Sugarcane Cultivars Research Articles

A novel Leifsonia xyli subsp. xyli quantitative LAMP-based diagnostic correlated with sugarcane ratoon stunting disease rating

Context Ratoon stunting disease (RSD), caused by Leifsonia xyli subsp. xyli (Lxx), poses a significant economic threat to sugarcane (Saccharum hybrid) worldwide. RSD is hard to manage due to its elusive visible symptomology and disease rating of cultivars is subjective. Aims We aimed to develop a sensitive, rapid, and quantitative Lxx diagnostic method able to correlate Lxx titre and disease resistance rating of sugarcane cultivars. Methods A Lxx diagnostic method was developed using heat lysis-based reagent-free DNA isolation from xylem sap followed by loop-mediated isothermal amplification (LAMP)-based colorimetric and fluorescence quantification within a single microcentrifuge tube. Bacterial titre was then statistically correlated with industry-agreed disease resistance ratings for key sugarcane cultivars. Key results The diagnostic was highly sensitive (1 cell/μL) and reproducible (%s.d. = <5%, for n = 3), and showed excellent linear dynamic range (i.e. 10 pM−1 aM or 107−100 copies/μL, r = 0.99) for quantitative Lxx detection. LAMP quantifications were completely concordant with quantitative polymerase chain reaction quantification from the same samples. Additionally, a strong correlation was determined between the detected quantitative bacterial titres and known cultivar disease resistance ratings (r = 0.82, n = 10, P < 0.001). Conclusion The novel LAMP-based Lxx diagnostic was validated as a fast, simple, and relatively cost-effective means of RSD resistance rating, making it a reliable contribution towards RSD management. Implications The development of this diagnostic tool provides a practical solution for accurately measuring Lxx titre and assessing disease resistance in sugarcane plants, aiding in effective risk management of RSD spread, and mitigating its economic impact on sugarcane crops worldwide.

A SNP variation in the Sucrose synthase (SoSUS) gene associated with sugar-related traits in sugarcane.

Sugarcane (Saccharum spp.) is an economically significant crop for both the sugar and biofuel industries. Breeding sugarcane cultivars with high-performance agronomic traits is the most effective approach for meeting the rising demand for sugar and biofuels. Molecular markers associated with relevant agronomic traits could drastically reduce the time and resources required to develop new sugarcane varieties. Previous sugarcane candidate gene association analyses have found single nucleotide polymorphism (SNP) markers associated with sugar-related traits. This study aims to validate these associated SNP markers of six genes, including Lesion simulating disease 1 (LSD), Calreticulin (CALR), Sucrose synthase 1 (SUS1), DEAD-box ATP-dependent RNA helicase (RH), KANADI1 (KAN1), and Sodium/hydrogen exchanger 7 (NHX7), in a diverse population in 2-year and two-location evaluations. After genotyping of seven targeted SNP markers was performed by PCR Allelic Competitive Extension (PACE) SNP genotyping, the association with sugar-related traits and important cane yield component traits was determined on a set of 159 sugarcane genotypes. The marker-trait relationships were validated and identified by both t-test analysis and an association analysis based on the general linear model. The mSoSUS1_SNPCh10.T/C and mSoKAN1_SNPCh7.T/C markers that were designed from the SUS1 and KAN1 genes, respectively, showed significant associations with different amounts of sugar-related traits and yield components. The mSoSUS1_SNPCh10.T/C marker was found to have more significant association with sugar-related traits, including pol, CCS, brix, fiber and sugar yield, with p values of 6.08 × 10-6 to 4.35 × 10-2, as well as some cane yield component traits with p values of 1.61 × 10-4 to 3.35 × 10-2. The significant association is consistent across four environments. Sucrose synthase (SUS) is considered a crucial enzyme involved in sucrose metabolism. This marker is a high potential functional marker that may be used in sugarcane breeding programs to select superior sugarcane with good fiber and high sugar contents.

