Kenji Beppu

Adverse effects of high temperature on the development of reproductive organs in ‘Hakuho’ peach trees

Summary To examine the effect of the temperature on the development of reproductive organs, potted plants of five year old ‘Hakuho’ peach were exposed to constant temperatures of 15°C, 20°C, 25°C, 30°C, and natural conditions. The rate of flower and leaf bud burst, and flowering were recorded every day. The characteristics of reproductive organs in each treatment were examined by measuring flower size, pollen germinabitily, pollen tube elongation, development of embryo sacs, and fruit set. Percentage of flower bud bursting at 30°C was about 80% within 3 d after the onset of the treatment, while it took 18 d to reach the same percentage in the control. Flower bud break preceded leaf bud break in all treatments. Flowering was earliest at 30°C, and the period from bud burst to flowering was as short as 3–4 d. Flower sizes were significantly decreased with increasing temperature. The pollen germination was negatively affected by higher temperature, but the pollen tube elongation in the pistils was faster at higher temperatures. On the other hand, the development of the embryo sac at high temperature was considerably less satisfactory than that at lower temperature and under field conditions. High temperatures also significantly reduced the percentages of fruit set. The results suggested that the high temperature above 25°C interferes with the normal development of reproductive organs especially embryo sac, and causes poor fruit set in ‘Hakuho’ peach.

Diversity of S-RNase genes and-s-haplotypes in Japanese plum (Prunus salicina Lindl.)

Summary This report demonstrates the diversity of S-haplotypes in Japanese plum by molecular cloning of genomic DNAs and cDNAs that encode S-RNases. Nine different DNA fragments, designated as Sa–Si, were obtained from 17 Japanese plum cultivars by PCR with an S-RNase gene-specific primer set, Pru-C2 and PCE-R. Eleven different S-haplotypes were found in these cultivars. The banding patterns obtained with another S-RNase gene-specific primer set, Pru-T2 and PCE-R, corresponded to the S-haplotypes predicted from the Pru-C2 and PCE-R primer set. Several cultivars had the same S-haplotypes. Partial genomic DNAs for eight S-RNase genes and cDNAs for two S-RNases were cloned and sequenced. Deduced amino acid sequences contained conserved regions among the rosaceous S-RNases. Comparisons of the sequences from cDNAs and genomic DNAs revealed the presence of two introns in the S-RNase genes of Japanese plum as in other Prunus S-RNase genes. Pollination incompatibility groups and self-compatibility in Japanese plum were discussed with reference to the S-haplotypes.

Determination of S-haplotypes of Japanese plum (Prunus salicina Lindl.) cultivars by PCR and cross-pollination tests

Summary S-haplotypes of Japanese plums were determined by PCR and cross-pollination tests. Five novel S-RNase genes corresponding to Sj- to Sn- haplotypes were identified by PCR with an S-RNase gene-specific primer set, Pru-C2 and PCE-R. Thirteen new S-genotypes (S-haplotype combinations) were found in the 19 cultivars used. Several cultivars had the same S-genotypes. Partial genomic DNAs for six S-RNase genes were cloned and sequenced. Deduced amino acid sequences contained conserved regions among the rosaceous S-RNases. Cross-pollination and pollen-tube growth tests revealed that pollen-tube growth was arrested in the upper middle part of stylar tissue in the crosses between the self-incompatible cultivars with the same S-genotypes. These results showed the first evidence for the existence of S-RNase-based cross-incompatibility in Japanese plum.

Effect of high temperature exposure time during flower bud formation on the occurrence of double pistils in 'Satohnishiki' sweet cherry

Abstract Exposure time of trees to high temperatures during flower differentiation influenced the occurrence of double pistils in ‘Satohnishiki’ sweet cherry. Mature trees were grown under both early and late forcing, and under non-forcing conditions until harvest in a commercial orchard located in Kagawa, southwestern Japan. In mid-July, when the maximum temperature began to rise rapidly following the rainy season, petal and stamen primordia had been formed in the buds under early forcing (93%) and late forcing (69%) conditions, but under non-forcing conditions most of the buds were still at the stage of sepal differentiation. Pistil doubling rarely occurred under forcing conditions, whereas 10.3% of the flowers developed double pistils under non-forcing conditions. In another experiment, potted trees were exposed to high temperatures (35°C/25°C, day/night) for 15 days at intervals of 15 days during the period from late-June to early-September. High temperature induced double pistils most severely in the buds that contained sepal and petal primordia at the beginning of the treatment, and the frequency of occurrence of double pistils was slightly lower in the buds treated at the earlier stage of flower differentiation. On the other hand, high temperature had little effect on pistil doubling in buds with differentiated stamen and pistil primordia. These results suggest that (1) the buds are most sensitive to the induction of double pistils at high temperatures at the transition stage from sepal to petal differentiation, and (2) forcing culture can be applied to sweet cherry production in warm areas to reduce double pistil formation by avoiding the exposure of buds to high temperatures while the buds are still in the sensitive period.

