Polyembryony, which is a specific true-seed propagation system generated by somatic embryogenesis in nucellar tissue, occurs widely in the genus Citrus. To refine the genetic map of the polyembryony locus in Citrus, we obtained DNA markers from bulked segregation analysis using an F₁ population derived from ‘Kiyomi’ (‘Miyagawa wase’ (Citrus unshiu Marcow) × ‘Trovita’ orange (C. sinensis (L.) Osbeck)) × ‘Miyagawa wase’. A total of 1681 primers designed from expressed sequence tag (EST) sequences and random 12-base primers were utilized for bulked segregation analysis with modification to screen markers systematically. Five markers linked to the polyembryony locus were obtained, of which two of these markers were converted to sequence characterized amplified region (SCAR) markers. These markers were integrated to a framework map previously constructed by EST-derived cleaved amplified polymorphic sequence (CAPS) markers and placed on the previously reported K-9 linkage group. The refined linkage group with new markers covered 47 cM flanking the polyembryony locus. From haplotype analysis of the region around the polyembyony locus in the progenies and their parents, it was shown that ‘Kiyomi’ had a recombinant haplotype in the flanking region close to the polyembryony locus. Information concerning the linkage map and haplotype structure contributes to marker-assisted selection and further study of the polyembryony locus in Citrus.

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On the 6th day after girdling, the photosynthesis rate of leaves on the 3-year-old stem, 2-year-old stem and new shoot of a branch of a field-grown 4-year-old apple tree decreased. The starch content in the leaves, bark and wood significantly increased, especially in shoot leaves. In the girdled branch, concomitant with the photosynthesis reduction, on the 6th day after girdling, the stomatal conductance of leaves on the 3-year-old stem, 2-year-old stem and new shoot declined. Under this condition, a significant correlation between the photosynthesis rate and stomatal conductance could be recognized. On the other hand, with girdling, the activity of ribulose-1,5-bisphosphate carboxylase (RuBPcase) per leaf area decreased on the basis of the decrease in RuBPcase activity per unit enzyme protein. The initial activity of RuBPcase per leaf area in shoot leaves decreased. Moreover, the activity of RuBPcase per leaf area significantly correlated with the photosynthesis rate. Based on these results, it is suggested that the decrease in the photosynthesis rate of the sink-limited branch of a young apple tree 6 days after girdling is mainly caused by closing of the stomatal aperture and reduction of RuBPcase activity per leaf area.

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Hydraulic conductance is an important index of water flow in plants. We constructed a simple device for measuring the relative hydraulic conductance of fruit tree shoots. The values of vines (kiwifruit and grape) were the highest among 17 species of major temperate fruit trees, followed by deciduous trees (e.g. chestnut, Japanese pear, and peach), evergreen citrus trees (e.g. Kawanonatsudaidai and Satsuma mandarin), and loquat. The diameter and number of vessels and total vessel area in shoots were calculated with image analysis software from photomicrographs of 13 of the species. The diameter of the vessels was largest in vines (kiwifruit and grape), followed by persimmon and chestnut, and smallest in deciduous trees (e.g. apple and Japanese apricot), citrus, and loquat. Relative hydraulic conductance had a higher correlation with the water flow index (Σr⁴/S × (xylem ratio)), calculated from the diameter and number of vessels in the xylem according to the Hagen–Poiseuille law, and than with total vessel area per unit of shoot cross-sectional area.

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We investigated the expression of Japanese pear (Pyrus pyrifolia) and quince (Cydonia oblonga) homologs of Arabidopsis thaliana flowering-related genes LEAFY (LFY) and TERMINAL FLOWER 1 (TFL1) in dissected floral tissues. Japanese pear and quince belong to the subfamily Maloideae (Rosaceae), which is an ancient polyploid; thus, the genome of each plant contains at least two different homologs of LFY and TFL1. We examined the expression of each homolog separately using gene-specific reverse transcription-polymerase chain reaction (RT-PCR). Under the experimental conditions used in this study, there was no difference in the expression pattern of LFY homologs, regardless of the species and homolog type. In contrast, TFL1 homologs were differentially expressed in Japanese pear and quince. In Japanese pear, PpTFL1-1 and PpTFL1-2 were expressed in the apical meristem prior to floral differentiation; however, during floral differentiation, PpTFL1-2 expression disappeared and PpTFL1-1 alone continued to be expressed in the developing inflorescence. In quince, CoTFL1-1 was the only TFL1 homolog detected prior to floral differentiation. Upon floral differentiation, both CoTFL1-1 and CoTFL1-2 were expressed mainly in the domed apical meristem. These expressions decreased to an undetectable level once the apical meristem had transformed into a single flower meristem. Thus, Japanese pear and quince TFL1 homologs are supposed to be involved in the formation of domed apical meristems during early reproductive development. Our results imply the importance of PpTFL1-1 in morphological development of Japanese pear inflorescence.