Cachaça production: from sugar cane to spirit

Why was the work done: Cachaça, the oldest distilled beverage in the Americas, has great historical and cultural significance. A review of cachaça production is important to preserve tradition, standardise industry processes, promote innovation and quality. This review offers a comprehensive overview of current knowledge and advancements in cachaça production, covering regulation, process control, product quality and future developments. What are the main findings: Thev production of Cachaça works within well defined regulations, with its production encompassing both field and industrial practice. The review focuses on sugar cane cultivation, fermentation, distillation, and ageing in wooden barrels. It underscores the significance of regional factors such as climate, soil, and sugar cane variety in shaping the sensory profile of cachaça. While a range of sugar cane cultivars have been developed and grown in different environments, further research on the adaptation of sugar cane crop is necessary. The fermentation of cachaça is spontaneous utilising the microbiota in the sugar cane juice. However, the use of wild sugar cane yeasts, complemented with commercial strains is increasingly used by producers. With regard to distillation, production of the spirit in copper still pots and ageing in tropical wood barrels remain prevalent in the industry. Why is the work important: This review contributes to ongoing efforts to enhance the quality of cachaça. Whilst the importance of traditional production methods is recognised, this review embraces advancements in technology coupled with insights to future perspectives.

Analysis of the endophytic microbiota of roots and culms of two commercial sugarcane cultivars inoculated with a synthetic microbial community

The adoption of bioinputs in agriculture has aroused great interest in recent years and, in this scenario, the inoculation of crops with synthetic microbial communities (SynComs) has shown to be promising. In sugarcane crop, inoculation with nitrogen-fixing bacteria (NFB) in consortium with arbuscular mycorrhizal fungi (AMF) has shown positive results on plant development and nutrition. However, considering that the microbiota plays a fundamental role in the growth and health of the host plant, especially the endophytes, which are closely associated, few studies have explored the effects of SynCom inoculation on the endophytic microbiota of sugarcane. This study aimed to evaluate the impact of SynCom inoculation on the structure of the endophytic microbiota of sugarcane. The results of the analyses revealed that the microbiota diversity remained unchanged due to the inoculation treatment, while differences in microbial communities were found between the two evaluated commercial cultivars, RB867515 and RB92579, and between the two plant organs, roots and culms, under field conditions at the end of the first crop growth cycle (~360 days). Furthermore, microbes specifically detected in roots or culms present potential valuable applications in sugarcane cultivation in the future. Altogether, our data support that the inoculated microorganisms exerted their beneficial effects during the initial stages of plant development, which opens up space for new research with SynComs in these primordial stages of cane cropping.

Comparison of Physiological, Anatomical, and Morphological Traits between Sugarcane Hybrids and Their Parents with Different Stalk Dry Weights in the Early Growth Stage under Hydroponic Conditions

The high stalk weight sugarcane cultivar has a special mechanism to obtain greater growth, which was inherited from its parents. Thus far, comparisons of the high stalk weight sugarcane cultivar growth with its parents and cultivars with a low stalk weight have never been reported. The purpose of this research was to reveal the growth mechanism of the high stalk dry weight cultivar KK3 by comparing its physiological, anatomical, and morphological traits to those of a low stalk dry weight cultivar (UT12) and their four parental cultivars under hydroponic conditions. Their growth characteristics were evaluated at 15-day intervals from 30 to 90 days after planting. The root traits were measured at 2 months after planting (MAP), whereas the anatomical and physiological parameters were collected at 3 MAP. Biomass was recorded at 1, 2, and 3 MAP. KK3 had similar anatomical root traits to its female parent, whereas it had similar aboveground morphological traits to its male parent. The comparison between UT12 and its parents revealed that almost all its root anatomical traits were similar to the female parent, but it did not differ in leaf anatomy and root system size. Some physiological traits of KK3 were not different from those of its parents. In contrast, the net photosynthesis rate (PN), height, tiller number, stem dry weight, and stomatal density of UT12 were lower than those of its parent. For KK3, its small root stele and vessel size and high root length, surface area, and volume supported water uptake. The increase in stomatal density and decreased stomatal pore length may be appropriate characteristics for reducing water loss in this drought-resistant cultivar. Furthermore, KK3 exhibited a high water use efficiency (WUE) to promote biomass accumulation and growth despite its low transpiration and photosynthesis rates. This basic knowledge will be useful for selecting the parents based on their characteristics to create new sugarcane cultivars with a high stalk dry weight for drought stress during the early-growth-stage breeding programs and predicting their performance.

