease management strategies for Fusarium wilt of banana in China, is urgently required

Pelargonium capitatum (L.) L'Herit. is one of the parent species of the cultivar Rose grown on the Island of Reunion for the production of geranium oil. The aim of the project was to identify chemotypes which could be included in hybridization programs to ennoble the cultivar Rose Forty populations were selected along the coast of South Africa to describe the essential oil composition and identify possible chemotypes in P. capitatum. A multivariate statistical analysis was performed on the essential oil data. Examination of the composition of the oils proved the species to display high levels of essential oil variation which allows for the species to be divided into eight chemotypes.

Fusarium subglutinans f.sp. pini (F.s. pini) is the causal agent of pitch canker of pines. The fungus has recently been found in South Africa on the diseased roots of Pinus patula seedlings, but has as yet not been detected on mature trees in commercial forests. Inoculation of 1-year-old P. patula, P. elliottii and P. radiata seedlings with isolates of F.s. pini resulted in canker development and shoot mortality. No significant differences in virulence were found among eight isolates of the pathogen on P. elliottii and P. radiata, but isolate MRC 6214 was significantly more virulent on P. patula seedlings than MRC 6209. Disease development was significantly more severe on P. patula and P. radiata than on P. elliottii. Pathogenicity tests on 4-year-old P. patula and P. elliottii trees yielded comparable results. Resinous cankers, similar to those described for pitch canker, developed on trees in the vicinity of inoculation points but development ceased before stems were girdled.

Background Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4), is considered the most lethal disease of Cavendish bananas in the world. The disease can be managed in the field by planting resistant Cavendish plants generated by somaclonal variation. However, little information is available on the genetic basis of plant resistance to Foc TR4. To a better understand the defense response of resistant banana plants to the Fusarium wilt pathogen, the transcriptome profiles in roots of resistant and susceptible Cavendish banana challenged with Foc TR4 were compared. Results RNA-seq analysis generated more than 103 million 90-bp clean pair end (PE) reads, which were assembled into 88,161 unigenes (mean size = 554 bp). Based on sequence similarity searches, 61,706 (69.99%) genes were identified, among which 21,273 and 50,410 unigenes were assigned to gene ontology (GO) categories and clusters of orthologous groups (COG), respectively. Searches in the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) mapped 33,243 (37.71%) unigenes to 119 KEGG pathways. A total of 5,008 genes were assigned to plant-pathogen interactions, including disease defense and signal transduction. Digital gene expression (DGE) analysis revealed large differences in the transcriptome profiles of the Foc TR4-resistant somaclonal variant and its susceptible wild-type. Expression patterns of genes involved in pathogen-associated molecular pattern (PAMP) recognition, activation of effector-triggered immunity (ETI), ion influx, and biosynthesis of hormones as well as pathogenesis-related (PR) genes, transcription factors, signaling/regulatory genes, cell wall modification genes and genes with other functions were analyzed and compared. The results indicated that basal defense mechanisms are involved in the recognition of PAMPs, and that high levels of defense-related transcripts may contribute to Foc TR4 resistance in banana. Conclusions This study generated a substantial amount of banana transcript sequences and compared the defense responses against Foc TR4 between resistant and susceptible Cavendish bananas. The results contribute to the identification of candidate genes related to plant resistance in a non-model organism, banana, and help to improve the current understanding of host-pathogen interactions.

Fusarium spp. produce fumonisins – mycotoxins that are of importance to maize production in South Africa. Fumonisins have been associated with human oesophageal cancer and cause various diseases in animals that are of concern to the animal feed industry. Maize samples, collected from subsistence farm fields in the Eastern Cape, KwaZulu-Natal, Limpopo and Mpumalanga provinces of South Africa during the 2006 and 2007 growing seasons, were analysed for Fusarium spp. and contamination with fumonisins. Fusarium verticillioides was the most common Fusarium species in maize followed by F. subglutinans and F. proliferatum . Levels of contamination with fumonisins ranged from 0 μg/g to 21.8 μg/g, depending on the region where samples were collected. Levels of fumonisins were highest in northern KwaZulu-Natal (Zululand) where 52% and 17% of samples collected in 2006 and 2007, respectively, exceeded 2 μg/g. Regression analyses showed a positive correlation between fumonisin-producing Fusarium spp. determined by real-time polymerase chain reaction and concentration of fumonisins ( r = 0.93). Many samples from Zululand, and some from Mokopane (Limpopo) and Lusikisiki (Eastern Cape), contained fumonisins at levels well above the maximum levels of 2 μg/g set by the Food and Drug administration (USA) and therefore also the limit of 1 μg/g set by the European Union for food intended for direct human consumption. Regulations governing contamination of grain with fumonisins are not yet implemented in South Africa. The high incidence of fumonisins in subsistence farming systems indicates the need for awareness programmes and further research.

