Molecular characterisation, pathogenesis and fungicide sensitivity of Pythium spp. from table beet (Beta vulgaris var. vulgaris) grown in the Lockyer Valley, Queensland

Table beet production in the Lockyer Valley of south-eastern Queensland is known to be adversely affected by soilborne root disease from infection by Pythium spp. However, little is known regarding the species or genotypes that are the causal agents of both pre- and post-emergence damping off. Based on RFLP analysis with HhaI, HinfI and MboI of the PCR amplified ITS region DNA from soil and diseased plant samples, the majority of 130 Pythium isolates could be grouped into three genotypes, designated LVP A, LVP B and LVP C. These groups comprised 43, 41 and 7% of all isolates, respectively. Deoxyribonucleic acid sequence analysis of the ITS region indicated that LVP A was a strain of Pythium aphanidermatum, with greater than 99% similarity to the corresponding P. aphanidermatum sequences from the publicly accessible databases. The DNA sequences from LVP B and LVP C were most closely related to P. ultimum and P. dissotocum, respectively. Lower frequencies of other distinct isolates with unique RFLP patterns were also obtained with high levels of similarity (>97%) to P. heterothallicum, P. periplocum and genotypes of P. ultimum other than LVP B. Inoculation trials of 1- and 4-week-old beet seedlings indicated that compared with isolates of the LVP B genotype, a higher frequency of LVP A isolates caused disease. Isolates with the LVP A, LVP B and LVP C genotypes were highly sensitive to the fungicide Ridomil MZ, which suppressed radial growth on V8 agar between approximately four and thirty fold at 5 μg/mL metalaxyl and 40 μg/mL mancozeb, a concentration far lower than the recommended field application rate.

Betalain rich functional extract with reduced salts and nitrate content from red beetroot (Beta vulgaris L.) using membrane separation technology

An initial laboratory-scale evaluation of separation characteristics of membranes with nominal molecular weight cut-offs (NMWCO) ranging from 30 kD down to 0.5 kD indicated effective separation of betalains in the 0.5 kD region. Subsequent pilot-level trials using 1 kD, loose reverse osmosis (LRO) and reverse osmosis (RO) spiral-wound membranes showed LRO membrane to be very efficient with up to 96% salt and 47% other dissolved solids removed while retaining majority of the pigment (∼98%) in the betalain rich extract (BRE). The total betalain content in the BRE increased up to 46%, the highest recovery reported so far at pilot scale level. Interestingly, more than 95% of the nitrates were removed from the BRE after the three diafiltrations. These studies indicate that membrane technology is the most efficient technique to produce BRE with highly reduced amounts of salts and nitrate content.

Spatio-temporal patterns in maturation of the chokka squid (Loligo vulgaris reynaudii) off the coast of South Africa

Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.

Pest-damage relationships for Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on soybean (Glycine max) and dry bean (Phaseolus vulgaris) during pod-fill.

The response of soybean (Glycine max) and dry bean (Phaseolus vulgaris) to feeding by Helicoverpa armigera during the pod-fill stage was studied in irrigated field cages over three seasons to determine the relationship between larval density and yield loss, and to develop economic injury levels. H. armigera intensity was calculated in Helicoverpa injury equivalent (HIE) units, where 1 HIE was the consumption of one larva from the start of the infestation period to pupation. In the dry bean experiment, yield loss occurred at a rate 6.00 ± 1.29 g/HIE while the rates of loss in the three soybean experiments were 4.39 ± 0.96 g/HIE, 3.70 ± 1.21 g/HIE and 2.12 ± 0.71 g/HIE. These three slopes were not statistically different (P > 0.05) and the pooled estimate of the rate of yield loss was 3.21 ± 0.55 g/HIE. The first soybean experiment also showed a split-line form of damage curve with a rate of yield loss of 26.27 ± 2.92 g/HIE beyond 8.0 HIE and a rapid decline to zero yield. In dry bean, H. armigera feeding reduced total and undamaged pod numbers by 4.10 ± 1.18 pods/HIE and 12.88 ± 1.57 pods/HIE respectively, while undamaged seed numbers were reduced by 35.64 ± 7.25 seeds/HIE. In soybean, total pod numbers were not affected by H. armigera infestation (out to 8.23 HIE in Experiment 1) but seed numbers (in Experiments 1 and 2) and the number of seeds/pod (in all experiments) were adversely affected. Seed size increased with increases in H. armigera density in two of the three soybean experiments, indicating plant compensatory responses to H. armigera feeding. Analysis of canopy pod profiles indicated that loss of pods occurred from the top of the plant downwards, but with an increase in pod numbers close to the ground at higher pest densities as the plant attempted to compensate for damage. Based on these results, the economic injury levels for H. armigera on dry bean and soybean are approximately 0.74 HIE and 2.31 HIE/m2, respectively (0.67 and 2.1 HIE/row-m for 91 cm rows).

