SIGNIFICANCE: Mentorship has always been a key component of postgraduate student education, and it is becoming increasingly important in the academic environment. Strong mentorship is widely recognised as a key aspect of professional development and career success. Our view is that mentorship is a lifelong process extending beyond just teaching, and encompasses a wide range of aspects of the relationship between someone who is more experienced and someone who is less experienced people. We see this as a two-way process, where both mentee and mentor benefit. It is ideally a personal relationship in which mentors are well respected in their fields, earning the respect of their mentees, who benefit from the ideas, insights and skills of their mentors. We argue that the lives and careers of both students and academics would benefit from universities establishing formal, non-bureaucratic structures to promote positive mentorship.

BACKGROUND: Sorocephalus imbricatus (Thunb.) R.Br. is a range-restricted species endemic to the Cape Floristic Region (CFR), South Africa. It is currently classified as Critically Endangered in accordance with the IUCN criteria. Like many other species endemic to the CFR, S. imbricatus is subjected to several major threats including habitat loss, habitat degradation and the impacts of invasive alien species. Sorocephalus imbricatus was recently identified as a species requiring improved representation in ex-situ collections. During field work undertaken to collect germplasm for this purpose, a concerning number of dead and dying plants were observed. OBJECTIVES: To determine the cause of rapid death of individuals in a remnant subpopulation of S. imbricatus. METHOD: A field visit to a subpopulation of the only extant population, Elands-kloof, was conducted to examine the symptoms associated with S. imbricatus mortality, and to collect samples for isolation and identification of putative pathogens. RESULTS: Dead and dying plants showed clear symptoms of root and collar rot, with Phytophthora cinnamomi Rands recovered from all samples. The collections highlighted the severe impact of P. cinnamomi on S. imbricatus, with the size of the subpopulation being reduced from 62 to 37 individuals (a 40% reduction) between October 2021 and May 2022. CONCLUSION: This study describes, for the first time, rapid mortality of the Critically Endangered Proteaceae species, S. imbricatus, likely caused by the invasive pathogen P. cinnamomi. This concerning discovery highlights the urgent need for greater recognition of the threat P. cinnamomi poses not only to S. imbricatus, but to the broader floristic diversity of the CFR. Importantly, it illustrates a need for a substantial body of work to be undertaken to address a significant lack of knowledge regarding the relative threat that P. cinnamomi poses to species of the CFR.

Foliar fungi, especially endophytic fungi, constitute an important part of the microbiome of plants. Yet little is known about the composition of these communities. In this study, we isolated fungi from leaf tissues of the desert plant Welwitschia mirabilis to determine the culturable diversity of the foliar fungal community. The isolated fungal taxa, which grouped into 17 distinct lineages, were identified by sequencing elongation factor 1 alpha, beta-tubulin 1, beta-tubulin 2 and the internal transcribed spacer region. The culturable community was mainly composed of cosmopolitan fungal genera despite the unique taxonomie position of the plant and its geographic isolation. To test for endemism in two of the common fungal genera, Altemaria and Aureobasidium, we built haplotype networks using a global data set. Even this broad data set showed little evidence for specialisation within this unique host or its geographical location. The data suggest that the culturable members of communities of leaf-associated fungi in habitats with little plant coverage, such as the Namib Desert, are mainly established by long-distance aerially distributed fungal inocula and few of these taxa co-evolve with the host within the habitat.SIGNIFICANCE: The culturable members of fungal communities associated with an ecological and evolutionary isolated plant have not co-speciated with their hosts, but to a large extent are composed of globally distributed fungal species. Harsh environmental conditions and the geographic isolation of host plants seem to favour ubiquitous fungal species over more specialist fungal species.

