Parasitic nematodes of sugarcane - a major productivity impediment and grand challenges in management.

Sugarcane is an important cash crop grown in 137 countries, accounting for 80% of global sugar production. It supports the livelihood of over 100 million people and up to 25% of the rural population in some countries. Plant parasitic nematodes are one significant constraint in sugarcane production and can lead to a loss of up to 30% in productivity. Over 300 species of parasitic nematodes have been discovered in sugarcane soil. Due to limited data, potential damage to sugarcane crops caused by parasitic nematodes is often underestimated. The main nematodes present in sugarcane fields are root-lesion (Pratylenchus spp), spiral (Helicotylenchus spp), root-knot (Meloidogyne spp), dagger (Xiphenema spp), stunt (Tylenchorhynchus spp.), ring (Criconemella spp.) and stubby (Paratichodorus spp). Among these, Meloidogyne javanica and Pratylenchus zeae are the most damaging nematode species. Management of nematodes is a challenging task as there are no clear symptoms of their presence, and they often come in multiple species with varying levels of pathogenicity. Moreover, the management options available are not always effective. Integrated nematode management (IMN) is a sustainable strategy for controlling nematode infestations. It involves utilizing all possible methods to suppress the parasitic nematode population in a compatible manner and reduce it below economic threshold levels. This article focuses on the challenges of managing nematodes in sugarcane and highlights the opportunity for implementing a sustainable nematode management strategy.

Ratoon Stunting Disease of Sugarcane: A Review Emphasizing Detection Strategies and Challenges.

Sugarcane (Saccharum hybrid) is an important cash crop grown in tropical and subtropical countries. Ratoon stunting disease (RSD), caused by a xylem-inhabiting bacterium, Leifsonia xyli subsp. xyli (Lxx) is one of the most economically significant diseases globally. RSD results in severe yield losses because its highly contagious nature and lack of visually identifiable symptoms make it harder to devise an effective management strategy. The efficacy of current management practices is hindered by implementation difficulties caused by lack of resources, high cost, and difficulties in monitoring. Rapid detection of the causal pathogen in vegetative planting material is crucial for sugarcane growers to manage this disease. Several microscopic, serological, and molecular-based methods have been developed and used for detecting the RSD pathogen. Although these methods have been used across the sugarcane industry worldwide to diagnose Lxx, some lack reliability or specificity, are expensive and time-consuming to apply, and most of all, are not suitable for on-farm diagnosis. In recent decades, there has been significant progress in the development of integrated isothermal amplification-based microdevices for accurate human and plant pathogen detection. There is a significant opportunity to develop a novel diagnostic method that integrates nanobiosensing with isothermal amplification within a microdevice format for accurate Lxx detection. In this review, we summarize (i) the historical background and current knowledge of sugarcane ratoon stunting disease, including some aspects related to transmission, pathosystem, and management practices; and (ii) the drawbacks of current diagnostic methods and the potential for application of advanced diagnostics to improve disease management.

Maximising Affordability of Real-Time Colorimetric LAMP Assays.

Molecular diagnostics have become indispensable in healthcare, agriculture, and environmental monitoring. This diagnostic form can offer rapid and precise identification of pathogens and biomarkers. However, traditional laboratory-based molecular testing methods can be expensive and require specialised training, limiting their accessibility in resource-limited settings and on-site applications. To overcome these challenges, this study proposes an innovative approach to reducing costs and complexity in portable colorimetric loop-mediated isothermal amplification (LAMP) devices. The research evaluates different resistive heating systems to create an energy-efficient, cost-effective, and compact device to heat a polydimethylsiloxane (PDMS) block for precise temperature control during LAMP reactions. By combining this novel heating system with an off-the-shelf red-green-blue (RGB) sensor to detect and quantify colour changes, the integrated system can accurately detect Leifsonia xyli subsp. xyli, the bacteria responsible for ratoon stunting disease (RSD) in sugarcane. The experimental validation of this system demonstrates its ability to detect the target pathogen in real time, making it an important development for low cost, portable, and easy-to-use molecular diagnostics in healthcare, agriculture, and environmental monitoring applications.

Simple solution to preserve plant samples for microbiome analyses.

Culture-independent survey techniques are fundamental tools when assessing plant microbiomes. These methods rely on DNA that is carefully preserved after collecting samples to achieve meaningful results. Immediately freezing samples to -80°C after collection is considered one of the most robust methods for preserving samples before DNA extraction but is often impractical. Preservation solutions can solve this problem, but commercially available products are expensive, and there is limited data comparing their efficacy with other preservation methods. In this study, we compared the impact of three methods of sample preservation on plant microbiome surveys: (1) RNAlater, a proprietary preservative, (2) a home-made salt-saturated dimethyl sulphoxide preservation solution (DESS), and (3) freezing at -80°C. DESS-preserved samples, stored at room temperature for up to four weeks, did not show any significant differences to samples frozen at -80°C, while RNAlater inflated bacterial alpha diversity. Preservation treatments did not distinctively influence fungal alpha diversity. Our results demonstrate that DESS is a versatile and inexpensive preservative of DNA in plant material for diversity analyses of fungi and bacteria.

