Genetic analyses of epicuticular waxes associated with the glossy foliage of ‘White Persian’ onion

Authors: MUNAIZ, EDUARDO - University Of Wisconsin; Havey, Michael

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2019
Publication Date: 12/19/2019
Citation: Munaiz, E.D., Havey, M.J. 2019. Genetic analyses of epicuticular waxes associated with the glossy foliage of ‘White Persian’ onion. Journal of the American Society for Horticultural Science. 145(1):67-72. https://doi.org/10.21273/JASHS04840-19.
DOI: https://doi.org/10.21273/JASHS04840-19

Interpretive Summary: Onion plants with lower amounts of waxes on foliage suffer less damage from the insect pest Thrips tabaci (thrips). Glossy onions accumulate significantly less wax compared to wild-type “waxy” onions, and a single recessive locus (gl) has been proposed to condition this phenotype. Genetic analyses of types and amounts of foliar waxes were completed using two segregating families from the cross of the glossy inbreds B9885 and B9897 (originally selected from the onion cultivar White Persian) with waxy inbred B8667 and semi-glossy (intermediate amounts of waxes) inbred B5351, respectively. F2 progenies were visually scored for foliage phenotypes and amounts and types of waxes were determined using Gas Chromatography Mass Spectrometry (GCMS). F2 progenies from one family from the cross of glossy B9885 by waxy B8667 fit a 1:3 ratio of visually scored glossy versus waxy foliage, and the phenotype mapped to chromosome 8 of onion. The same region on chromosome 8 was significantly associated with amounts of hentriacontanone-16 (H16), the most predominant wax on leaves of waxy onion, and fatty alcohols 1-octacosanol (Oct) and 1-triacontanol (Tri). Visually scored F2 progeny from the cross of glossy B9897 x semi-glossy B5351 did not fit expected models for one or two recessive loci. Significant quantitative trait loci (QTL) were revealed on chromosomes 5 and 8 controlling amounts of H16. Epistasis was detected between regions on chromosomes 1 and 8, and a 100-fold increase of H16 was conditioned by the homozygous genotypes for the B5351 allele on chromosome 1 with B9885 allele on chromosome 8. The three QTL model explained 41% of the phenotypic variation at logarithm of odds (LOD) 22.4. Amounts of Oct and Tri in the B9897 x B5351 family were associated with a major QTL on chromosome 1 explaining 37 to 46% of the phenotypic variation, respectively. This research demonstrates that foliage glossiness from ‘White Persian’ onion is conditioned by a recessive locus on chromosome 8 for which we propose the name glwp. These results will be important for selection of onions with unique profiles of epicuticular waxes to reduce losses due to thrips.

Technical Abstract: Onion (Allium cepa) plants with lower amounts of epicuticular waxes on foliage suffer less damage from the insect pest Thrips tabaci (thrips). Glossy onions accumulate significantly less epicuticular wax compared to wild-type “waxy” onions, and a single recessive locus (gl) has been proposed to condition this phenotype. Genetic analyses of types and amounts of epicuticular waxes were completed using two segregating families from the cross of the glossy inbreds B9885 and B9897 (originally selected from the onion cultivar White Persian) with waxy inbred B8667 and semi-glossy (intermediate amounts of waxes) inbred B5351, respectively. F2 progenies were visually scored for foliage phenotypes and amounts and types of epicuticular waxes were determined using Gas Chromatography Mass Spectrometry (GCMS). F2 progenies from one family from the cross of glossy B9885 by waxy B8667 fit a 1:3 ratio of visually scored glossy versus waxy foliage, and the phenotype mapped to chromosome 8 of onion. The same region on chromosome 8 was significantly associated with amounts of hentriacontanone-16 (H16), the most predominant epicuticular wax on leaves of waxy onion, and fatty alcohols 1-octacosanol (Oct) and 1-triacontanol (Tri). Visually scored F2 progeny from the cross of glossy B9897 x semi-glossy B5351 did not fit expected models for one or two recessive loci. Significant quantitative trait loci (QTL) were revealed on chromosomes 5 and 8 controlling amounts of H16. Epistasis was detected between regions on chromosomes 1 and 8, and a 100-fold increase of H16 was conditioned by the homozygous genotypes for the B5351 allele on chromosome 1 with B9885 allele on chromosome 8. The three QTL model explained 41% of the phenotypic variation at logarithm of odds (LOD) 22.4. Amounts of Oct and Tri in the B9897 x B5351 family were associated with a major QTL on chromosome 1 explaining 37 to 46% of the phenotypic variation, respectively. This research demonstrates that foliage glossiness from ‘White Persian’ onion is conditioned by a recessive locus on chromosome 8 for which we propose the name glwp. These results are important for selection of onions with unique profiles of epicuticular waxes to reduce losses due to thrips.