Tropical Biology Section
Borrone, James W. , Olano, Cecile T. , Kuhn, David N. , Brown, J. Steven , Violi, Helen A. , Ploetz, Randy C. , Schnell, Raymond J. .
An Estimation of Outcrossing in Florida Avocado (Persea americana Mill.) Using Microsatellite Markers.
Persea americana Mill. exhibits a unique flowering mechanism, synchronous dichogamy, in which the male and female parts of the perfect flower are functional at different times. Cultivars are classified based upon their flowering type. Type A cultivars open in the morning as functionally female flowers, close, then reopen in the afternoon the following day as functionally male flowers. The reverse occurs with Type B cultivars. This mechanism is believed to promote outcrossing, thus many commercial growers plant Type A and B cultivars in close proximity to maximize cross-pollination events. A hypothesis, based upon direct observation of floral pollination events, suggests that self-fertilization occurs in 95% of the flowers in Florida avocados. However, a significant number of fruits are aborted before maturation, and the hypothesis does not address whether mature fruit results from self- or cross-pollination events. To address this, 1,926 avocado fruit were purchased from a commercial grove consisting of three rows of one cultivar Simmonds (Type A) and a pollinator row of cultivar Tonnage (Type B) and germinated. Progeny of 'Simmonds' (729) and progeny of 'Tonnage' (701) were genotyped using microsatellite markers to determine the amount of outcrossing between the two cultivars. From the 'Simmonds' progeny, 38% were a result of a cross between 'Simmonds' and 'Tonnage', 26% were judged as self-pollinations, and 38% were off-types. From the 'Tonnage' progeny, 84% were a result of a cross between 'Simmonds' and 'Tonnage', 5% were judged as self-pollinations, and 10% were off-types. Therefore, the majority of harvested fruit was a result of cross-pollination events ('Simmonds' and 'Tonnage' hybrids and off-type hybrids), and suggests that interplanting cultivars increases the yield of commercially harvestable fruit. Seedlings derived from cross-pollinations between 'Simmonds' and 'Tonnage' will be maintained at the USDA-ARS as an F1 population, and evaluated for important agronomic traits.
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1 - United States Department of Agriculture, Agricultural Research Service, Subtropical Horticultural Research Station, National Germplasm Repository, 13601 Old Cutler Road, Miami, FL, 33158, USA
2 - University of Florida, Plant Pathology (Tropical Research and Education Center), PO Box 111569, Homestead, Florida, 330313314, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Ontario/Hilton
Date: Tuesday, July 10th, 2007
Time: 1:15 PM