Se-haplotype confers self-compatibility in Japanese plum (Prunus salicina Lindl.)

Summary Involvement of the Se-haplotype in self-compatibility in the Japanese plum cultivars ‘Santa Rosa’ (ScSe) and ‘Beauty’ (ScSe), was investigated. Self-pollination and pollen-tube growth tests confirmed that cv. ‘Rio’, which also has a Se-haplotype (SaSe), is self-compatible. In self- and cross-pollination experiments between cultivars with the ScSe haplotype, the resultant progenies segregated into two S-haplotypes, ScSe and SeSe, suggesting that only the Se-haplotype was inherited in progeny from the male parent. These results indicated that the Se-haplotype is responsible for self-compatibility. Expression analyses of S-RNase showed that the Se-RNase gene was transcribed in the style. Therefore, it appeared that inhibition of transcription of the S-RNase gene is not responsible for the self-compatibility in the Se-haplotype of Japanese plum.

Artificial shading reduces the occurrence of double pistils in ‘Satohnishiki’ sweet cherry

The effect of artificial shading in summer and early autumn on the occurrence of double pistils in ‘Satohnishiki’ sweet cherry was studied. Potted trees were grown in steel frame structures covered with woven shade cloth made of silvered polyethylene and providing 53% and 78% light reduction, from 23rd July to 4th October in 1995 and from 16th July to 16th September in 1997. In 1995, shading levels of 53% and 78% reduced the daily maximum air temperature by 1.88C and 3.28C, respectively, compared to the unshaded control. Forty-seven percent of the buds on nonshaded trees formed double pistil primordia, and 51% of them developed into flowers with double pistils the following spring. Reducing light 78% reduced the frequency of double pistils to 24% in buds and 1.5% at anthesis, whereas 53% shade reduced the frequency of double pistils only slightly. Doubling was classified into three groups based upon relative length of the two pistils: (1) one pistil much shorter than the other (S), (2) one pistil about half the length of the other (M), and (3) pistils of approximately equal length (L). The frequency of flower primordia with equally developed pistils in autumn buds corresponded to that of flowers with double pistils at anthesis. A 78% level of shading markedly reduced the rate of flower primordia with two equally developed pistils. Because of the relatively cool summer in 1997, the frequency of double pistils in autumn buds, even under unshaded conditions, was about half of that in 1995, but shadings still reduced the frequency of double pistils to less than 3%. These results suggest the possibility of applying artificial shading to reduce the occurrence of double pistils in ‘Satohnishiki’ sweet cherry grown in regions with hot summers. # 2000 Elsevier Science B.V. All rights reserved.

Inheritance of self-compatibility conferred by the Se-haplotype of Japanese plum and development of Se-RNase gene-specific PCR primers.

Summary The inheritance of self-compatibility conferred by the Se-haplotype in Japanese plum (Prunus salicina Lindl.) was investigated in various progeny. Only those progeny with the Se-RNase allele set fruit after self-pollination, indicating that self-compatibility conferred by the Se-haplotype was inherited in these progeny (i.e., the Se-haplotype co-segregated with self-compatibility). In addition, Se-RNase allele-specific PCR primers were developed, since detection of the Se-RNase allele using S-RNase consensus primers was time-consuming and not always reliable. PCR using the primer pair Se-Fw1-Plum and Se-Rv1-Plum, designed from a sequence in the second intron of the Se-RNase gene, resulted in a fragment present only in those cultivars and seedlings having the Se-haplotype. Thus, this primer pair specifically amplified the Se-RNase gene. These results suggest that PCR using this primer pair can be used for the early selection of self-compatible offspring with the Se-haplotype when breeding Japanese plum.

