Transfer of the Dominant Virus Resistance Gene AV-1 pro From Asparagus prostratus to Chromosome 2 of Garden Asparagus A. officinalis L.

Jens Keilwagen,Jörg Plieske,Janine König,Holger Budahn,Thomas Nothnagel,Eva-Maria Graner

doi:10.3389/fpls.2021.809069

Abstract

An introgression breeding programme was carried out to transfer the virus resistance gene AV-1pro from the wild species Asparagus prostratus to the garden asparagus Asparagus officinalis. Serious crossing barriers caused by genetic distance and different ploidy levels of the crossing parents have been overcome using embryo rescue for the F1, BC1, and BC2 generations. The male and female fertility was widely restored in BC2 and was shown to be comparable to the cultivated asparagus. Five AV-1 resistant diploid (2n = 2x = 20) BC2 plants were selected and reciprocally backcrossed with asparagus cultivars. Segregation analyses of fourteen seedborne BC3 progenies suggested a monogenic dominant inheritance of the AV-1 resistance. Genotyping by sequencing analysis gave a strong hint for location of the resistance gene on asparagus Chromosome 2. Using an Axiom single nucleotide polymorphism (SNP) genotyping array for the analysis of three BC3 families with 10 AV-1 resistant and 10 AV-1 susceptible plants each, as well as 25 asparagus cultivars, the AV-1pro locus on Chromosome 2 was further narrowed down. The SNP with the highest LOD score was converted to a kompetitive allele specific PCR (KASP) marker, shown to be useful for the further backcross programme and serving as the starting point for the development of a diagnostic marker.

Highlights

Asparagus (Asparagus officinalis) is a perennial plant of the Liliaceae family and one of the economically most important vegetable species
About 625 crosses resulted in sixty juvenile berries, showed a habit more similar to the A. prostratus parent with prostrate or ascending obliquely stems
The female and male flower architecture (Supplementary Figure 4) and berry development were expressed in highly similar manner, in both cross parents and all crossing progenies

Summary

Introduction

Asparagus (Asparagus officinalis) is a perennial plant of the Liliaceae family and one of the economically most important vegetable species. Nine virus species belonging to the genera Ilarvirus, Cucumovirus, Nepovirus, Tobamovirus, Potexvirus, and Potyvirus have been identified in asparagus (Tomassoli et al, 2012). The potyvirus Asparagus virus 1 (AV-1), a Resistance to Asparagus Virus 1 filamentous virus measuring 700–880 nm in length and 13 nm in width (Fujisawa et al, 1983), is the most important virus attacking garden asparagus worldwide. While the damage caused by AV-1 is often underestimated, because no symptoms are visible on shoots or cladophylls, various studies reported yield losses between 30 and 70% (Weissenfels and Schmelzer, 1976; Yang, 1979; Evans et al, 1990; De Vries-Paterson et al, 1992). A more recent greenhouse study by Lantos et al (2018) has demonstrated that AV-1 infection restricts the root development (root weight, ratio of storage root, and number of spear meristems), reduces the Brix value, and influences the quantity of terpenoids and other metabolic compounds

Methods

Results

Conclusion