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Evaluation of In-Field Inoculation Methods for Characterization of Macadamia Germplasm to Husk Spot Incidence and Severity
No full textHusk spot, a fungal disease of macadamia pericarps (Pseudocercospora macadamiae), induces premature abscission in several major commercial cultivars. Breeding for resistance to husk spot is a priority of the Australian macadamia industry. Due to the large tree size of macadamia and high numbers of progeny in breeding populations, inoculating for resistance screening is laborious and time consuming. Previously utilized methods included direct applications of P. macadamiae suspensions and the hanging of bags of diseased husks above developing fruit in tree canopies. In this study, both methods were modified to allow for efficient application in large-scale breeding populations, and their efficacy was evaluated. Two quantities of diseased husk per bag, ‘large’ (75 g) and ‘small’ (30 g), and two concentrations of sprayed P. macadamiae suspensions, ‘stock’ (5 × 105 propagules/ml) and ‘dilute’ (2.5 × 105 propagules/ml), were tested across two fruiting seasons. Treatments were compared against a control (sterile water) in commercial cultivars A38 and A4. Husk spot incidence and severity produced by small bags were significantly affected by season. A significant season effect was less common for other treatments. All four treatments infected over 50% of target fruit in each season, but the highest husk spot incidence across both seasons (≥85%) was produced from large bags. Overall, the large bags were the most reliable method for infection of target fruit. Results also demonstrate the importance of considering the effect of season when selecting husk spot inoculation methods
A review of fruit development in strawberry: high temperatures accelerate flower development and decrease the size of the flowers and fruit
No full textTemperature affects the growth and development of strawberry (Fragaria ×ananassa Duch.). This review examines the effect of temperature on fruit growth from the published literature. Higher temperatures under global warming will result in lower yields and smaller, less sweet berries in the future. Warm weather has a negative impact on the size of the flowers, germination of the pollen and on carbon assimilation, which all contribute to the production of smaller fruit. The relationship between fruit weight and temperature was assessed across studies. The slope from the linear regression ranged from − 0.11 to − 5.00, with a median of − 0.96, and a mean (± s.d. or standard deviation) of − 1.32 ± 1.22 (N = 23 studies). Differences in the response reflect variations in cultivars, yields, the structure of the inflorescence and the period used to assess growth. There were strong linear relationships between the number of stamens per flower (P < 0.001, R 2 = 0.62) and the number of carpels per flower (P < 0.001, R 2 = 0.77), and the size of the flowers. There were strong relationships between the size of the fruit at harvest and the size of the flowers at anthesis (P < 0.001, R 2 = 0.76; P < 0.001, R 2 = 0.86). High temperatures during flower development decreased the size of the flowers (8.5 mm × 4.8 mm at 15°C and 6.0 mm × 3.7 mm at 25°C) and the number of carpels (achenes) per flower (P = 0.023, R 2 = 0.29; and P = 0.003, R 2 = 0.59). High temperatures decreased the period of floral differentiation (P < 0.001, R 2 = 0.90) and the size of the fruit at harvest (P = 0.024, R 2 = 0.99; P = 0.032, R 2 = 0.99). The percentage of pollen grains which germinated was higher from 20° to 30°C, with lower germination at lower or higher temperatures. The slope from the linear regression between the fruit development period (FDP) and temperature ranged from − 0.77 to − 2.93, with a median of − 1.70, and a mean of − 1.71 ± 0.72 (N = 15 studies). Net CO2 assimilation was similar from 20° to 30°C, and only lower under extreme conditions (N = 15 studies). Respiration in the leaves increased with warm days and nights (P = 0.003 or 0.004, R 2 = 0.95 or 0.94), while respiration in the fruit increased exponentially from 10° to 36°C (P < 0.001, R 2 = 0.99). The effect of temperature on fruit growth in the field is confounded by changes in the structure of the inflorescences, with smaller fruit in the later inflorescences than in the first inflorescence (P < 0.001, R 2 = 0.85, 0.82 or 0.89). The production of small fruit during warm weather is associated with smaller flowers and fewer stamens, germinated pollen grains, carpels and achenes in each flower or fruit. Warm conditions increase respiration in the leaves and the fruit. Fruit weight is moderately heritable, with a mean broad-sense heritability (H 2) of 0.44 ± 0.23 (N = 11 studies) and a mean narrow-sense heritability (h 2) of 0.45 ± 0.22 (N = 28 studies). High temperatures accelerate the development of the flowers and decrease the size of flowers and fruit. Efforts should be made to develop cultivars with acceptable fruit size under hot conditions. Genome-wide association (GWA) and genomic prediction (GP) will accelerate the identification of large-fruited populations and individuals under global warming. These studies should examine the genes associated with cell division and expansion during the development of the flowers. © 2023 Crown Copyright
West Indian drywood termite, Cryptotermes brevis, in Australia: current understanding, ongoing issues, and future needs
