M.E. di Menna

Toxicity and toxin production by Fusarium isolates from New Zealand

Sixty-two isolates of Fusarium were obtained from pasture grass and soil from various areas of New Zealand and identified as F. anthophilum [2], F. avenaceum [17], F. crookwellense [8], F. culmorum [4], F. graminearum [1], F. nivale [3], F. oxysporum [3], F. sambucinum [17], F. semitectum [1], F. tricinctum [1] and an unidentified Fusarium spp. [5]. These isolates were grown on autoclaved rice and tested for toxicity to rats in feeding tests. Eighty two percent of the isolates were toxic, of which twenty-four percent were severely toxic and caused hemorrhages of stomach and intestine, hematuria, and finally death. Cultures of the most toxic isolates contained 0.1 to 104 ppm of deoxynivalenol, 0.7 and 7 ppm of 15- and 3-acetyldeoxynivalenol respectively, 0.2 to 4 ppm of fusarenon- X, 11 to 1021 ppm zearalenone, 40 to 272 ppm of the hemorrhagic factor (wortmannin), 2,100 to 7,200 ppm of moniliformin, 565 ppm of the cytotoxic factor (HM-8) and enniatin in substantial concentrations. F. sambucinum is reported as a moniliformin producer for the first time.

Effects of chitin amendment of soil on microorganisms, nematodes, and growth of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.)

Effects of soil amendment with crabshell chitin on the growth of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.), and on populations of soil bacteria, fungi, and plant-parasitic and free-living nematodes were investigated in a pot trial. Five soil samples were collected from Te Puke (Paengaroa Shallow Sand, a Typic Hapludand) and five from Hamilton (Bruntwood silt loam, an Aquic Hapludand), New Zealand. Subsamples of each soil were either amended with chitin or unamended and planted with white clover and ryegrass. The ryegrass shoot weight in amended soil was greater (P<0.01), most probably due to N mineralised from chitin. A significantly lower (P<0.01) root: shoot ratio of ryegrass in the amended soil also suggested improved N availability, and therefore less root mass was needed to support a given shoot mass. A reduction in nodulation was observed in 12-day-old white clover seedlings (P<0.05) and also in 6-week-old seedlings (P<0.01). The shoot weight of white clover was significantly lower (P<0.05) in amended soil, possibly due to phytotoxic effects of chitin. Chitin increased (P<0.01) the populations of bacteria and fungi by 13-fold and 2.5-fold, respectively. The cyst nematode of white clover, Heterodera trifolii, was significantly reduced in chitin-amended soil, possibly due to increased levels of chitinase produced by rhizosphere microorganisms. Two other plant-parasitic nematodes, Pratylenchus spp. and Tylenchus spp., were also reduced in ryegrass roots and in soil as a result of the chitin amendment. However, the total number of free-living nematodes increased 5.4-fold in amended soil.

A review of the Neotyphodium lolii / Lolium perenne symbiosis and its associated effects on animal and plant health, with particular emphasis on ryegrass staggers

Abstract Ryegrass staggers is a seasonal mycotoxicosis of grazing livestock characterised by tremors, in coordination and a staggering gait almost unaccompanied by physical lesions. Deaths occur only as a consequence of accident or starvation. Outbreaks, in summer and autumn, occur only on pasture in which endophyte (Neotyphodium lolii)-infected perennial ryegrass (Lolium perenne) predominates and usually on which animals are grazed intensively. Animals recover when moved to a different type of grazing or after rain has promoted pasture growth. The disease was recognised for 80 years before its cause was discovered as a consequence of a grazing trial of sheep on three ryegrass cultivars which happened to have three different levels of endophyte infection. The endophyte was first formally described as Acremonium loliae, later corrected to Acremonium lolii, and was finally placed in the genus Neotyphodium. It produces a number of secondary metabolites of which lolitrem B is the principal one causing ryegrass staggers symptoms. Ergopeptides are also produced which cause heat stress and lack of productivity. N. lolii is symptomless in the plant, seed borne and grows intercellularly in the aerial parts, mainly in reproductive tillers and leaf sheaths but sparsely in leaf blades. It dies in stored seed and infection rates of different ryegrass cultivars have depended on seed storage times during their production. In addition, N. Lolii produces insect feeding deterrents, among them peramine, which protects infected plants from pest predation. Because of this, control of ryegrass staggers by elimination of endophyte-infected ryegrass is not feasible in areas in which insect predation is a serious pasture problem. However, N. lolii strains vary in the secondary metabolites they produce allowing the selection of strains that produce desirable metabolites. By inoculating such strains into uninfected ryegrass plants it is possible to produce cultivars which do not cause ryegrass staggers but resist insect predation. This review aims to provide a comprehensive summary of the current understanding of the N. lolii / L. perenne symbiosis, the toxins it is known to produce, their effects on animals and plants and the strategies used to control their ill effects while maximising their beneficial ones

Fusaria and Fusarium toxins in New Zealand maize plants.

