Spatio-temporal evolution of climbing habit in the Dahlia-Hidalgoa group (Coreopsidae, Asteraceae).

In this paper we focus on Hidalgoa, a small genus distributed in cloud forest from Mexico to Colombia with the uncommon climbing habit of enlarging its petioles. This genus belongs to tribe Coreopsideae (Asteraceae), a group mostly from the Neotropics with a few taxa in Oceania and Polynesia. The phylogenetic position of Hidalgoa has not yet been determined though it will most probably be closely related to Dahlia. The aim of this paper is to understand the ecological and evolutionary consequences of the shift to a climbing growth form using a spatio-temporal approach to phylogenetic analyses, and by testing evolutionary models for ecological niche. Our results identified that Hidalgoa formed a sub- clade in a grade with Dahlia, with divergence occurring in the Pliocene. The ancestral life form for this clade was cryptophytic (e.g. geophytes). Analyses using the climate variables most important to the elements of the Dahlia-Hidalgoa clade indicate that they share the same preferences. Moreover, visualization by traitgrams of the significant climate variables shows no departure among clades. These results suggest that no evolutionary or ecological consequences have yet manifested, and that Hidalgoa can be considered a climbing Dahlia.

[Effects of drought stress on physiological and biochemical parameters of Dahlia pinnata].

Taking Dahlia pinnata 'Fenxishi' as test material, this paper studied its leaf physiological and biochemical responses to different degrees of drought stress and re-watering. With the increasing extent and duration of drought stress, the leaf relative water content, water potential, and chlorophyll content of D. pinnata 'Fenxishi' decreased significantly, leaf relative electric conductivity and malondialdehyde (MDA) content had a significant increase, plasma membrane was damaged, and massive ions were leaked out. The damage of plasma membrane was most serious under severe stress, and could not recover to the control level after re-watering. The leaf soluble sugar and proline contents also increased significantly with increasing extent and duration of drought stress. Especially for proline content, it was increased significantly in the later period of moderate and severe stresses, suggesting its lower sensitivity to water deficit. The leaf soluble protein content had a trend of down-up-down, while the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) decreased after an initial increase. There were some differences in the responses of the three enzymes to drought stress and reactive oxygen, exhibiting their coordinating role.

Simultaneous post-transcriptional gene silencing of two different chalcone synthase genes resulting in pure white flowers in the octoploid dahlia.

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.

Effect of different growing media on the growth and development of Dahlia (Dahlia pinnata) under the agro-climatic condition of Dera Ismail Khan.

An experiment was conducted to investigate the effect of different growing media on the growth and development of Dahlia (Dahlia pinnata). Seven different growing media including sand, silt, leaf mold, sand + silt, sand + leaf mold, silt + leaf mold and sand + silt + leaf mold, were used to check the growth and development of dahlia in pots. The over all best performance was recorded in media sand + silt + leaf mold for almost all the parameters; plant height (42.08 cm), stem thickness (1.93 cm), number of branches per plant (3.6), minimum days to flowering (91.66), number of flowers per plant (10.6), number of petals per flower (13), diameter of flower (8.8 cm) and vase life of flower (5 days). The media leaf mold alone also performed significantly well for all the parameters including the maximum 42.55 leaves per plant. Sand, when used alone as a growing medium showed the least response and provided unsatisfactory results for all the parameters.