Recent advances in the molecular biology of Leifsonia xyli subsp. xyli, causal organism of ratoon stunting disease

Twelve years ago our understanding of ratoon stunting disease (RSD) was confined almost exclusively to diagnosis of the disease and control via farm hygiene, with little understanding of the biology of the interaction between the causal agent (Leifsonia xyli subsp. xyli) and the host plant sugarcane (Saccharum spp. hybrids). Since then, research has focused on developing the molecular tools to dissect L. xyli subsp. xyli, so that better control strategies can be developed to prevent losses from RSD. Within this review, we give a brief overview of the progression in research on L. xyli subsp. xyli and highlight future challenges. After a brief historical background on RSD, we discuss the development of molecular tools such as transformation and transposon mutagenesis and discuss the apparent lack of genetic diversity within the L. xyli subsp. xyli world population. We go on to discuss the sequencing of the genome of L. xyli subsp. xyli, describe the key findings and suggest some future research based on known deficiencies that will capitalise on this tremendous knowledge base to which we now have access.

Comparison of Culture and a Novel 5' Taq Nuclease Assay for Direct Detection of Campylobacter fetus subsp. venerealis in Clinical Specimens from Cattle

A Campylobacter fetus subsp. venerealis-specific 5' Taq nuclease PCR assay using a 3' minor groove binder-DNA probe (TaqMan MGB) was developed based on a subspecies-specific fragment of unknown identity (S. Hum, K. Quinn, J. Brunner, and S. L. On, Aust. Vet. J. 75:827-831, 1997). The assay specifically detected four C. fetus subsp. venerealis strains with no observed cross-reaction with C. fetus subsp. fetus-related Campylobacter species or other bovine venereal microflora. The 5' Taq nuclease assay detected approximately one single cell compared to 100 and 10 cells in the conventional PCR assay and 2,500 and 25,000 cells from selective culture from inoculated smegma and mucus, respectively. The respective detection limits following the enrichments from smegma and mucus were 5,000 and 50 cells/inoculum for the conventional PCR compared to 500 and 50 cells/inoculum for the 5' Taq nuclease assay. Field sampling confirmed the sensitivity and the specificity of the 5' Taq nuclease assay by detecting an additional 40 bulls that were not detected by culture. Urine-inoculated samples demonstrated comparable detection of C. fetus subsp. venerealis by both culture and the 5' Taq nuclease assay; however, urine was found to be less effective than smegma for bull sampling. Three infected bulls were tested repetitively to compare sampling tools, and the bull rasper proved to be the most suitable, as evidenced by the improved ease of specimen collection and the consistent detection of higher levels of C. fetus subsp. venerealis. The 5' Taq nuclease assay demonstrates a statistically significant association with culture (2 = 29.8; P < 0.001) and significant improvements for the detection of C. fetus subsp. venerealis-infected animals from crude clinical extracts following prolonged transport.