The essential oils of forty natural populations of Pelargonium capitatum were steam distilled and analyzed by GC and GC/MS. The composition of the oil is extremely variable from one population to another, leading to the conclusion that there are several chemotypes in this species. The main constituents found were α-pinene, α-phellandrene, p-cymene, γ-terpinene, β-caryophyllene, guaia-6, 9-diene, germacrene D, δ-cadinene, citronellol, terpinen-4-ol, 10-epi-γ-eudesmol, citronellyl formate, and an unidentified sesquiterpene.

SUMMARY Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of bananas. In the tropics and subtropics, Cavendish banana varieties are highly susceptible to Foc race 4 (VCG 0120). Cavendish selection GCTCV-218 was shown to have significantly lower disease severity and incidence compared with susceptible cultivar Williams in replicated greenhouse and field trials. Suppression subtractive hybridization (SSH) was previously carried out to identify genes induced in roots of GCTCV-218, but not in Williams, after infection with Foc'subtropical' race 4. Seventy-nine SSH clones were sequenced and revealed 13 non-redundant gene fragments, several of which showed homology to defence-associated genes, including cell wall-strengthening genes. Quantitative RT-PCR was used to confirm up-regulation and differential expression of a number of genes throughout a time-course, following Foc infection in the tolerant GCTCV-218 when compared with susceptible cv. Williams. Tolerance of GCTCV-218 was linked to significantly increased induction of cell wall-associated phenolic compounds.

SYNOPSIS Fungal diseases are responsible for severe losses of Pinus and Eucalyptus seedlings in South African forest nurseries. Pathogens such as Botrytis cinerea, Fusarium oxysporum, Rhizoctonia solani, Phytophthora cinnamomi, Cylindrocladium scoparium and Colletotrichum spp. are commonly associated with disease symptoms. Control can be achieved by means of cultural, chemical and biological methods, while ectomycorrhizae could also play an important role in resistance of seedlings to pathogens.

Fusarium oxysporumf. sp.cubense, the causal agent of fusarium wilt of banana (Musaspp.), is one of the most destructive strains of the vascular wilt fungusF. oxysporum. Genetic relatedness among and within vegetative compatibility groups (VCGs) ofF. oxysporumf. sp.cubensewas studied by sequencing two nuclear and two mitochondrial DNA regions in a collection of 70F. oxysporumisolates that include representatives of 20 VCGs ofF. oxysporumf. sp.cubense, other formae speciales, and nonpathogens. To determine the ability ofF. oxysporumf. sp.cubenseto sexually recombine, crosses were made between isolates of opposite mating types. Phylogenetic analysis separated theF. oxysporumisolates into two clades and eight lineages. Phylogenetic relationships betweenF. oxysporumf. sp.cubenseand other formae speciales ofF. oxysporumand the relationships among VCGs and races ofF. oxysporumf. sp.cubenseclearly showed thatF. oxysporumf. sp.cubense's ability to cause disease on banana has emerged multiple times, independently, and that the ability to cause disease to a specific banana cultivar is also a polyphyletic trait. These analyses further suggest that both coevolution with the host and horizontal gene transfer may have played important roles in the evolutionary history of the pathogen. All examined isolates harbored one of the two mating-type idiomorphs, but never both, which suggests a heterothallic mating system should sexual reproduction occur. Although, no sexual structures were observed, some lineages ofF. oxysporumf. sp.cubenseharboredMAT-1andMAT-2isolates, suggesting a potential that these lineages have a sexual origin that might be more recent than initially anticipated.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Fusarium wilt is considered one of the most important diseases of bananas. The disease can only be managed by using resistant cultivars and by preventing its introduction into new fields. The objectives of this study were to evaluate newly available fungicides, in vitro and in vivo, for their efficacy against the responsible pathogen Fusarium oxysporum f.sp. cubense, and to evaluate surface sterilants that could be used for sterilization purposes. Of the fungicides, prochloraz and propiconazole significantly inhibited mycelial growth at concentrations of 1 and 5 μg ml−1, respectively. Benomyl and the demethylation-inhibiting fungicides significantly reduced the disease severity of Foc when applied as a root dip treatment, showing disease reduction up to 80.6%. The results also demonstrated that certain quaternary ammonium compounds are effective as sterilants against Foc and should replace the ineffective sterilants that are currently being used. Further field evaluations of the fungicides are required.

