Macadamia (Proteaceae) is a rainforest genus indigenous to Queensland and northern New South Wales, Australia. It includes four species, two of which, and their hybrids, are grown commercially for their high-value nuts in Australia and other countries. Macadamia is now being grown in several orchards and in gardens on the Bolaven plateau in southern Lao People’s Democratic Republic (PDR). In November 2018, leaf spot disease symptoms were observed on young leaves of macadamia trees in a demonstration garden 15 km west of Paksong, on the Bolaven Plateau in Champasak Province, Lao PDR. A fungus isolated from the leaf spots was identified by morphological and DNA sequence comparisons as Calonectria pseudoreteaudii. This is the first report of this species in the Lao PDR.

The objectives of this study were to investigate the occurrence of eyespot in commercial spring cereal crops in four climatic areas in Tunisia and characterize the dominant species of Oculimacula responsible for the disease. A total of 294 wheat, barley and oat fields were surveyed for eyespot incidence and severity during four cropping seasons from 2010 to 2014. Eyespot was identified in 63.5% of the fields with an average incidence of 23.1% infected stems. The number of infected fields as well as the incidence and severity of disease increased significantly during the 5 years of the study. A significant difference in the occurrence of eyespot among the climatic regions was noted with the wetter areas having greater disease incidence. The highest incidence of eyespot was recorded in durum wheat and bread wheat fields, whereas barley was significantly less infected. The effect of previous crop on eyespot incidence was not significant. All 70 isolates collected in this study were identified as O. yallundae and among them, 39 were identified as MAT1-2 and 31 as MAT1-1. This study highlights the influence of climatic conditions on the distribution of eyespot in the cereal growing areas of Tunisia as well as the increasing occurrence of the disease. The predominance of O. yallundae is an important consideration in the choice of integrated management strategies for eyespot. The presence of both mating types of O. yallundae in similar proportions suggests that sexual reproduction may be occurring.

Citrus tristeza virus was detected for the first time in the Lao People's Democratic Republic. Samples were collected from citrus trees across the southern provinces for testing in Australia. RNA was extracted and tested using conventional and real-time reverse transcription polymerase chain reactions with the virus detected in 12 of 59 samples tested. Viral identities were confirmed by sequencing. Additional confirmation was obtained by an enzyme-linked immunosorbent assay. The implications of the presence of this virus for citrus production in Lao are discussed briefly.

Citrus exocortis viroid, citrus bent leaf viroid, hop stunt viroid and citrus dwarfing viroid were detected for the first time in Lao PDR. Samples were collected from citrus trees across southern Lao PDR for laboratory testing in Australia. RNA was extracted and amplified using quantitative reverse transcription polymerase chain reaction (qRT-PCR); viroid identities were confirmed by sequencing.

Cereal cultivation is a major component of Tunisian agriculture. Take-all of cereals caused by the soil-borne ascomycete Gaeumannomyces tritici (syn.Gaeumannomyces graminis var. tritici) and G. avenae (syn. G. graminis. var. avenae) is a common disease worldwide. The objectives of this study were to evaluate the incidence and distribution of the disease across the cereal growing areas in different climatic regions of Tunisia, to assess the relative importance of the two species, and to investigate the impact of crop sequences on inoculum density in soil and disease incidence. During the cropping seasons of 2009/10, 2010/11, 2012/13, and 2013/14, the percentage of fields infested varied from 8.1% in 2011 to 39.6% in 2013 and the incidence of take-all varied from 0 to 60% in the 298 fields surveyed. Disease incidence was significantly higher in wetter climatic regions than in semi-arid regions. The disease was not detected in the driest area. The highest incidence of take-all was recorded in durum wheat fields. However, overall, no significant differences were observed in the incidence between durum wheat, bread wheat, and barley crops. Take-all was not detected in any oat crop. All findings in this study including surveys, molecular identification of isolated fungi, and determination of DNA concentration in soil, indicate that G. tritici is the dominant species and that G. avenae is rarely found in Tunisian cereal cropping soils. Rotation trials conducted over four cropping seasons on the experimental station showed that a one year break crop could significantly reduce the incidence and severity of take-all in durum wheat. In addition, the inoculum density of Gt/Ga in soil estimated by quantitative PCR was significantly reduced after a legume crop compared to monoculture of durum wheat, and consequently there was a significant decrease in the incidence and severity of the disease in the following year. This study highlights the influence of climatic conditions on the distribution of take-all in the cereal growing areas of Tunisia and the importance of rotation in reducing incidence and severity of take-all.