Natural lignin modulators improve bagasse saccharification of sugarcane and energy cane in field trials

AbstractThe burgeoning cellulosic ethanol industry necessitates advancements in enzymatic saccharification, effective pretreatments for lignin removal, and the cultivation of crops more amenable to saccharification. Studies have demonstrated that natural inhibitors of lignin biosynthesis can enhance the saccharification of lignocellulose, even in tissues generated several months post‐treatment. In this study, we applied daidzin (a competitive inhibitor of coniferaldehyde dehydrogenase), piperonylic acid (a quasi‐irreversible inhibitor of cinnamate 4‐hydroxylase), and methylenedioxy cinnamic acid (a competitive inhibitor of 4‐coenzyme A ligase) to 60‐day‐old crops of two conventional Brazilian sugarcane cultivars and two energy cane clones, bred specifically for enhanced biomass production. The resultant biomasses were evaluated for lignin content and enzymatic saccharification efficiency without additional lignin‐removal pretreatments. The treatments amplified the production of fermentable sugars in both the sugarcane cultivars and energy cane clones. The most successful results softened the most recalcitrant lignocellulose to the level of the least recalcitrant of the biomasses tested. Interestingly, the softest material became even more susceptible to saccharification.

Lignocellulosic Composition Not Associated with Stem Borer Resistance in Select Louisiana Sugarcane Cultivars

The two most economically damaging insect pests of sugarcane in Louisiana are the sugarcane borer (SCB) and the newly invasive Mexican rice borer (MRB), both of which can be managed in part with cultivar resistance. High stalk fiber levels is a well-documented aspect of stem borer resistance but is inversely correlated with recoverable sugar levels. However, lignocellulosic components such as hemicellulose, cellulose, and lignin are associated with resistance to other borer species in poaceous crops, potentially indicating mechanisms that may provide resistance without substantial trade-offs in yield. The goal of this study was to determine whether lignocellulosic composition varied among four cultivars—HoCP 85-845, HoCP 04-838, Ho 07-613, and HoCP 00-950—selected based on known variation in SCB and MRB resistance and total fiber content. We estimated lignocellulosic composition as well as Brix throughout the growing season and the total stalk fiber and recoverable sugar content at harvest for both plant cane and first ratoon crop years. We found that the Brix content throughout the growing season, as well as total fiber and sugar content at harvest, were significantly associated with the cultivar, aligning with previously documented trends in borer resistance (i.e., higher Brix and lower total fiber indicate a more susceptible cultivar). While lignocellulosic composition during the growing season was not associated with cultivar or resistance to either borer species, it was significantly impacted by sampling month and crop year. These data indicate the potential influence of alternative resistance mechanisms and interactions with abiotic conditions.

Molecular Dissection of the 5S Ribosomal RNA-Intergenic Transcribed Spacers in Saccharum spp. and Tripidium spp.

Due to complex polyploid, sugarcane whole genome sequencing and characterization lag far behind other crops. PCR-based DNA markers are a viable low-cost option to evaluate genetic diversity and verify genotypes. In this study, the 5S ribosomal RNA-intergenic spacer (ITS) of 171 accessions of Saccharum spp. and Tripidium spp. was dissected, including 30 accessions of S. officinarum, 71 of S. spontaneum, 17 of S. robustum, 25 of S. barberi, 13 of S. sinense, 2 of S. edule, 5 sugarcane cultivars (Saccharum spp. hybrids), 6 of Tripidium spp. (formally Erianthus spp.), and 2 of unknown species. The ITS spacers were amplified from 10 ng of the leaf DNA of each accession with the universal PCR primers PI and PII. The PCR-amplified spacers (amplicons) were analyzed by both agarose gel and capillary electrophoresis (CE). While agarose gel electrophoresis revealed five banding patterns, a total of 42 polymorphic amplicons, ranging from 60 to 506 bp, were detected by CE. Three amplicons, 234-, 235-, and 236-bp in size, were amplified from all accessions of six Saccharum species, except for three S. robustum accessions (Molokai 5573, NG 57-054, and NG 77-235) that lacked the 236-bp amplicon. The 234-, 235-, 236-bp banding pattern found in S. spontaneum was less consistent than other Saccharum species, sometimes missing a few but not all the bands in this region. An amplicon of 61-bp was amplified only from the sugarcane hybrid varieties. The PI/PII patterns indicated diversity and subpopulations within Saccharum, which could potentially be used in Breeding. Moreover, all Saccharum-specific amplicons were mostly absent in Tripidium spp. accessions, which produced 405-bp and 406-bp amplicons, and any pattern of the exceptions indicated misidentification. The T. bengalense accession Kalimpong had a unique CE-banding pattern that was different from all other accessions. Although the clustering pattern of the 42 amplicons only discriminated at the genus level, these amplicons helped identify nine misclassified accessions. This study further demonstrates that these PI/PII amplicons could be particularly useful markers for breeders at sugarcane field stations to quickly confirm and discriminate among the accessions of germplasm collections.

