Because fruit trees such as apple (Malus xdomestica Borkh.) flower and set fruit only after an extended juvenile phase lasting several years, efficient breeding of fruit trees is limited. We ...previously suggested that MdTFL1 (Malus xdomestica TFL1) functions analogously to TERMINAL FLOWER 1 (TFL1) and that MdTFL1 is involved in the maintenance of the juvenile/vegetative phase in apple. To clarify the function of MdTFL1 in apple, we produced transgenic 'Orin' apple trees expressing MdTFL1 antisense RNA. One of them flowered only 8 months after the transfer to the greenhouse, whereas the nontransformed control plants have not flowered in nearly 6 years. As expected, the expression of endogenous MdTFL1 was suppressed in the transgenic lines that showed precocious flowering. In addition, the expression level of the transgene was correlated with the reduction of the juvenile phase. These findings confirm that MdTFL1 functions like TFL1 and that MdTFL1 maintains the juvenile and vegetative phase in apple. Flower organs of the transgenic apple trees were normal in appearance, and a precocious flowering transgenic line set fruit and seeds. Interestingly, some flowers of the transgenic apple trees developed without undergoing dormancy. The expression of MdTFL1 in apple may affect flower development as well as flower induction.
Transgenic apple plants that overexpressed Arabidopsis FLOWERING LOCUS T (FT) under the control of the rolC promoter showed early flowering, while the introduction of FT driven by the 35S promoter ...induced flower development directly from transgenic apple callus in vitro, but vegetative growth was not maintained and the explant died. GFP-FT fusion proteins were detectable in transgenic apple tissues but never caused early flowering in the transformants. Under the control of the rolC promoter, the fused protein was localized in vascular tissues and fluorescence was detectable in companion cells in the stem and petiole. The transgenic apple lines that expressed AtFT driven by the rolC promoter showed differences in inflorescence architecture and floral organ number from those typical of nontransformed apple. Flowers of transgenic apple lines often contained more numerous petals, fewer stamens, and no pistils, and the pollen grains were incapable of germinating. The transgenic apple lines showed perpetual flowering without the requirement for low temperature and obvious photoperiodism. The expression patterns of six floral meristem identity genes and floral organ genes in flowers of transgenic apple lines were investigated. Among the floral meristem identity genes, expression of MdFT2 was suppressed and that of AFL2 was dramatically enhanced in the transformants. Of the floral organ genes, expression of MdMADS13, which functions as a class B gene, was unchanged from that of the flower of wild type one, whereas expression of MdMADS-NB, a possible class C gene, was suppressed.
Crown gall, caused by
Agrobacterium tumefaciens
, causes severe damage to apple saplings resulting in weak growth and loss of commercial value. Developing molecular markers linked to crown gall ...resistance genes, and establishing a marker-assisted selection (MAS) for such a trait would be an effective way to improve rootstock breeding for crown gall resistance. The wild apple
Malus sieboldii
Sanashi 63 carries the crown gall resistance gene
Cg
effective against the
A. tumefaciens
strain Peach CG8331 (biovar 2). Applying the genome scanning approach on the mapping population JM7 (
cgcg
) ×
Malus sieboldii
Sanashi 63 (
Cgcg
),
Cg
was mapped on the linkage group (LG) 2. The constructed linkage map of LG 2 of Sanashi 63 spans 59.8 cM and has an average marker density of 3.5 cM per marker. The 191 bp allele of the simple sequence repeat (SSR) NZmsEB119405 co-segregated perfectly with
Cg
in a segregating population of 119 individuals. Quantitative trait loci, accounting for 75.3% to 84.3% of phenotypic variation were detected in the same position. Testing eight additional rootstocks with the NZmsEB119405 SSR marker revealed that the 191 bp allele is also present in crown gall-susceptible rootstock accessions. Only the markers CH03b01 and NZmsPal92 mapping at 0.9 and 4.3 cM from
Cg
, respectively, showed “private” alleles associated to
Cg
.
The two FLOWERING LOCUS T (FT)-like genes of apple (Malus x domestica Borkh.), MdFT1 and MdFT2, have been isolated and characterized. MdFT1 and MdFT2 were mapped, respectively, on distinct linkage ...groups (LGs) with partial homoeology, LG 12 and LG 4. The expression pattern of MdFT1 and MdFT2 differed in that MdFT1 was expressed mainly in apical buds of fruit-bearing shoots in the adult phase, with little expression in the juvenile tissues, whereas MdFT2 was expressed mainly in reproductive organs, including flower buds and young fruit. On the other hand, both genes had the potential to induce early flowering since transgenic Arabidopsis, which ectopically expressed MdFT1 or MdFT2, flowered earlier than wild-type plants. Furthermore, overexpression of MdFT1 conferred precocious flowering in apple, with altered expression of other endogenous genes, such as MdMADS12. These results suggest that MdFT1 could function to promote flowering by altering the expression of those genes and that, at least, other genes may play an important role as well in the regulation of flowering in apple. The long juvenile period of fruit trees prevents early cropping and efficient breeding. Our findings will be useful information to unveil the molecular mechanism of flowering and to develop methods to shorten the juvenile period in various fruit trees, including apple.