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To search for specifically expressed genes during resistant responses against Rhizobium vitis infection from grapevine leaves, the project employed a new and accurate reverse transcription-polymerase chain reaction (RT-PCR) method using annealing control primers (ACPs) to minimize the incidence of false-positive clones. Twenty ACPs were used to identify and sequence 31 differentially expressed genes (DEGs). Basic Local Alignment Search Tool (BLAST) searches revealed that 27 of these genes are known. Of the known genes, six were selected and further characterized using semi-quantitative RT-PCR analysis to assess their specific expression in plants infected with R. vitis. Results of the analysis suggest that the ACP system is a very useful tool for identifying disease resistance-specific genes in grapevines. Further analysis of the cloned differentially expressed genes will provide insights into the molecular basis of disease resistance expression.

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The present experiment was conducted to clarify the effects of different fertigation systems (drip or sub fertigation) in combination with 2 formulae of nutrient solution (modified Enshi formulation or Shizudai tomato formulation) at EC 4 dS·m⁻¹ on the response of “High soluble solid content tomato” grown in soilless culture systems from September, 2005 to February, 2006. The growth, total yield and size of fruit decreased in the sub fertigation system regardless of the nutrient solution formulation. On the other hand, the soluble solid content was higher in the sub fertigation system. Sub fertigation inhibited water uptake compared to drip fertigation. EC of the medium solution was higher in the sub than drip fertigation system, and higher with the Shizudai than the Enshi formulation. The highest and lowest EC values were 29.6 and 16.1 dS·m⁻¹ in Sub × Shizudai and Drip × Enshi treatment, respectively. The matric potential of medium in the sub fertigation system was higher than that in the drip fertigation system. The proline concentration of leaves taken on November 17 and December 2 was higher in the sub than the drip fertigation system regardless of the nutrient solution formulation. Judging from the above results, growth and yield suppression in the sub fertigation system seems to be mainly caused by salinity stress, not by water stress.

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A restriction fragment length polymorphism (RFLP) marker, HC352b, has identified as closely linked to the CRa locus responsible for clubroot resistance (CR) in a study dissecting CR loci in Chinese cabbage (Brassica rapa L. ssp pekinensis). Unfortunately, the RFLP pattern, including HC352b detected by the cDNA clone HC352, was complicated and confused in its interpretation because it represented multiple-copy loci. To provide a practical HC352b marker for CR breeding programs, a sequence characterized amplified region (SCAR) marker was constructed along the analysis of HC352 genes, followed by its evaluation for CR selection. Schematic characterization of signals was achieved by identification of HC352 homologous genes with their restriction sites, employing CRa-positive and -negative doubled haploid (DH) lines. Genomic sequence information from a set of HC352 homologous genes was analyzed to identify the CRa linked paralog HC352b, followed by the successful designation of a SCAR marker. This correctly predicted the CR phenotypes of all tested individuals of F₂ and back-crossed progenies.

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Seeds of 14 lettuce cultivars for spring or summer cultivation were sown in cell trays filled with seeding mixture and kept in growth cabinets at 20, 30, or 35°C for six days to study emergence inhibition at high temperatures. All cultivars commenced emergence on day three after sowing at 20°C, on day two at 30°C, and on days two to five at 35°C. Emergence rates on the day of emergence (at 35°C, on the day when many cultivars began to emerge) and the day after, and the final emergence rate were 52–97%, 77–98%, and 81–100%, respectively, at 20°C; 7–66%, 25–87%, and 61–98%, respectively, at 30°C; and 0–43%, 0–50%, and 1–63%, respectively, at 35°C. All cultivars showed emergence inhibition at 30°C or higher but the degree of inhibition varied greatly between them. The upper temperature limit for emergence, T₅₀, depended greatly on the cultivar, ranging from 31°C for ‘Olympia’ to higher than 35°C for ‘Château’, ‘King Cisco’, and ‘Sacramento’. Comparison of the present results with those of previous reports suggests that breeding efforts over recent decades have generally improved the performance of lettuce emergence at increased temperatures.

