Bud dormancy allows most deciduous fruit tree species to avoid injury in unsuitable environments, synchronize their annual growth, and adapt to a temperate zone climate. Because bud dormancy affects next season’s fruit production and vegetative growth, it is considered one of the most important physiological factors that control fruit production. Recent global climate changes require us to better understand the genetic factors regulating bud dormancy, especially those that induce dormancy release and subsequent bud break. In this review, environmental factors that affect the seasonal dormancy depth of Japanese apricot (P. mume Siebold & Zucc.) and peach [P. persica (L.) Batsch] are first outlined. Next, recent progress of genetic, biochemical, and molecular biological studies of Prunus dormancy regulation is described. Recent advances in functional genomics have promoted the discovery of gene function and gene networks associated with bud dormancy regulation. A group of candidate genes for bud dormancy regulation, the DORMANCY-ASSOCIATED MADS-box (DAM) genes in Prunus, are focused. Recently reported expressional analysis suggests a significant role for DAMs in dormancy release and bud break of Japanese apricot and peach vegetative buds. Transformation studies of PmDAM6 have demonstrated that it has an inhibitory effect on the apical growth of poplar (Populus spp.). As bud dormancy is a quantitative polygenic trait, not only DAMs, but also other genes and gene networks appear to regulate bud dormancy. Ongoing and future studies will undoubtedly facilitate the unveiling of the molecular aspects of bud dormancy regulation in temperate fruit tree species of Prunus.

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Peach (Prunus persica) as a species is self-compatible (SC), although most other Prunus fruit tree species are partially or fully self-incompatible. We previously identified 3 mutated S haplotypes, S¹, S², and S^2m, that confer self-compatibility on commercial peach cultivars for fruit production. In this report, we identified 2 novel SC S haplotypes, S³ and S⁴, among 130 peach cultivars and strains consisting mainly of ornamental cultivars and wild strains. The S³ haplotype was found only in ornamental cultivars, while the S⁴ haplotype was found mainly in wild strains. S-RNases in the S³ and S⁴ haplotypes appeared to have no defects in their primary structures. S haplotype-specific F-box (SFB) sequences were also present in the S locus downstream of the S³- and S⁴-RNases. These SFB sequences were in a reverse transcriptional orientation as has been reported in most other functional Prunus S haplotypes; however, both SFB³ and SFB⁴ appeared to be mutated. DNA sequencing of the entire downstream region of SFB³, extending about 12 kbp to the stop codon of S-RNase, revealed the presence of a premature stop codon 975 bp downstream from the SFB³ start codon. No sequence homologous to SFB downstream of the stop codon was found. There was a 4946 bp insertion in the middle of SFB⁴. The original SFB⁴ sequence, obtained by removing the inserted sequence, encodes a typical SFB. Based on the 3 previously identified peach S haplotypes, we supposed that the S³ and S⁴ haplotypes were also SC pollen part mutant (PPM) S haplotypes. Here, we also discuss possible reasons for all peach S haplotypes identified so far having the PPM SC S haplotype.

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Sexuality of crops affects both cultivation and breeding systems. Cultivated persimmon (Diospyros kaki Thunb) has a morphologically well-characterized polygamous or gyonodioecious sexual system. However, the genetic basis of sexuality in D. kaki has yet to be characterized. Here, we used dioecious D. lotus L., a diploid wild relative species to hexaploid or nonaploid D. kaki, as a model to clarify the genetic basis of sexuality in Diospyros and to develop molecular markers associated with the sexuality of individuals. Using 62 F₁ offspring segregated into distinct male/female phenotypes, we found two amplified fragment-length polymorphism markers, DlSx-AF4 and DlSx-AF7, which cosegregated with maleness. This could suggest that the sexuality of D. lotus is controlled by a single gene/haploblock, and the male is dominant over the female. Thus, D. lotus’s sexuality can be described as the heterogametic male type, the XY-type, as reported for most other dioecious plant species. For unknown reasons, segregation of the phenotype of a sequence-characterized amplified region marker developed from DlSx-AF4 (DlSx-AF4S) and/or the male/female phenotype in two different crosses in D. lotus showed an apparent bias towards femaleness and better fitted 1:2 than 1:1, which is the theoretical segregation for a single genetic locus or haploblock in diploid D. lotus. DlSx-AF4S could distinguish D. kaki cultivars with female and male flowers from cultivars with only female flowers, strongly indicating that the same genetic system controls D. kaki’s sexuality and that DlSx-AF4S could be used as a genetic marker for sexuality in D. kaki breeding programs.

