Persimmon breeding in Japan for pollination-constant non-astringent (PCNA) type with marker-assisted selection

Abstract

Oriental persimmon (Diospyros kaki) originated in Eastern Asia, and many indigenous cultivars have been developed in China, Japan, and Korea. These cultivars are classified into four groups based on their natural astringency loss on the tree and seed formation: pollination-constant non-astringent (PCNA), pollinationvariant non-astringent (PVNA), pollination-constant astringent (PCA), and pollination-variant astringent (PVA). PCNA is the most desirable type because the fruit can be eaten without any postharvest treatment; therefore, one of the goals of our persimmon breeding programs is to release superior PCNA cultivars. The PCNA genotype is recessive to the other three non-PCNA genotypes, and PCNA-type F 1 offspring are obtained exclusively from crosses among PCNA genotypes. Moreover, the number of superior PCNA crossparents have been limited. In the late 1980s, inbreeding depression became obvious, especially in terms of fruit size, tree vigor, and productivity. To mitigate the inbreeding, a backcross program using PCNA [(non-PCNA × PCNA) × PCNA] was started in 1990. This process, however, was inefficient because only 15% of the offspring were PCNA, and all offspring had to be grown to the fruiting stage. Therefore, molecular markers linked to the PCNA locus were developed for discriminating PCNA offspring. A molecular marker linked to Chinese PCNA has also been developed.

Genetic Diversity and Breeding of Persimmon

“…Persimmon growing regions are also spreading widely in Japan and Korea, thus some old well-known Persimmon varieties which were still being produced were selected from these countries. Persimmon has been a major fruit crop in Japan for many years [21] and for Japanese persimmon commercial production, 'Fuyu' (PCNA), 'Hiratanenashi' (PVA) and 'Tonewase' have been the three important cultivars. About 57% of the total area is devoted to these varieties [22].…”

“…Although persimmon is produced in Brazil, Israel, Italy, Spain, Azerbaijan, Uzbekistan, New Zealand and Australia, new persimmon cultivars developed by cross breeding have been released only in Japan and Korea [21] and also in these countries persimmon cultivars have been selected over time for commercial production. Hybridization method can also be used in persimmon breeding.…”

Comparative Mapping of the <i>ASTRINGENCY</i> Locus Controlling Fruit Astringency in Hexaploid Persimmon (<i>Diospyros kaki</i> Thunb.) with the Diploid <i>D. lotus</i> Reference Genome

“…The commercial significance of the astringency characteristic has led to the development of molecular markers co-segregating with the PCNA trait; these markers are being extensively used in ongoing breeding programs (Kanzaki et al, 2010;Sato and Yamada, 2016). To date, however, genetic mapping of AST has not been completed partly because of the high heterozygosity, long juvenile phase, and complex allelic composition of the D. kaki polyploid genome (mainly 2n = 6x = 90).…”

“…Among the four classes, PCNA type cultivars stop accumulating PAs in the early stages of fruit development by down-regulation of enzymes in the PA biosynthesis pathway (Akagi et al, 2009a;Ikegami et al, 2005;Yonemori and Matsushima, 1985). This PCNA trait has been targeted in modern persimmon breeding programs in Japan to reduce the need for labor-intensive and expensive artificial de-astringency treatments that are required to render non-PCNA fruit palatable for consumers (Sato and Yamada, 2016). It has been shown that the PCNA trait is conferred by a recessive allele (ast) at a single locus referred to as ASTRINGENCY (AST) (Akagi et al, 2012;Ikeda et al, 1985;Yamada and Sato, 2002).…”

“…This PCNA trait has been targeted in modern persimmon breeding programs in Japan to reduce the need for labor-intensive and expensive artificial de-astringency treatments that are required to render non-PCNA fruit palatable for consumers (Sato and Yamada, 2016). It has been shown that the PCNA trait is conferred by a recessive allele (ast) at a single locus referred to as ASTRINGENCY (AST) (Akagi et al, 2012;Ikeda et al, 1985;Yamada and Sato, 2002).The commercial significance of the astringency characteristic has led to the development of molecular markers co-segregating with the PCNA trait; these markers are being extensively used in ongoing breeding programs (Kanzaki et al, 2010;Sato and Yamada, 2016). To date, however, genetic mapping of AST has not been completed partly because of the high heterozygosity, long juvenile phase, and complex allelic composition of the D. kaki polyploid genome (mainly 2n = 6x = 90).…”