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  • Author or Editor: Masahiko Yamada x
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The textural properties of grape berry flesh were evaluated with a puncture test using a total of 87 cultivars, consisting of 62 vinifera cultivars (Vitis vinifera L.) and 25 labruscana cultivars (Vitis labruscana Bailey) in order to search cultivars with crisp flesh texture for table grape breeding. Crisp texture is the most desirable texture for tableuse, and was determined as easy breakdown on mastication and firm flesh, which was measured as small deformation at the first major peak (DFP) and large maximum force (MF), respectively, in force-deformation curve of the test. For the vinifera cultivars, the mean values of DFP and MF were significantly smaller and larger in table-use cultivars than wine-use and dual-purpose cultivars, respectively. The result indicated that the vinifera wine-use and the dual-purpose cultivars had soft and non-crisp flesh. Based on the puncture tests, the cultivars with a crisp texture (2.5 mm ≥ for DFP and 0.9 N ≤ for MF) were limited to 11 vinifera table-use cultivars such as `Baladi', `Cardinal', and `Muscat of Alexandria'; and one vinifera dual-purpose cultivar (`Terbash'). The DFP was generally high in labruscana cultivars, which include table-use and dual-purpose cultivars, resulting in lacking cultivars with crisp texture among labruscana cultivars. These results indicate that the cultivars with a crisp texture were restricted to a small source within vinifera cultivars.

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Environmental variance components were estimated for calyx-end fruit cracking in pollination-constant and nonastringent cultivars and selections of Japanese persimmon (Diospyros kaki Thunb.). The cracking value of a tree in a cultivar or selection (genotype) (X) was evaluated as the number of fruit that cracked divided by the total number (25) of fruit evaluated from each tree. Because the mean value of X was correlated with the variance of X, analyses of variance were performed using its square root value. The variance associated with genotyp× year interaction was the largest of environmental variance components. The variances associated among years and among trees within genotypes were very small. The mean percentage of cracked fruit in evaluation for 10 years was 3% for `Fuyu', 11% for `Matsumotowase-Fuyu', and 12% for `Izu'. On the basis of the environmental variance components obtained, it is proposed that all offspring genotypes exhibiting a phenotypic cracking incidence of less than 20% and 11% should be selected in single-year and three-year evaluations, respectively, when those genotypes are evaluated using 25 fruits from a single tree, in order to successfully select all genotypes with an genotypic incidence of less than 3%.

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We estimated environmental variance components for fruit weight (FW), ease of peeling (EP), firmness of segment membrane (FSM), soluble solids content (SSC), and acidity of 20 mandarin and related cultivars used as cross-parents in citrus breeding in Japan. The variance by year was largest for FW (38% of the total) and SSC (23%), but negligible for EP, FSM, and acidity. Variance among trees and tree × year interaction were negligibly small except for FW, whereas the genotype × year interaction variance ranged from 9% to 22% of the total. Variance among fruits from the same tree was the largest environmental component for EP and FSM. Broad-sense heritability (h B 2) was 0.29 for FW, 0.52 for EP, 0.11 for FSM, 0.34 for SSC, and 0.65 for acidity in evaluations performed using single-year measurements of one tree with one fruit. Yearly repetition was more efficient than tree replication for increasing h B 2 of all traits investigated. Increasing fruit number from one to five in combination with yearly repetition also increased h B 2, especially for EP and FSM.

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The effectiveness of detected quantitative trait loci (QTLs) and molecular markers associated with them in tree fruit breeding is measured by the percentages of the variance associated with detected QTL effects accounting for not phenotypic variance, but genetic variance of the trait. The genetic variance can be obtained by subtracting environmental variance from the phenotypic variance. Once accurate environmental variance components are obtained for a given selection field, environmental variances under any number of replications and measurement repetitions can be estimated. We estimated environmental variance components of fruit ripening date measured by days in a Japanese pear (Pyrus pyrifolia Nakai) breeding field in the National Institute of Fruit Tree Science, Tsukuba, Ibaraki, Japan. We estimated variance among fruits within a tree (σf 2) as 25.6, among trees within a genotype (σt 2) as 0.2, among years (σy 2) as 9.4, associated with genotype × year interaction (σgy 2) as 7.9, and associated with tree × year interaction (σty 2) as 1.2. Because σf 2 was the largest environmental variance component, increasing the number of fruit evaluated would most effectively reduce the environmental variance, and tree replication would not because of very small σt 2 and σty 2. The 95% confidence limit of a genotypic value was ± 10 days in the evaluation of five fruits on a single tree in a year and ± 7 days over 2 years. Broad-sense heritability in a family, each offspring in which was evaluated using five fruits on a single tree in a single year, was estimated at 0.83 for three full-sib families analyzed.

