Diversity and differentiation in two populations of Gibberella circinata in South Africa

Gibberella circinata [anamorph Fusarium circinatum (=  F. subglutinans f.sp. pini )] causes pitch canker and is an important pathogen in South African pine nurseries. The initial outbreak of the pitch canker fungus was limited to a single nursery at Ngodwana in Mpumalanga Province. Subsequently, several other pine nurseries in South Africa became infected. Most of these outbreaks were relatively small except for the outbreak in the Klipkraal nursery (Mpumalanga Province). The genetic diversity, population differentiation and relative frequencies of the sexual and asexual cycles among two South African subpopulations were determined to establish whether immigration, mutation and/or recombination contributed towards population structure. The allelic diversity of the initial population (Ngodwana) was observed to be lower (0·16) than that of the more recent Klipkraal population (0·25). Approximately 4% ( G _ST = 0·04) of total gene diversity could be attributed to differences among the subpopulations. Furthermore, six new vegetative compatibility groups (VCGs) have been identified since the initial outbreak of G. circinata in South Africa 10 years ago. The relatively low allelic diversity and low level of genetic differentiation suggest restricted gene flow among subpopulations, and indicate that the pathogen has been introduced recently. However, the amount of allelic and VCG diversity suggests that multiple genotypes have been introduced into South Africa. The increases in effective population number, allelic diversity and new VCGs over the past 10 years suggest that sexual reproduction might be occurring.     

Identification of Armillaria isolates from Bhutan based on DNA sequence comparisons

Armillaria root rot is a serious disease in fir and mixed conifer forests of Bhutan, Eastern Himalayas. The species causing this disease have, however, never been identified. The aim of this study was to identify field isolates collected at four localities in Bhutan. Identification was based on RFLP analysis of the IGS-1 region, comparisons of ITS and IGS-1 sequence data with those available on GenBank, cladistic analyses and sexual compatibility studies. Isolates were found to reside in two distinct RFLP groups. RFLP group 1 isolates from Pinus wallichiana at Yusipang had RFLP profiles and IGS-1 sequences similar to those of Armillaria mellea ssp. nipponica . Although ITS sequence data are not available for A. mellea ssp. nipponica , sequences from this DNA region were most similar to the closely related A. mellea from Asia. The RFLP profile and IGS-1 sequences for RFLP group 2 isolates from Abies densa at Changaphug, Tsuga dumosa at Chimithanka as well as Picea spinulosa and T. dumosa in the Phobjikha valley were similar to those published for Armillaria borealis , Armillaria cepistipes , Armillaria gemina and Armillaria ostoyae . Distance analysis based on IGS-1 and ITS sequence data indicated that these isolates are closely related to A. cepistipes , Armillaria gallica and Armillaria sinapina . The isolates were, however, sexually incompatible with tester strains of A. cepistipes , A. gallica and A. sinapina . Although closely related to these species, they appear to represent a distinct taxon that will be referred to as Bhutanese phylogenetic species I (BPS I) until basidiocarps are found and the species can be described.     

Comparison of populations of the wilt pathogen Ceratocystis albifundus in South Africa and Uganda

Ceratocystis albifundus is an important fungal pathogen of Acacia mearnsii trees in South Africa. In a previous study, a high level of gene diversity was demonstrated in a South African population of C. albifundus . This, together with the occurrence of the pathogen on native Protea species and its exclusive occurrence in South Africa, led to the hypothesis that C. albifundus is probably native to that country. More recently, C. albifundus has been reported from A. mearnsii in south-western Uganda. The aim of this study was to compare the populations of C. albifundus from Uganda and South Africa based on genetic diversity, population structure and possible gene flow. This was achieved using codominant microsatellite markers developed for the closely related species Ceratocystis fimbriata . Available isolates for comparison were from six different areas of South Africa and six jungle stands in Uganda. Eight of the 11 available markers amplified loci in C. albifundus . Gene diversity was higher in the Ugandan population, but genotypic diversity was greater for the South African isolates. There were no common genotypes between the two populations and they shared only 22% of the total alleles. The populations were genetically isolated from each other and highly substructured within. There was no association between isolates collected from the same geographic locations, and gene flow between the two populations was low. Results suggest that C. albifundus was probably not introduced into Uganda from South Africa but rather that an ancestral population, yet to be discovered, is the source of both populations.     