The aim of this study was to describe the morphology, anatomy and function of underground structures associated with colonies of Solanum centrale J.M.Black (Australian bush tomato), a perennial sub-shrub found in arid areas of Australia and an important traditional staple food for Aboriginal people. It is known that this species forms clonal communities, but there is little understanding of the mechanisms of formation in either natural or cultivated situations. The underground connections within seven clonal communities from Central and South Australia were documented and samples of secondary roots, thick lateral roots and stems were examined under both laboratory and glasshouse conditions. Clonal communities were observed at all sites with individual ramets arising from lateral roots (root-suckers) that ranged from 2–10 mm in diameter growing in a network 5–15 cm below the soil surface. Lateral roots have dicotyledonous root anatomy and rapidly resprout to form new clonal ramets. They also have the capacity to accumulate starch in parenchyma cells. The morphology and root-suckering ability resemble those of weedy Solanum spp. from other parts of the world, as well as species from a variety of genera adapted to arid climates. Methods to capitalise on the ability of lateral roots to form clonal ramets in cultivated situations, particularly given the difficulties in establishing crops from seed, are discussed.

The Australian Processing Tomato Industry (APTI) has observed a decline in yield over recent years and speculates that soil-borne pathogens may be a contributing factor. The decline is characterised by poor stand establishment and the presence of stunted plants sporadically spread throughout the field. In preliminary surveys, Pythium spp. were commonly isolated from the roots of plants showing symptoms of poor growth. The aim of this study was to identify those Pythium species and assess their pathogenicity. Four field surveys were undertaken during the 2016/17 season and plants exhibiting symptoms of putative Pythium disease were collected. Pythium isolates were identified based on morphology and ITS sequences. Eight species of Pythium were identified including some common pathogens and some species which have not been previously reported on tomatoes. The in vitro pathogenicity test showed P. aphanidermatum, P. ultimum var. ultimum and P. irregulare were the most aggressive pathogens. In a glasshouse test P. ultimum var. ultimum and P. recalcitrans significantly reduced plant height 1 month after inoculation. Overall, the pathogenicity results confirmed that pathogens in the genus Pythium were most damaging in the pre-emergence and early seedling phases of tomato plant growth. However, some species also had the capacity to continue to reduce the growth of plants at later stages, potentially leading to yield reduction. Further studies are necessary to better understand the aetiology of these and additional Pythium species in the APTI context, and their ultimate effect on tomato yield.

The isolation of Fusarium fujikuroi from rice plants with elongated stems typical of bakanae disease in the Lao PDR is reported for the first time. The identification was based on both molecular and morphological markers. Koch’s postulates were fulfilled. Bakanae disease has long been recognized in the Lao PDR based on symptomatology, but the etiology of the disease has not been clearly defined. This study was part of a continuing program to assist with the development of checklists of pathogens and plant diseases for Lao PDR for biosecurity purposes and integrated disease management.