Sugarcane Smut, Caused by Sporisorium scitamineum, a Major Disease of Sugarcane: A Contemporary Review.

Sugarcane smut caused by the fungus Sporisorium scitamineum is one of the major diseases of sugarcane worldwide, causing significant losses in productivity and profitability of this perennial crop. Teliospores of this fungus are airborne, can travel long distances, and remain viable in hot and dry conditions for >6 months. The disease is easily recognized by its long whiplike sorus produced on the apex or side shoots of sugarcane stalks. Each sorus can release ≤100 million teliospores in a day; the spores are small (≤7.5 µ) and light and can survive in harsh environmental conditions. The airborne teliospores are the primary mode of smut spread around the world and across cane-growing regions. The most effective method of managing this disease is via resistant varieties. Because of the complex genomic makeup of sugarcane, selection for resistant traits is difficult in sugarcane breeding programs. In recent times, the application of molecular markers as a rapid tool of discarding susceptible genotypes early in the selection program has been investigated. Large effect resistance loci have been identified and have the potential to be used for marker-assisted selection to increase the frequency of resistant breeding lines in breeding programs. Recent developments in omics technologies (genomics, transcriptomics, proteomics, and metabolomics) have contributed to our understanding and provided insights into the mechanism of resistance and susceptibility. This knowledge will further our understanding of smut and its interactions with sugarcane genotypes and aid in the development of durable resistant varieties.

Saccharum spontaneum, a Novel Source of Resistance to Root-Lesion and Root-Knot Nematodes in Sugarcane.

Root-lesion nematode (Pratylenchus zeae) and root-knot nematode (Meloidogyne javanica) are two important pathogens of sugarcane (Saccharum hybrid). No commercial cultivars are resistant to these nematodes in Australia. Twenty accession lines of S. spontaneum, a wild relative of sugarcane, were tested against these two nematode species. S. spontaneum lines were tested twice for resistance to root-lesion nematode and three times for root-knot nematode. Reproduction (final population/starting population) of root-lesion nematodes was significantly lower in 17 of the 20 S. spontaneum accession lines tested in two experiments compared with two commercial cultivars. Four S. spontaneum lines supported a significantly lower number of root-lesion nematodes per gram of root than that of two commercial sugarcane cultivars. Reproduction of root-knot nematodes was significantly lower in 16 S. spontaneum lines compared with two commercial cultivars. Fourteen of the S. spontaneum lines tested supported significantly fewer eggs per gram of root compared with two commercial cultivars. This study showed that S. spontaneum lines possessed resistance for root-lesion and root-knot nematodes. Targeted crossing with commercial hybrid parental lines should be conducted to introduce nematode resistance into sugarcane cultivars for the Australian sugar industry.

Analysis of the resistance mechanisms in sugarcane during Sporisorium scitamineum infection using RNA-seq and microscopy.

Smut caused by biotrophic fungus Sporisorium scitamineum is a major disease of cultivated sugarcane that can cause considerable yield losses. It has been suggested in literature that there are at least two types of resistance mechanisms in sugarcane plants: an external resistance, due to chemical or physical barriers in the sugarcane bud, and an internal resistance governed by the interaction of plant and fungus within the plant tissue. Detailed molecular studies interrogating these two different resistance mechanisms in sugarcane are scarce. Here, we use light microscopy and global expression profiling with RNA-seq to investigate these mechanisms in sugarcane cultivar CP74-2005, a cultivar that possibly possesses both internal and external defence mechanisms. A total of 861 differentially expressed genes (DEGs) were identified in a comparison between infected and non-infected buds at 48 hours post-inoculation (hpi), with 457 (53%) genes successfully annotated using BLAST2GO software. This includes genes involved in the phenylpropanoid pathway, cell wall biosynthesis, plant hormone signal transduction and disease resistance genes. Finally, the expression of 13 DEGs with putative roles in S. scitamineum resistance were confirmed by quantitative real-time reverse transcription PCR (qRT-PCR) analysis, and the results were consistent with the RNA-seq data. These results highlight that the early sugarcane response to S. scitamineum infection is complex and many of the disease response genes are attenuated in sugarcane cultivar CP74-2005, while others, like genes involved in the phenylpropanoid pathway, are induced. This may point to the role of the different disease resistance mechanisms that operate in cultivars such as CP74-2005, whereby the early response is dominated by external mechanisms and then as the infection progresses, the internal mechanisms are switched on. Identification of genes underlying resistance in sugarcane will increase our knowledge of the sugarcane-S. scitamineum interaction and facilitate the introgression of new resistance genes into commercial sugarcane cultivars.

Urinary bladder paraganglioma presenting as micturition-induced palpitations, dyspnea, and angina.