A time course study was made of the development of Fusarium infection and the appearance of the three Fusarium toxins, nivalenol (NV), deoxynivalenol (DON) and zearalenone (ZEN), in various fractions of maize plants from two sites in New Zealand, one in the Manawatu region and one in the Waikato. Fusarium infection was seen in leaf axil fractions in January, at the time of tassel emergence, and was detectable in stalks, leaf blades, rachis and peduncles during February and in kernels in April. NV, DON and ZEN were only detectable some time after infection was demonstrable. NV, in high concentrations relative to DON (up to 287 mg/kg for NV and up to 8 mg/kg for DON), was found in fractions from the Manawatu site where F. crookwellense and F. culmorum were the predominant toxigenic species. NV and DON at similar levels (up to 25 mg/kg) were found in fractions from the Waikato site at which F. graminearum and F. subglutinans predominated. Highest levels of NV and DON were in rachis and peduncle. ZEN was found most consistently in leaf axils and blades at both sites (up to 8 mg/kg at the Manawatu site and up to 75 mg/kg at the Waikato site) but at times there were high levels in rachis fractions (up to 417 mg/kg at the Manawatu site).

Some Observations on Neurotoxin Production in Perennial Ryegrass

Abstract Sir,- The presence of neurotoxins, two of which were named lolitrem A and lolitrem B, in perennial ryegrass associated with outbreaks of ryegrass staggers (RGS) in sheep was reported in 1981.(6) Lolitrems are lipid-soluble compounds which induce protracted tremors when dosed i.p. to mice and which have also been found in a number of lines of ryegrass seed.(4) Lolitrem-containing seed, fed to sheep, produced symptoms similar to those of RGS, whereas no symptoms were seen in sheep fed lolitrem-free seed.(04) The reversability of the induced neurotoxicity, a well-known feature of RGS(05) (07) was observed in these experiments.

Influence of harvest date and hybrid on the mycotoxin content of maize (Zea mays) grain grown in New Zealand

Abstract The changes in concentrations of the Fusarium mycotoxins nivalenol (NIV), deoxynivalenol (DON), and zearalenone (ZEN) in harvested maize (Zea mays) grain with time of harvest were determined, as well as how those changes were affected by the hybrid grown. The study used five hybrids in commercial use, three of these resistant to mycotoxin accumulation under New Zealand growth conditions (3902, 3787, 3394) and two less resistant (3751, 3514). The trial was conducted at five well‐maintained long‐term maize research sites over the three major maize‐growing regions of New Zealand. Results showed that apart from seasonal effects, hybrid choice was the major factor affecting the incidence and concentration of mycotoxins in harvested maize grain. Susceptible hybrids were significantly more likely to contain mycotoxins and to have high concentrations. It was determined that harvest date also had an impact on mycotoxin concentrations, with the best indicators of increased mycotoxin risk being either a prolonged time elapsed since the crop first reached 28% kernel moisture, or a very late (late June or July) harvest. The possibility of a site effect was also observed. At one site in the Waikato region, cob and kernel moisture contents were determined over most of the season, and the collected grain measured for infection by Fusarium species, and for contamination by mycotoxins. This showed that once the kernel moisture content fell below 30%, a substantial increase in Fusarium infection is likely. When this occurs, further delays in harvest can compromise grain quality and lead to increased mycotoxin contamination. The level of fungal infection and mycotoxin contamination would have been markedly less if the crops had been harvested earlier than they were, with the most susceptible hybrids being most affected. The study showed that although there may exist a reasonably wide harvest window for resistant hybrids planted at good sites, with more susceptible hybrids it is imperative to harvest as soon as practical, but that even then, mycotoxin contamination can be present.

