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Dahlias (Dahlia variabilis) exhibit a wide range of flower colours because of accumulation of anthocyanin and other flavonoids in their ray florets. Two lateral mutants were used that spontaneously occurred in 'Michael J' (MJW) which has yellow ray florets with orange variegation. MJOr, a bud mutant producing completely orange ray florets, accumulates anthocyanins, flavones, and butein, and MJY, another mutant producing completely yellow ray florets, accumulates flavones and butein. Reverse transcription–PCR analysis showed that expression of chalcone synthase 1 (DvCHS1), flavanone 3-hydroxylase (DvF3H), dihydroflavonol 4-reductase (DvDFR), anthocyanidin synthase (DvANS), and DvIVS encoding a basic helix–loop–helix transcription factor were suppressed, whereas that of chalcone isomerase (DvCHI) and DvCHS2, another CHS with 69% nucleotide identity with DvCHS1, was not suppressed in the yellow ray florets of MJY. A 5.4 kb CACTA superfamily transposable element, transposable element of Dahlia variabilis 1 (Tdv1), was found in the fourth intron of the DvIVS gene of MJW and MJY, and footprints of Tdv1 were detected in the variegated flowers of MJW. It is shown that only one type of DvIVS gene was expressed in MJOr, whereas these plants are likely to have three types of the DvIVS gene. On the basis of these results, the mechanism regulating the formation of orange and yellow ray florets in dahlia is discussed.

Garden dahlias (Dahlia variabilis) are autoallooctoploids with redundant genes producing wide color variations in flowers. There are no pure white dahlia cultivars, despite its long breeding history. However, the white areas of bicolor flower petals appear to be pure white. The objective of this experiment was to elucidate the mechanism by which the pure white color is expressed in the petals of some bicolor cultivars. A pigment analysis showed that no flavonoid derivatives were detected in the white areas of petals in a star-type cultivar 'Yuino' and the two seedling cultivars 'OriW1' and 'OriW2' borne from a red-white bicolor cultivar, 'Orihime', indicating that their white areas are pure white. Semi-quantitative RT-PCR showed that in the pure white areas, transcripts of two chalcone synthases (CHS), DvCHS1 and DvCHS2 which share 69% nucleotide similarity with each other, were barely detected. Premature mRNA of DvCHS1 and DvCHS2 were detected, indicating that these two CHS genes are silenced post-transcriptionally. RNA gel blot analysis revealed that small interfering RNAs (siRNAs) derived from CHSs were produced in these pure white areas. By high-throughput sequence analysis of small RNAs in the pure white areas with no mismatch acceptance, small RNAs were mapped to two alleles of DvCHS1 and two alleles of DvCHS2 expressed in 'Yuino' petals. Therefore, we concluded that simultaneous siRNA-mediated post-transcriptional gene silencing of redundant CHS genes results in the appearance of pure white color in dahlias.

Owing to applications in the food and nutraceutical industries, inulinases, fructosyltransferases and sucrases have gained considerable attention in recent times. Twenty-five fungal strains were screened for production of these enzymes on three different media formulated using inulin-rich plant extracts prepared from asparagus root, dahlia tuber and dandelion root extract. Culture filtrates of the fungi were examined for hydrolytic activities. Fungi belonging to genus Aspergillus, A. niger GNCC 2655 (11.3 U/ml), A. awamori MTCC 2879 (8.2 U/ml), A. niger ATCC 26011 (7.9 U/ml) secreted high titers of inulinase followed by Penicillium sp. NFCCI 2768 (2.6 U/ml) and Penicillium citrinum MTCC 1256 (1.1 U/ml). High sucrase activity was noticed in A. niger GNCC 2613 (113 U/ml) and A. awamori MTCC 2879 (107.8 U/ml). Analysis of end products of inulinase action by HPLC revealed that most of the enzymes were exo-inulinases liberating fructose exclusively from inulin. Five fungi, P. citrinum MTCC 1256, Penicillium rugulosum MTCC 3487, Penicillium sp. NFCCI 2768, A. fumigatus GNCC 1351 and A. niger ATCC 26011 however, produced a mixture of endo- and exo-inulinases liberating oligosaccharides (GF3 and GF2) along with fructose. High inulinase/sucrase yielding strains were evaluated for extracellular and intracellular hydrolytic and transfructosylating activities and intracellular enzyme profiles were found to be considerably different in terms of titers and end products.

