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Height, basal diameter, diameter at breast height, bud burst, and leaf development were recorded in a 5-year-old hybrid aspen clonal trial. The field trial consisted of four aspen hybrid clones (Populus tremula x Populus tremuloides) and one local P. tremula seedling source. Phenological traits were observed in the 3rd year. Growth patterns were recorded during the 3rd and 4th years. Phenological traits were explored in relation to hybrid vigor expressed as growth traits. Differences were observed for phenological and growth traits among hybrid clones and P. tremula. The growth period varied from 143â158 days for the four hybrid clones, and was 112 days for P. tremula. The correlation between growth period and yield was highly significant. The annual growth rate of height for the hybrids was 4.2 cm per 7 days (2.4 for P. tremula) in the 3rd year and 6.4 cm per 7 days (2.9 for P. tremula) in the 4th year. After 5 years, mean estimated stem volume of the hybrids was 3.9 times that of P. tremula. Significant clone by year interaction was observed for height, diameter, and volume growth. The hybrid vigor seems to be mainly attributable to a longer growth period.

Stomatal, CO2 exchange parameters and several leaf and growth traits were recorded in a five-year-old hybrid aspen clone trial. The field trial consisted of four aspen hybrid clones (Populus tremula L. x P. tremuloides Michx.) and one local Populus tremula seedling source. The mean estimated height of hybrid aspen clones was 1.6 times higher than for P. tremula. Similarly, basal diameter was 1.5 times and breast diameter 1.8 times higher in the hybrids. Differences were observed for physiological and growth traits among hybrid clones and P. tremula, but, only stomatal characters of hybrid clones differed significantly from those in P. tremula. Hybrid clones had larger guard cells (22.9 mm) than P. tremula (19.2 mm), whereas P. tremula had a higher stomatal density (211.3/mm2) than the hybrid clones (164.4/mm2). Among four hybrid clones, net photosynthesis was strongly correlated with foliar nitrogen. Height correlated significantly with foliar nitrogen, but negatively with leaf fresh weight, leaf dry weight and stomatal density. The results suggested that yield components could be controlled by many genes, specific to each clone. No single gas exchange or morphological variable can provide a reliable indicator of yield potential.

Huanglongbing (HLB), or citrus greening, is the most devastating disease in citrus worldwide. Commercial citrus varieties including sweet orange (Citrus sinensis) are highly susceptible to HLB, and trifoliate orange (Poncirus trifoliata, a close Citrus relative) is widely considered resistant or highly tolerant to HLB. In this study, an intergeneric F1 population of sweet orange and trifoliate orange was genotyped by Genotyping-by-Sequencing, and high-density SNP-based genetic maps were constructed separately for trifoliate orange and sweet orange. The two genetic maps exhibited high synteny and high coverage of the citrus genome. Progenies of the F1 population and their parents were planted in a replicated field trial, exposed to intense HLB pressure for 3 years, and then evaluated for susceptibility to HLB over 2 years. The F1 population exhibited a wide range in severity of HLB foliar symptom and canopy damage. Genome-wide QTL analysis based on the phenotypic data of foliar symptom and canopy damage in 2 years identified three clusters of repeatable QTLs in trifoliate orange linkage groups LG-t6, LG-t8 and LG-t9. Co-localization of QTLs for two traits was observed within all three regions. Additionally, one cluster of QTLs in sweet orange (linkage group LG-s7) was also detected. The majority of the identified QTLs each explained 18-30% of the phenotypic variation, indicating their major role in determining HLB responses. These results show, for the first time, a quantitative genetic nature yet the presence of major loci for the HLB tolerance in trifoliate orange. The results suggest that sweet orange also contains useful genetic factor(s) for improving HLB tolerance in commercial citrus varieties. Findings from this study should be very valuable and timely to researchers worldwide as they are hastily searching for genetic solutions to the devastating HLB crisis through breeding, genetic engineering, or genome editing.