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Head weight of cabbage plants grown using half the nitrogen fertilizer applied to control plants (hereinafter referred to as the half-treatment group) and plants harvested on 22 November (November group) was markedly less than that obtained from control plants to which the standard amount of nitrogen fertilizer was applied and harvested on 29 July (July group). Cells from the half-treatment and the leaves from the November groups were smaller than those of the control and the July groups, respectively. Glucose and fructose content in the half-treatment and the November groups was higher than in the control and the July groups. It is therefore suggested that the higher sugar content in leaves of cabbage plants grown on media containing less nitrogen fertilizer and at low temperature occurs in response to the smaller cells in the leaves.

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The effects of four root-volume restrictions (1, 6, 16, and 26 L per plant) and water and salinity stresses on the yield and quality of processing tomato (Solanum lycopersicum Mill. ‘NDM051TM’), including the γ-aminobutyric acid (GABA) content, were investigated under open-field and greenhouse conditions with a fertigation system. In open-field conditions, salinity treatment of EC 5 dS/m in nutrient solution did not increase the total soluble solids (TSS) or GABA content. In salinity treatment of nutrient solution (EC 7 dS/m), TSS (Brix %) was 57% higher and GABA content was 22% higher than non-salinity treatment in a greenhouse. Under open-field conditions, salinity treatment (EC 7 dS/m) and the soil water level of pF 2.7 increased the TSS, but only to 7.0 Brix %, lower than that observed under the salinity-stress conditions in a greenhouse. In addition, salinity stress did not increase the GABA content of tomato fruits under open-field conditions, but tended to increase TSS and GABA under salinity stress with 1 and 6 L root-volume restriction treatment than in 16 L and 26 L treatment. In addition, root-volume restriction suppressed the growth of shoots, especially lateral-shoot elongation, and also decreased the number of tomato fruits produced, but the effects of root-volume restriction on fruit yield were less than salinity stress.

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This study was carried out to investigate the effect of total nitrogen (N) concentration of nutrient solution on the growth and nutrient uptake of Chinese chive (Allium tuberosum Rottler ex Spreng.) and to determine the suitable N concentration for hydroponic nutrient solution. The effects of four total nitrogen concentrations (N3: 3 me/L, N6: 6 me/L, N12: 12 me/L and N24: 24 me/L, NO₃-N : NH₄-N = 2 : 1) on Chinese chive at the nursery stage were studied by deep flow technique (DFT) system. The results showed that the dry weight of N3 treatment was the highest and was 0.70 g/plant. The dry weight and content of potassium (K), calcium (Ca), phosphorus (P), and magnesium (Mg) decreased with the increase of total N concentration of nutrient solution. The result that the dry weight of N3 treatment was highest among the treatments demonstrated that the suitable total N concentration in nutrient solution of hydroponically cultured Chinese chive at the nursery stage was 3 me/L under the conditions of this experiment (NO₃-N : NH₄-N = 2 : 1), and the NH₄-N, NO₃-N, P, K, Ca, and Mg uptake per gram dry matter was 28.6, 36.6, 8.2, 55.2, 10.8, and 2.7 mg, respectively. It also showed that, although the NO₃-N uptake per gram dry matter hardly changed in N24 treatment, the NH₄-N uptake per gram dry matter in N24 treatment increased by 71.7% compared with that of N3 treatment, indicating that overdose and excessive uptake of NH₄-N might be a direct reason for the dry weight reduction of Chinese chive with the elevation of N concentration of nutrient solution in the range of 3 me/L to 24 me/L.

