Bolting Time Research Articles

Comparative Mapping of Growth Habit, Plant Height, and Flowering QTLs in Two Interspecific Families of Leymus

Leymus cinereus (Scribn. & Merr.) Á. Löve and L. triticoides (Buckley) Pilg. are tall caespitose and short rhizomatous perennial Triticeae grasses, respectively. Circumference of rhizome spreading, proportion of bolting culms, anthesis date, and plant height were evaluated in two mapping families derived from two interspecific hybrids of L. cinereus Acc:636 and L. triticoides Acc:641 accessions, backcrossed to one L. triticoides tester. Two circumference, two bolting, and two height QTLs were homologous between families. Two circumference, seven bolting, all five anthesis date, and five height QTLs were family specific. Thus, substantial QTL variation was apparent within and between natural source populations of these species. Two of the four circumference QTLs were detected in homoeologous regions of linkage groups 3a and 3b in both families, indicating that one gene may control much of the dramatic difference in growth habit between these species. A major height QTL detected in both families may correspond with dwarfing mutations on barley 2H and wheat 2A. The L. cinereus parent contributed negative alleles for all four circumference QTLs, five of nine bolting QTLs, two of five anthesis date QTLs, and one of seven height QTLs. Coupling of synergistic QTL allele effects within parental species was consistent with the divergent growth habit and plant height of L. cinereus and L. triticoides Conversely, antagonistic QTL alleles evidently caused transgressive segregation in reproductive bolting and flowering time.

Leaf-specific suppression of deoxyhypusine synthase in Arabidopsis thaliana enhances growth without negative pleiotropic effects

Deoxyhypusine synthase (DHS) mediates the first of two enzymatic reactions required for the post-translational activation of eukaryotic translation initiation factor 5A (eIF5A), which in turn is thought to facilitate translation of specific mRNAs. Analyses of GUS activity in transgenic Arabidopsis plants expressing the GUS reporter gene under regulation of the promoter for AtDHS revealed that the expression of DHS changes both spatially and temporally as development progresses. In particular, DHS is expressed not only in rosette leaves, but also in the anthers of developing flowers. To determine the role of DHS in leaves, transgenic plants in which DHS was selectively suppressed in rosettes of Arabidopsis plants were prepared. This was achieved by expressing AtDHS 3′-UTR cDNA as a transgene under regulation of the promoter for AtRbcS2, a gene encoding the small subunit of Rubisco. The dominant phenotypic traits of the DHS-suppressed plants proved to be a dramatic enhancement of both vegetative and reproductive growth. As well, the onset of leaf senescence in the DHS-suppressed plants was delayed by ∼1 week, but there was no change in the timing of bolting. In addition, there was no evidence for the negative pleiotropic effects, including stunted reproductive growth and reduced seed yield, noted previously for transgenic plants in which DHS was constitutively suppressed. The results indicate that DHS plays a pivotal role in both growth and senescence.

Effects of individual plant phenology on dormancy of Rumex obtusifolius seeds at dispersal

In 1998–2000, the relationship was investigated between the time of bolting of shoots and the percentage of germinability in seeds from individual plants of Rumex obtusifolius. Each year, the date of bolting of shoots was recorded in 30–108 plants, which were then grown intact until maturation, and their seeds were collected before dispersal. The proportion of germinable seeds increased with the date on which the shoots bolted. The timing of shoot bolting and seed germinability for individual plants persisted over the years of observation. To discriminate between the effect of mother plant and timing of seed maturation, shoot bolting of another 40 (1998) and 50 (1999) plants was recorded, and their shoots were then cut in late June The shoots of cut plants regrew and matured nearly simultaneously, later than in intact plants, whereas overall seed germinability decreased. In individual plants, the seed germinability was still significantly correlated with the date when plants originally bolted.

The morphological and ecological studies on the cultivated and wild Mitsuba Cryptotaenia japonica HASSK

Cryptotaenia japonica HASSK., hence forward referred to by its generic name alone, is a member of Umbelliferae. It is a herbaceous perennial plant indigenous to the Far East Asian temperate zone and is commonly cultivated throughout Japan as a vegetable crop. It grows widely in the mountainous regions of the country in wild state and is called as“Mitsuba”in Japanese.Thirty-six wild-grown stocks and five cultivars of Cryptotaenia, collected from various parts of Japan, were cultivated in Sakai, Osaka prefecture. The morphological and ecological studies were made during 1955-1958 on varietal differences among the cultivars and characteristic differences between the wild strains and the cultivars of Cryptotaenia, . The geographical differentiations among the wild strains were also investigated.1. In comparison with the wild strains, all of the cultivars had generally more valuable morphological characters as a vegetable crop and uniformity among the cultivars. Green color of the leaf and stem, erect plant type and large size of the plant are very distinctive features. On the contrary, the wild strains showed a wide range of variations in characters and the plants generally tended to be more prostrate in plant type, but there was no apparent relation between the characters and geographical conditions of the native habitat.2. In regard to the bolting and flowering time, all of the cultivars and the wild strains collected from warm climate zones showed the tendency of earlier bolting and flowering than those from cooler climate zones. It was found that the time of bolting and flowering of the wild strains is related to the latitude and temperature of the areas where they were collected.3. Varietal differences of premature bolting of the cultivars distributed in both Kanto and Kansai districts were investigated by means of four different sowing trials at different time. It was found that the cultivars of Cryptotaenia can be divided into two main ecological types, namely the Kansai Ao-mitsuba of early-bolting and the Kanto Shirokuki-mitsuba of the late-bolting. Both types seem to have been selected for the special methods of cultivation in these two districts.4. A similar geographical trend as seen in the bolting and flowering time was found in the seed dormancy of wild Cryptotaenia collected from cool climate zones when they were sowed immediately after harvest, while strains having none or shallow dormancy were found in both of the cultivars and the wild strains collected from warm climate zones.Effective treatments for breaking the seed dormancy are also investigated, and a chilling pretreatmemt at 5°C for 10-60 days was effective, but the optimum period of chilling varies with strains.