BACKGROUND: Sympathetic urinary bladder paragangliomas are rare catecholamine-secreting neuroendocrine tumors arising from neural crest cells. They are uncommon urinary bladder neoplasms. Symptoms classically include micturition-related or unrelated palpitations and syncope with hypertension, headaches, diaphoresis, and hematuria. Other than being attributable to vasovagal reactions, micturition-induced cardiovascular symptoms should prompt a search for catecholamine-secreting tumors such as a urinary bladder paraganglioma, as in this case. CASE REPORT: A 45-year-old asthmatic African-American female presented with episodic hematuria that began 4 years ago and episodes of micturition-induced palpitations, dyspnea, substernal tightness, sweating, and throbbing headaches. Computed tomography with contrast revealed an enhancing mass along the anterior urinary bladder wall, measuring 2.4×3.5 cm. On Positron emission Tomography with [18F] fluorodeoxyglucose integrated with computed tomography (18F-FDG PET/CT), the urinary bladder mass was 18F-FDG avid. Serum normetanephrine and supine plasma norepinephrine were significantly elevated and there was mild elevation of supine plasma epinephrine. Transurethral resection of the bladder mass revealed a neoplasm with microscopic features and immunohistochemical profile positive for synaptophysin and chromogranin, with negative screening cytokeratin AE1/AE3, suggesting a paraganglioma. Following resection of the paraganglioma, there was complete resolution of micturition-induced cardiovascular symptoms on long-term follow-up. CONCLUSIONS: Micturition-related cardiovascular symptoms are commonly attributed to vasovagal reactions. However, urinary bladder pathologies must be ruled out as a cause, as in this rare case of a urinary bladder paraganglioma exhibiting catecholaminergic symptoms.

New Method of Controlling Sugarcane Smut using Flutriafol Fungicide.

Sugarcane smut, caused by Sporisorium scitamineum, is one of the most devastating diseases of sugarcane worldwide. Triazole fungicides such as propiconazole and triadimefon have been routinely used as dip treatments to protect seed-cane (stalk cuttings) from infection by sugarcane smut fungus. However, dip treatments can be applied only to mother stock (nursery) planting materials because of the logistics of dipping large quantities of seed-cane and it is difficult to dispose of the large volumes of waste fungicide solution in an environmentally safe manner. There was a need for a new fungicide that can be applied using more practical methods. The efficacy of flutriafol fungicide to control smut was evaluated in inoculated and infected stalks of a highly susceptible cultivar using various application methods. In a 2007 experiment, flutriafol fungicide was equally effective or better in controlling sugarcane smut as a dip than were two fungicides, propiconazole and triadimefon, registered in Australia. In 2009, two experiments determined the effectiveness of flutriafol when applied by mixing with fertilizer or spraying on the seed-cane at planting. All fungicide treatments significantly suppressed smut in one experiment but, in the second experiment, flutriafol-fertilizer mix treatments were ineffective. In 2010, two experiments verified the efficacy and effective rates of flutriafol against sugarcane smut when applied through existing spray equipment designed to spray fungicide on cuttings as they drop into the planting furrow on a commercial planter. Area under the disease progress curve values of smut incidence were reduced significantly to 47 and 56% with low (125 g a.i. ha-1) and high (375 g a.i. ha-1) application rates, respectively, in both experimental sites compared with the inoculated control plots. Sugar yield increased by 46 to 65% in one experiment and 157 to 203% in the second experiment compared with the inoculated control. This research formulated a more practical method of application of flutriafol and suggests greater applications of this fungicide for the management of sugarcane smut.

Pathogenic Variation in Spore Populations of Sporisorium scitamineum, Causal Agent of Sugarcane Smut in Australia.

An incursion of sugarcane smut in Queensland was identified in 2006 in Bundaberg, Ingham, and Mackay. In 2008, two cultivars, 'Q205' and 'Q170', were highly susceptible in Bundaberg but remained disease free on a heavily infested farm in Mackay. A glasshouse experiment was established to determine whether the differences in disease expression were due to the sources of the two cultivars sourced from Bundaberg and Mackay in 2009. These were inoculated with the Mackay population of Sporisorium scitamineum spores. These cultivars had the same levels of disease, indicating that the variation in the clonal source of the cultivars was not responsible for the observed differences. A second glasshouse experiment in 2013 confirmed that highly susceptible Q205 and Q170 were resistant to the Mackay population of S. scitamineum but remained susceptible to the Bundaberg population. In 2010, S. scitamineum populations of smut fungi from Mackay and Bundaberg were compared in a field trial and the Mackay population had significantly less disease than the Bundaberg population on four cultivars (Q170, Q205, 'Q174', and 'Q138') but had significantly more disease in 'Q188'. These results confirmed the field observations and suggested that there was a differential response among the cultivars for the smut fungi collected from Mackay compared with Bundaberg and are genetically different. This finding suggests that a mixture of spores should be used to inoculate sugarcane clones for resistance screening.