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The effect of exposing runner plants cut from strawberry (Fragaria × ananassa Duch. ‘Tochiotome’) to low temperature to stimulate rooting was examined for its usefulness as a practical strategy for raising seedlings from cuttings taken from runner plants dropping in the air to force elevated bed strawberry culture during the summer. The rooting of cuttings cultured at various temperatures for 7 days was good at 15°C to 25°C but was reduced at 5°C and 30°C; however, cuttings excised from ten different cultivars showed varying responses for the most suitable temperature for rooting. The rooting of cuttings from ‘Tochiotome’ cultured at 30°C for 5 days after pretreatment at 5°C for 2 days was almost the same as for cuttings cultured at a constant 15°C for 7 days, but rooting of cuttings cultured at 30°C for 7 days was retarded. Interestingly, rooting was observed by storing only the crown at 5°C for 2 days even if both foliage and shoot tip were detached. Rooting was better in dark conditions than with 16-h day length, and was best for the subsequent development stage of runner plants with 2.5 leaves attached. Our results showed that rooting occurred during summer by culturing cut runner plants with 2.5 leaves at 30°C for 5 days after pretreatment at 5°C in the refrigerator for 2 days in the dark.

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Chromosome doubling by colchicine treatment, and the morphological characteristics of tetraploids and their inheritance were investigated in Salvia. Colchicine treatment of seeds had little effect on germination, but adversely affected true leaf development and the survival rate of seedlings. A 50% reduction in true leaf development was observed at 500 ppm colchicine in S. coccinea ‘Coral Nymph’, at 250 ppm in ‘Lady in Red’ and at 750 ppm in S. patens ‘Blue Angel’. Of 50 seeds of S. coccinea ‘Coral Nymph’ treated with 500 ppm colchicine, 12 seedlings survived, of which five individuals were confirmed to be tetraploid, including two presumed chimeric polyploids. The tetraploid plants had larger, thicker leaves and enlarged inflorescences and flowers compared with diploid plants, which increased their ornamental value. Most of the tetraploid plants produced viable pollen and self-pollinated seeds were obtained from four tetraploid individuals. The 18 second-generation seedlings were confirmed to be tetraploids and their flower and leaf morphologies were identical to those of the tetraploid parents.

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The contents of total nitrogen and free amino acids of Eustoma grandiflorum were investigated during flower development and senescence in potted flowers, and were compared between potted and cut flowers, with or without sucrose supply. The total nitrogen content declined gradually as flower development and senescence proceeded in potted flowers. Detectable free amino acids by high performance liquid chromatography (HPLC) analysis in the petals were Asp, Glu, Asn, Gln, Ser, Phe, Gly, Thr, Ala, Tyr, and Val. The level of Gln was consistently high throughout flower development and senescence. Asn levels exhibited remarkable accumulation during flower senescence. The levels of other amino acids were much lower, but most showed a gradual increase until the initiation of wilting. Cut flowers without sucrose supply showed insufficient flower development and lower content of dry matter; however, total nitrogen content per corolla was not significantly different from potted flowers and cut flowers supplied with sucrose, resulting in a higher content of nitrogen per dry weight. These cut flowers without sucrose supply exhibited excessive accumulation of Asn and Gln at anthesis. Although nitrogen content per fresh weight or dry weight was slightly lower in the cut flowers with sucrose supply, their keeping quality was equivalent to potted flowers.

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A recently developed positron-emitting tracer imaging system (PETIS) noninvasively produces quantitative real-time images of the movement of various compounds in plants. To clarify the mechanism of the growth and development of the fruit of eggplant (Solanum melongena L.), we fed ¹¹CO₂ to a leaf and monitored the translocation of ¹¹C-labeled photoassimilate into the fruit by PETIS. Continuous images of the translocation of [¹¹C]photoassimilate from the leaf to the fruit and inside the fruit were produced, with a shorter time resolution than reported previously. ¹¹C signal intensity in the fruit increased gradually, and its distribution was not uniform. The fruits were sliced after PETIS measurement and exposed to the imaging plates of a bio-imaging analyzer system. The resultant images showed the localization of ¹¹C activity inside the fruit, and indicated that translocation of photoassimilate within the fruit was not uniform. The velocity of photoassimilate translocation in the peduncle and changes in the rate of translocation of photoassimilate in the fruit were estimated by analysis of PETIS data. The velocity of photoassimilate translocation through the peduncle was estimated as 1.17 cm·min⁻¹. About 60 min after the start of ¹¹CO₂ feeding, the ¹¹C activity of the fruit began to increase, and by 120 min it had reached about 8% of feeding ¹¹CO₂. These results indicate that it took about 60 min for the first [¹¹C]photoassimilates to reach the fruit. Real time observation of photoassimilate translocation within a fruit has never been reported. PETIS may be a powerful tool for revealing the mechanisms of fruit development and maturity.

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