ARS | Publication request: Outcrossing in Florida and California commercial avocado (Persea americana Mill) orchards estimated using microsatellite markers and the development of a genetic linkage map

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 10, 2010
Publication Date: N/A

Technical Abstract: Avocado has an unusual flowering mechanism, diurnally synchronous protogynous dichogamy, which promotes cross pollination. Comemrcial groves usually contain pollinizer rows adjacent to the more desirable commercial cultivars. Conflicting results on the effect of pollinizer rows on out-crossing rates and on yield have been reported. To estimate the rate of outcrossing in Florida and California, microsatellite markers were used. In Florida fruit were harvested from a commercial orchard of the cultivars 'Simmonds' (Flowering Type A) and 'Tonnage' (Flowering Type B). Progeny were genotyped using eight fully informative microsatellite markers. Seventy-four percent (536) of the 'Simmonds' progeny (726) and 96% (672) of the 'Tonnage' progeny (699) were the result of cross-pollination. In California outcrossing was estimated in a commercial 'Hass' (Flowering Type A) orchard with adjacent 'Bacon' (Flowering Type B) pollinizers using five fully informative microsatellite markers. Among the 919 seedlings of 'Hass', 688 (75%) were hybrids with 'Bacon'. Among the 850 seedlings of 'Bacon', 382 (45%) were hybrids with'Hass'. In Florida and California, the A type parents ('Hass' and 'Simmonds') had similar outcrosing rates (~75%); however, the B type parents ('Bacon' and 'Tonnage') had highly skewed outcrossing rates of 45% and 96% respectively. A genetic linkage map was constructed using 163 microsatellite loci from the cross of 'Simmonds' and 'Tonnage' consisting of 715 individuals. Map construction was accomplished with JoinMap 4.0. A composite linkage map was generated for the F1 population by combining data of the reciprocal crosses. The composite map contains 12 linkage groups with a total length of 1088cM.