The new variety Betula pendula 'Dalecarlica', selected from Betula pendula , shows high ornamental value owing to its lobed leaf shape. In this study, to identify the genetic components of leaf shape formation, we performed bulked segregant analysis and molecular marker-based fine mapping to identify the causal gene responsible for lobed leaves in B. pendula 'Dalecarlica'. The most significant variations associated with leaf shape were identified within the gene BpPIN1 encoding a member of the PIN-FORMED family, responsible for the auxin efflux carrier. We further confirmed the hypomethylation at the promoter region promoting the expression level of BpPIN1 , which causes stronger and longer veins and lobed leaf shape in B. pendula 'Dalecarlica'. These results indicated that DNA methylation at the BpPIN1 promoter region is associated with leaf shapes in B. pendula. Our findings revealed an epigenetic mechanism of BpPIN1 in the regulation of leaf shape in Betula   Linn. (birch), which could help in the molecular breeding of ornamental traits. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB) caused by 'Candidatus Liberibacter asiaticus' (CLas) is the most costly disease for the global citrus industry. Currently, no effective tools have been found to control HLB. Most commercial citrus varieties are susceptible to HLB, though some citrus hybrid cultivars have reduced sensitivity to the disease. Citrus breeding populations contain a large diversity of germplasm, with thousands of unique genotypes exhibiting a broad range of phenotypes. Understanding phenotypic variation and genetic inheritance in HLB-affected mandarin hybrid populations are crucial for breeding tolerant citrus varieties. In this study, we assessed 448 diverse mandarin hybrids coming from 30 crosses, and 45 additional accessions. For HLB tolerance, we measured HLB severity visual score and CLas titers by qPCR. We also measured seven morphophysiological traits indirectly related to HLB tolerance with leaf area index (LAI), leaf area (LA), leaf mass per area (LMA), photosystem II parameters (Fv/Fo, Fv/Fm), and photochemical performance index (PIabs). By estimating the genetic variation in five half-sib families, we estimated the heritability of phenotypic traits and found a significant genetic effect on HLB visual score and photosynthesis parameters, which indicates opportunities for the genetic improvement of HLB tolerance. In addition, although it is easy to identify infected trees based on HLB symptomatic leaves, visually phenotyping whole trees can be difficult and inconsistent due to the interpersonal subjectivity of characterization. We investigated their relationships and found that LAI was highly correlated with HLB score, with correlation coefficients of r = 0.70 and r = 0.77 for the whole population and five half-sib families, respectively. Photochemical parameters showed significant correlation with HLB severity and responded differentially with the side of the canopy. Our study suggests that LAI and photochemical parameters could be used as a rapid and cost-effective method to evaluate HLB tolerance and inheritance in citrus breeding programs. [ABSTRACT FROM AUTHOR]

Sweet orange originated from the introgressive hybridizations of pummelo and mandarin resulting in a highly heterozygous genome. How alleles from the two species cooperate in shaping sweet orange phenotypes under distinct circumstances is unknown. Here, we assembled a chromosome-level phased diploid Valencia sweet orange (DVS) genome with over 99.999% base accuracy and 99.2% gene annotation BUSCO completeness. DVS enables allele-level studies for sweet orange and other hybrids between pummelo and mandarin. We first configured an allele-aware transcriptomic profiling pipeline and applied it to 740 sweet orange transcriptomes. On average, 32.5% of genes have a significantly biased allelic expression in the transcriptomes. Different cultivars, transgenic lineages, tissues, development stages, and disease status all impacted allelic expressions and resulted in diversified allelic expression patterns in sweet orange, but particularly citrus Huanglongbing (HLB) shifted the allelic expression of hundreds of genes in leaves and calyx abscission zones. In addition, we detected allelic structural mutations in an HLB-tolerant mutant (T19) and a more sensitive mutant (T78) through long-read sequencing. The irradiation-induced structural mutations mostly involved double-strand breaks, while most spontaneous structural mutations were transposon insertions. In the mutants, most genes with significant allelic expression ratio alterations (≥1.5-fold) were directly affected by those structural mutations. In T19, alleles located at a translocated segment terminal were upregulated, including CsDnaJ, CsHSP17.4B, and CsCEBPZ. Their upregulation is inferred to keep phloem protein homeostasis under the stress from HLB and enable subsequent stress responses observed in T19. DVS will advance allelic level studies in citrus. [ABSTRACT FROM AUTHOR]

Some furanocoumarins in grapefruit (Citrus paradisi) are associated with the so-called grapefruit juice effect. Previous phytochemical quantification and genetic analysis suggested that the synthesis of these furanocoumarins may be controlled by a single gene in the pathway. In this study, cDNA-amplified fragment length polymorphism (cDNA-AFLP) analysis of fruit tissues was performed to identify the candidate gene(s) likely associated with low furanocoumarin content in grapefruit. Fifteen tentative differentially expressed fragments were cloned through the cDNA-AFLP analysis of the grapefruit variety Foster and its spontaneous low-furanocoumarin mutant Low Acid Foster. Sequence analysis revealed a cDNA-AFLP fragment, Contig 6, was homologous to a substrate-proved psoralen synthase gene, CYP71A22, and was part of citrus unigenes Cit.3003 and Csi.1332, and predicted genes Ciclev10004717m in mandarin and orange1.1g041507m in sweet orange. The two predicted genes contained the highly conserved motifs at one of the substrate recognition sites of CYP71A22. Digital gene expression profile showed the unigenes were expressed only in fruit and seed. Quantitative real-time PCR also proved Contig 6 was down-regulated in Low Acid Foster. These results showed the differentially expressed Contig 6 was related to the reduced furanocoumarin levels in the mutant. The identified fragment, homologs, unigenes, and genes may facilitate further furanocoumarin genetic study and grapefruit variety improvement. Key words: Citrus paradisi, grapefruit juice effect, psoralen synthase, differential expression. Certaines furocoumarines chez le pamplemousse (Citrus paradisi) sont associees a ce qu'on appelle l'effet du jus de pamplemousse. Des quantifications phytochimiques et des analyses genetiques anterieures ont suggere que la synthese de ces furocoumarines serait controlee par un seul gene au sein du sentier metabolique. Dans ce travail, une analyse cDNA-AFLP (polymorphisme des produits d'amplification au sein d'ADNc) a ete realisee sur les tissus du fruit pour identifier un ou des genes candidats associes avec une faible teneur en furocoumarines chez le pamplemousse. Quinze fragments potentiellement exprimes de maniere differentielle ont ete clones via l'analyse cDNA-AFLP de la variete de pamplemousse Foster et de son variant spontane a faible teneur en furocoumarines Low Acid Foster. L'analyse des sequences a montre qu'un amplicon cDNA-AFLP, nomme Contig 6, est homologue a CYP71A22, une psoralene-synthase dont le substrat est connu, et provient des unigenes Cit.3003 et Csi.1332 chez les agrumes ainsi que des genes predits Ciclev10004717m chez le mandarinier et orange1.1g041507m chez l'oranger douce. Les deux genes predits contiennent des motifs fortement conserves a l'un des deux sites de reconnaissance du substrat chez le CYP71A22. Des profils digitaux d'expression genique ont montre que les unigenes etaient exprimes seulement chez les fruits et les graines. Des analyses en PCR quantitatif ont aussi montre que le Contig 6 etait sous-exprime chez la variete Low Acid Foster. Ces resultats montrent que le Contig 6 a expression differentielle est implique dans la reduction de la teneur en furocoumarines chez le mutant. Le fragment identifie, ses homologues, unigenes et genes pourront faciliter l'analyse genetique des furocoumarines et l'amelioration genetique du pamplemousse. [Traduit par la Redaction] Mots-cles: Citrus paradisi, effet du jus de pamplemousse, psoralene synthase, expression differentielle., Introduction Some abundant furanocoumarins (FC) in grapefruit (Citrus paradisi Macf.) juice, such as bergamottin, 6,7-dihydroxy bergamottin (6,7-DHB), and paradisin C, have potent adverse interaction with certain human drugs (Ohnishi et [...]

