For identification of genes responsible for varietal differences in flowering time and leaf morphological traits, we constructed a linkage map of Brassica rapa DNA markers including 170 EST-based markers, 12 SSR markers, and 59 BAC sequence-based markers, of which 151 are single nucleotide polymorphism (SNP) markers. By BLASTN, 223 markers were shown to have homologous regions in Arabidopsis thaliana, and these homologous loci covered nearly the whole genome of A. thaliana. Synteny analysis between B. rapa and A. thaliana revealed 33 large syntenic regions. Three quantitative trait loci (QTLs) for flowering time were detected. BrFLC1 and BrFLC2 were linked to the QTLs for bolting time, budding time, and flowering time. Three SNPs in the promoter, which may be the cause of low expression of BrFLC2 in the early-flowering parental line, were identified. For leaf lobe depth and leaf hairiness, one major QTL corresponding to a syntenic region containing GIBBERELLIN 20 OXIDASE 3 and one major QTL containing BrGL1, respectively, were detected. Analysis of nucleotide sequences and expression of these genes suggested possible involvement of these genes in leaf morphological traits.
The complete tack of pungency in pepper {Capsicum annuum L.) is controlled by a single recessive gene (c). To develop a molecular marker linked to ttie C locus, two segregating F2 populations (TM2 and TF2) derived from crosses between occasionally pungent and nonpungent peppers in C. annuum were used. Using the RAPD (random amplified polymorphic DNA) technique in combination with a butked segregation analysis, two RAPD markers, OPD20-800 and OPY09-800, were obtained. Of the two markers, the more closely linked marker, OPY09-800, was converted into a codominant CAPS (cleaved amplified polymorphic sequence) marker using data from the alignment ofthe two allelic sequences. This CAPS marker was linked to the C locus (3.6 cM in the TF2 population), and polymorphism was detected among accessions within C. annuum. This marker might be helpful for the selection of a c gene in backcross and progeny tests in a conventional breeding system.
With the rooted cutting ir radiated in the incubator at dif ferent light intensities (PPFD:Photosynthetic Photon Flux Density;0,2,7,70,1300µmolm-2 s-1), changes in leaf color and the ingredients of the new shoots were investigated. For three weeks from the two-leaf stage of the first crop of tea, the changes in PPFD, leaf color and the ingredients of the new shoots were investigated while directly covered at different shading rates (0%, 85%, 98%, 100%). PPFD 70µmolm-2 s-1 made the leaf color dark green, PPFD 7 2µmolm-2 s-1 made it a lighter green, and PPFD 0µmolm-2 s-1 etiolated it to white. In the field test, 85% shading made the leaf color dark green, 98% shading made it a lighter green, while 100% shading etiolated it to white. In the daytime, as the shading rate increased, PPFD decreased; 930µmolm-2 s-1 under open air, 112µmolm-2 s-1 under 85%, 7µmolm-2 s-1 under 98%, and 0µmolm-2 s-1 under 100%. PPFD on a rainy day decreased to 10% on a fine day, and was at the same level as it was when under 85% shading on a fine day. PPFD under 85% shading on a rainy day was at the same level as it was when under 98% shading on a fine day. The content of amino acids in the new shoot increased as PPFD lowered and the rate of shading rose. Particularly, the amino acids in shoots with 100% shading increased more than double, as compared with the starting time of their covering. Arginine increased about 3 times, serine about 4 times, and asparagine about 50 times. The content of catechin, in the new shoot was higher when it was under PPFD1300µmolm-2 s-1 and 0µmolm-2 s-1 than under PPFD70µmolm-2 s-1. The content of caffeine increased as PPFD was lowered and the rate of shading rose. In conclusion, it was found that decreased PPFD levels makes the leaf color of new shoots dark green. PPFD7 2µmolm-2 s-1 makes it a lighter green, PPFD0µmolm-2 s-1 etiolates it to white, and the content of amino acids in new shoots increases remarkably.
The tea (Camellia sinensis cv. 'Yabukita') leaves grown under the strong shading treatment are tinged with white as well as increase the content of amino acids. We investigated the effects on the tea leaves by this treatment, using nine distantly-related cultivars. As a result, all cultivars' leaves turned white color dramatically and increased the content of amino acids. It was considered that the change of tea leaf color under this treatment has nothing to do with genotype, since amino acids in white leaves grown under this treatment differ in composition from those in normal white leaf tea cultivars. Accordingly, this technique is expected to be applicable for any tea cultivars.
We identified three physical positions associated with embryo yield in microspore culture of Brassica rapa by segregation distortion analysis. We also confirmed their genetic effects on the embryo yield. Isolated microspore culture is well utilized for the production of haploid or doubled-haploid plants in Brassica crops. Brassica rapa cv. 'Ho Mei' is one of the most excellent cultivars in embryo yield of microspore culture. To identify the loci associated with microspore embryogenesis, segregation analysis of 154 DNA markers anchored to B. rapa chromosomes (A01-A10) was performed using a population of microspore-derived embryos obtained from an F1 hybrid between 'CR-Seiga', a low yield cultivar in microspore-derived embryos, and 'Ho Mei'. Three regions showing significant segregation distortion with increasing 'Ho Mei' alleles were detected on A05, A08 and A09, although these regions showed the expected Mendelian segregation ratio in an F2 population. The additive effect of alleles in these regions on embryo yield was confirmed in a BC3F1 population. One region on A08 containing Br071-5c had a higher effect than the other regions. Polymorphism of nucleotide sequences around the Br071-5c locus was investigated to find the gene possibly responsible for efficient embryogenesis from microspores.
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