Physical and compositional characteristics of ‘mitsuko’ and local hardy kiwifruits in Japan

The fruit characteristics of hardy kiwifruit (Actinidia arguta) in Japan were investigated at several growth stages. Fruit weight of A. arguta ‘Mitsuko’ increased showing a double sigmoid curve. After fruit set, starch accumulated gradually and reached maximum concentration 90 days after full bloom (DAFB). Along with the reduction of the starch, sugar contents increased. Sucrose was a major sugar component in mature fruit. At the early stage of fruit development, myo-inositol was predominant. Quinic acid was prevalent in the young fruit. The amount of quinic acid decreased once in mid-season, and then increased slightly again. Citric acid increased gradually with maturation. The amount of malic acid and soluble oxalic acid was little affected by fruit maturity. The concentration of ascorbic acid was relatively high at the early stage of fruit development. It decreased in mid-season and then remained constant. Among the 2 cultivars and 14 local collections, the fruit shape varied being obovate, oblate, ellipsoid, and clavate. The fresh weight of 16 collected fruits ranged from 3.6 to 25.1 g. Fruit skin was glabrous and the surface color varied from green to dark green. Flesh color was basically green or dark green. Soluble solids content (SSC) of juice ranged from 10.2 to 17.0%. Sugar content varied from 4.1 to 9.5 mg · 100 g−1 FW. Myo-inositol content ranged from 266.4 to 771.1 mg · 100 g−1 FW. Major organic acids were quinic, citric, and malic acid, and citric acid was predominant. Total acid content ranged from 1.4 to 2.1 mg · 100 g−1 FW. Total ascorbic acid content ranged from 22.8 to 222.1 mg · 100 g−1 FW. Protease activity in the juice was generally high and varied from 6.1 to 92.6 nmol ρNA released · min−1, among the cultivars and local collections.

A Y-encoded suppressor of feminization arose via lineage-specific duplication of a cytokinin response regulator in kiwifruit

Duplication of a cytokinin response regulator, followed by the acquisition of a novel expression pattern, generated a Y-encoded sex-determining gene, named Shy Girl in kiwifruit (Actinidia spp). Dioecy, the presence of male and female flowers on distinct individuals, has evolved independently in multiple plant lineages, and the genes involved in this differential development are just starting to be uncovered in a few species. Here, we used genomic approaches to investigate this pathway in kiwifruits (genus Actinidia). Genome-wide cataloging of male-specific subsequences, combined with transcriptome analysis, led to the identification of a type-C cytokinin response regulator as a potential sex determinant gene in this genus. Functional transgenic analyses in two model systems, Arabidopsis thaliana and Nicotiana tabacum, indicated that this gene acts as a dominant suppressor of carpel development, prompting us to name it Shy Girl (SyGI). Evolutionary analyses in a panel of Actinidia species revealed that SyGI is located in the Y-specific region of the genome and probably arose from a lineage-specific gene duplication. Comparisons with the duplicated autosomal counterpart, and with orthologs from other angiosperms, suggest that the SyGI-specific duplication and subsequent evolution of cis-elements may have played a key role in the acquisition of separate sexes in this species.

Expression analysis of UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene in an interspecific hybrid grape between Vitis ficifolia var. ganebu and Vitis vinifera cv. Muscat of Alexandria

Kadainou R-1, an interspecific hybrid grape derived from red (Vitis ficifolia var. ganebu) and white (V. vinifera cv. Muscat of Alexandria) grapes, accumulates high concentrations of anthocyanin in the berry skin. Hence, the expression of uridine 5′-diphosphate (UDP)-glucose:flavonoid 3-O-glucosyltransferase (UFGT), the key enzyme of the anthocyanin pathway, was examined in the berry skin of Kadainou R-1. As information on gene sequences of V. ficifolia var. ganebu and other wild grape species was unavailable, we performed GeneChip hybridization using biotin-labeled genomic deoxyribonucleic acid (DNA) to investigate how the genomic sequences of V. vinifera varieties and that of V. ficifolia var. ganebu differ. The study showed a lower correlation coefficient between V. vinifera cultivars and V. ficifolia var. ganebu than that among V. vinifera cultivars. The sequences of the UFGT gene derived from both parents of the red and white cultivars were sequenced in Kadainou R1 and revealed that both were expressed irrespective of the fact that it was not expressed in the white grape (male parent).