All nonhomologous chromosomes and rearrangements in Saccharum officinarum × Saccharum spontaneum allopolyploids identified by oligo-based painting.

Modern sugarcane cultivars (Saccharum spp., 2n = 100~120) are complex polyploids primarily derived from interspecific hybridization between S. officinarum and S. spontaneum. Nobilization is the theory of utilizing wild germplasm in sugarcane breeding, and is the foundation for utilizing S. spontaneum for stress resistance. However, the exact chromosomal transmission remains elusive due to a lack of chromosome-specific markers. Here, we applied chromosome-specific oligonucleotide (oligo)-based probes for identifying chromosomes 1-10 of the F1 hybrids between S. officinarum and S. spontaneum. Then, S. spontaneum-specific repetitive DNA probes were used to distinguish S. spontaneum in these hybrids. This oligo- fluorescence in situ hybridization (FISH) system proved to be an efficient tool for revealing individual chromosomal inheritance during nobilization. We discovered the complete doubling of S. officinarum-derived chromosomes in most F1 hybrids. Notably, we also found defective S. officinarum-derived chromosome doubling in the F1 hybrid Yacheng75-4191, which exhibited 1.5n transmission for all nonhomologous chromosomes. Altogether, these results highlight the presence of variable chromosome transmission in nobilization between S. officinarum and S. spontaneum, including 1.5n + n and 2n + n. These findings provide robust chromosome markers for in-depth studies into the molecular mechanism underlying chromosome doubling during the nobilization, as well as tracing chromosomal inheritance for sugarcane breeding.

Soil and foliar Si fertilization alters elemental stoichiometry and increases yield of sugarcane cultivars

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L−1 in soil during planting; sodium silicate spray at 40 mmol L−1 on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha−1) in stalk yield, 9.0% (12 Mg ha−1) in total recoverable sugar, and 20% (4 Mg ha−1) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality.

Why different sugarcane cultivars show different resistant abilities to smut?

To elucidate the mechanisms underlying the resistance to smut of different sugarcane cultivars, endophytic bacterial and fungal compositions, functions and metabolites in the stems of the sugarcane cultivars were analyzed using high-throughput sequencing techniques and nontargeted metabolomics. The results showed that the levels of ethylene, salicylic acid and jasmonic acid in sugarcane varieties that were not sensitive to smut were all higher than those in sensitive sugarcane varieties. Moreover, endophytic fungi, such as Ramichloridium, Alternaria, Sarocladium, Epicoccum, and Exophiala species, could be considered antagonistic to sugarcane smut. Additionally, the highly active arginine and proline metabolism, pentose phosphate pathway, phenylpropanoid biosynthesis, and tyrosine metabolism in sugarcane varieties that were not sensitive to smut indicated that these pathways contribute to resistance to smut. All of the above results suggested that the relatively highly abundant antagonistic microbes and highly active metabolic functions of endophytes in non-smut-sensitive sugarcane cultivars were important for their relatively high resistance to smut.

Comparative expression analysis of sucrose phosphate synthase gene family in a low and high sucrose Pakistani sugarcane cultivars.