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In order to improve the use efficiency of a cover crop, hairy vetch (Vicia villosa R., HV), and supplemental chemical N fertilizer, N release and uptake patterns from HV, fast-release N fertilizer (Fast), and slow-release N fertilizer (Slow) in fresh market tomato (Solanum lycopersicum L.) production were investigated using the ¹⁵N-labeling method. In the incubation of soil-added N at two mix rates, 20% Fast + 80% Slow (FS) and 100% Slow (S), a large amount of inorganic N, mainly NH₄⁺-N, was released by FS in 4 weeks. Tomato ‘House momotaro’ was grown in 1/2000 a Wagner pots incorporating such N fertilizer and ¹⁵N-labeled HV residue (30 g DW/pot, about 200 kg N·ha⁻¹). Plant biomass in tomato grown with HV was larger than that grown without HV. HV-derived N (N_dfhv) was taken up by the tomatoes mainly until 4 weeks after transplant (WAT). The uptake amount of N_dfhv was the same in the pot with HV-FS and HV-S. The rate of N uptake derived from HV to total N uptake in tomato plants (%N_dfhv) was 43% in HV-S, higher than that in HV-FS (34%) in 4 WAT; however, such a difference disappeared after 4 WAT. N uptake by tomato plants continued until 12 WAT. Based on these results, HV acted as a fast-release fertilizer. There was competition in N uptake between chemical fertilizer N and HV-released N in the early stage of tomato cultivation. A large amount of chemical fertilizer tended to suppress the uptake of N_dfhv. N uptake by tomato plant continued until the late stage. These results can be applied to establish a suitable combination of HV and chemical fertilizer for tomato production.

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To produce tomato fruits with 6% average Brix without decreasing yield, we investigated the effect of moderate salinity stress on Brix and yield in a single-truss, high-density tomato production system. Because tomato fruit development can be predicted from cumulative temperature, we also assessed cumulative temperature after anthesis as a potential indicator for determining the starting points of salinity stress treatments. When transverse diameters of the first fruit reached 4 cm (i.e., early increase treatment) or the first fruits were at the mature green stage (i.e., late increase treatment), nutrient solution electrical conductivity was slowly increased until the breaker stage from 1.8 dS·m⁻¹ to 6.0 dS·m⁻¹. Plants subjected to the late increase treatment produced tomato fruits with Brix values of 6% without reductions in marketable yield. We also increased nutrient solution electrical conductivity based on cumulative temperature after anthesis and found that early-treated plants produced tomatoes with higher Brix levels and yields than late-treated plants. In summary, moderate salinity stress to avoid excessive stress on plants increased sugar concentrations without decreasing fruit yield and resulted in tomato fruits with average Brix of about 6% when nutrient solution electrical conductivity was increased at a rate of 0.1 dS·m⁻¹·day⁻¹. Because seasonal differences in cumulative temperature influence the appropriate timing of salinity stress applications, further study is needed to optimize year-round growth under moderate salinity stress in single truss, high-density tomato production systems.

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To improve the yield of a Japanese tomato (Solanum lycopersicum) cultivar and determine how fruit yield changes as a result of grafting, we investigated the effects of a Dutch rootstock [‘Maxifort’ (S. lycopersicum × S. habrochaites): Mx] on the dry matter (DM) production and fruit yield of Dutch and Japanese cultivars. The Japanese cultivar (‘Momotaro York’: My) grafted onto Mx (My/Mx: scion/rootstock) had significantly higher fresh and dry weights of fruits per unit area than My/My. Fruit fresh weight yield per unit area was highly correlated with fruit dry weight (DW) yield (r = 0.96–0.97, P < 0.001), and DW yield was significantly correlated with total aboveground DM (r = 0.71–0.96, P < 0.001) and with DM allocation to the fruits (r = 0.52–0.75, P < 0.01). Total aboveground DM (TDM) was significantly and highly correlated with light-use efficiency (r = 0.98, P < 0.001). However, there was no significant correlation between light-use efficiency and the maximum photosynthetic rate, stomatal conductance, or the light-extinction coefficient. Although stomatal conductance significantly (P < 0.05) differed between the rootstocks at 57 and 119 days after transplanting (DAT), there was no significant difference in the maximum photosynthetic rate between the scion/rootstock combinations at 57 and 119 DAT. These results indicated that the fruit yield of My could be improved by grafting onto Mx, and that the increases in yield and TDM were mainly determined by the increase in light-use efficiency.

