Department of Agriculture and Fisheries (Queensland)

Mango (Mangifera indica L.) is a globally significant tropical fruit crop, widely cultivated across South and Southeast Asia, with Pakistan recognized as a major center of production and varietal diversity. However, the genetic potential of mango in Pakistan remains underutilized due to limited morphological characterization of its diverse germplasm. This study assessed the morphological diversity of 89 Mangifera indica L. genotypes at the Mango Research Station (MRS), Shujabad, Pakistan. The germplasm included indigenous varieties, hybrids, and exotic genotypes originated from diverse eco-geographical regions. A total of 43 qualitative and 14 quantitative traits related to tree, leaf, inflorescence, fruit, and stone were recorded and analyzed. The Shannon-Weaver diversity index indicated high variability in traits such as canopy shape, young leaf color, fruit shape, blush color (ripe and unripe), and stone fiber texture. Quantitative traits including fruit weight, stone weight, tree height, and trunk diameter exhibited high diversity with a coefficient of variation exceeding 35%. Significant differences were observed among genotypes for all the quantitative traits. Some of the promising genotypes were identified for commercial cultivation and breeding initiatives. Correlation analysis helped to identify associations among key traits, facilitating the selection of superior germplasm for breeding. Principal component analysis revealed four principal components for quantitative traits and seventeen for qualitative traits, each with eigenvalues greater than 1, contributed over 75% of the total variation. Cluster analysis grouped genotypes into five clusters based on quantitative traits and six clusters based on qualitative traits, reflecting both geographical origin and morphological similarities. This study highlights the rich phenotypic diversity of a large collection of mango germplasm in Pakistan and provides valuable insights for its conservation, genetic improvement, and sustainable utilization in future mango breeding programs in the region.

Disease outbreaks in commercial larval rearing systems of the tropical rock lobster (Panulirus ornatus) pose significant challenges to the culture of this species. This study investigates bacterial succession during outbreaks of white leg disease (WLD), the latter associated with infections by Aquimarina spp. in early-stage P. ornatus phyllosoma. Bacteriome profiling was conducted to assess changes in bacterial composition and identify potential sources of pathogenic taxa. Transmission electron microscopy was used to depict ultrastructural changes in the pereiopods of diseased specimens. Oxford Nanopore 16S rRNA gene sequencing was used to profile bacterial diversity and community structure across larval development (0–16 days post-hatch, dph), revealing temporal shifts coinciding with the onset of disease. A marked decline in alpha diversity between 8 and 16 dph was observed concomitant with an increase in diseased animals. During this period, the pathogenic genus Aquimarina became dominant, replacing early taxa such as Vibrio, Ruegeria, Shimia, and Phaeobacter, and concurring with massive coagulative necrosis and the subsequent formation of ellipsoid, electron-dense, proteinaceous bodies in pereiopod tissues. Beta diversity analysis further revealed significant shifts in community structure, implying that bacterial dysbiosis may be an early indicator of WLD development. The findings suggest that disease results from a combination of bacterial maternal or environmental transmission, environmental acquisition, and bacteria-bacteria interactions. The study highlights the importance of maintaining bacterial balance to support a healthy aquaculture system for larval lobsters, suggesting that early bacterial disruption can facilitate disease emergence. • The temporal bacterial shift in Panulirus ornatus coincided with white leg disease onset. • Aquimarina dominated larvae at 16 dph, replacing early pioneer taxa. • TEM showed necrosis and electron-dense bodies in diseased pereiopods. • Infection pathways involved maternal and environmental sources. • Bacterial interactions play an important role in pathogenesis.

Invasive ants are some of the most important environmental and economic pests globally, with granular corn-grit based baits being a common method of control. One of the limitations of these baits is their perceived ineffectiveness after rainfall or heavy dew, with control programs frequently suspending treatment due to these conditions. Empirical research to support or refute these restrictions, however, is lacking, and has not delineated the effects of water on the attractiveness of baits to ants and the effectiveness of baits in controlling colony activity. Here, we compare the number of ants interacting with baits (attractiveness) and the activity levels of colonies after baiting (efficacy) across wet and dry baits in the field, using S. invicta colonies in Queensland, Australia. Dry baits were removed by ants at a greater rate than wet baits, but more ants were observed interacting with wet than with dry baits. Dry baits outperformed control baits (with no active ingredient), but not wet baits, in supressing colony activity. These results suggest that the complete suspension of baiting during wet conditions may place unnecessary restrictions on management.

