New Male Specific Markers for Hop and Application in Breeding Program

Andreja Čerenak,Jernej Jakše,Emily Buck,Simon P Whittock,Petra Sehur,Zala Kolenc,Anthony Koutoulis,Suzana Škof,Ron Beatson,Branka Javornik

doi:10.1038/s41598-019-50400-z

Abstract

Male specific DNA sequences were selected from a Diversity Arrays Technology (DArT) mapping study to evaluate their suitability for determination of the sex phenotype among young seedlings in a hop (Humulus lupulus L.) breeding program. Ten male specific DArT markers showed complete linkage with male sex phenotype in three crossing families. Following optimization, four were successfully converted into PCR markers and a multiplex PCR approach for their use was developed. Among 197 plants (97 from the world collection; 100 from three segregating families), 94–100% positive correlation with sex phenotypic data was achieved for the single PCR amplification, whereas the multiplex approach showed 100% correlation. To develop a fast and low-cost method, crude sample multiplex PCR was evaluated in 253 progenies from 14 segregating populations without losing accuracy. The study describes, for the first time, the routine application of molecular markers linked to male sex in an intensive Slovenian hop breeding program. The methods described could be employed for screening of sex at the seedling stage in other hop programs worldwide, thereby saving resources for desirable female plants.

Highlights

In dioecious species such as hop, each individual normally produces either male or female reproductive organs[8]
Since the hop karyotype contains sex chromosome Y, which is transmitted from generation to generation only by the male line, it was first assumed that majority of polymorphisms on Y chromosome should be male specific
10 Diversity Arrays Technology (DArT) markers were discovered that were present in the male parent, absent in the female parent and present in all male siblings

Summary

Introduction

In dioecious species such as hop, each individual normally produces either male or female reproductive organs[8]. In almost all studied dioecious species, the sex phenotype is linked to genetic differences between male and female www.nature.com/scientificreports/. Seefelder et al.[25] were the first to construct a genetic linkage map of the male hop, and they found 24 molecular markers which were sex specific. Danilova and Karlov[26] were successful in the development of male specific molecular markers with the inter-simple sequence repeat polymerase chain reaction (ISSR-PCR) method on hop plants of Russian and European origin. Buck et al.[30] developed four sex linked markers; three sequenced characterised amplified region (SCAR) markers, and one high-resolution melting (HRM) curve analysis marker the latter of which has been successfully applied within the New Zealand hop breeding programme[31]. Hill et al.[22] identified a pseudoautosomal region (PAR), and male-specific regions of the Y-chromosome, along with genes located in these parts of the sex chromosomes

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