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‘No.80’ (Capsicum chinense) from the Caribbean is a valuable genetic source from the aspect of its non-pungent and highly aromatic traits. In the present study, the non-pungency, volatile components, and phylogenetic origin of ‘No.80’ were analyzed with another C. chinense cultivar, ‘No.2’ from Brazil, which is also non-pungent but less aromatic. Expressions and deduced amino acid sequences of acyltransferase (Pun1) of ‘No.80’ and ‘No.2’ were normal compared with a pungent cultivar, ‘Habanero’. Insertions of 7-bp and 8-bp resulting in frameshift mutations were found in the coding regions of putative aminotransferase (p-AMT) of ‘No.80’ and ‘No.2’, respectively. Co-segregation of these insertions with the non-pungent phenotypes in F₁ and F₂ populations obtained from crossing ‘No.80’ or ‘No.2’ with ‘Habanero’ suggested that non-pungency in these cultivars arose from genetic mutations of p-AMT that occurred independently. Moreover, molecular phylogenetic analysis suggested that ‘No.80’, a close relative of ‘No.2’, originates from capsicums migrated from the South American mainland. In addition to pungency, we assessed the volatile components of the highly aromatic ‘No.80’, the less aromatic ‘No.2’, and their F₁ hybrid using gas chromatography. ‘No.80’ contained higher levels of aroma-contributing volatiles than ‘No.2’, which correlated with the stronger and weaker aromas of two cultivars. Further, the fruit of F₁ progenies emitted a number of volatile compounds between or higher than their corresponding parents. Based on these results, the approaches for breeding highly aromatic non-pungent cultivars are discussed.

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Ornamental cabbage (Brassica oleracea var. acephala f. tricolor) cultivars of Japanese seed companies are grown in Europe. Unpleasant odors from cut flowers have become a problem in this region. We investigated volatiles emitted from cut flowers of ‘Hatsubeni’ and ‘Haresugata’, two major Japanese ornamental cabbage cultivars in Europe, by gas chromatography-mass spectrometry (GC-MS). Dimethyl disulfide was identified as the major odor-active component emerging from plants as well as from vase water. Vase water was a major source of unpleasant scents, and odor development was prevented by changing the water frequently. We tested the effects of potential suppressors of dimethyl disulfide emission from cut flowers applied to vase water. Cyprodinil, an inhibitor of the synthesis of dimethyl disulfide from methionine, and aminooxyacetic acid, an inhibitor of enzymatic reactions involved in dimethyl disulfide biosynthesis, did not show any effects. In contrast, isothiazolinonic germicide, a cut-flower preservative, inhibited the rot of cut ends of flower stems and reduced dimethyl disulfide emission from cut flowers by 30–40%. In addition, this germicide significantly inhibited emissions from vase water. Isothiazolinonic germicide is a promising candidate inhibitor of unpleasant scents from cut flowers of ornamental cabbage.

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Two anthocyanins (pigments 1 and 2) were detected from the blue flowers of Nemophila menziesii ‘Insignis blue’ and the purple flowers of its variants as the main floral anthocyanins. These two anthocyanins were isolated from the blue flowers and elucidated to be petunidin 3-O-[6-O-(cis-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside] (1) and petunidin 3-O-[6-O-(trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside] (2), respectively, by chemical and spectroscopic means, and pigment 1 was confirmed as a new anthocyanin in plants. Two flavonol glycosides (pigments 3 and 5) and two flavone glycosides (pigments 4 and 6) were also isolated from the blue flowers, and were identified to be kaempferol 3-(6-rhamnosyl)-glucoside-7-glucoside (3), apigenin 7,4′-di-glucoside (4), kaempferol 3-(2,6-di-rhamnosyl)-glucoside (5), and apigenin 7-glucoside-4′-(6-malonyl)-glucoside (6) as major flavonoids. Among these four flavonoids, however, pigments 4 and 6 (flavones) were not detected in the purple flowers. These results might be attributed to color production in blue and purple flowers.

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