Abstract
BackgroundCleistogamic flowers are a main barrier in pollen dispersal for cross-pollination necessary in wheat hybrid breeding. The aim of our study was to gain new knowledge on the biology of wheat flowering, in particular on the differences between the cleisto- and chasmogamic forms which has certainly cognitive significance, but it can also be used in practice when seeking a female and male ideotypes for cross hybridization.ResultsWe characterized the most significant features defining the flowering specificity in two wheat cultivars with contrasting tendency to cleistogamy: Piko (chasmogamous) and Dacanto (cleistogamous). In the field observations we assessed diurnal pattern of anther extrusion and anther extrusion capacity. For the first time we adapted the time lapse method for measuring kinetics of the spikelet movement and 3-D image correlation technique for the non-invasive measurements of potential deformations of the spikelet lemmas. We found that the two cultivars differ in the potential of pollen dispersion for-cross-pollination and in the spikelet kinetics. We also described some anatomical traits that can have potential functional role in floret opening. None of the cultivars showed any symptoms of lemma surface deformation.ConclusionsThe cleistogamic and chasmogamic wheat cultivars differ significantly in the potential for pollen dispersion for cross-pollination, which is mainly related to anther extrusion capacity. Although none of these features differentiated the cultivars clearly, we assume, based on spikelet kinetics and the lack of lemmas surface deformation, that the water transport and turgor of cells is essential for the floret opening and anther extrusion in wheat. The search for parental ideotype should be supported by marker assisted selection, e.g. based of polymorphisms in genes related to aquaporin biosynthesis.
Highlights
Cleistogamic flowers are a main barrier in pollen dispersal for cross-pollination necessary in wheat hybrid breeding
The male components of cross hybridization, regardless of the mechanism on which it is based – natural or artificial should have chasmogamous flowers that are open at anthesis which facilitate anther extrusion and, pollen shedding for cross-pollination [9,10,11,12]
The aim of our study was to gain new knowledge on the biology of wheat flowering, in particular on the differences between the cleisto- and chasmogamic forms which has certainly cognitive significance, but it can be used in practice when seeking a female and male ideotypes for cross hybridization
Summary
Cleistogamic flowers are a main barrier in pollen dispersal for cross-pollination necessary in wheat hybrid breeding. The ‘second opening’ of wheat floret was recently described and the authors suggested that unfertilized ovary increase in radial dimensions and generates lateral push of the rigid lemma and palea [22]. It is still not clear whether during the ‘first opening’ the lemma undergoes deformations, which could increase the efficiency of floret opening and anther extrusion. There has been no experimental data on the possibility of lemma deformation during rapid expansion of swelling lodicules and ovary base that occur at the time of the floret opening at anthesis in cereals. Most cultivated forms of common wheat produce low amounts of pollen, which is indicated as a significant limitation in wheat hybrid breeding programs [7, 11, 29]
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