The host range and biology of Cometaster pyrula; a biocontrol agent for Acacia nilotica subsp. indica in Australia

Prickly acacia, Acacia nilotica subsp. indica (Benth.) Brenan, a major weed of the Mitchell Grass Downs of northern Queensland, Australia, has been the target of biological control projects since the 1980s. The leaf-feeding caterpillar Cometaster pyrula (Hopffer) was collected from Acacia nilotica subsp. kraussiana (Benth.) Brenan during surveys in South Africa to find suitable biological control agents, recognised as a potential agent, and shipped into a quarantine facility in Australia. Cometaster pyrula has a life cycle of approximately 2 months during which time the larvae feed voraciously and reach 6 cm in length. Female moths oviposit a mean of 339 eggs. When presented with cut foliage of 77 plant species, unfed neonates survived for 7 days on only Acacia nilotica subsp. indica and Acacia nilotica subsp. kraussiana. When unfed neonates were placed on potted plants of 14 plant species, all larvae except those on Acacia nilotica subsp. indica and Acacia nilotica subsp. kraussiana died within 10 days of placement. Cometaster pyrula was considered to be highly host specific and safe to release in Australia. Permission to release C. pyrula in Australia was obtained and the insect was first released in north Queensland in October 2004. The ecoclimatic model CLIMEX indicated that coastal Queensland was climatically suitable for this insect but that inland areas were only marginally suitable.

Local dispersion and damage of Corymbia citriodora subsp. variegata (Myrtaceae) regrowth by eriophyid mites (Acari: Eriophyoidea).

Eriophyid mites (Acari: Eriophyoidea: Eriophyidae: Rhombacus sp. and Acalox ptychocarpi Keifer) are recently-emerged pests of commercial eucalypt plantations in subtropical Australia. They cause severe blistering, necrosis and leaf loss to Corymbia citriodora subsp. variegata (F. Muell.) K.D. Hill & L.A.S. Johnson, one of the region's most important hardwood plantation species. In this study we examine the progression, incidence and severity of these damage symptoms. We also measure within-branch colonisation by mites to identify dispersive stages, and estimate the relative abundance of the two co-occurring species. Rhombacus sp., an undescribed species, was numerically dominant, accounting for over 90% of all adult mites. Adults were the dispersive stage, moving mostly within branches, but 12% of recruitment onto new leaves occurred on previously uninfested branches. Damage incidence and severity were correlated, while older leaves had more damage than younger leaves. "Patch-type" damage was less frequent but was associated with higher mite numbers and damage scores than "spot-type" damage, while leaf discoloration symptoms related mostly to leaf age.

Isolation and functional characterization of a lycopene beta-cyclase gene that controls fruit colour of papaya (Carica papaya L.).

The colour of papaya fruit flesh is determined largely by the presence of carotenoid pigments. Red-fleshed papaya fruit contain lycopene, whilst this pigment is absent from yellow-fleshed fruit. The conversion of lycopene (red) to beta-carotene (yellow) is catalysed by lycopene beta-cyclase. This present study describes the cloning and functional characterization of two different genes encoding lycopene beta-cyclases (lcy-beta1 and lcy-beta2) from red (Tainung) and yellow (Hybrid 1 B) papaya cultivars. A mutation in the lcy-beta2 gene, which inactivates enzyme activity, controls lycopene production in fruit and is responsible for the difference in carotenoid production between red and yellow-fleshed papaya fruit. The expression level of both lcy-beta1 and lcy-beta2 genes is similar and low in leaves, but lcy-beta2 expression increases markedly in ripe fruit. Isolation of the lcy-beta2 gene from papaya, that is preferentially expressed in fruit and is correlated with fruit colour, will facilitate marker-assisted breeding for fruit colour in papaya and should create possibilities for metabolic engineering of carotenoid production in papaya fruit to alter both colour and nutritional properties.

Wood properties and knot occlusion of plantation grown Eucalyptus dunnii and Corymbia citriodora subsp. variegata in a pruning and thinning experiment.