Two distinct caulimoviruses, Dahlia mosaic virus (DMV) and Dahlia common mosaic virus, and an endogenous plant pararetroviral sequence (DvEPRS) were reported in Dahlia spp. DvEPRS, previously referred to as DMV-D10, was originally identified in the US from the cultivated Dahlia variabilis, and has also been found in New Zealand, Lithuania and Egypt, as well as in wild dahlia species growing in their natural habitats in Mexico. Sequence analysis of three new EPRSs from cultivated dahlias from Lithuania [D10-LT; 7,159 nucleotide level (nt)], New Zealand (D10-NZ, 7,156 nt), and the wild species, Dahlia rupicola, from Mexico (D10-DR, 7,133 nt) is reported in this study. The three EPRSs have the structure and organization typical of a caulimovirus species and showed identities among various open reading frames (ORFs) ranging between 71 and 97 % at the nt when compared to those or the known DvEPRS from the US. Examination of a dataset of seven full-length EPRSs obtained to date from cultivated and wild Dahlia spp. provided clues into genetic diversity of these EPRSs from diverse sources of dahlia. Phylogenetic analyses, mutation frequencies, potential recombination events, selection, and fitness were evaluated as evolutionary evidences for genetic variation. Assessment of all ORFs using phylogenomic and population genetics approaches suggests a wide genetic diversity of EPRSs occurring in dahlias. Phylogenetic analyses show that the EPRSs from various sources form one clade indicating a lack of clustering by geographical origin. Grouping of various EPRSs into two host taxa (cultivated vs. wild) shows little divergence with respect to their origin. Population genetic parameters demonstrate negative selection for all ORFs, with the reverse transcriptase region more variable than other ORFs. Recombination events were found which provide evolutionary evidence for genetic diversity among dahlia-associated EPRSs. This study contributes to an increased understanding of molecular population genetics and evolutionary pathways of these reverse transcribing viral elements.

The genome structure and organization of a new and distinct caulimovirus that is widespread in dahlia (Dahlia variabilis) was determined. The double-stranded DNA genome was ca. 7.0 kb in size and shared many of the features of the members of the genus Caulimovirus, such as the presence of genes potentially coding for the movement protein, the inclusion body protein, and the reverse transcriptase (RT), and an intergenic region consisting of a potential 35S promoter. However, the virus differed from the previously described dahlia mosaic caulimovirus and other known caulimoviruses in that the aphid transmission factor (ATF) was absent and the putative coat protein contained a C-terminal deletion and was fused in-frame with the RT. Sequence identity at the amino acid level with known caulimoviruses including a previously reported caulimovirus from dahlia was low and ranged from 32 to 72%. The absence of an ATF and the highly divergent nature of the genomic sequence are characteristics of this new caulimovirus that is widely associated with dahlia.

Inulin is a reserve carbohydrate in about 15 % of the flowering plants and is accumulated in underground tubers of e.g. chicory, dahlia and Jerusalem artichoke. This carbohydrate consists of linear chains of β-(2,1)-linked fructose attached to a sucrose molecule. Inulinases hydrolyse inulin into fructose and glucose. To find efficient inulin degrading fungi, 126 fungal strains from the Fungal Biotechnology Culture Collection (FBCC) at University of Helsinki and 74 freshly isolated strains from soil around Jerusalem artichoke tubers were screened in liquid cultures with inulin as a sole source of carbon or ground Jerusalem artichoke tubers, which contains up to 19 % (fresh weight) inulin. Inulinase and invertase activities were assayed by the dinitrosalicylic acid (DNS) method and a freshly isolated Penicillium strain originating from agricultural soil (FBCC 1632) was the most efficient inulinase producer. When it was cultivated at pH 6 and 28 °C in 2 litre bioreactors using inulin and Jerusalem artichoke as a carbon source, inulinase and invertase activities were on day 4 7.7 and 3.1 U mL −1 , respectively. The released sugars analysed by TLC and HPLC showed that considerable amounts of fructose were released while the levels of oligofructans were low, indicating an exoinulinase type of activity. Taxonomic study of the inulinase producing strain showed that this isolate represents a new species belonging in Penicillium section Lanata - divaricata . This new species produces a unique combination of extrolites and is phenotypically and phylogenetically closely related to Penicillium pulvillorum . We propose the name Penicillium subrubescens sp. nov. (CBS 132785 T  = FBCC 1632 T ) for this new species.

The genome structure and organization of endogenous caulimovirus sequences from dahlia ( Dahlia spp), dahlia mosaic virus (DMV)-D10 from three wild species, D. coccinea (D10-DC), D. sherffii (D10-DS) and D. tenuicaulis (D10-DT), were determined and compared to those from cultivated species of dahlia, D. variabilis (DvEPRS). The complete ca. 7-kb dsDNA genomes of D10-DC, D10-DS, and D10-DT had a structure and organization typical of a caulimovirus and shared 89.3 to 96.6% amino acid sequence identity in various open reading frames (ORF) when compared to DvEPRS . The absence of the aphid transmission factor and the truncated coat protein fused with the reverse transcriptase ORF were common among these DMV-D10 isolates from wild Dahlia species.

A distinct caulimovirus, associated with dahlia mosaic, was cloned and sequenced. The caulimovirus, tentatively designated as dahlia common mosaic virus (DCMV), had a double-stranded DNA genome of ca. 8 kb. The genome organization of DCMV was found to be typical of members of the genus Caulimovirus and consisted of six major open reading frames (ORFs), ORFs I-VI, and one minor ORF, ORF VII. Sequence comparisons with the DNA genomes of two known caulimoviruses isolated from dahlia, Dahlia mosaic virus (DMV) and an endogenous caulimovirus, DMV-D10, showed that DCMV is a member of a distinct caulimovirus species, with sequence identities among various ORFs ranging from 25 to 80%.