With 5 figures and 2 tables ABSTRACT: Fruit acidity is an important characteristic to determine the marketability of apple (Malus × domestica Borkh.). To reveal the mode of inheritance in fruit ...acidity and to estimate the genetic parameters, we performed segregation analysis using a population from an apple breeding programme. Four models (mixed, Mendelian, polygenic and environmental) were compared to find the most likely mode of the inheritance of acidity. The phenotypic variance of acidity in the population was properly explained using a mixed model of a major gene and polygenes. The genotypic values of the major gene (AA, Aa and aa) were estimated to be 0.45, 0.52 and 0.92 g/100 ml in titratable acidity, respectively. The values of the homozygote (AA) and the heterozygote (Aa) were very close and lower than that of the other homozygote (aa), indicating that an allele of the major gene appeared to have complete dominance with a function of lowering acidity. The estimate of the heritability after accounting for the major gene was moderately high, 0.43, in the mixed model. This means that even with removal of the effect of the major gene, acidity could fluctuate considerably by the effect of polygenes. The proportions of progeny with adequate acidity differed greatly, depending on which genotype was used as parents for the crossing. Therefore, it is very important to know the genotypes of parental cultivars before crossing.
Geoparks in Japan have been introduced into high-school education in various forms. However, most take the viewpoint of earth science and lack connections among geoscience, history and culture. A ...geo-story with a geographical viewpoint that treats the arts, social sciences, and natural science comprehensively is required to solve this problem. High-school education at Muroto UNESCO Global Geopark is discussed. Muroto Senior High School conducts Geopark study classes, in which students study geoscience, history, and culture, while planning and carrying out Geopark tours. In classes, students with poor communication skills come to have a sense of self-affirmation by carrying out interview surveys of local residents. In the music class, a geographical viewpoint is introduced to the practice of learning songs related to commercial fishing from local residents. Students learn that the activities of the earth relate to the histories of fisheries together with relations between submarine topography formed by subducting plates and the ecology of sea life. Stimulated by these classes, some students will participate in local traditional festivals and activate the local region in the future. Students learn various things from local residents and find new value in their hometown through their activities. Moreover, schools, government, and local residents, who had not interacted with each other acquire new connections with each other through the Geopark. A chain of new “chemical reactions” among people is one of the values of Geopark activities. To develop such Geopark activities, Geopark specialists, who have geographical knowledge and are capable of thinking and acting with local residents, are essential.
The firmness of the flesh in 27 apple (Malus xdomestica Borkh.) cultivars and selections (genotypes) was measured as an indicator of storage potential at 20 days after harvest under 20 +/- 2 degrees ...C, 80% +/- 5% relative humidity storage conditions. Softening ranged from 9% to 58% of initial values among genotypes after 20 days of storage. In some genotypes, softening was not continuous, a minimum firmness being reached before day 20. After a period of rapid softening, firmness declined to at least 20% of that at harvest. For each genotype, linear regression analysis of firmness changes from harvest until when firmness decreased by 20% was carried out. In genotypes in which firmness did not drop >20% within 20 days of storage, the entire dates to 20 days were used for analysis. The homogeneity of the regression residual variances and their normal distribution was not rejected at P = 0.05, and the linear regression analysis was assumed to be applicable to the change in firmness for each genotype. Results of the regression analysis showed that the regression was significant for all genotypes except one. Therefore, storage potential could be evaluated by comparing the regression coefficient of each genotype.
Progenies from 38 unbalanced crosses using 20 apple (
Malus
×
domestica
Borkh.) cultivars/selections as parents were evaluated for changes in flesh firmness after harvest in two seasons to determine ...the mechanism of inheritance of fruit softening. The change in firmness was fitted by linear regression, and the softening rate (N·d
−1
) expressed as the regression coefficient was used as the phenotypic value of softening after harvest. Fruit were stored under 20 °C and 85% relative humidity after harvest for up to 40 days. The softening rates in the progeny populations were distributed continuously around the softening rates of parents, despite a distinct segregation in the degree of mealiness at 30 days of storage. The narrow-sense heritability of the softening rate was estimated by parent-offspring regression, and the estimate was high (h
2
= 0.93). Because the softening rate can be influenced by mealiness, an undesirable trait in the apple industry, the progenies were divided into individuals with and without mealiness, and the breeding values of the parents were estimated based on the softening rate of the nonmealy progeny. The softening rate of the nonmealy progeny was analyzed using a mixed linear model and the restricted maximum likelihood method, with general combining ability (GCA) as parental effects and specific combining ability (SCA) as parental interaction effects. The variance of GCA was significant, but the variance of SCA was small and nonsignificant. The narrow-sense heritability of the softening rate in the nonmealy progeny was estimated by sib analysis, and the estimate was moderately high (h
2
= 0.55). A significant correlation was observed between the phenotypic value and the breeding value (twice the GCA effects) in nonmealy parents, but the phenotypic value did not significantly correlate with the breeding value in mealy parents. Therefore, contribution of a mealy parent to the softening rate of nonmealy progenies cannot be predicted by its phenotypic value.
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