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Modern sugarcane (Saccharum spp.) cultivars originated from an intricate hybridization process, resulting in complex polyploid and aneuploid genomes. Flow cytometry (FCM), which has emerged as a precise and fast method for research on genome size in plants, has potential to unveil key aspects of sugarcane cytogenetics. In this study, FCM probes were conducted to estimate 2C DNA content in 175 Saccharum genotypes embracing phenotypically contrasting canes (commercial cultivars, energy‐cane hybrids, and a Saccharum spontaneum accession) and full‐sib sugarcane families. FCM‐mediated DNA content estimates exhibited high accuracy in predicting chromosome numbers, offering a time‐efficient alternative to classical cytogenetic procedure. Low‐magnitude correlations detected between DNA content and phenotypic traits suggest that indirect selection of agronomic traits using FCM‐mediated DNA content estimates may not be efficient. DNA content variation patterns in sugarcane families varied according to the crossing, and revealed transgressive variations associated with rampant aneuploidy. Altogether, the findings uncover that loss or gain of genetic material constitutes a source of high genetic variability that may substantially impact on crop breeding. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum spp.) is a genetically complex crop with great potential for the second-generation (2 G) ethanol industry. Despite this, there is scarce knowledge of the variability of bagasse cell-wall components and its association with agronomic traits that could be used in the selection of cultivars with improved bagasse digestibility. In this work, the acid detergent fiber method was used to determine cellulose, hemicellulose, and acid detergent lignin (ADL) in a sugarcane progeny from crossing two commercial cultivars, and in two energy-cane biotypes. Additionally, acetyl bromide-soluble lignin was determined and compared with ADL values. Despite the crossed parents showing similar bagasse composition, transgressive inheritance observed in the progeny for all bagasse cell-wall components underlines the possibility of improving sugarcane for specific bioenergetic uses. Additionally, the low association between cell-wall and yield components found in this work, suggests that indirect selection of cell-wall components for 2 G ethanol industry through agronomic traits would have a limited impact on improving the biomass composition. [ABSTRACT FROM AUTHOR]

Large‐scale evaluation of genetic diversity in crops with large and complex genomes benefits from the selective enrichment of relevant genomic regions prior to sequencing. Given the complexity of the sugarcane (Saccharum spp.) genome and the limited exploration of quantitative trait loci (QTL) for important energy traits, we used comparative genomics with the related diploid crop sorghum (Sorghum bicolor) to mine for regions associated with bioenergy production. Twenty‐one meta‐QTL (mQTL) were identified after surveying 286 QTL from 24 different studies using the Sorghum QTL Atlas. Comparative genomics revealed that at least 35% of genes located within QTL can be found in highly conserved sorghum/sugarcane collinear chromosome blocks. Additionally, a targeted candidate search identified 200 genes known for their involvement in sugar and cell wall metabolism. For a subset of these sorghum genes, we evaluated sugarcane gene copy number, sequence identity, and homoeolog expression in target tissues. This work is an initial step towards targeting and resequencing sugarcane orthologous genomic regions to discover single nucleotide polymorphisms (SNPs) as a resource for genomics‐assisted breeding. [ABSTRACT FROM AUTHOR]

The common potato, Solanum tuberosum L. (2n = 4x = 48), has 100–200 related wild taxonomic species endemic to the Americas, which constitute invaluable sources of genetic diversity. They form a polyploid series with 2n = 2x – 6x (x = 12) and can reproduce asexually by tubers and stolons and/or sexually by seeds. Information is scarce on their preponderant mode of reproduction and its consequences on the genetic population structure over time. In previous work, a morphologically variable wild potato population from northwestern Argentina was sampled in two consecutive years. Two populations were ex situ regenerated from the sampled propagules (seeds in 2013 and tubers in 2014) for morphological and reproductive studies; these populations exhibited differences in reproductive behavior that could not be related to morphological phenotypes. To ascertain if the observed differences could be related to the captured genetic diversity in each year, a molecular analysis was carried out with seven microsatellite primer pairs located in seven chromosomes of the basic set. The captured genetic diversity, based on the proportion of individuals with a unique pattern of amplified fragments, varied significantly (χ2 α =.05) between sampling years. This could be due to changes in the preponderant mode of reproduction, differential genotype fitness resulting from genotype × environment interactions, or both. Wild potato accessions at germplasm banks are one‐time collection samples; thus, they may not be representative of the genetic diversity of the sampled population. To properly ex situ conserve the available genetic diversity, it is advisable to resample the sites whenever possible and to conform each accession with the successive samples. Core Ideas: Population samples (accessions) are sources of genetic diversity for potato breeding.Samples of a natural wild potato population, taken over 2 yr, were characterized.Morphological variability and genetic diversity for SSR markers were not associated.The captured genetic diversity varied between sampling years.Populations need to be sampled more than once to conserve the natural diversity. [ABSTRACT FROM AUTHOR]

