The Power of Genomic in situ Hybridization (GISH) in Interspecific Breeding of Bulb Onion (Allium cepa L.) Resistant to Downy Mildew (Peronospora destructor [Berk.] Casp.).

Ludmila Khrustaleva,Grigory Monakhos,Majd Mardini,Pavel Sokolov,Dmitry Romanov,Rada Alizhanova,Natalia Kudryavtseva

doi:10.3390/plants8020036

Abstract

We exploited the advantages of genomic in situ hybridization (GISH) to monitor the introgression process at the chromosome level using a simple and robust molecular marker in the interspecific breeding of bulb onion (Allium cepa L.) that is resistant to downy mildew. Downy mildew (Peronospora destructor [Berk.] Casp.) is the most destructive fungal disease for bulb onions. With the application of genomic in situ hybridization (GISH) and previously developed DMR1 marker, homozygous introgression lines that are resistant to downy mildew were successfully produced in a rather short breeding time. Considering that the bulb onion is a biennial plant, it took seven years from the F1 hybrid production to the creation of S2BC2 homozygous lines that are resistant to downy mildew. Using GISH, it was shown that three progeny plants of S2BC2 possessed an A. roylei homozygous fragment in the distal region of the long arm of chromosomes 3 in an A. cepa genetic background. Previously, it was hypothesized that a lethal gene(s) was linked to the downy mildew resistance gene. With the molecular cytogenetic approach, we physically mapped more precisely the lethal gene(s) using the homozygous introgression lines that differed in the size of the A. roylei fragments on chromosome 3.

Highlights

IntroductionGenomic in situ hybridization (GISH) is a modification of FISH (fluorescence in situ hybridization), which was introduced into molecular cytogenetics almost three decades ago [1]
Genomic in situ hybridization (GISH) is a modification of FISH, which was introduced into molecular cytogenetics almost three decades ago [1]
A huge number of molecular markers are required in order to analyze the whole chromosomes of parental complements while genomic in situ hybridization (GISH) distinguishes the parental genomes and allows the introgression of alien material to be monitored at the chromosome level

Summary

Introduction

Genomic in situ hybridization (GISH) is a modification of FISH (fluorescence in situ hybridization), which was introduced into molecular cytogenetics almost three decades ago [1]. GISH has become one of the most powerful tools to analyze natural polyploids, hybrid plants and their backcross progenies for alien gene introgressions, genomic composition, intergenomic rearrangements and the integration of chromosome and recombination maps [2,3,4,5,6]. The great advance in GISH lies in its ability to distinguish between parental genomes in interspecific plant hybrids with no sequence knowledge required. Molecular markers are an effective method for tracking valuable genes, which allows for the acceleration of the breeding [12]. A huge number of molecular markers are required in order to analyze the whole chromosomes of parental complements while GISH distinguishes the parental genomes and allows the introgression of alien material to be monitored at the chromosome level

Methods

Results

Discussion

Conclusion