Fenugreek is an annual leguminous crop grown for hay and grains in Tunisia. It is also considered a valuable rotation crop with cereals. Sclerotinia rot was observed in production fields since 2010. The survey conducted in 2013 revealed that the incidence of diseased plants varied between 5 and 20%. The identification of isolates of Sclerotinia obtained from fenugreek plants with symptoms of stem rot was determined using morphological and molecular criteria. The size, shape and abundance of sclerotia in potato dextrose agar (PDA) cultures were used to classify isolates as S. sclerotiorum or S. trifoliorum. A comparison of colony diameter on PDA after 24, 48 and 72 h at 25 °C, showed that one isolate grew faster (36 mm/day) than the other 10 isolates (14.8 mm/day). There was a significant difference in sclerotial size between the fast and the slow growing isolates, but there was no significant difference in the number of sclerotia produced after 3 weeks on PDA. Two of the slow growing isolates exhibited ascospore dimorphism, whereas the fast growing isolate did not. PCR amplification with the primer pair ITS5/ITS4 produced a fragment of 560 base pairs from the fast growing isolate and 1000 base pairs from all of the slow growing isolates. The ITS sequences of the fast growing isolate had 100% homology with S. sclerotiorum, whereas those of the slow growing isolates had 100% homology with S. trifoliorum. Isolates of both species were pathogenic on fenugreek seedlings in the greenhouse assay and there was no significant difference in the percentage of dead plants two weeks after inoculation between the two species.

Phytophthora capsici is reported for the first time in the Lao PDR. It was isolated from soil collected from the root zone of wilting red chilli ( Capsicum annuum ) plants in a polyhouse farm in Paksong district of Champasak province. The wilting chilli plants had typical symptoms of infection by P. capsici including root rot and necrosis of the outer cortex of the stem base. The isolate was identified using morphological and molecular markers. A pathogenicity trial demonstrated that the culture was pathogenic to a local cultivar of chilli seedlings.

Ralstonia pseudosolanacearum is reported for the first time from the Lao PDR. Typical symptoms of wilt and vascular exudate were observed in potatoes and tomatoes in Paksong district, Champasak province. Pathogenicity was proven and identification was based on symptoms, commercial diagnostic test kits and sequence of the egl gene.

Fusarium oxysporum f.sp. niveum is reported for the first time in the Lao PDR. It was isolated from watermelons ( Citrullus lanatus ) in Songkhon district, Savannahkhet province following a limited ad hoc survey during January and February of 2015. Infected plants showed symptoms of wilt, vascular discolouration, necrosis in the collar region, lower stem base and upper taproot regions, and whole plant death. Identification of the pathogen was confirmed through phylogenetic analysis of the EF1 - α locus and a pathogenicity test satisfying Koch’s postulates.

Six new species of Fusarium associated with soil and plant hosts from ecosystems of minimal anthropogenic disturbance in Australia are described. Fusarium coicis from Coix gasteenii, F. goolgardi from Xanthorrhoea glauca, F. mundagurra from soil and Mangifera indica, F. newnesense from soil, F. tjaetaba from Sorghum interjectum and F. tjaynera from soil, Triodia microstachya, Sorghum interjectum and Sorghum intrans. Morphology and phylogenetic analysis of EF-1α, RPB1 and RPB2 sequence data were used to delineate species boundaries. The new species were phylogenetically distributed in the Fusarium sambucinum, F. fujikuroi, and F. chlamydosporum species complexes, and two novel species complexes. These six new species have particular phylogeographic significance as not only do they provide further insight into the geographic patterns of Fusarium evolution but also challenge current phylogeographic hypotheses.

Rhizoctonia solani anastomosis group AG-4 HG-I is reported for the first time from the Lao PDR. It was isolated from gai lan ( Brassica oleracea var. alboglabra ) affected by collar rot, seedling death, root rot and stunting of older plants from the Paksong area of Champasak province. The anastomosis group was confirmed by sequencing and Koch’s postulates were fulfilled.

In August 2012 a severe stem rot (stem canker) disease was observed in a purple-fruit variety of passionfruit, Passiflora edulis , in Nghe An province, Vietnam. The stem rot progressed rapidly along the stem affecting branches and fruit, leading to chlorosis, wilting and death of the distal part of the stem. It did not progress below the graft junction into the stem or roots of the rootstock, Passiflora edulis var. flavicarpa . The disease spread within and between plantings causing 100 % loss of some plantings. Phytophthora nicotianae was consistently isolated from diseased tissue and the morphological identification was confirmed by sequencing, and two cultures were deposited in the Murdoch University Culture Collection as MUCC707 and MUCC708. The former culture proved pathogenic in stem inoculations and P. nicotianae was reisolated fulfilling Koch’s postulates. This report represents a new record of Phytophthora stem rot of purple passionfruit in Vietnam.