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Japanese persimmon (Diospyros kaki Thunb.) cultivars are classified into four types depending on the nature of astringency loss of the fruit. The pollination-constant, non-astringent (PCNA) persimmons lose their astringency on the tree as the fruits develop. This PCNA trait is qualitatively inherited and recessive to the other three types, pollination-constant, astringent (PCA), pollination-variant, nonastringent (PVNA), and pollination-variant, astringent (PVA). In fact, crosses among Japanese PCNA cultivars yield only PCNA type in F1 generation as shown in recent breeding programs at the National Institute of Fruit Tree Science. Despite these previous results, we demonstrated here that non-PCNA (PVNA, PVA, and PCA) type offspring were derived at relatively high rates in the F1 generation from a cross between `Luo Tian Tian Shi', a PCNA accession from China, and the Japanese PCNA cultivar, `Taishu', despite the fact that `Luo Tian Tian Shi' was confirmed to be a true PCNA type by measuring tannin cell size, a principal morphological characteristic to distinguish PCNA cultivars from non-PCNA ones. When segregations of tannin cell size and tannin content in three progenies of the breeding populations derived from Chinese PCNA `Luo Tian Tian Shi' × Japanese PCNA `Taishu', Japanese PCNA `Shinshu' × Japanese PCNA `Taishu', and Japanese PVNA (non-PCNA) `Kurokuma' × Japanese PCNA `Taishu' were investigated, all offspring between Japanese PCNA cultivars contained only small tannin cells and were PCNA types, and those between Japanese PVNA × PCNA cultivars contained only large tannin cells and were non-PCNA types. However, hybrids between `Luo Tian Tian Shi' and `Taishu' segregated into populations of small and large tannin cells, indicating that `Luo Tian Tian Shi' is likely heterozygous for astringency. Therefore, Chinese PCNA `Luo Tian Tian Shi' should be different from Japanese PCNA cultivars in genetic makeup.

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Early ripening [earlier than 1 Aug during fruit harvest time (FHT)], large fruit weight (FW; >1000 g), high sugar content [>17% soluble solids content (SSC)], and low acidity in fruit juice (<0.7%) are important breeding targets of pineapple for table fresh fruit use in Japan. We investigated the efficiency of primary selection based on the four fruit traits using 129 first-fruiting F1 offspring population of ‘Yugafu’ × ‘Yonekura’ without replicates. Separately, environmental variances were estimated by an analysis of variance using evaluation data from 50 or 49 offspring in three replicates and two-year repeats. The phenotypic distribution in the 129 F1 population approached a normal distribution (P > 0.05). The genotypic distribution was obtained as a normal distribution with the population mean as the mean and genotypic variance obtained by subtracting the environmental variance from the phenotypic variance. The target genotypes were estimated at 14.4%, 58.7%, 5.0%, and 50.0% of the F1 population for FHT, FW, SSC, and acidity, respectively. Critical phenotypic values were established as the upper (FHT and acidity) and lower (FW and SSC) limits of the critical genotypic values at the 95% probability level. The phenotypic selection was made based on the critical phenotypic value, resulting in 45.0%, 88.4%, 27.1%, and 79.1% of the offspring selected for FHT, FW, SSC, and acidity, respectively, and 12.4% simultaneously for all four fruit traits. The results showed that the phenotypic primary selection reduced the population size to 12.4%, avoiding the discarding of target genotypes with a low risk. If breeders intend to further reduce the population size, then increasing the number of traits subject to primary selection would be effective.

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Pollination-constant and non-astringent (PCNA)-type persimmon has probably originated from astringent (non-PCNA)-type as a mutant that terminates condensed tannin accumulation at an early stage of fruit development. This trait is confirmed to be recessive and is controlled by a single locus. Since PCNA-type fruit stops tannin accumulation at an early stage, comparison of the gene expressions between PCNA- and non-PCNA-type will reveal the genes conferring condensed tannin accumulation in persimmon fruit. We performed suppression subtractive hybridization (SSH) analysis for detecting differentially expressed genes in non-PCNA-type fruit using BC1 offspring from a cross between PCNA `Fuyu' and non-PCNA “275-13” (F1 progeny derived from non-PCNA `Aizumishirazu' × PCNA `Taishu'). Fruits from seven individuals of PCNA or non-PCNA offspring in BC1 were sampled at early two stages of fruit development and total RNA was extracted by hot borate method from each fruit of different stage. Then, RNA was pooled as PCNA or non-PCNA bulk at two stages and cDNA was synthesized from each bulk for SSH analysis. A total of 5000 clones expressed differentially in non-PCNA-type fruit were picked from SSH library of two stages and 198 positive clones confirmed by differential screening were sequenced. The homologous sequences for the genes involved in flavonoid biosynthesis (CHS, CHI, F3H, F3'5'H, DFR, UFGT, and ANS) were obtained from the clones. The genes that are not considered to be involved in flavonoid biosynthesis so far (SCPL and DHQ) were also detected with high frequencies. We will discuss the role of these genes for condensed tannin accumulation in persimmon fruit.

