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In normal course, plants produce sexually where the egg and the sperm fertilises to produce a zygote. But in apomixis, plants reproduce asexually (where just one sex is involved)to produce seeds.The genetic make-up of the seeds is identical to that of the mother plant and the seeds inherit the same adaptive traits. That is why, it is also known as seed cloning. Apomictic seeds can also arise from a plant's sexual (germ) cells, which fail to go through the cellular mechanism required for meiosis. Alternatively, seeds can be generated from non-sexual (somatic) cells. Apomictic plants produce cloned seeds that in turn can reproduce both sexually and asexually. Asexual seed production ("self-cloning") improves chances of yields of major food, feed, fiber and biomass crops and reduces hybrid seed production costs. In nature, apomixis is of quite rare occurrence. It occurs in around 10 per cent of the 400 families of flowering plants, but only in 1 per cent of the 40,000 species that make up those families. Most commonly, apomixis occurs in Gramineae (the cereal family),Asterceae (the dandelion family), Compositae (sunflower family) and Rosaceae (rose family including fruit trees).In dandelions and blackberries, apomixis enables them to spread rapidly since they can bypass pollination and fertilisation. Only a handful of crop plants are apomictic:citrus,mango,some tropical forages, etc. Apomixis is also significantly seen in polyploids (organisms possessing more than one set of chromosomes).It has offered a survival benefit to these polyploids which would have become extinct due to their sexual sterility arising from a faulty meiotic process.(During the process of gamete formation, dysjunction of chromosomes prevents proper segregation of chromosomes and hence normal gametes are not formed. When such abnormal gametes fuse, they form polyploids.) Applications in agriculture Extensive research attempts have been made on various cereal crops in the last two decades and the results have been significant.One such cereal crop has been rice whose smallest and evolutionary ancestral cereal genome appears to be an ideal model system for apomixis breeding using all the three approaches (i)introgression of apomixis (or its components) from related Poaceae species (ii) mutagenesis and (iii)molecular biology and genetic engineering approaches. Recent progress on molecular markers for apomixis, genetic mapping and their synteny -existence of several genetic loci on the same chromosome (classical genetics)or the order of genes on chromosomes of related species, as a result of descent from a common ancestor (comparative genomics)provides a strong platform. Simultaneous research is being conducted on rice in several countries includingPhilippines, Australia, China, India and the US but attempts to commercialise apomixis in rice has not been successful so far. |
PERSONAL GENOMES: Imagine this:you visit your clinician, undergo genetic testing,and then you are handed a miniature hard drive containing your personal genome sequence, which is subsequently uploaded onto publicly accessible databases. This may sound like science fiction, but it is scientific fact, and it is already happening. Within five years, DNA sequencing technologies will be affordable enough that personal genomics will be integrated into routine clinical care, scientists predict. Companies are responding by offering services for ancestry tracing, forensics, nutritional advice and reproductive assistance. It won't be long before companies are able to offer Facebook-like social networking services centred around our genomes. In an article published in Science, University of Alberta researchers highlight the need to proceed with caution when it comes to personal genomics projects that represent research milestones but are also fraught with ethical, social and clinical implications. SUPER RICE: Scientists have the genetic information needed to create a new disease-resistant strain of ‘super rice ’ that grows more crops using less polluting fertiliser. The challenge is how to put a mix of favourable genes into one productive strain, according to geneticists at the National Key Laboratory of Crop Genetic Improvement in Wuhan, China.Countries that depend on rice need an environmentally benign variety of rice that maintains yields while abating fertiliser and pesticide pollution.At least 19 genes can give protections against brown planthoppers,and dozens more resist blight and fungus.Other genes have been identified to help plants use nutrients and water more efficiently. |
