Dataset Information

Tetraploidization events by chromosome doubling of nucellar cells are frequent in apomictic citrus and are dependent on genotype and environment.

ABSTRACT:

Background and aims

Polyploidy is a major component of plant evolution. The citrus gene pool is essentially diploid but tetraploid plants are frequently encountered in seedlings of diploid apomictic genotypes. The main objectives of the present study were to establish the origin of these tetraploid plants and to ascertain the importance of genotypic and environmental factors on tetraploid formation.

Methods

Tetraploid seedlings from 30 diploid apomictic genotypes were selected by flow cytometry and genotyped with 24 single sequence repeat (SSR) markers to analyse their genetic origin. Embryo rescue was used to grow all embryos contained in polyembryonic seeds of 'Tardivo di Ciaculli' mandarin, followed by characterization of the plantlets obtained by flow cytometry and SSR markers to accurately establish the rate of tetraploidization events and their potential tissue location. Inter-annual variations in tetraploid seedling rates were analysed for seven genotypes. Variation in tetraploid plantlet rates was analysed between different seedlings of the same genotype ('Carrizo' citrange; Citrus sinensis × Poncirus trifoliata) from seeds collected in different tropical, subtropical and Mediterranean countries.

Key results

Tetraploid plants were obtained for all the studied diploid genotypes, except for four mandarins. All tetraploid plants were identical to their diploid maternal line for SSR markers and were not cytochimeric. Significant genotypic and environmental effects were observed, as well as negative correlation between mean temperature during the flowering period and tetraploidy seedling rates. The higher frequencies (20 %) of tetraploids were observed for citranges cultivated in the Mediterranean area.

Conclusions

Tetraploidization by chromosome doubling of nucellar cells are frequent events in apomictic citrus, and are affected by both genotypic and environmental factors. Colder conditions in marginal climatic areas appear to favour the expression of tetraploidization. Tetraploid genotypes arising from chromosome doubling of apomictic citrus are extensively being used as parents in breeding programmes to develop seedless triploid cultivars and have potential direct use as new rootstocks.

SUBMITTER: Aleza P

PROVIDER: S-EPMC3119611 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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Publications

Tetraploidization events by chromosome doubling of nucellar cells are frequent in apomictic citrus and are dependent on genotype and environment.

Aleza Pablo P Froelicher Yann Y Schwarz Sergio S Agustí Manuel M Hernández María M Juárez José J Luro François F Morillon Raphael R Navarro Luis L Ollitrault Patrick P

Annals of botany 20110517 1

<h4>Background and aims</h4>Polyploidy is a major component of plant evolution. The citrus gene pool is essentially diploid but tetraploid plants are frequently encountered in seedlings of diploid apomictic genotypes. The main objectives of the present study were to establish the origin of these tetraploid plants and to ascertain the importance of genotypic and environmental factors on tetraploid formation.<h4>Methods</h4>Tetraploid seedlings from 30 diploid apomictic genotypes were selected by ...[more]

PMID: 21586529

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Project description:BACKGROUND:Somatic embryogenesis in nucellar tissues is widely recognized to induce polyembryony in major citrus varieties such as sweet oranges, satsuma mandarins and lemons. This capability for apomixis is attractive in agricultural production systems using hybrid seeds, and many studies have been performed to elucidate the molecular mechanisms of various types of apomixis. To identify the gene responsible for somatic embryogenesis in citrus, a custom oligo-DNA microarray including predicted genes in the citrus polyembryonic locus was used to compare the expression profiles in reproductive tissues between monoembryonic and polyembryonic varieties. The full length of CitRKD1, which was identified as a candidate gene responsible for citrus somatic embryogenesis, was isolated from satsuma mandarin and its molecular function was investigated using transgenic 'Hamlin' sweet orange by antisense-overexpression. RESULTS:The candidate gene CitRKD1, predominantly transcribed in reproductive tissues of polyembryonic varieties, is a member of the plant RWP-RK domain-containing protein. CitRKD1 of satsuma mandarin comprised two alleles (CitRKD1-mg1 and CitRKD1-mg2) at the polyembryonic locus controlling embryonic type (mono/polyembryony) that were structurally divided into two types with or without a miniature inverted-repeat transposable element (MITE)-like insertion in the upstream region. CitRKD1-mg2 with the MITE insertion was the predominant transcript in flowers and young fruits where somatic embryogenesis of nucellar cells occurred. Loss of CitRKD1 function by antisense-overexpression abolished somatic embryogenesis in transgenic sweet orange and the transgenic T1 plants were confirmed to derive from zygotic embryos produced by self-pollination by DNA diagnosis. Genotyping PCR analysis of 95 citrus traditional and breeding varieties revealed that the CitRKD1 allele with the MITE insertion (polyembryonic allele) was dominant and major citrus varieties with the polyembryonic allele produced polyembryonic seeds. CONCLUSION:CitRKD1 at the polyembryonic locus plays a principal role in regulating citrus somatic embryogenesis. CitRKD1 comprised multiple alleles that were divided into two types, polyembryonic alleles with a MITE insertion in the upstream region and monoembryonic alleles without it. CitRKD1 was transcribed in reproductive tissues of polyembryonic varieties with the polyembryonic allele. The MITE insertion in the upstream region of CitRKD1 might be involved in regulating the transcription of CitRKD1.

Dataset Information

Tetraploidization events by chromosome doubling of nucellar cells are frequent in apomictic citrus and are dependent on genotype and environment.

Background and aims

Methods

Key results

Conclusions

Publications

Tetraploidization events by chromosome doubling of nucellar cells are frequent in apomictic citrus and are dependent on genotype and environment.

Similar Datasets

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