The burrowing nematode Radopholus similis is one of the major constraints to banana (Musa spp.) production worldwide. Resource-poor farmers can potentially manage R. similis by using naturally occurring banana endophytes, such as nonpathogenic Fusarium oxysporum, that are inoculated into tissue culture banana plantlets. At present, it is unclear at what stage in the R. similis infection process the endophytes are most effective. In this study, the effect of three endophytic F. oxysporum isolates (V5w2, Eny1.31i and Eny7.11o) on R. similis host preference of either endophyte-treated or untreated banana plants was investigated. No differences were observed between the proportion of nematodes attracted to either root segments excised from endophyte-treated or untreated plants, or in experiments using endophyte-treated and untreated tissue culture banana plantlets. These results imply that the early processes of banana plant host recognition by R. similis are not affected by endophyte infection.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; The aim of this study was to evaluate the ability of nonpathogenic F. oxysporum and Trichoderma isolates from suppressive soils in South Africa to suppress fusarium wilt of banana in the glasshouse. Several biological control agents and commercial biological control products were included in the study. The isolates were first screened in vitro on potato dextrose agar. In glasshouse evaluations, the fungal and bacterial isolates were established on banana roots before they were replanted in pathogen-infested soil, while the commercial biocontrol agents were applied as directed by the supplier. Banana plantlets were evaluated for disease development after 7 weeks. In vitro tests showed none of the nonpathogenic isolates suppressed Fusarium oxysporum f.sp. cubense (Foc), while slight suppression was observed with the two Trichoderma isolates. Results of the glasshouse evaluations revealed that two of the nonpathogenic F. oxysporum isolates, CAV 255 and CAV 241, reduced fusarium wilt incidence by 87·4 and 75·0%, respectively. The known biological control agent Fo47 did not suppress Foc significantly. Pseudomonas fluorescens strain WCS 417, known for its ability to suppress other fusarium wilt diseases (WCS 417), reduced disease incidence by 87·4%. These isolates should be further evaluated for potential application in the field, independently and in combination.

Fusarium oxysporum f. sp. cubense (Foc) is responsible for fusarium wilt of bananas. The pathogen consists of several variants that are divided into three races and 21 vegetative compatibility groups (VCGs). Several DNA-based techniques have previously been used to analyse the worldwide population of Foc, sometimes yielding results that were not always consistent. In this study, the high-resolution genotyping method of AFLP is introduced as a potentially effective molecular tool to investigate diversity in Foc at a genome-wide level. The population selected for this study included Foc isolates representing different VCGs and races, isolates of F. oxysporum f. sp. dianthi, a putatively non-pathogenic biological control strain F. oxysporum (Fo47), and F. circinatum. High-throughput AFLP analysis was attained using five different infrared dye-labelled primer combinations using a two-dye model 4200s LI-COR automated DNA analyser. An average of approx. 100 polymorphic loci were scored for each primer pair using the SAGAMX automated AFLP analysis software. Data generated from five primer pair combinations were combined and subjected to distance analysis, which included the use of neighbour-joining and a bootstrap of 1000 replicates. A tree inferred from AFLP distance analysis revealed the polyphyletic nature of the Foc isolates, and seven genotypic groups could be identified. The results indicate that AFLP is a powerful tool to perform detailed analysis of genetic diversity in the banana pathogen Foc.

An unknown speckle disease was recently observed on Cavendish banana leaves in Levubu, the most northern of the five banana-growing regions of South Africa. Morphological examination of infected material and single conidial isolates of the causal organism revealed that it was Cladosporium musae. Isolates of the fungus were subjected to pathogenicity testing and sequencing of the ITS region (ITS-1 and ITS-2) and the 5.8S gene of the rDNA operon, and compared with an authentic strain of C. musae. These results verified the identity of the fungus as C. musae and constitute the first confirmed report of Cladosporium speckle on banana leaves in South Africa.