A 2 × 2 factorial combination of thinned or unthinned, and pruned or unpruned 11-year-old Eucalyptus dunnii (DWG) and 12-year-old Corymbia citriodora subsp. variegata (CCV) was destructively sampled to provide 60 trees in total per species. Two 1.4 m long billets were cut from each tree and were rotary veneered in a spindleless lathe down to a 45 mm diameter core to expose knots which were classified as either alive, partially occluded or fully occluded. Non-destructive evaluation of a wider range of thinning treatments available in these trials was undertaken with Pilodyn and Fakopp tools. Disc samples were also taken for basic density and modulus of elasticity. Differences between treatments for all wood property assessments were generally small and not significantly different.Thinning and pruning had little effect on the stem diameter growth required to achieve occlusion, therefore occlusion would be more rapid after thinning due to more rapid stem diameter growth. The difference between the treatments of greatest management interest, thinned and pruned (T&P) and unthinned and unpruned (UT&UP) were small. The production of higher value clear wood produced after all knots had occluded, measured as the average stem diameter growth over occlusion of the three outermost knots, was approximately 2 centimetres diameter. Two of the treatments can be ruled out as viable management alternatives: (i) the effect of thinning without pruning (T&UP) is clear, leading to a large inner core of stem wood containing knots (large knotty core diameter) and (ii) pruning without thinning (UT&P) results in a small knotty core diameter, however the tree and therefore log diameters are also small.

Reproductive Biology of Corymbia citriodora subsp. variegata and Effective Pollination across its Native Range.

The spotted gum species complex represents a group of four eucalypt hardwood taxa that have a native range that spans the east coast of Australia, with a morphological cline from Victoria to northern Queensland. Of this group, Corymbia citriodora subsp. variegata (CCV) is widespread in south-eastern Queensland and northern New South Wales. It is currently the most commonly harvested native hardwood in Queensland. However, little basic knowledge of the reproductive biology of the species is available to inform genetic improvement and resource management programmes. Here we take an integrative approach, using both field and molecular data, to identify ecological factors important to mating patterns in native populations of CCV. Field observation of pollinator visitation and flowering phenology of 20 trees showed that foraging behaviour of pollinator guilds varies depending on flowering phenology and canopy structure. A positive effect of tree mean flowering effort was found on insect visitation, while bat visitation was predicted by tree height and by the number of trees simultaneously bearing flowers. Moreover, introduced honeybees were observed frequently, performing 73% of detected flower visits. Conversely, nectar-feeding birds and mammals were observed sporadically with lorikeets and honeyeaters each contributing to 11% of visits. Fruit bats, represented solely by the grey-headed flying fox, performed less than 2% of visits. Genotyping at six microsatellite markers in 301 seeds from 17 families sampled from four of Queensland's native forests showed that CCV displays a mixed-mating system that is mostly outcrossing (tm = 0.899 ± 0.021). Preferential effective pollination from near-neighbours was detected by means of maximum-likelihood paternity analysis with up to 16% of reproduction events resulting from selfing. Forty to 48% of fertilising pollen was also carried from longer distance (>60 m). Marked differences in foraging behaviour and visitation frequency between observed pollinator guilds suggests that the observed dichotomy of effective pollen movement in spotted gums may be due to frequent visit from introduced honeybees favouring geitonogamy and sporadic visits from honeyeaters and fruit bats resulting in potential long-distance pollinations.

Norsesquiterpene Glycosides in Bracken Ferns (Pteridium esculentum and Pteridium aquilinum subsp wightianum) from Eastern Australia: Reassessed Poisoning Risk to Animals.

Austral bracken Pteridium esculentum contains three unstable norsesquiterpene glycosides: ptaquiloside, ptesculento-side, and caudatoside, in variable proportions. The concentration of each of the glycosides was determined in this study as their respective degradation products, pterosin B, pterosin G and pterosin A, by HPLC-UV analysis. Samples of P. esculentum collected from six sites in eastern Australia contained up to 17 mg of total glycoside/g DW, with both ptaquiloside and ptesculentoside present as major components accompanied by smaller amounts of caudatoside. Ratios of ptaquiloside to ptesculentoside varied from 1:3 to 4:3, but in all Australian samples ptesculentoside was a significant component. This profile differed substantially from that of P. esculentum from New Zealand, which contained only small amounts of both ptesculentoside and caudatoside, with ptaquiloside as the dominant component. A similar profile with ptaquiloside as the dominant glycoside was obtained for Pteridium aquilinum subsp. wightianum (previously P. revolutum) from northern Queensland and also P. aquilinum from European sources. Ptesculentoside has chemical reactivity similar to that of ptaquiloside and presumably biological activity similar to that of this potent carcinogen. The presence of this additional reactive glycoside in Australian P. esculentum implies greater toxicity for consuming animals than previously estimated from ptaquiloside content alone.