Three puiaiive terpenoid UDP-glycosyltransferase (UGT) genes, designated CsUGT1, CsUGT2, and CsUGT3, were isolated and characterized in 'Valencia' sweet orange (Citrus sinensis L. Osbeck), CsUGT1 consisted of 1493 nucleotides with an open reading frame encoding 492 amino acids, CsUGT2 consisted of 1727 nucleotides encoding 504 amino acids, and CsUGT3 consisted of 1705 nucleotides encoding 468 amino acids. CsUGT3 had a 145 bp intron at 730-874, whereas CsUGT1 and CsUGT2 had none. The three deduced glycosyltransferase proteins had a highly conserved plant secondary product glycosyltransferase motif in the C terminus. Phylogenetic analysis showed that CsUGT1 and CsUGT3 were classified into group L of glycosyltransferase family 1, and CsUGT2 was classified into group D. Through Southern blotting analysis, CsUGT1 was found to have two copies in the sweet orange genome, whereas CsUGT2 and CsUGT3 had at least seven and nine copies, respectively. CsUGT1, CsUGT2, and CsUGT3 were constitutively expressed in leaf, flower, and fruit tissues. The results facilitate further investigation of the function of terpenoid glycosyltransferases in citrus and the biosynthesis of terpenoid glycosides in vitro. Key words: aroma compound, expression profile, monoterpene glycosyltransferase. Trois genes codant putativement pour des terpenoides UDP-glycosyltransferases (UGT), nommes CsUGT1, CsUGT2 et CsUGT3, ont ete isoles et caracterises chez l'oranger doux 'Valencia' (Citrus sinensis L. Osbeck). CsUGT1 compte 1493 nucleotides et une region codante de 492 acides amines. CsUGT2 totalise 1727 nucleotides et code pour tine proteine de 504 acides amines. CsUGT3 compte 1705 nucleotides pour une proteine de 468 acides amines. CsUGT3 a tin intron de 145 pb entre les positions 730 et 874, tandis que les genes CsUGT1 et CsUGT2 n'en comptent aucun. Les trois sequences predites des glycosyl transferases presentent un motif PSPG (plant secondary product glycosyltransferase) tres conserve a l'extremite C-terminale. Une analyse phylogenetique a montre que CsUGT1 et CsUGT3 appartiennent au groupe L au sein de la famille 1 des glycosyltransferases, alors que CsUGT2 appartient au groupe D. Des analyses Southern ont revele que le gene CsUGT1 est present en deux copies dans le genome de l'oranger doux, tandis que CsUGT1 et CsUGT3 comptent respectivement au moins sept et neuf copies. Les trois genes sont exprimes de maniere constitutive chez les feuilles, les fleurs et les fruits. Ces resultats faciliteront des investigations ulterieures portant sur la fonction des terpenoides glycosyltransferases chez les agrumes et la biosynthese des terpenoides glycosides in vitro. Mots-cles : compose aromatique, profil d'expression, monoterpene glycosyltransferase. [Traduit par la Redaction], Introduction Glycosyltransferases, belonging to a highly divergent, polyphyletic, multigene superfamily (Mackenzie et al, 1997), are categorized into 91 families according to their sequence similarities, signature motifs, and substrate specificities (http://www.cazy.org/fam/acc_GT.html). [...]