Investigation of pollen competition between wild and cultivated sorghums (<Emphasis Type="Italic">Sorghum bicolor</Emphasis> (L.) Moench) using simple sequence repeats markers |
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| Authors: | Moses M Muraya Hartwig H Geiger Santie de Villiers Fabrice Sagnard Ben M Kanyenji Dan Kiambi Heiko K Parzies |
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| Institution: | 1.Leibniz Institute of Plant Genetics and Crop Plant Research,Gatersleben,Germany;2.Institute of Plant Breeding, Seed Science and Population Genetics,University of Hohenheim,Stuttgart,Germany;3.CIRAD—UMR Développement et Amélioration des Plantes,Nairobi,Kenya;4.International Crops Research Institute for the Semi-Arid Tropics (ICRISAT-Nairobi),Nairobi,Kenya;5.Kenya Agricultural Research Institute (KARI-Embu),Nairobi,Kenya |
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| Abstract: | In self-compatible plant species stigmata receive a mixture of self and outcrossed pollen and competition between them is
expected to play a major role in determining the pollen-mediated gene flow. The use of male sterile bait plants in field trials
to demonstrate the rate of gene flow is questionable due to lack of pollination competition. However, little direct evidence
has been published. A field experiment of male sterile and male fertile sorghum pollen recipient bait plants was conducted
to evaluate pollen competition between wild and cultivated sorghums and the effects of pollen competition on gene flow assessment.
Pollen competition between wild and cultivated sorghums was estimated from two-component pollen mixtures of wild and cultivated
sorghum (1:1 ratio) applied to wild, cultivated and male-sterile maternal bait plants. Paternity was determined in the progeny
using two diagnostic Simple Sequence Repeat markers. The study found that self pollen has higher seed-siring success. Maternal
genotype influences the siring ability of the pollen donor components which significantly deviated from the 1:1 pollen loads.
The study showed that published estimates of gene flow derived from studies using male-sterile bait plants seriously overestimate
gene flow and that pollen competition may be a significant factor influencing outcrossing rates. The results suggest that
the predominant direction of gene flow is from cultivated to wild sorghum, potentially leading to introgression of crop genes
into wild sorghum. Pollen competition should be taken into account in gene flow estimation, since presence of self-pollen
can account for over half of seed produced irrespective of maternal genotype. |
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