Rotary veneering of plantation-grown spotted gum (Corymbia citriodora subsp. variegata) and Dunn's white gum (Eucalyptus dunnii)

This report evaluates the wood and veneer properties of plantation-grown spotted gum (Corymbia citriodora subsp. variegata, or CCV) and Dunn's white gum (Eucalyptus dunnii), grown at different stockings, in thinning trials near Ellangowan in north-east New South Wales (mean annual rainfall 1050 mm) and Kingaroy in south-east Queensland (mean annual rainfall 873 mm). Thinning trials were established at age seven years. Both species showed a significant increase in stem diameter growth of the dominant trees in response to thinning. At age 10 years, trees from the unthinned (950–1270 stems ha-1) and 300 stems ha-1 treatments were selected for veneering. Five dominant trees were felled from each combination of species x sites x thinning treatment. Diameter at breast height over bark of the selected trees ranged from 20 cm to 27 cm at Ellangowan, and 19 cm to 26 cm at Kingaroy. From each tree, 1.5 m long billets were removed at two positions: a butt billet from 0.3–1.8 m above ground and a top billet from approximately 5.5–7.0 m. Log end splitting was assessed 24 hours after harvesting and again after steaming, approximately four days after harvesting. Disks from just above both billets were collected for assessment of wood properties. Billets were peeled on a spindleless veneer lathe to produce a full veneer ribbon with a target green thickness of 2.8 to 3.0 mm. The 1.55 m wide (tangential dimension) veneer sheets were dried and graded according to AS/NZ Standard 2269:2008, which describes four veneer grades. Veneer samples taken along the length of the veneer ribbon, at regular intervals of 1.55 m, were tested for stiffness, shrinkage and density. Veneer length measurements were used to calculate the radial distance of each sample from the central axis of the billet. Overall veneer gross recoveries ranged from 50% to 70%. They were significantly lower at the Kingaroy site, for both species. The veneer recoveries achieved were 2–3 times higher than typical green off saw recoveries from small plantation hardwood logs of similar diameter. Most of the veneer recovered was classified as D-grade. CCV trees from the Ellangowan site yielded up to 38% of the better C-grade and higher grade veneers. The main limiting factors that prevented veneer from meeting higher grades were the presence of kino defects and encased knots. Splits in E. dunnii veneer also contributed to reduced grade quality. Log end splits were higher for E. dunnii than for CCV, and logs from Ellangowan exhibited more severe splitting. Split index was generally higher for top than for butt billets. Split index was strongly correlated with the average veneer grade from corresponding billets. The Ellangowan site, where rainfall was higher and trees grew faster, yielded significantly denser and stiffer veneers than did the drier sites near Kingaroy, where tree growth was slower. The difference was more pronounced for E. dunnii than for CCV. Differences in measured wood properties between thinned and unthinned treatments were generally small and not significant. On average, 10% of billet volume was lost during the peeling rounding-up process. Much of the wood laid down following thinning was removed during rounding-up, meaning the effect of thinning on veneer properties could not be effectively assessed. CCV was confirmed as having high veneer density and very good veneer stiffness, exceeding 15 GPa, making it very suitable for structural products. E. dunnii also demonstrated good potential as a useful structural plywood resource, achieving stiffness above 10 GPa. Veneer stiffness and density in CCV increased from pith to bark at both sites, while for E. dunnii there was a radial increase in these properties at the Ellangowan site only. At the drier Kingaroy site, veneer stiffness and density declined from mid-radius to the log periphery. This may be associated with prolonged drought from 2005 to 2009, corresponding to the later years of tree growth at the Kingaroy site. CCV appeared to be less sensitive to drought conditions. Standing tree acoustic velocity, determined by the Fakopp time-of-flight method, provided a reliable prediction of average veneer stiffness for both species (R2=0.78 for CCV and R2=0.90 for E. dunnii) suggesting that the Fakopp method may be a useful indicator of tree and stand quality, in terms of veneer stiffness in standing trees.