South Africa is a country with very limited natural forest cover. Consequently, the timber and fibre needs of the country cannot be provided for from indigenous forest. It is largely for this reason that South Africa initially developed a highly productive plantation forest industry, which today makes a substantial contribution to the local economy. These plantations are based on non-native species of Eucalyptus, Pinus and Australian Acacia. In the early years of establishment, South African plantations were relatively free of pest and pathogen problems. But, over time, an increasing number of insects, fungi and bacteria have emerged as serious threats to the sustainability of the forestry industry. Numerous native pests and pathogens, especially insects, have adapted to these introduced tree species to cause damage or disease. The problem is compounded by the accidental introduction of non-native pests and pathogens, and this has been at a rapidly increasing rate over the past three decades. Some of these introduced pests and pathogens also threaten the fitness and even the survival of many indigenous South African tree species. Fortunately, South Africa has developed an impressive knowledge base and range of integrated management options to deal with these problems. This development was first driven by government programmes, and in more recent years by public-private partnerships between industry, universities and government. It is clear from the pattern of emergence of pests and pathogens in recent years that South Africa will deal with an increasing number of these problems and a continuously changing tree health environment. This requires robust investment in both quarantine and mitigation mechanisms to protect the country's biodiversity as well as to ensure the sustainability of its wood and fibre industries.SIGNIFICANCE: • This review about tree health in South Africa was in part inspired by the 2020 International Year of Plant Health. Plant health, and particularly tree health, is an important topic in regard to the sustainability of our forestry industry and conservation of our native forests. South Africa has been a leader in the field and this review highlights some of the achievements that researchers in the country, both past and present, have attained.

Actinomycete bacteria are often associated with insects that have a mutualistic association with fungi. These bacteria are believed to be important to this insect-fungus association as they produce antibiotics that exclude other saprophytic fungi from the immediate environment. The aim of this study was to investigate the presence of potentially protective actinomycetes associated with Orthotomicus erosus, an alien invasive pine bark beetle, in South Africa. This bark beetle and its relatives have an association with Ophiostomatales species which are often the only fungi found in the bark beetle galleries. We hypothesised that antibiotic-producing actinomycetes could be responsible for the paucity of other fungi in the galleries by producing compounds to which the Ophiostoma spp. are tolerant. Several actinomycetes in the genus Streptomyces and one Gordonia sp. were isolated from the beetle. Interestingly, most isolates were from the same species as actinomycetes associated with other pine-infesting insects from other parts of the world, including bark beetles and the woodwasp Sirex noctilio. Most actinomycetes isolated had strong antifungal properties against the selected test fungi, including Ophiostoma ips, which is the most common fungal symbiont of Orthotomicus erosus. Although the actinomycetes did not benefit Ophiostoma ips and the hypothesis was not supported, their sporadic association with Orthotomicus erosus suggests that they could have some impact on the composition of the fungal communities present in the bark beetle galleries, which is at present poorly understood. SIGNIFICANCE: • Discovery of four putative undescribed Streptomyces spp. with antibiotic potential • First record of the introduction of actinomycete bacteria with pine-infesting insects into South Africa • Actinomycetes from South Africa group with undescribed Streptomyces spp. from pine-infesting insects of North America

The purpose of this study was to evaluate the resistance to coffee leaf rust (CLR) caused by Hemileia vastatrix and to Ceratocystis canker (Cc) in coffee genotypes derived from crosses of Coffea arabica var. Caturra with accessions of C. canephora backcrossed to Caturra. Twenty-three F3BC1 progenies including C. arabica var. Caturra and var. Colombia as controls were established in a field experiment. CLR evaluations were made during five years of natural infection, using an incidence rating scale. For Cc, artificial stem inoculations were made with an isolate of Ceratocystis colombiana and the results were assessed after one year. The selection process also included agronomic aspects such as plant height, canopy diameter, number of branch pairs, yield and grain characteristics. Twenty progenies showed >70% of rust resistance. Twelve progenies exhibited >80% of Cc resistance, while no resistance was observed in either of the controls. Only three progenies performed well for all criteria, including resistance to both pathogens and agronomic characteristics.

Microorganisms inhabit virtually every possible niche on Earth, including those at the outer envelope of survival. However, the focus of most conservation authorities and ecologists is the 'legs and leaves' side of biology -the 'macrobiology' that can be seen with the naked eye. There is little apparent concern for the preservation of microbial diversity, or of unique microbial habitats. Here we show examples of the astounding microbial diversity supported by South Africa's ecosystems and argue that because microbes constitute the vast majority of our planet's species they should be considered seriously in the future protection of our genetic resources.

Chrysoporthe cubensis is an important fungal pathogen of Eucalyptus species worldwide. The fungus is also known on many other hosts, all residing in the order Myrtales. Previous studies have suggested that Chr. cubensis might be native to South America and southeast Asia and that it has been introduced into Africa. Recently, surveys have been conducted in eastern and southern Africa to assess the distribution of Chrysoporthe spp. in this region. Chr. cubensis was found on Eucalyptus spp. in Kenya, Malawi and Mozambique. The aim of the study reported here was to determine the genetic diversity of Chr. cubensis populations from these countries. Population diversity studies were conducted using five pairs of microsatellite markers previously developed for Chr. cubensis. Results show that there is a very low genetic diversity within the populations of Chr. cubensis from Kenya, Malawi and Mozambique, implying that the fungus was probably recently introduced in these countries. Based on phylogenetic analyses, the origin of East African Chr. cubensis is most likely Asia.