Sugarcane is the world's largest cultivated crop by biomass and is the main source of sugar and biofuel. Sucrose phosphate synthase (SPS) enzymes are directly involved in the synthesis of sucrose. Here, we analyzed and compared one of the important gene families involved in sucrose metabolism in a high and low sucrose sugarcane cultivar. A comprehensive in silico analysis of the SoSPS family displayed their phylogenetic relationship, gene and protein structure, miRNA targets, protein interaction network (PPI), gene ontology and collinearity. This was followed by a spatial expression analysis in two different sugarcane varieties. The phylogenetic reconstruction distributed AtSPS, ZmSPS, OsSPS, SoSPS and SbSPS into three main groups (A, B, C). The regulatory region of SoSPS genes carries ABRE, ARE, G-box, and MYC as the most dominant cis-regulatory elements. The PPI analysis predicted a total of 14 unique proteins interacting with SPS. The predominant expression of SPS in chloroplast clearly indicates that they are the most active in the organelle which is the hub of photosynthesis. Similarly, gene ontology attributed SPS to sucrose phosphate synthase and glucosyl transferase molecular functions, as well as sucrose biosynthetic and disaccharide biological processes. Overall, the expression of SPS in CPF252 (high sucrose variety) was higher in leaf and culm as compared to that of CPF 251 (low sucrose variety). In brief, this study adds to the present literature about sugarcane, sucrose metabolism and role of SPS in sucrose metabolism thereby opening up further avenues of research in crop improvement.

Response of Sugarcane Cultivars to Different Irrigation Regime under Peninsular Zone of Maharashtra, India

A field experiment was conducted during the years 2019-20, 2020-21 and 2021-22 suru seasons with eight sugarcane cultivars and two irrigation regimes were evaluated in the strip plot design with three replications. The impact of water stress on various morphological characters such as plant height, leaf area, leaf area index and tiller count was recorded at 0.3 and 1.0 IW/CPE irrigation regime. Drought treatment caused an average reduction of 11.10, 33.47, 29.08, 15.33, 22.14 and 18.78 % in plant height, leaf area index, specific leaf weight, dry matter, root dry matter at 200 DAP and cane yield respectively. Cultivar VSI 08005 and CoM 0265 transpired less water and showed relatively higher photosynthetic rate with significant improvement in growth attributes, viz., plant height, leaf area index, specific leaf weight, dry matter accumulation and root dry weight as well as single cane weight and cane yield. Yield and its parameters showed remarkable changes due to inadequate water availability during the formative phase. Water stress led to a reduction in cane and sugar yield to the tune of 23.00 and 29.05 percent.

Identification of ARF transcription factor gene family and its defense responses to bacterial infection and salicylic acid treatment in sugarcane.

Auxin response factor (ARF) is a critical regulator in the auxin signaling pathway, involved in a variety of plant biological processes. Here, gene members of 24 SpapARFs and 39 SpnpARFs were identified in two genomes of Saccharum spontaneum clones AP85-441 and Np-X, respectively. Phylogenetic analysis showed that all ARF genes were clustered into four clades, which is identical to those ARF genes in maize (Zea mays) and sorghum (Sorghum bicolor). The gene structure and domain composition of this ARF family are conserved to a large degree across plant species. The SpapARF and SpnpARF genes were unevenly distributed on chromosomes 1-8 and 1-10 in the two genomes of AP85-441 and Np-X, respectively. Segmental duplication events may also contribute to this gene family expansion in S. spontaneum. The post-transcriptional regulation of ARF genes likely involves sugarcane against various stressors through a miRNA-medicated pathway. Expression levels of six representative ShARF genes were analyzed by qRT-PCR assays on two sugarcane cultivars [LCP85-384 (resistant to leaf scald) and ROC20 (susceptible to leaf scald)] triggered by Acidovorax avenae subsp. avenae (Aaa) and Xanthomonas albilineans (Xa) infections and salicylic acid (SA) treatment. ShARF04 functioned as a positive regulator under Xa and Aaa stress, whereas it was a negative regulator under SA treatment. ShARF07/17 genes played positive roles against both pathogenic bacteria and SA stresses. Additionally, ShARF22 was negatively modulated by Xa and Aaa stimuli in both cultivars, particularly LCP85-384. These findings imply that sugarcane ARFs exhibit functional redundancy and divergence against stressful conditions. This work lays the foundation for further research on ARF gene functions in sugarcane against diverse environmental stressors.

Survival of five diazotrophic bacterial strains in different substrates used in sugarcane seedling propagation.

