Molecular markers associated with relevant agronomic traits could significantly reduce the time and cost involved in developing new sugarcane varieties. Previous sugarcane genome-wide association analyses (GWAS) have found few molecular markers associated with relevant traits at plant-cane stage. The aim of this study was to establish an appropriate GWAS to find molecular markers associated with yield related traits consistent across harvesting seasons in a breeding population. Sugarcane clones were genotyped with DArT (Diversity Array Technology) and TRAP (Target Region Amplified Polymorphism) markers, and evaluated for cane yield (CY) and sugar content (SC) at two locations during three successive crop cycles. GWAS mapping was applied within a novel mixed-model framework accounting for population structure with Principal Component Analysis scores as random component. A total of 43 markers significantly associated with CY in plant-cane, 42 in first ratoon, and 41 in second ratoon were detected. Out of these markers, 20 were associated with CY in 2 years. Additionally, 38 significant associations for SC were detected in plant-cane, 34 in first ratoon, and 47 in second ratoon. For SC, one marker-trait association was found significant for the 3 years of the study, while twelve markers presented association for 2 years. In the multi-QTL model several markers with large allelic substitution effect were found. Sequences of four DArT markers showed high similitude and e-value with coding sequences of Sorghum bicolor, confirming the high gene microlinearity between sorghum and sugarcane. In contrast with other sugarcane GWAS studies reported earlier, the novel methodology to analyze multi-QTLs through successive crop cycles used in the present study allowed us to find several markers associated with relevant traits. Combining existing phenotypic trial data and genotypic DArT and TRAP marker characterizations within a GWAS approach including population structure as random covariates may prove to be highly successful. Moreover, sequences of DArT marker associated with the traits of interest were aligned in chromosomal regions where sorghum QTLs has previously been reported. This approach could be a valuable tool to assist the improvement of sugarcane and better supply sugarcane demand that has been projected for the upcoming decades.

The plant microbiome plays an important role in nutrient acquisition and buffering plant hosts against abiotic and biotic stress. During in vitro propagation of sugarcane, pathogenic microorganisms are eliminated and most of the beneficial endophytic microorganisms. The objective of this study was to isolate and characterise potential plant growth-promoting bacteria (PGPB) from sugarcane and to analyse their ability to improve the survival of micropropagated sugarcane plantlets during the acclimatisation stage. First, bacterial isolates from sugarcane were identified by partial 16S rDNA sequencing and tested for plant growth-promoting (PGP) features, such as inorganic and organic phosphate solubilisation nitrogen fixation, siderophore synthesis, indole-3-acetic acid production, tolerance to abiotic stress and antibiotics production. Then three bacterial strains with multiple PGP traits were independently applied to micropropagated seedlings of the sugarcane variety TUC 03-12 when the plants were transferred to a nursery for ex vitro acclimatisation. The effect of selected PGPB on survival rates of micropropagated plantlets was evaluated in three independent assays, using different batches of seedlings. Thirty days after inoculation, 182-Bacillus and 336-Pseudomonas isolates significantly improved the transferred plants survival rate. High variability in plant survival among independent experiments was observed, but treatments with the 336-Pseudomonas strain showed a low mortality rate (20%) in all assays. This procedure constitutes a biological tool to improve the survival of micropropagated plants during greenhouse acclimatisation. Furthermore, it provides an initial tool for selecting bacteria with possible PGP effects in the field. Highlights - A total of 162 isolates obtained from the rhizosphere, rhizoplane, roots, and stems of sugarcane were characterised for plant growthpromoting features and identified by partial 16S rDNA sequencing. - Two PGPBs strains isolated from sugarcane (182-Bacillus and 336-Pseudomonas) significantly improved survival rates of micropropagated seedlings during the acclimatisation stage. - Under different stress conditions, the 336-Pseudomonas strain improved the survival of micropropagated plants during the acclimatisation stage.

Sugarcane diseases can be controlled by an integrated management approach where biotechnological tools can successfully contribute. The Obispo Colombres Agroindustrial Experimental Station (EEAOC) in Tucumán (Argentina’s main sugarcane producer) has successfully implemented multiple strategies that greatly enhance the productivity of sugarcane fields. The local breeding program develops resistant varieties by applying molecular markers to reveal the presence of Bru1 gene for brown rust resistance throughout the EEAOC germplasm collection. In addition, SNP alleles linked to novel sources of resistance were identified following a selective genotyping strategy. Another strategy is the implementation of a seed cane sanitation project using hydrothermal therapy, an in vitro culture technique, molecular diagnosis of diseases, and bionanoparticles. As a result, the incidence of systemic diseases has significantly decreased in the production fields. More recently, the use of biological products has shown to be effective for disease control in EEAOC varieties. In summary, several biotechnological strategies including molecular markers associated with resistant sources, in vitro culture of apical meristems, molecular diagnostic techniques, and the use of bioproducts are being successfully used for the sustainable management of sugarcane diseases in Tucumán, Argentina.

Understanding the genetic diversity and population structure of sugarcane germplasm banks is essential for generating progenies with maximum variability. In this study, 350 accessions from the EEAOC germplasm bank were genotyped using DArT-seq markers. Genetic diversity, population structure, and variability were assessed through Bayesian analysis, principal coordinate analysis (PCoA), and analysis of molecular variance (AMOVA). Additionally, different sizes of core collections were evaluated. After filtering, 74,969 high-quality SNPs were retained, and two outlier genotypes were excluded. The mean observed heterozygosity (HO) was 0.28, while the mean expected heterozygosity (HE) was 0.3. Polymorphic information content (PIC) values ranged from 0 to 0.38 (mean 0.22), and the mean discrimination power (Dj) was 0.28. Structure and PCoA analyses consistently revealed three genetic clusters. AMOVA indicated that most of the genetic variation was found within subpopulations, while 10.25% was attributable to differences among them (p < 0.0001), where ΦFST suggested moderate genetic differentiation. Core collection analysis showed that a subset of 35 genotypes (10%) captured nearly 96% of the total genetic diversity, while a 30% core captured over 98%. These results provide valuable information for the effective management and utilization of sugarcane genetic resources and support the design of breeding strategies to develop superior cultivars.

Due to a mistake, the affiliation of Prof. Anna Maria Puglia was incorrectly reported in this article, published in Italian Journal of Agronomy in 2022 (DOI: 10.4081/ija.2022.2006). The correct affiliation appears above. Italian Journal of Agronomy DOI: 10.4081/ija.2022.2150