Specific flavour traits in papaya significantly influence consumer acceptance, with unfavourable flavours limiting marketability. However, limited evidence links metabolites to sensory characteristics in papaya. This study characterised flavour profiles of 27 papaya genotypes from Australia and South-east Asia (nine commercial cultivars, 18 breeding lines), using metabolomic and sensory data. Ten trained panellists performed descriptive analysis using 20-attribute descriptors, and 125 consumers evaluated flavour acceptance. Variance decomposition analysis revealed that aroma characteristics and volatile organic compounds accounted for most of the variance in consumer liking (31% and 63%, respectively). Ensemble machine learning determined that lipid-derived compounds (e.g. γ-octalactone) and terpenoids (e.g. linalool oxide) influenced the sensory attributes and fruit liking. Gradient boosting regression predicted consumer acceptance using three key metabolites: sulcatone (81%, variable importance), Brix (10%), and β-ionone (9%). These findings provide a novel approach to quantify fruit flavour in papaya, facilitating the development of new cultivars.

The necrotrophic fungus Ascochyta rabiei poses a significant threat to chickpea cultivation worldwide, leading to severe yield losses and quality reduction. Understanding the molecular mechanisms behind the pathogenicity of A. rabiei is essential for developing effective management strategies. This study employed transcriptomic analyses to compare the gene expression profiles among two A. rabiei isolates with differing pathogenicity levels (highly pathogenic AR0231 and low pathogenic AR0225) during interaction of PBA HatTrick chickpea genotype at the early podding stage. PBA HatTrick is classified as moderately susceptible to A. rabiei based on field trial ratings from the GRDC National Variety Trials. Like most cultivated chickpea varieties, its resistance to A. rabiei is generally considered polygenic and quantitative in nature, with no major resistance gene identified to date. A total of 105 differentially expressed genes (DEGs) were identified, including 57 upregulated and 48 downregulated in AR0231. Notably, effector-related genes were prominent among the upregulated DEGs, including EKO05_0002468, a homolog of the CoNIS1 effector gene that suppresses plant immunity, and EKO05_0010552, a homolog of PsGIP2/PsGIP1 encoding a glucanase inhibitor that protects fungal cell walls from host enzymes. Additionally, EKO05_0001368, homologous to PesCDA/VdPDA1, encodes a chitin-binding effector linked to immune evasion. Downregulated DEGs included EKO05_0006947, a LysM-domain effector homolog implicated in masking fungal chitin from host detection. These findings provide new insights into the molecular mechanisms employed by A. rabiei during infection of mature chickpea tissue and highlight candidate genes for future research on improving chickpea resistance to Ascochyta blight.

Ascochyta blight caused by the ascomycete Ascochyta rabiei poses a major biotic threat to chickpea (Cicer arietinum) industries worldwide and incurs substantial costs to the Australian multimillion-dollar chickpea industry in both disease control and yield loss. The fungus was introduced to Australia in the 1970s from an unknown source population and, within a few decades, successfully established in all Australian agroecological chickpea-growing regions. Although genetically highly clonal, a broad range of phenotypic variation in terms of aggressiveness exists among the Australian A. rabiei isolates. More recently, highly aggressive isolates capable of causing severe disease symptoms on moderate to highly resistant chickpea cultivars have increased in frequency. To identify genetic loci potentially associated with A. rabiei aggressiveness on Australian chickpea cultivars, we performed deep genome sequencing of 230 isolates collected from a range of agroecological chickpea-growing regions between 2013 and 2020. Population genetic analyses using genome-wide SNP data identified three main clusters of genetically closely related isolates in Australia. Phylogenetic analyses showed that highly aggressive phenotypes developed multiple times independently throughout the phylogeny. The results point to a minor contribution of multiple genetic regions and most likely epigenomic variations to aggressiveness of A. rabiei isolates on Australian chickpea cultivars.

Dingoes are culturally and ecologically important free-living canids whose ancestors arrived in Australia over 3,000 B.P., likely transported by seafaring people. However, the early history of dingoes in Australia—including the number of founding populations and their routes of introduction—remains uncertain. This uncertainty arises partly from the complex and poorly understood relationship between modern dingoes and New Guinea singing dogs, and suspicions that post-Colonial hybridization has introduced recent domestic dog ancestry into the genomes of many wild dingo populations. In this study, we analyzed genome-wide data from nine ancient dingo specimens ranging in age from 400 to 2,746 y old, predating the introduction of domestic dogs to Australia by European colonists. We uncovered evidence that the continent-wide population structure observed in modern dingo populations had already emerged several thousand years ago. We also detected excess allele sharing between New Guinea singing dogs and ancient dingoes from coastal New South Wales (NSW) compared to ancient dingoes from southern Australia, irrespective of any post-Colonial hybrid ancestry in the genomes of modern individuals. Our results are consistent with several demographic scenarios, including a scenario where the ancestry of dingoes from the east coast of Australia results from at least two waves of migration from source populations with varying affinities to New Guinea singing dogs. We also contribute to the growing body of evidence that modern dingoes derive little genomic ancestry from post-Colonial hybridization with other domestic dog lineages, instead descending primarily from ancient canids introduced to Sahul thousands of years ago.

Inconsistency in flavour is one of the major challenges to the Australian papaya industry. However, objectively measurable standards of the compound profiles that provide preferable taste and aroma, together with consumer acceptability, have not been set. In this study, three red-flesh papayas (i.e., ‘RB1’, ‘RB4’, and ‘Skybury’) and two yellow-flesh papayas (i.e., ‘1B’ and ‘H13’) were presented to a trained sensory panel and a consumer panel to assess sensory profiles and liking. The papaya samples were also examined for sugar components, total soluble solids, and 14 selected volatile compounds. Additionally, the expression patterns of 10 genes related to sweetness and volatile metabolism were assessed. In general, red papaya varieties had higher sugar content and tasted sweeter than yellow varieties, while yellow varieties had higher concentrations of citrus floral aroma volatiles and higher aroma intensity. Higher concentrations of glucose, linalool oxide, and terpinolene were significantly associated with decreased consumer liking. Significant differences were observed in the expression profiles of all the genes assessed among the selected papaya varieties. Of these, cpGPT2 and cpBGLU31 were positively correlated to glucose production and were expressed significantly higher in ‘1B’ than in ‘RB1’ or ‘Skybury’. These findings will assist in the strategic selective breeding for papaya to better match consumer and, hence, market demand.