Noyes, Richard D. , Derlikowski, Amy .
Quantitative variation in the expression of apomixis in Erigeron annuus and E. strigosus (Asteraceae).
While it is known that most apomictic plants are facultative, quantitative evaluations of female function in apomictic plants have rarely been conducted. In this study, reproductive development and autonomous seed production was quantified for 30 apomictic genotypes of Erigeron annuus and 40 apomictic genotypes of E. strigosus. Assessment of seed production indicates that on average apomictic plants dedicate just over 70% of ovules to the production of autonomous seed. However, multiple measures of seed production per plant indicate that while this trait varies only modestly within plants, there is considerable among plant variation with values ranging from 14.0 to 95.5%. Surprisingly, all plants, regardless of amount of seed formed, exhibit a high proportion of diplosporous ovules (~95%) and about the same proportion of fully formed female gametophytes. However, examination of flowers three days post anthesis indicates that plants with low seed production suffer from a diversity of maladies including failure of the egg cell to develop, degeneration of the embryo sporophyte, and improper endosperm formation, among others. In addition, this survey indicates that meiotic ovule formation in apomicts is relatively rare, occurring on average in only about 2% of ovules. Thus levels of autonomous seed formation among apomictic plants are not negatively correlated with the occurrence of meiotic ovules, as might be expected. Instead, these results are consistent with the hypothesis that expression of apomixis is influenced by genetic modifiers that affect parthenogenetic development from unreduced eggs.
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1 - University of Central Arkansas, Department of Biology, 180 Lewis Science Center, Conway, Arkansas, 72035, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood D/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 2:00 PM