An inoculant containing selected bacterial strains can be easily applied during the nursery please process, but in this case, substrate composition can affect its survival and, in consequence, bacterial colonization. The aim of this study was to evaluate the survival of five diazotrophic bacterial strains/species applied individually on 13 different substrates used in sugarcane seedling nurseries considering an active population higher than 105 cells g-1. In addition, one experiment was performed using two commercial substrates, coconut fiber, and Multiplant™, inoculated or not with a mixture of five bacterial strains to evaluate plant growth after 30days. These strains are combined inoculants selected for sugarcane acting as plant growth promoters. Bacterial counts were determined every seven days using the Most Probable Number technique with four different semi-solid N-free media specific for each strain tested over 35days. The survival order, independent of the substrate tested, was: Paraburkholderia tropica Pt-PPe8T > Nitrospirillum amazonense Na-CBAMc > Herbaspirillum seropedicae Hs-HRC54 = H. rubrisubalbicans Hr-HCC103 > Gluconacetobacter diazotrophicus Gd-PAL5T. All tested substrates influenced the bacterial survival, especially after 21days of incubation. The population size can be partially controlled by the substrate pH and stimulated by the addition of slow-release fertilizer. Besides the differences in the bacterial population present in the two commercial substrates, plant growth was found to be stimulated by the inoculated bacteria, depending on the substrate and its sugarcane cultivar tested. The selection of a substrate used to produce new plantlets of sugarcane can contribute to bacterial survival and improve bacterial colonization.

Yellow Leaf Disease Resistance and Melanaphis sacchari Preference in Commercial Sugarcane Cultivars.

Sugarcane yellow leaf disease (YLD) caused by sugarcane yellow leaf virus (ScYLV) is a major threat for the sugarcane industry worldwide, and the aphid Melanaphis sacchari is its main vector. Breeding programs in Brazil have provided cultivars with intermediate resistance to ScYLV, whereas the incidence of ScYLV has been underestimated partly due to the complexity of YLD symptom expression and identification. Here, we evaluated YLD symptoms in a field assay using eight sugarcane genotypes comprising six well-established commercial high-sucrose cultivars, one biomass yield cultivar, and a susceptible reference under greenhouse conditions, along with estimation of virus titer through RT-qPCR from leaf samples. Additionally, a free-choice bioassay was used to determine the number of aphids feeding on the SCYLV-infected cultivars. Most of the cultivars showed some degree of resistance to YLD, while also revealing positive RT-qPCR results for ScYLV and virus titers with non-significant correlation with YLD severity. The cultivars IACSP01-5503 and IACBIO-266 were similar in terms of aphid preference and ScYLV resistance traits, whereas the least preferred cultivar by M. sacchari, IACSP96-7569, showed intermediate symptoms but similar virus titer to the susceptible reference, SP71-6163. We conclude that current genetic resistance incorporated into sugarcane commercial cultivars does not effectively prevent the spread of ScYLV by its main aphid vector.

Advancing cane-quality management in the South African smallholder-farmer sector through participatory on-farm demonstration and knowledge exchange

Cane-quality management involving chemical ripening is an important component of profitable sugarcane production by large-scale commercial farmers in South Africa. For smallholder farmers (SHFs), however, sugarcane field size and adjacent alternative land-uses render conventional aerial crop-spraying methods unsuitable. The recent availability of spraying drones has created opportunities for chemical ripening to be introduced to the smallholder farmer sector. A network of demonstration trials based on strong partnerships of researchers, extension specialists and smallholder farmers, and participation by various industry stakeholders was established in 11 smallholder farmer regions. Knowledge exchange in each region involved an initial stakeholder engagement workshop, a series of practical field days during the execution of the trial, and post-trial information sharing events. The initial workshops were aimed at creating project awareness, defining the relative advantage that ripening with drones could deliver, identifying negative perceptions and potential barriers that might hinder adoption, and reaching consensus on trial methodology. Field days were focused on demonstrating the processes of maturity assessment to establish the need for chemical ripening and applying a ripener with a drone to parts of the fields. At the same time, control portions were left untreated, and assessing the efficacy of ripening benefits and harvest readiness. These demonstrations illustrated the judicious use of agrochemicals by only spraying fields suited to ripening. In-field estimates of cane yield and cane quality in the ripened and control treatments shortly before harvest, and in some cases, field production data from the sugar factories, revealed a range of improvements in recoverable crystal (ERC) due to ripening that was influenced by location and sugarcane cultivar. Although the SHFs expressed genuine interest in chemically ripening their crops with spraying drones, industry challenges will need to be addressed prior to wider adoption.

