Forestry Glossary

Forestry Glossary

Forestry Glossary

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Source: Autumn view of Slioch from Grudie, Loch Maree, A

Forestry Tags > Tag based links for Apomixis

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1. Recombination and loss of complementatio n: a more than two-fold cost for parthenogenesi s: Journal of Evolutionary Biology, Vol. 17, No. 5. (2004), pp. 1084-1097.Abst ract Certain types of asexual reproduction lead to loss of complementatio n, that is unmasking of recessive deleterious alleles. A theoretical measure of this loss is calculated for apomixis, automixis and endomitosis in the cases of diploidy and polyploidy. The effect of the consequent unmasking of deleterious recessive mutations on fitness is also calculated. Results show that, depending on the number of lethal equivalents and on the frequency of recombination, the cost produced by loss of complementatio n after few generations of asexual reproduction may be greater than the two-fold cost of meiosis. Maintaining complementatio n may, therefore, provide a general short-term advantage for sexual reproduction. Apomixis can replace sexual reproduction under a wide range of parameters only if it is associated with triploidy or tetraploidy, which is consistent with our knowledge of the distribution of apomixis.
   
   Source: Journal of Evolutionary Biology, Vol. 17, No. 5. (2004), pp. 1084-1097.
   
   
2. Patterns, sources and ecological implications of clonal diversity in apomictic Ranunculus carpaticola (Ranunculus auricomus complex, Ranunculaceae): Molecular Ecology, Vol. 15, No. 4. (April 2006), pp. 897-910.
   
   Source: Molecular Ecology, Vol. 15, No. 4. (April 2006), pp. 897-910.
   
   
3. Chemical induction of apomictic seed formation in maize: Euphytica, Vol. 56, No. 2. (1 July 1991), pp. 97-105.Silks of 18 maize (Zea may L.) F1 hybrids were treated with different combinations of 9 growth regulators, colchicine, and dimethyl sulfoxide (DMSO) for the purpose to induce apomixis (agamospermy) in 1988 and 1989. Hybrid K301 × K303 gave the highest (0.36%) average frequency of seed induction among the hybrids. The most effective treatments were DMSO, gibberellic acid plus 6-benzyl aminopurine (6-BA), and DMSO plus methanesulfoni c acid. Individually, the highest frequency of seed induction was 1.4% for hybrid K731×K306 when treated with a-naphthalene acetic acid (NAA)-zeatin mixture. The frequency of seed induction seemed to depend partially on the interaction between chemicals and hybrids. Cytological observation of root-tip cells indicated that the majority of the seeds obtained were diploid, some were mixoploid, and a few were haploid. Diploid plants from induced seeds from the same parent were morphologicall y uniform and resembled the parent. Variations in plant and ear heights were comparable to those of the hybrid parent. Cytological and morphological investigations suggested that the chemically induced seeds originated mainly from somatic tissue but occasionally came from reduced cells in the embryo sac, leading to haploids. The results showed that chemical induction of adventitious embryony in maize hybrids is possible, but the more effective chemicals, their concentrations , and ways of application for increasing the frequency of seed induction need to be explored for practical use.
   
   Source: Euphytica, Vol. 56, No. 2. (1 July 1991), pp. 97-105.
   
   
4. Towards understanding the dynamics of hybridization and apomixis in the evolution of the genus Boechera (Brassicaceae): Systematics and Biodiversity, Vol. 5, No. 03. (2007), pp. 321-331.
   
   Source: Systematics and Biodiversity, Vol. 5, No. 03. (2007), pp. 321-331.
   
   
5. Genetic and embryological evidences of apomixis at the diploid level in Paspalum rufum support recurrent auto-polyploid ization in the species: Sexual Plant Reproduction, Vol. 21, No. 3. (2008), pp. 205-215.Abstra ct  Gametophyt ic apomixis is an asexual mode of reproduction by seeds. This trait is present in several plant families and is strongly associated with polyploidy. Paspalum rufum is a forage grass with sexual self-incompati ble diploids (2n = 2x = 20) and aposporous-apo mictic pseudogamous tetraploids (2n = 4x = 40). In previous work embryological observations of the diploid genotype Q3754 showed 8.8?26.8% of the ovaries having one meiotic plus an aposporous-lik e embryo sac, suggesting some capability for apomictic reproduction. The objective of this work was to characterize progenies derived from Q3754 to determine if aposporous sacs were functional and generated progenies via apomixis at the diploid level. Re-examination of Q3754 ovaries showed that 12.5% of them contained one sexual plus an aposporous sac confirming previous results. Progeny tests were carried out on two experimental families (H1 and S1) employing heterozygous RAPD marker loci. Family H1 was obtained crossing Q3754 with a natural diploid genotype (Q3861) and S1 derived from the induced self-pollinati on of Q3754. Genetic analysis of H1 showed that all individuals derived from sexual reproduction. However, 5 out of 95 plants from S1 showed the same heterozygous state as the mother plant for 14 RAPD loci suggesting a clonal origin. Further experiments, designed to test the functionality of aposporous sacs by flow cytometric analyses, were carried out on a third family (M1) obtained by crossing Q3754 with the tetraploid plant Q3785. Histograms of 20 M1 plants showed 15 diploids (75%), 4 triploids (20%) and 1 tetraploid (5%). Triploids and the tetraploid may have originated from functional aposporous embryo sacs. Likewise, the reconstruction of the developmental route of 40 individual seeds demonstrated that 11 of them (27.5%) derived from fertilized aposporic sacs. The results presented in this work indicate that gametophytic apomixis is effectively expressed at the diploid level in Paspalum rufum and could be the foundation of a recurrent auto-polyploid ization process in the species.
   
   Source: Sexual Plant Reproduction, Vol. 21, No. 3. (2008), pp. 205-215.
   
   
6. In search of the molecular basis of heterosis.: Plant Cell, Vol. 15, No. 10. (October 2003), pp. 2236-2239.
   
   Source: Plant Cell, Vol. 15, No. 10. (October 2003), pp. 2236-2239.