Fusarium oxysporum f. sp. cubense (Foc) is a fungus that infects banana roots and causes a destructive plant disease called Fusarium wilt. Foc consists of three pathogenic races (Foc races 1, 2 and 4), classified according to their selective impairment of banana cultivars. Foc race 4 is economically important as it comprises strains that infect Cavendish bananas, which are the most widely planted variety of bananas in the world, in both the tropics (Foc TR4) and subtropics (Foc STR4). The aim of this study was to investigate which genes are potentially involved in fungal pathogenicity by comparing transcript-derived cDNA fragments (TDFs) from Foc STR4 and TR4 to those from non-pathogenic F. oxysporum using cDNA-AFLP analysis. This comparison resulted in the identification of 229 unique gene fragments which include the putative pathogenicity-related TDFs encoding chitinase class V (chsV), GTPase activating protein, Major Facilitator Superfamily (MFS) multidrug transporter and serine/threonine protein kinase (ste12) genes. Quantitative analysis of transcript abundance showed a significant increase in expression of chsV, MFS multidrug transporter and ste12 genes in Foc STR4 and TR4 compared with the non-pathogenic F. oxysporum. These genes play a role in escaping host defence responses and in cell wall degradation. In addition, pathogenicity-related genes from other formae speciales of F. oxysporum, such as the sucrose non-fermenting, cytochrome P450 and F-box protein required for pathogenicity genes, were significantly up-regulated in Foc STR4 and TR4 but not in F. oxysporum isolates non-pathogenic to banana. This study provides the first in vitro comparative analysis of TDFs expressed in pathogenic Foc race 4 isolates and non-pathogenic F. oxysporum isolates from banana.

Fusarium oxysporum f.sp. cubense (Foc) is the causal agent of Fusarium wilt of banana and is divided into three races and 21 vegetative compatibility groups (VCGs). Within a VCG, Foc proved to be genetically homogenous. Previous studies on phenotypic characteristics were performed with isolates that represented different races and VCGs from different banana-producing countries. The aim of this study was to determine the phenotypic variation in a genetically similar South African population of Foc, where all isolates belong to VCG 0120. Twenty-six isolates of Foc ‘subtropical’ race 4 (VCG 0120) were selected for this study. Differences in growth rate, spore production and the number of spores were determined. Virulence of Foc isolates was determined by inoculating susceptible, tissue-cultured, banana plantlets. Differences in cultural characteristics and virulence among isolates were found. The South African isolates can be divided into sporodochial, cottony and slimy pionnotal types. All isolates produced microconidia in abundance, but production of macroconidia and sporodochia varied. Disease severity varied from no vascular discoloration to complete discoloration of vascular tissue. This study showed that, although the South African population of Foc is homogenous in terms of its genetic make-up, it varies considerably in terms of phenotypic characteristics.

Three species of Mycosphaerella are known to cause Sigatoka leaf diseases in banana. M. musicola causes yellow Sigatoka, M. fijiensis causes black Sigatoka and M. eumusae causes eumusae leaf spot. Linie is known about the presence of Sigatoka leaf diseases of banana in South Africa. Although yellow Sigatoka has previously been reported, the identity of the causal organism has never been confirmed. Extensive surveys of the five banana-growing areas in South Africa were conducted between 1999 and 2001, which resulted in the collection of various Sigatoka-like leaf spot samples. After morphological examination of the infected material, monoconidial isolates of the causal organism were established from each sample. A molecular confirmation of identity was conducted using species-specific primers for M. musicola and M. fijiensis. Sequence data of the ITS region was further obtained to compare the South African Mycosphaerella isolates from banana with M. musicola, M. fijiensis and M. eumusae. These results confirm that only M. musicola is presently associated with yellow Sigatoka symptoms in South Africa.

White rust of sunflower (Helianthus annuus L.), caused by Albugo tragopogonis (Pers.) S. F. Gray, appeared in South African fields not previously planted to sunflower. Spread to these fields from infested fields was unlikely, as some of the newly affected fields were planted out of season and were more than 300 km away from other sunflower production fields. Several reports of this nature led us to investigate the possibility of seed transmission of the causal organism. Extensive colonization of sunflower heads by A. tragopogonis was observed in field trials and breeding nurseries. Head infections consisted of two distinct lesion types. White rust pustules, typical of those formed on abaxial sides of leaves, were recognized on abaxial sides of involucral bracts. Grayish, localized lesions containing dark-colored oospores of the fungus, similar to those formed on stems and petioles (1), were produced in sub-epidermal tissue and extended 3 to 5 mm deep into receptacles. Colonization of seeds was found in only a few lines. Oospores were produced in the pericarps and testae of seeds. No oospores or hyphae, however, were observed in the embryo. This is the first report of A. tragopogonis being seed-borne. Since the incidence of seed infection is low, spread of disease to infested fields is expected to be insignificant. Of more concern, however, is the possible long-range dissemination of the fungus by means of infected seed into regions or countries where the disease has not been previously reported. Reference: (1) P. S. Van Wyk et al. Helia 18:83, 1995.