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Pollination-constant and nonastringent (PCNA) is one of the most desirable traits in persimmons as this type of cultivar loses its astringency while still on the tree before harvest. Among Japanese PCNA cultivars, the trait is qualitatively inherited and recessive to pollination-constant, astringent (PCA), pollination-variant, nonastringent (PVNA), and pollination-variant, astringent (PVA) types. However, in a previous trial, both astringent and nonastringent types segregated in the F1 population that resulted from a cross between a Chinese PCNA `Luo Tian Tian Shi' and a Japanese PCNA cultivar. Because of the unusual segregation, in this study, we crossed another Japanese PCNA `Okugosho' with `Luo Tian Tian Shi' to confirm the segregation of astringent types by measuring the tannin cell size and tannin concentration at harvest. Previously, we found that astringent types have larger tannin cells than PCNA-type. The F1 hybrid progenies from the cross segregated into both PCNA and astringent-type individuals in approximately 1:1 ratio. Likewise, the F1 population from the astringent-type `Yotsumizo' and `Iwasedo' × `Luo Tian Tian Shi' were ascertained to contain both PCNA and astringent types, which indicates that the PCNA trait of `Luo Tian Tian Shi' was dominant. Thus, this Chinese cultivar has the potential to become an important parental material for future breeding of PCNA persimmons.

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There is a non-astringent type of persimmon that loses its astringency naturally on trees, despite the absence of seeds. This type is called pollination-constant and non-astringent (PCNA)-type. PCNA-type was thought to have originated in Japan as a mutant that terminates tannin accumulation at an early stage of fruit development. This trait is confirmed to be recessive and the PCNA-type must be homozygous in all alleles. In fact, crossing among PCNA-type individuals yields only the PCNA-type in F1, while crossing between PCNA-type and non-PCNA-type yields only the non-PCNA-type. However, a new PCNA cultivar, `Luo Tian Tian Shi', was reported in 1982 to exist in Luo Tian County, China, and this PCNA-type seemed to have different mechanisms to be PCNA-type. Our previous report showed that a crossing between `Luo Tian Tian Shi' and Japanese PCNA `Taishu' yielded both PCNA-type and astringent-type in F1, indicating that the trait of PCNA in `Luo Tian Tian Shi' may be dominant. To confirm this hypothesis, we made crossings between `Luo Tian Tian Shi' and Japanese astringent-type `Yotsumizo' or `Iwasedo', and top-grafted these seedlings for earlier fruiting. As we had some fruits in a total of 25 F1 individuals last year, we investigated segregation of astringency among these individuals. We also confirmed the parental relationships of these progenies by analyzing several SSR markers. We confirmed the segregation of PCNA-type and astringent-type in F1. No mistake of artificial pollination was shown in all individuals by SSR markers. Thus, we concluded that the trait of astringency-loss in `Luo Tian Tian Shi' is dominant and the use of this cultivar as a parent will open a new window for breeding PCNA-type persimmon.

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‘Porotan’ is a Japanese chestnut cultivar (Castanea crenata Sieb. et Zucc.) that was selected from offspring of the cross 550-40 × ‘Tanzawa’ and released in 2006. Its nut is distinguished by a pellicle that is easy to peel after roasting; previously, all Japanese chestnut cultivars were thought to have a pellicle that was difficult to peel. Both 550-40 and ‘Tanzawa’ are Japanese chestnuts, and 550-40 is a selection descended from ‘Tanzawa’. Both 550-40 and ‘Tanzawa’ have a pellicle that is difficult to peel. Among 59 offspring of a cross of 550-40 × ‘Tanzawa’, 12 had an easy-peeling pellicle and 47 had a difficult-peeling pellicle; this ratio is not significantly different from the 1:3 expected ratio for monogenic inheritance based on a chi-square test at P = 0.05. A half-diallel cross without selfings was made among ‘Porotan’, ‘Tanzawa’, and ‘Tsukuba’. All the offspring from ‘Tanzawa’ × ‘Tsukuba’ and from ‘Tsukuba’ × ‘Porotan’ had a difficult-peeling pellicle; in contrast, 39 offspring from ‘Tanzawa’ × ‘Porotan’ segregated in a ratio of 19 difficult-peeling pellicle to 20 easy-peeling pellicle, which is not significantly different from the expected 1:1 ratio for monogenic segregation based on a chi-square test at P = 0.05. These results suggest that the easy-peeling pellicle trait of ‘Porotan’ is controlled by a major recessive gene at a single locus. We designated the pellicle peelability locus as P/p. According to this model, the ‘Tsukuba’ genotype is homozygous-dominant (PP), the ‘Tanzawa’ genotype is heterozygous (Pp), and the ‘Porotan’ genotype is homozygous-recessive (pp).

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