No full textWest Indian drywood termite, Cryptotermes brevis, is an invasive pest of particular importance due to its global distribution, cryptic lifecycle, potential to spread and economic impact. The species has been under a Queensland Government-funded prevention and control program since its detection in the 1960s, but this program ceased in 2021. It is now increasingly important to develop alternative methods for managing this pest and slowing its spread. This review synthesises information on C. brevis, its commercial impact, and the unique factors contributing to its global spread. We highlight areas where information on the species is lacking and identify corresponding research needed to fill these gaps. Results from these future research efforts may help improve the management of this termite in terms of improved detection and spot-control of colonies and creating a better understanding of at-risk timber species
Identification of a Major QTL-Controlling Resistance to the Subtropical Race 4 of Fusarium oxysporum f. sp. cubense in Musa acuminata ssp. malaccensis
Get PDFVascular wilt caused by the ascomycete fungal pathogen Fusarium oxysporum f. sp. cubense (Foc) is a major constraint of banana production around the world. The virulent race, namely Tropical Race 4, can infect all Cavendish-type banana plants and is now widespread across the globe, causing devastating losses to global banana production. In this study, we characterized Foc Subtropical Race 4 (STR4) resistance in a wild banana relative which, through estimated genome size and ancestry analysis, was confirmed to be Musa acuminata ssp. malaccensis. Using a self-derived F2 population segregating for STR4 resistance, quantitative trait loci sequencing (QTL-seq) was performed on bulks consisting of resistant and susceptible individuals. Changes in SNP index between the bulks revealed a major QTL located on the distal end of the long arm of chromosome 3. Multiple resistance genes are present in this region. Identification of chromosome regions conferring resistance to Foc can facilitate marker assisted selection in breeding programs and paves the way towards identifying genes underpinning resistance
Real-time automated species level detection of trade document systems to reduce illegal wildlife trade and improve data quality
No full textBiodiversity fuels the international wildlife trade, much of which is illegal and/or unsustainable. Border agents are typically overburdened, having to manually inspect import documents to ensure the legality of contents for often ≥100 shipments per day. Delaying shipments for inspection must be balanced against maintaining live animal welfare and reducing undue costs for traders. Biodiversity within the wildlife trade cannot be accurately estimated because of the multiple harmonization systems used to organize business transactions. Harmonizing wildlife trade data ignores species level classifications and aggregates data at less granular taxonomic or commodity level groupings. Here we describe a Real-Time Automated Species-Level Detection (RTASLD) system that assesses shipment declarations and invoices to collect data on species being traded. We use this to demonstrate how taxonomic imprecision on declarations and invoices can blur trade statistics and, at worst, be intentionally manipulated to conceal illegal wildlife. We address how taxonomic imprecision can interplay with Convention on the International Trade in Endangered Species of Wild Fauna and Flora (CITES) listed species. When only one or a subset of species within a genus are CITES listed, referred to as a Mixed-CITES-Genus, illegal trade can occur by identifying only to the genus level, and not to the species level which requires a declaration and CITES paperwork. RTASLD can be used to help border wildlife inspectors identify increased risk or presence of illegal wildlife trade that is occurring. Accurate species-level collection of trade data will help to better track biodiversity, stop illegal wildlife trade and maintain business expedience
Diaporthe gulyae colonizes seeds of sunflower (Helianthus annuus) systematically through leaf, petiole and stem infection
No full textDiaporthe gulyae, first identified as causing stem lesions and mid-stem lodging on sunflower in Australia, is a highly virulent pathogen now also reported on sunflower in Argentina, Canada, China and North America. This report details the first observations of sunflower leaf infection by D. gulyae in the field and confirms a leaf-to-stem infection pathway by glasshouse experiments. Further, capitula tissues and seed were also infected by D. gulyae following stem infection, demonstrating that hyphae associated with stem lesions can colonize upwards into the capitulum under favourable conditions. Leaf and stem lesion symptoms caused by D. gulyae are very similar to those caused by D. helianthi, the cause of Phomopsis stem canker (PSC) of sunflower in China, Europe, North and South America and Russia. Leaf colonization followed by stem infection is also the recognized infection pathway of D. helianthi and the almost identical symptoms and signs caused by D. gulyae and D. helianthi on sunflower highlight the difficulties of differentiating these species in the field. Additionally, seedlings that emerged from infected seeds with pericarp halves attached were shown to be a viable source of D. gulyae inoculum, which may contribute to further spread both locally and internationally. The name Diaporthe Stem Canker (DSC) is attributed here to the disease caused by D. gulyae to enable distinction from PSC caused by D. helianthi
SNP and haplotype-based genomic prediction of fruit quality traits in sweet cherry (Prunus avium)