Fusarium circinatum is the causal agent of a serious disease of seedlings in South African pine nurseries. Insects, especially fungus gnats (Diptera: Sciaridae, Mycetophlidae), are suspected of transmitting this fungus in nurseries. The aim of this study was to ascertain which species of gnats are present in South African pine nurseries, and to consider whether these and other Diptera carry F. circinatum. Dipteran fauna were surveyed in four major forestry nurseries between 2000 and 2001. Fungi were isolated from these flies and the resulting Fusarium species were identified. Bradysia difformis was the only fungus gnat species found and it occurred in all nurseries. Other Dipteran families collected included Agromyzidae, Cecidomyiidae, Chironomidae, Ephydridae, Muscidae, Simulidae and Tachinidae. This is the first report of B. difformis in South Africa. Fusarium circinatum was not isolated from any of the Diptera collected. Fusarium oxysporum and F. stil-boides were isolated from Chironomidae, but these fungi are not considered important pathogens in the nurseries surveyed.

El género Ceratocystis sensu stricto incluye un alto número de hongos fitopatógenos de plantas angiospermas y gimnospermas en diversas regiones del mundo. Entre las principales enfermedades causadas por estos hongos se destacan los marchitamientos vasculares, manchado de maderas, chancros y pudriciones radiculares, de tallos y frutos. Muchas especies producen metabolitos volátiles con olores que atraen una amplia variedad de insectos a los tejidos vegetales infectados, sin embargo, el grado de asociación entre los insectos y las diferentes especies de Ceratocystis es altamente variable, presentandose asociaciones mutualistas tales como aquellas entre C. polonica, C. laricicola y C. rufipenni e insectos escolítidos, así como también relaciones no específicas como en los casos de C. paradoxa, C. fagacearum y C. fimbriata con nitidúlidos, moscas y diversos coleópteros. El alto grado de similitud morfológica encontrada entre estos hongos hace difícil la definición de los límites entre las especies de Ceratocystis. Durante la pasada década, la utilización de estudios filogenéticos basados en comparaciones de DNA ha contribuido sustancialmente a clarificar la taxonomía de este grupo de hongos, así por ejemplo, dichos estudios han permitido concluir que algunas especies de Ceratocystis realmente representan complejos de especies crípticas. Esta revisión tiene como objetivo principal proveer una introducción a los estudios experimentales desarrollados para las especies de Ceratocystis sensu stricto y brevemente discutir aspectos relacionados con los denominados hongos ophiostomatoides.

The genus Ceratocystis sensu stricto Ellis & Halst. includes many economically important plant pathogens of both angiosperms and gymnosperms, worldwide. Diseases caused by these fungi include vascular wilts, sap stains on logs and lumber, stem cankers and rots of roots, stems and fruits. Most Ceratocystis species are well adapted to dispersal by insects. Many species produce volatile metabolites with fruity odors that attract a wide range of insects to infected tissues. However, the degree of this association between insects and Ceratocystis species is highly variable, ranging from a mutualistic relationship such as that between C. polonica, C. laricicola and C. rufipennis and their specific bark beetle vectors, to nonspecific associations, as are found in the case of C. paradoxa, C. fagacearum and C. fimbriata, with nitidulid beetles, flies and ambrosia beetles. The high degree of morphological similarity found amongst these fungi probably results from convergent evolution driven by selection for insect dispersal, and has made it difficult to clearly define the boundaries between species of Ceratocystis. During the course of the last decade, the use of phylogenetic studies based on comparisons of DNA sequence data has contributed substantially to clarify the taxonomy of this group of fungi. These studies have led to the conclusion that some Ceratocystis species thought to be single entities in the past actually represent complexes of cryptic species. This review is primarily intended to provide an introduction to experimental studies presented on species of Ceratocystis sensu stricto. However, in order to provide a firm background to this fungal genus, a brief outline is presented on related fungi that can broadly be referred to as the ophiostomatoid fungi.