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@Field of Research on Crop Production Management Systems
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@Field of Research on Crop Genomic Breeding
@Field of Research on Fruit Tree Genomic Breeding
@Field of Research on the Development and Utilization of New Breeding Materials for Ornamental Plants

Outline of field of research on Fruit Tree Genomic Breeding
EStudy on DNA markers, molecular genetics, and genomic breeding of deciduous fruit trees
EResearch on the application of mass data for genomes in apple breeding
EStudy on impact of climate change on fruit production and development of adaptation measures

Toshihiko Sugiura
Because perennial crops have narrower adaptability to climate than annual crops, fruit trees are considered vulnerable to climate change. Recent warming trends have already significantly affected nearly all types of fruit tree species. Therefore, the response to global warming is the most important issue in current fruit tree production.

Since fruit trees are only replanted once in about 30 years, the impact assessment in the future is the information necessary for producers to select the tree species and cultivars to be planted. We are developing models to assess the effects of high temperature on fruit trees and are developing maps that shows the impact on future domestic production by simulation.

In addition, we are developing fertilization management and cultivation methods to reduce the adverse effects of climate change. At the same time, we are studying the introduction of subtropical fruit trees from the viewpoint of the use of global warming.


Left: Assessment of global warming impact (apple 'Fuji')
Right: The suitable regions of the subtropical citrus (Tuncan) production, which is currently cultivated mainly in the Nansei Islands, will spread to the coastal area of western and eastern Japan in the future.
Toshiya Yamamoto
@@We conduct genetic analyses targeting fruit trees in Rosaceae (e.g. pear, peach, apple, loquat, plum, Japanese apricot, apricot, sweet cherry), which account for approximately half of the fruit production in Japan. Specifically, we develop DNA markers, conduct DNA profiling, construct genetic linkage maps, and characterize selection markers forimportant traits.

@@In DNA profiling, a large number of SSR markers (also designated as microsatellites, widely used for parentage analysis in human) with high reliability and high discriminative ability were developed in peach and pear. As a result, it was revealed that the documented parentages of many bud mutation varieties were wrong in peach, and that there were also many examples of false parentage in pear. (Figure 3: PDF). The parentage of the pear cultivar Housui, production of which is the second-highest in Japan, was successfully ascertained by DNA analysis approximately 50 years after its crossing. In addition, DNA identification revealed that the origin of the peaches cultivated in Japan was identified to be a specific variety cultivated in China called eShanhai-Suimitsutouf. DNA identification technique is expected to play a role in preventing the false labeling of fruit tree varieties, preventing illegal fruit imports from foreign countries, and solving problems relevant to cultivar registration and breederfs rights.

@A genetic linkage map was created by using hybrid progenies from a cross between the peach varieties Akame and Juseitou (Figure 4: PDF). Genes conferring morphological traits such as resistance to root-knot nematode, leaf color, flower color, cling or free stoneCflesh color around the stone, and tree height were identified and mapped, and the DNA markers linked to these traits were obtained. In addition, the positions of genes controlling flesh color, acid level, and male sterility were identified. These information and the linked DNA markers are expected to enable us to efficiently breed new varieties of peach, which has a long generation cycle and requires a broad area for cultivation. Furthermore, it was also revealed that the genetic linkage map and DNA markers obtained from peach could be used in almond, Japanese plum, Japanese apricot apricot, sweet cherry, and flowering cherry. These fruit tree species, along with the peach, are the members of the genus Prunus, and their genome structures were highly conserved within the genus.

@For pear, a genetic linkage map was constructed for the first time in the world. We are currently creating a more detailed genetic linkage map by using a hybrid population between the Japanese pear Housui and the European pear Bartlett. We found that the SSR markers developed from apple, closely related species to the pear, could also be utilized in pear. The SSR markers of pear and apple located at almost the same positions on the genetic linkage maps, indicating that genome structures of both species are highly homologous. This information can be applied to loquat, Chinese quince, and quince, which belong to the same sub-family Maloideae. Furthermore, we have begun large scale sequencing analysis on functional genes expressed in pear fruits. We expect to isolate the genes related to fruit quality, fruit development and to identify their function.

Miyuki Kunihisa
Recently, the genetic research is rapidly progressing, through the development of next generation sequencing system. We can obtain even the whole genome sequence of ourselves; therefore, we need to find the steady way and purpose when using the flooding data produced one after another. We have been studying about the genetics of Rosaceae fruits tree, especially apple, for the application to the breeding systems, by using these new technology or mass data.

The genetic dissection of eFujif apple
eFujif is one of the most popular and highly-produced apple cultivars worldwide, due to its long-shelf life and superior taste. It has been frequently used in breeding programs, and many new descendant cultivars were produced. Through the re-sequencing of whole genome of eFujif, we traced the inheritance of eFujiffs chromosomes in these relatives (Figure 1). By comparing the superior characteristics and chromosomes of eFujif inherited to these relatives, we detected the genomic region regulating eFujiffs valuable characteristics (QTL), e.g. long-shelf life and watercore (Figure 2). Such information would support the breeders to select the seedlings having desirable characteristics inherited from eFujif, before fruiting.

The genetic analyses using offsprings of domestic cultivars, e.g. eOrinf and eAkanef
The populations generated from the identical cross of parents are ideal and rare materials for genetic analyses of fruit tree. By using these populations held in apple breeding stations, we detected the QTLs for harvest time, acidity, juice browning, russet, cracking, pre-harvest drop or skin color (Figure 3). Based on these knowledge, we are working on the development of methods for the selection of cross parents that generates the offspring with desired characteristics, or for the prediction of fruit quality before fruiting.