No full textThe use of haplotypes in genomic prediction, instead of the widely used individual SNP approach, may improve the accuracy of genomic predictions due to a high probability of complete linkage disequilibrium (LD) between haplotypes and causative quantitative trait loci (QTLs), more accurate estimation of realized relationships between pairs of individuals, and ability to capture local epistatic interactions. We estimated genomic breeding values for three sweet cherry traits (fruit firmness (FF), soluble solids content (SSC) and titratable acidity (TA)) using individual SNPs and genealogy-based haplotypes fitted as pseudo-biallelic loci in a population of 334 sweet cherry individuals obtained from the RosBREED project. 1617 high-quality SNPs obtained from the sweet cherry 6K Array and 2087 haplotypes from 196 genealogy-based haploblocks were used to perform 5-fold cross-validations in a GBLUP framework. We found no differences in predictive ability (PA) between pseudo-biallelic loci and individual SNPs. The highest genomic PA was observed for fruit firmness (0.67), and the lowest PA was observed for titratable acidity (0.45). Predictive abilities (0.67, 0.51 and 0.45 for FF, SSC and TA, respectively) from GBLUP models using both pseudo-biallelic loci and individual SNPs were significantly (p<0.05) higher than pedigree-based predictive abilities (0.64, 0.48 and 0.35 for FF, SSC and TA, respectively). We concluded that using pseudo-biallelic loci instead of individual SNPs did not improve or reduce PA. Further research will be undertaken to compare these models for traits with lower heritability and populations with different structures. © 2023 International Society for Horticultural Science. All rights reserved
Balancing pre- and post-anthesis growth to maximise water-limited yield in cereals
No full textTo maximize cereal yield in water-limited environments where crops rely on stored soil moisture, pre-anthesis growth and water-use must be balanced to create a sink demand at anthesis that can be filled by the remaining water after anthesis. We hypothesize that canopy development in cereals is a key regulator of biomass and water allocation before and after anthesis, affecting stem reserve mobilization, nitrogen dynamics and grain yield in water-limited environments. In drought-prone regions where crops heavily depend on stored soil moisture, crops facing end-of-season drought must conserve water during early growth to ensure that sufficient water is available for grain filling. To better understand this balance, we expressed the ratio between post- and pre-anthesis biomass as an index, designated as the ‘biomass rationing index’ (BRI). This index was evaluated in three cereal species (sorghum, wheat and barley) in multiple seasons and environments to examine the extent to which it could be manipulated by genetics and management. BRI was negatively correlated with canopy size at anthesis and was positively correlated with stay-green, change in post-anthesis stem biomass, nitrogen content at maturity, and ultimately grain yield. Results suggest that post-anthesis water availability was closely linked to pre-anthesis green leaf area and biomass, and that at least in environments where crops relied on stored soil moisture, limiting canopy size was an effective strategy to ensure adequate water availability for grain filling in the face of end-of-season drought. A range of genetic strategies (genes regulating tillering, leaf size, stomatal conductance, transpiration per leaf area, hydraulic resistance, root architecture) and management strategies (pre-crop factors, plant density, nitrogen fertilization, weed control, crop rotations, weed control, soil type) could be used to manipulate BRI.We propose BRI as a simple indicator to provide new insights on how water-limited yield in cereals can be maximized by better balancing pre- and post-anthesis growth
Effect of soil water on flowering and pod-set in chickpea: implications for modelling and managing frost and heat stress
Get PDFPhenological development is critical for crop adaptation. Phenology models are typically driven by temperature and photoperiod, but chickpea phenology is also modulated by soil water, which is not captured in these models. This study is aimed at evaluating the hypotheses that accounting for soil water improves (i) the prediction of flowering, pod-set, and flowering-to-pod-set interval in chickpea and (ii) the computation of yield-reducing frost and heat events after flowering. To test these hypotheses, we compared three variants of the Agricultural Production System Simulator (APSIM): (i) APSIMc, which models development with no temperature threshold for pod-set; (ii) APSIMx, which sets a threshold of 15 °C for pod-set; and (iii) APSIMw, derived from APSIMc with an algorithm to moderate the developmental rate as a function of soil water, in addition to temperature and photoperiod common to all three models. Comparison of modelled and actual flowering and pod-set of a common cheque cultivar PBA BoundaryA in 54 diverse environments showed that accuracy and precision were superior for APSIMw. Because of improved prediction of flowering and pod-set timing, APSIMw improved the computation of the frequency of post-flowering frosts compared to APSIMc and APSIMx. The number of heat events was similar for all three models. We conclude that accounting for water effects on plant development can allow better matching between phenology and environment
Stock Assessment of Ballot's saucer scallop (Ylistrum balloti) in Queensland, Australia, with data to October 2022
Get PDFThe Queensland east coast Ballot’s saucer scallop (Ylistrum balloti, formerly Amusium balloti) is a marine bivalve mollusc with a hinged shell. They are mainly found between 22 degrees South and 27 degrees South in shelf water depths of 20 to 60 metres. Saucer scallops can potentially grow to about 12 to 14 cm in shell height and, in some instances, live for up to 4 years. Scallops generally mature between 11 and 18 months of age.
This stock assessment indicates that biomass declined between 1956 and 2016 to 10% unfished biomass. In 2022, the stock level was estimated to be 15% unfished biomass (95% confidence interval 10–25%)