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The analytic-synthetic scheme makes use of haploidization and 2 n gametes-mediated sexual polyploidization to incorporate genetic diversity from wild related species in potato breeding. Whereas 2 n pollen can be directly screened by microscopy, 2 n eggs are routinely screened indirectly by interploid crosses, a time-consuming and inaccurate technique. In five haploid tbr × wild diploid species families with variability for agronomic characters, 2 n eggs were screened indirectly to incorporate this germplasm into a useful form and directly by microscopy to establish the feasibility of this approach. For the indirect screening, at least 15 flowers of each of 49 genotypes/family were crossed with a commercial cultivar. Eighty-five fruits were produced; only 15 of them had seeds (1–25). Chromosome numbers were determined in a random sample of five seeds/fruit, resulting diploid in two genotypic combinations and tetraploid in another two. For the direct screening, eight combinations of staining and destaining (times and concentrations) were evaluated in detached ovules to adjust a clarification technique. The best combination was one day of staining and one day of destaining in 0.5 % acetic acid. In an indirectly detected diplogynoid, the average diameters of the central cell nuclei (CCN) and nucleoli (CCNu) were, respectively, 9.3 μ and 3.4 μ. Gametophytes with diametres 1.26 times the average were considered 2 n. By crosses, eleven seeds were obtained in one fruit of this clone whereas the 2 n egg frequency determined by microscopy was 7%. The direct technique is easy to carry out once the eye is trained and its results better reflect actual 2 n gamete frequencies. [ABSTRACT FROM AUTHOR]

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Sugarcane and energy-cane are important Saccharum spp. hybrids that encompass desirable features for energy production. Their stem lignocellulose can be used as the raw material for the second-generation ethanol industry, contributing to accelerated fossil-fuel replacement. However, knowledge on the internode composition and saccharification of these hybrids is still needed to optimize their uses, especially in energy-cane. In this work, the agronomical, chemical, and histological internode features and saccharification potential were analyzed in sugarcane and energy-cane hybrids across four critical developmental stages (tillering, grand growth, early ripening and late ripening) and several internode positions along the stem. Except for galactose content that was higher in the sugarcane hybrid compared to the energy-cane, cell-wall composition was fairly similar in both types of cane across the growing cycle. Among main cell-wall components, maximum crystalline cellulose and matrix polysaccharides contents were observed at tillering and late ripening, respectively. Lignin concentrated towards upper internode positions and advanced developmental stages. Saccharification potential augmented towards apical internodes and early developmental stages, and negatively correlated to lignin and xylose contents. The energy-cane hybrid showed lower number of vascular bundles and metaxylem diameter and its lignin deposition was more extended towards the parenchymal tissue, when compared to the commercial sugarcane throughout the growth cycle. Taken together, these findings demonstrate that developmental stage and internode position largely affect cell-wall composition and its recalcitrance to enzymatic degradation. The use of sugarcane/energy-cane lignocellulose from early developmental stages could be beneficial for the second generation ethanol production. Novel management practices for that usage should consider economic, social and environmental sustainability standards under a sugar/ethanol production scheme. [Display omitted] • Sugarcane and energy-cane had similar cell-wall composition, except for galactose. • Stage and internode position affected cell-wall composition and saccharification. • Sugarcane and energy-cane differed in shape, number and size of vascular bundles. • Lignin and xylose were associated with increased biomass recalcitrance [ABSTRACT FROM AUTHOR]