Vanilla stem rot, caused by Fusarium oxysporum f. sp. vanillae (Fov), is the main constraint to increasing vanilla production in the major vanilla‐producing countries, including Indonesia. The current study investigated the origin of Fov in Indonesia using a multigene phylogenetic approach. Nineteen Fov isolates were selected to represent Indonesia, the Comoros, Mexico and Réunion Island. The translation elongation factor 1 alpha gene and the mitochondrial small subunit ribosomal RNA gene phylogenies resolved the Fov isolates into three distinct clades in both phylogenetic species of the F. oxysporum species complex, indicating a polyphyletic pattern of evolution. In addition, Fov isolates from Indonesia were also polyphyletic. These results suggest that the vanilla stem rot pathogen in Indonesia has a complex origin. The implications for disease management are discussed.

Cob rot epidemics occurred in NSW in sweet corn in 2002 and maize in 2003. Investigations were undertaken to establish the species of Fusarium associated with both instances. Dependent on region, F. verticillioides , F. proliferatum , and F. subglutinans were isolated more frequently. The epidemics were unique in their occurrence being in two corn types, in consecutive years, and in two regions.

Fusarium is one of the most remarkable genera of the fungi. It is remarkable for it’s genetic and morphological diversity, it’s wide geographic distribution, the diversity of it’s relationships with plants, the diversity of plant diseases for which it is responsible, and its abundance and diversity in natural ecosystems. Evidence to support this contention is presented and discussed focusing on the author’s career-long and continuing research on the genus. The diversity and socio-economic importance of Fusarium diseases is illustrated by reference to diseases common in the Australasian region. Examples include the Fusarium wilts caused by formae speciales of F. oxysporum and the stalk and cob rots of maize and cereal head blights caused by F. graminearum . The importance of Fusarium mycotoxins is noted. Endophytic colonization of living plant tissue by Fusarium species remains a poorly understood and insidious phenomenon. Examples are provided in relation to crop plants and plants in natural ecosystems. The role of natural ecosystems as reservoirs of crop pathogens and potential emerging pathogens is discussed briefly in relation to disease management and biosecurity.

A major problem with contamination of fungal and bacterial cultures by Neurospora in the diagnostic laboratory of the Plant Pathology Unit at the Plant Protection Centre in Vientiane, Laos, occurred in May 2009 and again in April-May 2010. The problem persisted despite sterilization of all contaminated cultures and stringent disinfection procedures. Initial attempts to identify the source were unsuccessful. However in May 2010 the senior author realised that the orange fungus common on old sticky rice in traditional baskets was Neurospora. A limited survey indicated that this was a key source of conidia in the precinct around the laboratory, and elsewhere in Vientiane. A sample was collected and forwarded to the second author at the Plant and Microbial Biology Department in the University of California, Berkeley, California, USA, for confirmation of the genus, and identification of the species. It was identified as N. intermedia (Tai Mycologia 27:289–294 1935), and the isolate used in the phylogenetic study was deposited in the Fungal Genetics Stock Centre as FGSC10868. This is the first report of a Neurospora species in Lao.

In May 2010 basal stem rot of snake bean (long bean) (Vigna unguiculata subsp. sesquipedalis) caused by Sclerotium rolfsii was discovered in Vientiane Capital, Lao PDR, during an ad hoc disease survey. The disease had resulted in death of some infected plants. The basal stem region had a bleached appearance, a typical symptom of this disease. Abundant small, round, brown sclerotia were present on the stem base, and on the adjacent soil and dead leaf material. The fungus was isolated into pure culture and Koch’s postulates were fulfilled. This is the first report of S. rolfsii in the Lao PDR, and the first report of basal stem rot of snake bean caused by this pathogen in the Lao PDR.