Fungal infection and mycotoxin contamination of maize in the Humid forest and the western highlands of Cameroon

Fungal incidence and mycotoxin contamination of farm-stored maize were assessed and compared in grain samples from three villages each in two agroecological zones over time. Maize samples were collected at 2 and 4 months after stocking from 72 farmers’ stores in 1996 and 1997 in the Humid Forest (HF) and Western Highlands (WHL) of Cameroon. Mycological assays of these samples revealed several fungal species.Nigrospora spp. were the most prevalent fungi in HF (32%) and WHL (30%) in 1996,Fusarium verticillioides (22%) andF. graminearum (27%) were also isolated from these samples. In the WHL in 1996, no significant difference in fungal incidence was found among villages for samples collected 2 months after harvest, but at 4 months incidence was significantly higherP<0.05). In 1997 the levels of fungal contamination were lower than in 1996. The incidence ofAspergillus spp. was low in general, ranging from 0.0 to 5.9% infected kernels. Analysis with thin layer chromatography detected low levels of aflatoxins in a few samples.F. verticillioides mycotoxin fumonisin Bi (300-26,000 ng/g) andF. graminearum metabolites deoxynivalenol (<100–l,300 ng/g) and zearalenone (<50–110 ng/g) were determined by means of polyclonal antibody competitive direct enzyme-linked immunosorbent assay. A significant correlation (r=0.72; P=0.0001) was found between the incidence ofF. graminearum and the contamination with deoxynivalenol. Storage time (2vs 4 months after stocking) had a significant positive effect (r=0.39; P=0.013) on the level of fumonisin B₁. This is the first report of the natural occurrence of these mycotoxins in maize in Cameroon.     

Population structure and possible origin of Amylostereum areolatum in South Africa

The woodwasp, Sirex noctilio , and its symbiotic fungus, Amylostereum areolatum , cause extensive damage to pine plantations in the Southern Hemisphere. S. noctilio was first reported from South Africa in 1994. In this study, the population diversity of A. areolatum isolates from South Africa, South America, Australasia and Europe was determined by vegetative incompatibility testing. All 108 South African and 26 South American isolates belonged to the same vegetative compatibility group (VCG). This VCG showed a weak incompatibility reaction with the single Tasmanian and single New Zealand isolates tested. This VCG differed from VCGs from Europe. It also differed from isolates associated with the biocontrol nematode, Deladenus siricidicola , which is produced in Australia. It is concluded that the South African and South American populations of A. areolatum share a common origin .     

Increased Lactate Concentrations in III and Injured Dogs

Venous blood lactate concentrations were measured on 109 ill dogs and 20 clinically normal dogs. Ill dogs were grouped into survivor and nonsurvivor groups, and categorized based on their primary problem. Ninety-five percent of ill dogs had lactate concentrations higher than clinically normal dogs and published normal values. Seventy-six percent of ill dogs with increased lactate concentrations survived to be discharged. Lactate concentrations were significantly higher in nonsurvivors than in survivors and clinically normal dogs. Lactate concentrations in dogs with major trauma and intoxications, and with cardiopulmonary, gastrointestinal, and neurologic problems were significantly higher than in clinically normal dogs and dogs with other problems. (Vet Emerg & Crit Care, 1998; 8: 117–127)     

Relationship between endometritis and oxidative stress in the follicular fluid and luteal function in the buffalo

In this study, alteration in the follicular fluid composition and luteal function was investigated in the buffalo with endometritis. Genitalia were classified into cytological and purulent endometritis on the basis of polymorphonuclear cell cut off while non‐endometritis served as control (n = 10/group). In the follicular phase, the number of surface follicles was counted, diameter of the largest follicle was measured and the follicular fluid was assayed for total protein, cholesterol, malondialdehyde (MDA), total antioxidant capacity (TAC), oestradiol (E₂) and progesterone (P₄). The P₄ content of corpus luteum during mid‐luteal phase was estimated by radioimmunoassay. Ovaries from the follicular phase of oestrous cycle showed no significant difference in the total number of surface follicles, size of the largest follicle and volume of follicular fluid in the buffaloes with and without endometritis (p > .05). However, the antral fluid of the largest follicle from the genitalia of buffalo with cytological and purulent endometritis showed a significant decrease in the concentration of total protein, cholesterol, TAC and E₂ and a significant increase in the concentration of MDA and P₄ (p < .05). The results indicated that there is an association between endometritis and decreased ovarian function.