Identification of Parental Genome Construction and Inherited Morphological Characteristics in Triploid and AneuploidIntergeneric Hybrids from a Diploid−Diploid Cross between Citrus and Fortunella

Kiichi Yasuda,Hisato Kunitake,Masaki Yahata,Akiyoshi Tominaga,Mai Sato,Miki Sudo

doi:10.3390/agronomy11101988

Kiichi Yasuda, Hisato Kunitake + Show 4 more

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https://doi.org/10.3390/agronomy11101988

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Abstract

We previously obtained two intergeneric hybrids with different ploidies, i.e., aneuploid (2n = 28) and eutriploid, from diploid−diploid crosses between ‘Kiyomi’ tangor (Citrus unshiu Marcow. × C. sinensis (L.) Osbeck) and Meiwa kumquat (Fortunella crassifolia Swingle) as novel breeding materials for a seedless kumquat. In this study, we attempted to clarify the construction of the parental genomes of these hybrids by SSR genotyping and genomic in situ hybridization (GISH)−chromomycin A3 (CMA) analysis. SSR genotyping in NSX43 (LG5) and CiBE2227 (LG8) loci revealed that both hybrids inherited one allele from ‘Kiyomi’ tangor and two heterozygous alleles from Meiwa kumquat. The GISH analysis failed due to the high genomic homology between Citrus and Fortunella. At the same time, the CMA karyotype compositions of the two intergeneric hybrids (H15-701: 2A + 1B + 3C + 13D + 7E + 1F + 1Dst; H15-702: 3A + 1B + 2C + 15D + 4E +1F + 1Dst) and both parents (‘Kiyomi’ tangor: 1A + 2B + 2C + 6D + 7E; Meiwa kumquat: 2A + 2C + 12D + 1F + 1Dst) were completely revealed. We identified the parental genome construction and polyploidization processes in both intergeneric hybrids on the basis of these SSR genotypes and CMA karyotype compositions according to the following theory: the SSR genotypes and chromosome compositions were the same as those of the somatic chromosome and two-fold after the first division (even number) in unreduced gametes caused by first-division restitution (FDR) and second-division restitution (SDR), respectively. Consequently, we determined that both intergeneric hybrids may have had two genomes derived from the 2n male unreduced gamete as a result of the FDR of the Meiwa kumquat. In addition, most horticultural traits of the leaves, flowers, and fruits of both hybrids showed intermediate traits of the parents, but the fruit sizes and flowering habits were more like those of the two inherited genomes of Meiwa kumquat.

Highlights

This article is an open access articleThe kumquat (Fortunella) is closely related to Citrus and Poncirus in the subfamilyAurantioideae (Citroideae) of the family Rutaceae [1]
The clearly separated bands available for simple sequence repeat (SSR) genotyping on polyacrylamide gel were detected in 11 (LG1–6, 8, and 9) of the 18 SSR loci (Table 1)
‘Kiyomi’ tangor and Meiwa kumquat each had one or two alleles, while each intergeneric hybrid inherited one to three parental alleles, except that an allele nonspecific to both parents was detected in SSR08B62

Summary

Introduction

This article is an open access articleThe kumquat (Fortunella) is closely related to Citrus and Poncirus in the subfamilyAurantioideae (Citroideae) of the family Rutaceae [1]. The kumquat (Fortunella) is closely related to Citrus and Poncirus in the subfamily. In Japan, the Meiwa kumquat (F. crassifolia Swingle) is eaten mainly in raw form or processed as candied fruit, jam, or marmalade. For this species, achieving seedlessness is one of the most important goals, because the relatively large seeds in the bite-size fruits are a major impediment to the distributed under the terms and conditions of the Creative Commons. Only two varieties of kumquat have been registered as seedless or as having few seeds under the Plant Variety Protection and Seed.

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