Fusarium subglutinans is a well-known pathogen of many crops. The fungus causes a serious disease of pines known as pitch canker. A proposal has been made to designate isolates from pines E subglutinans f. sp. pini (F. s. f. sp. pini). An enigma regarding the nomenclature is that some F. s. f. sp. pini isolates have been reported to induce decay of gladiolus corms whereas certain isolates of F. subglutinans from gladiolus corms were also found to be weakly to moderately pathogenic to pine seedlings. In this study we re-examined three previously studied isolates from gladiolus in the United States that had been referred to as F. subglutinans ( = F. moniliforme var. subglutinans) or F. moniliforme in the literature. We found that these isolates were typical of F. proliferatum. They were mildly pathogenic on pine seedlings and significantly less virulent than an isolate of F. s. f. sp. pini. Inoculation of gladiolus corms with these isolates of F. proliferatum from gladiolus, F. oxysporum from pine seedlings, and E subglutinans from pines (F. s. f. sp. pini), corn, mango, and pineapple indicated that only isolates of E proliferatum were moderately pathogenic to gladiolus corms. This study therefore supports the proposal that isolates of F. subglutinans from pines represent a specific forma specialis within the species.

Viljoen. A., Wingfield, M. J., and Marasas. W. F. 0.1994. First report of Fusarium subglurinans f. sp. pini on pine seedlings in South Africa. Plant Dis. 78:309-312. A study of fungi responsible for root rot of Pinus parula seedlings in a forest nursery yielded Fusarium subglutinans f. sp. pini and F. oxysporum. F. s. pini was isolated most frequently from diseased seedlings and proved to be the most virulent fungus in pathogenicity tests conducted on germinated seed and 2-mo-old seedlings. Inoculation of 3-yr-old trees with F. s. pini yielded symptoms reminiscent of pitch canker. This is the first report of F. s. pini causing root disease of pine seedlings and is also the first record of the fungus in the Southern Hemisphere.

Pelargonium capitatum (L.) L’Herit. is one of the parent species oi the cultivar Rose grown on the Island of Reunion for its essential oil. The ultimate aim of this project is to identify chemotypes which could be included in hybridization programmes to ennoble the cultivar Rose. Forty populations of P. capitatum were selected along the west and east coasts of South Africa to describe the essential oil and macromorphological diversity in relation to geographical distribution. A multivariate statistical analysis was performed on the essential oil data. A survey of the composition of the volatile oils proved the species to display high levels of essential oil variation which allows for the species to be divided into chemotypes correlating to geographical distribulion. No clear-cut macromorphological discontinuities were apparent between populations, but an obvious congruence between the essential oil composition and macro-morphology was accentuated in extreme cases.

Author: Ncube, E. Flett, B.C. Waalwijk, C. Viljoen, A. Vol 27 Issue 2 Publication: 2010 Page: 195-198 : Aflatoxins are carcinogenic mycotoxins produced by Aspergillus spp. in groundnut kernels. Forty-six groundnut samples were collected from subsistence farmers in three provinces of South Africa, namely KwaZulu-Natal (KZN), Mpumalanga (MP) and Limpopo (LP), in 2006 and 2007. Aflatoxin levels of groundnut kernels were quantified using an ELISA technique. The occurrence of A. parasiticus colonies was predominant and it was isolated at twice the frequency of A. flavus. Aflatoxins were present in groundnut produced in the northern parts of KZN, where aflatoxin levels of up to 131 parts per billion (ppb) were found. In Mpumalanga and Limpopo, the highest aflatoxin levels were 160 ppb and 2 ppb, respectively. In the Makhanisi and Mbazwane localities situated in KwaZulu-Natal, and in Boshoffontein in Mpumalanga, aflatoxin levels were higher than the maximum permitted level set by the Food and Drug Administration in the USA (20 ppb), the European Union (6 ppb) and the Department of Health in South Africa (10 ppb) for groundnut that is intended for direct human consumption. This study indicates the need for mycotoxin awareness campaigns and control programs to be implemented in rural areas of South Africa.

Banana weevil is a serious pest of bananas and plantains in Africa. The development of resistant cultivars is seen as the long term and more sustainable control strategy. The difficulty in conventional breeding of bananas and plantains has prompted efforts towards the use of genetic transformation for banana and plantain improvement. In this review, the current status of banana weevil resistance, sources of resistance and resistance mechanisms is assessed. Further, current efforts and future prospects for identifying resistance genes outside the genus Musa with potential to control banana weevil in a transgenic approach are outlined and discussed. Key words : Banana weevil, host plant resistance, pest resistance genes, transgenic plants African Journal of Biotechnology Vol. 2 (12), pp. 563-569, December 2003