MOLECULAR CHARACTERIZATION OF DOUBLED HAPLOID ONION LINES USING SSRS AND AFLPS

Ryan Walker, Leonard Pike, Monica Menz, Kil Sun Yoo

Texas A & M University, Department of Horticulture MS 2133, College Station, TX 77843, Phone 979-458-3487. Fax 979-845-2337. Email: r-walker@tamu.edu

Onion suffer from severe inbreeding depression, which has prevented the creation of honozygous inbreds in breeding programs. The creation of doubled haploid (DH) lines in onion is an anomaly, and provides a unique opportunity to study both how these lines would perform in a breeding program and what allows them to tolerate homozygosity. Seven DH lines were developed at Texas A&M University from five different short-day F2 populations. Five equivalent conventional inbred lines, breeding lines developed from the same parents as the DH lines, have been identified from the onion-breeding program. These lines, and their parents, have been analyzed using give published SSR markers. The analysis has shown remnant heterozygosity both in the parental lines and in the conventional inbreds. It has also confirmed the uniformity of the DH lines. AFLPs are currently being using to estimate the parental contribution of the DH lines and the conventional inbred lines. These data will also be used to calculate the genetic similarity between each DH line and its equivalent conventional inbred to determine the suitability of pairing them in a diallele analysis looking at yield heterosis.

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