Fusaria and Fusarium mycotoxins in leaves and ears of maize plants 2. A time course study made in the Waikato region, New Zealand, in 1997

Abstract The patterns of fungal infection and mycotoxin contamination in leaf and ear sections of plants of two maize (Zea mays L.) hybrids, one resistant to mycotoxin accumulation under New Zealand conditions (Pioneer 3902 (P3902)) and one less so (Pioneer 3751 (P3751)), have been measured. Sampling commenced early in the season, well before ear and tassel formation, and continued until harvest. A number of fungi were isolated, the most common overall being Fusarium. Most common in leaf fractions were Epicoccum, Fusarium, and Alter‐naria, whereas in ear fractions the most common were Fusarium, Penicillium, Cladosporium, and Mucor. The most common fusaria isolated from leaf fractions were the toxigenic species F. crookwellense and F. graminearum. These species were evident from late February although other, non‐toxigenic, species were present in leaf axils from early January. For ear fractions the most common species were F. graminearum, F. crookwellense, and F. subglutinans. Fusarium infection was eviden...

Effects of plant-parasitic nematodes and rhizosphere microorganisms on the growth of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.)

A pot trial was carried out to study the effects of plant-parasitic nematodes and rhizosphere microorganisms on the growth of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Plants were grown together in Horotiu sandy loam (Vitric Hapludand). The treatments consisted of: untreated field soil (UT); soil frozen to −20°C to reduce nematodes (FR); soil fumigated with chloroform to kill most soil organisms (FU); and fumigated soil inoculated with a layer of frozen soil to reintroduce organisms present in frozen soil (FUI). The mean wet weights of white clover and ryegrass grown in UT soil for 6–9 weeks were only 10 and 60%, respectively, of those grown in FR soil and 5.8 and 56%, respectively, of those grown in FU soil. The severe growth reduction of white clover in UT was attributed to early invasion of roots by two nematode species, Heterodera trifolii and Meloidogyne hapla, which were detected in stunted 7-day-old seedlings. In the FR and FUI treatments, the freeze-thaw process appeared to have killed the second stage juveniles but not the eggs, which hatched to release more juveniles to invade white clover roots. Plant growth in FR, and to a lesser extent in FUI treatments, was reduced in comparison with FU, where there was no nematode invasion. The bacterial numbers in surface-sterilized roots were unaffected by any of the treatments. This suggests that the entry of bacteria into root tissues is independent of the wounding caused by nematodes. The mean bacterial numbers of the medians (means of log cfus across treatments and plant species of the median numbers across replicates) for “total” bacteria, fluorescent pseudomonads, Gram-negative bacteria and Gram-positive bacteria from surface-sterilized roots were 4.26, < 2, 2.94 and 3.08 for the four treatments, respectively. The most common bacterial genera identified were Pseudomonas and Bacillus. Fungi isolated from surface-sterilized roots included Fusarium oxysporum, Codinaea fertilis and many sterile fungi, with F. oxysporum being the most common identified fungus in FU and FUI treatments. C. fertilis was killed by the soil freezing process. F. oxysporum did not appear to be associated with a decrease in dry matter production of either white clover or ryegrass, but C. fertilis may have adversely affected the ryegrass dry matter production in the treatment UT.

Presence of zearalenone in New Zealand pasture leaves.

(1985). Presence of zearalenone in New Zealand pasture leaves. New Zealand Veterinary Journal: Vol. 33, No. 11, pp. 193-193.

Presumptive tremorgenic mycotoxicosis in a dog in New Zealand, after eating mouldy walnuts

Abstract CASE HISTORY: A 1-year-old, intact male Labrador-cross dog vomited after eating walnuts that had been on the ground for 5 months. The dog then developed tremors, ataxia, increased salivation, and hyperaesthesia. CLINICAL FINDINGS: The dog had marked generalised tremors, ataxia and a temperature of 39.9°C. Both pupils were of normal size and normally responsive to light. Vomiting was induced, and walnut shell was visible in the vomitus. DIAGNOSIS: Due to the sudden onset of tremors, lack of exposure to other convulsive toxins, and the evidence of ingestion of walnuts, the provisional diagnosis was tremorgenic mycotoxicosis. The dog was treated symptomatically, and made a full recovery over 18 hours. Tremorgenic mycotoxins were detected within walnuts collected from the dogs environment. CLINICAL RELEVANCE: Fungi that produce tremorgenic mycotoxins are present in New Zealand. Intoxication should be suspected in dogs that suddenly develop muscle tremors, especially if there is a history of ingestion of mouldy food 2–3 hours prior to the development of tremors.