There are advantages and disadvantages in apomixis process. Similarity values ranged between 2—70% with an average of 34%. It produces seedling progeny identical to the mother parent. This study aimed to develop new microsatellite markers as additional tools in genetic studies on mangoes Mangifera indica L. It was obtained an elevated taxa of vigorous zygotic plantlets which possibly explains the disuniformity on height of trees at commercial mango orchards.
The plants formed from such embryos are mostly sterile, e. The present study aims to answer the following questions. It develops uniform seedlings similar to asexual reproduction. Microsatellite marker evidence suggests that as few as four Indian cultivars, and the land race known as 'Turpentine', were involved in the early cultivar selections. Therefore, the seed having it is non-viable. Parental allelic structure was analysed to select a set of primers for each parental combination to discriminate between nucellar and zygotic origin, as well as between independent zygotic origins.
Similarity to Mother Plant They are clones of the mother plant. However, another hypothesis could relate to hormonal dominance of the initial zygotic embryo or an inhibition of adventitious embryo development. The time until first flowering was found to be the limiting factor in evaluation of seedlings. Embryos were at globular to early cotyledonary stage and variable in size macroscopically some embryos were so small that they were difficult to identify, whereas others reached a size of approx. The egg formed is diploid. Preferred mango varieties vary from country to country, with subcontinental Asian varieties typically being monoembryonic and South East Asian varieties being polyembryonic.
This involves many complex mechanisms associated with interactions of pollen and stigmatic tissues. Only in 'Haden' did the allozymes of all of the studied loci segregate in the expected Mendelian ratios. Since its inception in 1994 the program has generated more than 1800 hybrids from 33 parental combinations using controlled pollination methods. The percentage occurrence of polyembryony in tree borne oil seeds ranges from 1 to 35% in Calophyllum inophyllum, Amoora rohituka, Madhuca latifolia, Ponammia pinnata, Azadirachta indica, Garcinia indica, Garcinia mangostana etc. Production of hybrid seeds every year is costly thus increasing the cost of crop production. A total of 131 embryos were obtained and 93 plants were regenerated, all of which displayed trifoliate leaves Table. Cuttings form lateral roots and nucellar seedlings develop tap roots better root system.
Also, a major gene linked to apomixis has recently been identified by , by using amplified fragment length polymorphism markers. Phenotypic observations indicated that none of the plants produced by nucellus culture in vitro maintained the maternal phenotype C. Due to this Polyembryony occurs. Recurrent agamospermy recurrent apomixis; apospory and diplospory In this kind of agamospermy, a diploid embryo sac is formed either from the diploid megaspore mother cell by diplospory, for example, Areva tomentose or from the diploid nucellar cells by apospory, for example, pricky pear, mango, citrus, etc. Such embryos subsequently come to lie in the embryo sac and are nourished by the endosperm.
It is of two types, non-recurrrent and recurrent. The diploid egg develops parthenogenetically without the act of fertilization into an embryo. Our results therefore confirm the proposal made by after analysis of 2 x × 4 x progeny with just a single isozyme marker. Similarly, we have made the same observations in many 2 x × 4 x crosses in our triploid breeding programme; however, the causes underlying this type of polyembryony remain unknown. The second is associated with interploidy 2 x × 4 x hybridizations.
The use of seed fractions was not considered an efficient method for maximizing E. We aimed to better understand the cultivars enhanced breeding histories and to support crossbreeding planning. However, apomixis is a complex phenomenon which does not have a clear genetic basis. Some of these stimuli induce anatomical and physiological modifications that are generally modulated by gene expression. Here, the development of endosperm occurs only after the fusion of the male- nucleus with the polars, and therefore, a mature apomictic embryo in these plants is formed only after pollination. Days taken for completion of germination was early in 'Peach' and 'Nekkare', while 'Bappakkai' and 'Vellaikulumban' took more days to complete germination 136 days. In parallel, 529 isolated embryos were rescued from the same seeds and cultivated in vitro.
Hybrid seeds have to be produced every year because seeds collected from hybrid plants, if sown subsequently, do not maintain hybrid characters due to segregation of traits. Here the megaspore mother cell undergoes the usual meiotic divisions and forms a tetrad. Generating targeted recombination remains one of the most important factors for crop genetic enhancement. These results suggest that the polymorphic bands may be related to the expression of genes linked to polyembryony in maize. Morphological markers generally include those pivotal features that can be scored and distinguished by naked eye and easily be expressed in all environmental conditions. If the cultivar is self-fruitful, a solid block can be planted, but if it depends on cross-pollination, at least two compatible cultivars must be interplanted. The genus Mangifera consists of many species with M.
They are not genetically identical to the mother plant. This type of free development of fruit is known as parthenocarpy. Consistent formation of multiple embryos in seeds of non-apomictic citrus genotypes has been observed in two systems. Methods The genetic structure ploidy and allelic constitution with microsatellite markers of plants obtained from polyembryonic seeds arising from 2 x × 4 x sexual hybridizations and those regenerated from nucellus culture in vitro was systematically analysed in different non-apomictic citrus genotypes. Adventive embryony has been frequently reported in Citrus, Euphorbia dulcis, Capparis frondosa, Mangifera indica and Hiptage madablota.
The outer cells divide further by anticlinal division forming a peripheral layer of epidermal cells, the dermatogen. Characterization through different markers is an important need for mango germplasm conservation and its utilization for various breeding purposes. The segregation pattern of individuals originating from selfing of several monoembryonic cultivars and one polyembryonic line indicated that polyembryony in mango was of genetic nature. Similarly, the occurrence of polyembryony has been reported by plethora of workers in tree borne oil seeds at the nursery stage. However, in spite of the large volume of mango production almost all of the product is consumed domestically in its country of origin: less than 4% 908,000 tonnes of production is exported. Mango can be propagated by seeds or by grafting. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription.