Early selection of novel triploid hybrids of shrub willow with improved biomass yield relative to diploids

BACKGROUND: Genetic improvement of shrub willow (Salix), a perennial energy crop common to temperate climates, has led to the development of new cultivars with improved biomass yield, pest and disease resistance, and biomass composition suitable for bioenergy applications. These improvements have largely been associated with species hybridization, yet little is known about the genetic mechanisms responsible for improved yield and performance of certain willow species hybrids. RESULTS: The top performing genotypes in this study, representing advanced pedigrees compared with those in previous studies, were mostly triploid in nature and outperformed current commercial cultivars. Of the genotypes studied, the diploids had the lowest mean yield of 8.29 oven dry Mg ha(−1) yr(−1), while triploids yielded 12.65 Mg ha(−1) yr(−1), with the top five producing over 16 Mg ha(−1) yr(−1). Triploids had high stem area and height across all three years of growth in addition to greatest specific gravity. The lowest specific gravity was observed among the tetraploid genotypes. Height was the early trait most correlated with and the best predictor of third-year yield. CONCLUSIONS: These results establish a paradigm for future breeding and improvement of Salix bioenergy crops based on the development of triploid species hybrids. Stem height and total stem area are effective traits for early prediction of relative yield performance

Characterization of a large sex determination region in Salix purpurea L. (Salicaceae).

Dioecy has evolved numerous times in plants, but heteromorphic sex chromosomes are apparently rare. Sex determination has been studied in multiple Salix and Populus (Salicaceae) species, and P. trichocarpa has an XY sex determination system on chromosome 19, while S. suchowensis and S. viminalis have a ZW system on chromosome 15. Here we use whole genome sequencing coupled with quantitative trait locus mapping and a genome-wide association study to characterize the genomic composition of the non-recombining portion of the sex determination region. We demonstrate that Salix purpurea also has a ZW system on chromosome 15. The sex determination region has reduced recombination, high structural polymorphism, an abundance of transposable elements, and contains genes that are involved in sex expression in other plants. We also show that chromosome 19 contains sex-associated markers in this S. purpurea assembly, along with other autosomes. This raises the intriguing possibility of a translocation of the sex determination region within the Salicaceae lineage, suggesting a common evolutionary origin of the Populus and Salix sex determination loci

High-Resolution Melting Analysis Enables Efficient Detection and Differentiation of Two Boxwood Blight Pathogens by qPCR Assays

Boxwood blight is a devastating disease caused by the fungal pathogens Calonectria henricotiae (Che) and C. pseudonaviculata (Cps). Identification and detection of these pathogens from infected plant material could play a significant role in breeding and selection of resistant cultivars and development of disease management strategies in the ornamental nursery industry. We designed a simple, single-tube method for extraction of PCR-amplifiable DNA from boxwood leaves and cultures of the Calonectria pathogens. Previously developed fungal-specific primers based on histone and calmodulin regions were used to detect and distinguish between Che and Cps using real-time PCR and high-resolution melting (HRM) analysis, with discernable melting temperature differences of 0.5°C between amplified products. Here, we describe a single-tube acetone-based DNA extraction method and qPCR-HRM assay targeting single nucleotide polymorphisms within the calmodulin and histone H3 DNA regions as a fast and highly sensitive molecular method to detect and differentiate between Che and Cps species directly from plant tissue. [Graphic: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license

Integrative genomics reveals paths to sex dimorphism in Salix purpurea L.

Sex dimorphism and gene expression were studied in developing catkins in 159 F2 individuals from the bioenergy crop Salix purpurea, and potential mechanisms and pathways for regulating sex development were explored. Differential expression, eQTL, bisulfite sequencing, and network analysis were used to characterize sex dimorphism, detect candidate master regulator genes, and identify pathways through which the sex determination region (SDR) may mediate sex dimorphism. Eleven genes are presented as candidates for master regulators of sex, supported by gene expression and network analyses. These include genes putatively involved in hormone signaling, epigenetic modification, and regulation of transcription. eQTL analysis revealed a suite of transcription factors and genes involved in secondary metabolism and floral development that were predicted to be under direct control of the sex determination region. Furthermore, data from bisulfite sequencing and small RNA sequencing revealed strong differences in expression between males and females that would implicate both of these processes in sex dimorphism pathways. These data indicate that the mechanism of sex determination in Salix purpurea is likely different from that observed in the related genus Populus. This further demonstrates the dynamic nature of SDRs in plants, which involves a multitude of mechanisms of sex determination and a high rate of turnover