This study investigated the epidemiology and incidence of citrus Huanglongbing (HLB) disease in citron (Citrus medica L.) under varying field conditions. This research specifically aimed to quantify disease severity, assess populations of the primary vector, the Asian citrus psyllid (Diaphorina citri), and identify potential alternative host plants sustaining the vector and the pathogen. Field surveys were executed across three sites characterised by distinct elevations and management practices. Site-level soil nutrient profiles exhibited moderate acidity (pH 4.67-5.74) and significant differences in organic matter and nitrogen. These findings suggest that localised deficiencies in calcium and boron may exacerbate disease severity, contributing to the varied epidemiological patterns observed across sites. Analysis revealed that both HLB disease severity and D. citri population density were significantly influenced by altitude, field condition, and orchard management. The low-elevation site (860 m above sea level (ASL)), characterised by poor maintenance, exhibited the highest mean psyllid populations (averaging 13 individuals per sticky trap per day) and the most severe disease symptoms. Conversely, the high-elevation site (1674 m ASL) displayed significantly lower infection rates and healthier tree conditions. Symptomatic citron trees across all sites consistently exhibited characteristic HLB foliar and fruit symptoms (blotchy mottle and lopsided fruits). Quantitative Polymerase Chain Reaction (qPCR) successfully detected the causal agent, Candidatus Liberibacter asiaticus (CLas), in symptomatic citron samples from all locations, with the highest relative fold-change (2-Delta Delta Ct = 4628.24). Crucially, multiple developmental stages of D. citri were observed infesting the common weed Bidens pilosa. Furthermore, qPCR confirmed the presence of CLas DNA within the B. pilosa tissue itself (2-Delta Delta Ct = 210.84). This finding constitutes the first field-based evidence that B. pilosa can serve as a novel alternative host that supports both the D. citri vector and the CLas pathogen. These results establish citron as a highly susceptible host and identify B. pilosa as a new, critical epidemiological link in the HLB transmission cycle, thereby underscoring the necessity for integrated, landscape-level disease management strategies.

Citrus Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), is the most destructive citrus disease worldwide, characterised by phloem occlusion via callose (β-1,3-glucan) deposition and subsequent pathological starch accumulation. This study investigated genotype-specific metabolic shifts in Citrus medica L. (Citron), C. reticulata cv. Fremont (Fremont mandarin), and C. reticulata cv. Sai-Nam-Phueng (Tangerine) under asymptomatic and symptomatic HLB conditions and evaluated the potential of enzymatic hydrolysis to mitigate polysaccharide accumulation. Multi-platform metabolomics (LC-MS, GC-MS, and ¹H-NMR) combined with glycoarray profiling revealed that CLas infection triggers comprehensive biochemical restructuring. While symptomatic tissues universally exhibited high bacterial load and genotype-dependent antioxidant responses, metabolic reprogramming was genotype-dependent. Citron displayed the most profound disruption, characterised by the depletion of signalling lipids (α-linolenic acid) and defence-related coumarins, alongside the retention of osmoprotectants (Proline betaine). Conversely, Fremont mandarin exhibited a highly stable metabolic profile, while Sai-Nam-Phueng showed significant callose accumulation and flavonoid induction. A conserved stress-response volatile marker was identified across all infected genotypes at GC-MS retention time 56.39min (Rtx-5ms capillary column, 30m × 0.25mm ID, 0.25µm). Glycoarray analysis indicated the dominance of β-1,3-glucans in symptomatic tissues, which correlated with the formation of massive starch aggregates (300–500 μm) visualised by scanning electron microscopy. Crucially, ex vivo application of commercial α-amylase partially hydrolysed up to 10% of these starch deposits under ex vivo conditions. These findings elucidate distinct tolerance mechanisms involving lipid signalling turnover and osmotic regulation and suggest that while amylase specifically targets starch rather than callose, reducing this secondary starch accumulation represents a preliminary proof-of-concept that warrants further in vivo investigation before therapeutic claims can be substantiated.