A Large-Scale Candidate-Gene Association Mapping for Drought Tolerance and Agronomic Traits in Sugarcane.

Dissection of the genetic loci controlling drought tolerance traits with a complex genetic inheritance is important for drought-tolerant sugarcane improvement. In this study, we conducted a large-scale candidate gene association study of 649 candidate genes in a sugarcane diversity panel to identify genetic variants underlying agronomic traits and drought tolerance indices evaluated in plant cane and ratoon cane under water-stressed (WS) and non-stressed (NS) environments. We identified 197 significant marker-trait associations (MTAs) in 141 candidate genes associated with 18 evaluated traits with the Bonferroni correction threshold (α = 0.05). Out of the total, 95 MTAs in 78 candidate genes and 62 MTAs in 58 candidate genes were detected under NS and WS conditions, respectively. Most MTAs were found only in specific water regimes and crop seasons. These MTAs explained 7.93-30.52% of phenotypic variation. Association mapping results revealed that 34, 59, and 104 MTAs involved physiological and molecular adaptation, phytohormone metabolism, and drought-inducible genes. They identified 19 pleiotropic genes associated with more than one trait and many genes related to drought tolerance indices. The genetic and genomic resources identified in this study will enable the combining of yield-related traits and sugar-related traits with agronomic value to optimize the yield of sugarcane cultivars grown under drought-stressed and non-stressed environments.

Transgenic sugarcane with higher levels of BRK1 showed improved drought tolerance.

Transgenic sugarcane overexpressing BRK1 showed improved tolerance to drought stress through modulation of actin polymerization and formation of interlocking marginal lobes in epidermal leaf cells, a typical feature associated with BRK1 expression under drought stress. BRICK1 (BRK1) genes promote leaf epidermal cell morphogenesis and division in plants that involves local actin polymerization. Although the changes in actin filament organization during drought have been reported, the role of BRK in stress tolerance remains unknown. In our previous work, the drought-tolerant Erianthus arundinaceus exhibited high levels of the BRK gene expression under drought stress. Therefore, in the present study, the drought-responsive gene, BRK1 from Saccharum spontaneum, was transformed into sugarcane to test if it conferred drought tolerance in the commercial sugarcane cultivar Co 86032. The transgenic lines were subjected to drought stress, and analyzed using physiological parameters for drought stress. The drought-induced BRK1-overexpressing lines of sugarcane exhibited significantly higher transgene expression compared with the wild-type control and also showed improved physiological parameters. In addition, the formation of interlocking marginal lobes in the epidermal leaf cells, a typical feature associated with BRK1 expression, was observed in all transgenic BRK1 lines during drought stress. This is the first report to suggest that BRK1 plays a role in sugarcane acclimation to drought stress and may prove to be a potential candidate in genetic engineering of plants for enhanced biomass production under drought stress conditions.

Meiotic abnormalities in sugarcane (Saccharum spp.) and parental species: Evidence for peri‐ and paracentric inversions

AbstractThe modern cultivars of sugarcane (Saccharum spp.) are highly polyploid and accumulate aneuploidies due to their history of domestication, genetic improvement and interspecific hybrid origin involving the domesticated sweet species Saccharum officinarum (‘noble cane’) and the wild Saccharum spontaneum, both with an evolutionary history of polyploidy. The first hybrids were backcrossed with S. officinarum, and selection from progenies in subsequent generations established the genetic basis of modern cultivars. Saccharum genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture and cytogenetics. Herein, we conducted a comparative analysis of the meiotic behaviour of representatives of the parentals S. officinarum and S. spontaneum, and the commercial variety, SP80‐3280. S. officinarum, an octoploid species, exhibited regular meiotic behaviour. In contrast, S. spontaneum and SP80‐3280 exhibited several abnormalities from metaphase I to the end of division. We reported and typified, for the first time, the occurrence of peri‐ and paracentric inversions. Using in‐situ hybridisation techniques, we were able to determine how pairing association occurred at diakinesis, the origin of lagging chromosomes and, in particular, the mitotic chromosome composition of SP80‐3280. Interestingly, S. spontaneum and recombinant chromosomes showed the most marked tendency to produce laggards in both divisions. Future attempts to advance knowledge on sugarcane genetics and genomics should take meiotic chromosome behaviour information into account.