plant breeding plants are the most important organisms on this planet they occupy the bottom most part of the food chain they are often referred to as producers and all other organisms are directly or indirectly dependent on plants almost 85 percent of the world's food consumed by humans is plant-based the plants grown for food are called food crops food crops are highly dependent on water availability soil and climatic conditions sometimes due to environmental conditions like draught the crops do not produce sufficient food or the crops fail this leads to acute shortage of food in that region it is called as famine in the year 1943 the Great Bengal famine is estimated to have caused the deaths of up to four million people also as the population increases food production must also increase and if the food production does not increase it will cause food crisis as the land for agriculture is very limited it is necessary to improve the productivity of the crops per acre previously we have learned that by implementing animal breeding we were able to improve the quality and productivity of farm animals similarly by plant breathing it is also possible to improve the quality and productivity of the food crops plant breeding is defined as science of changing the genetic traits of plants in order to create desired plant types that are better suited for cultivation gives better Alysse and have good resistance to diseases plant breeding is not a new technology it is a very old one earlier man used to deliberately crossbreed closely related plant varieties to produce a new plant of desired trait nowadays breeders try to incorporate the following desirable traits in an improved variety increased crop yield improved quality increased tolerance to environmental stresses like salinity extreme temperatures draught and frost increased resistance to pathogens increased tolerance to insect pests this process of breeding closely related individuals that are genetically different to produce a hybrid offspring is known as hybridization scientists Gregor Mendel and Charles Darwin effectively demonstrated hybridization within a plant species after that the process was further developed by many plant breeders plant breeding is a systematic process the entire process of plant breeding starting from choosing desirable qualities of plant to the final product is broadly divided into five main steps let us learn about them one by one step one collection of variability we know that plant of particular species will have different varieties on different parts of the planet each variety will have few different sets of traits that are different from each other this is known as genetic variation for example Rocky there are about total 121 natural variants of Wragge on this planet every one of them is different from each other by few traits some show disease resistance to particular bunk and show draught resistance some give high yield and no resistance to drawn some give less ield and show drought resistance etc all these are desirable characters so to create a new variety of Wragge with better characteristics it would be better if one knows all the natural varieties of Wragge available on this planet from that it would be easy to select the best require traits for new plants from the year 1971 under the guidance of International Board of plant genetic resources IB PG are several Institute's have started collecting all the naturally available plants and seeds having all diverse alleles for all genes in a given crop from different geographic locations on this planet and made a library out of it this library is called as germ plasm collection this forms a resource from which new varieties are created currently most of the crops have germ plasm with more than hundred varieties due to availability of vast germ plasm any breeder can now easily manipulate different combination of alleles in order to create a superior plant there are two germ plasm collection centers in India these are International crops Research Institute for semi-arid tropics ICR is a tea at Hyderabad and National Bureau of plant genetic resources and BPG are at New Delhi step 2 evaluation and selection of parents when varieties were first collected it was completely based on easily distinguishable characters however plants variations are due to the environmental conditions present at that time which is temporary for example suppose researchers collected a dwarf plant from draught region and named it as dwarf plant but when this variety was cultivated under normal environmental conditions the plant grew tall it means that the dwarf Necedah trait of the plant it was just a result of environmental conditions in order to avoid such type of errors careful evaluation and characterization is required to know about the composition of the germ plasm and the diversity of the given crop let us learn how the plants are evaluated and characterized before the plants are evaluated the plants are tested for purées if a plant has more than one type of allele for a particular trait it is called heterozygous such plants are rejected and only pure plants or homozygous plants are subjected to further evaluation now let's learn about plant evaluation first all the samples are grown in the field under controlled environmental conditions with good protection then it is made sure that the plants completely adapt to the place they are grown this ensures that all the traits are completely expressed once they are adapted the plants are tested under various stressful conditions such as pathogens salinity dot etc all the responses are recorded apart from this the plants are also tested in laboratory for different molecular and biochemical characteristics once all the enzymes and the bio chemicals produced are known the information is neatly recorded and labeled on the plants using this wide range of information scientists can easily select plants for breeding the selected plants are later inbred or self pollinated to obtain pure copies of the homozygous parents cross hybridization among the selected parents now since we have selected pure line parents with desired characteristics the parents are now cross hybridized cross hybridization helps to produce hybrid progeny this helps to bring desired traits from different plant lines into one plant line for example if we cross a low yielding high disease resistant Wragge plant with high yielding low disease resistance draghi plant since the parents that are crossed up your line the f1 hybrid obtained will have superior characters of both the parents the progeny here will be high yielding and high disease resistant rocky plant this tendency of hybrids to obtain superior characteristics of both parents is known as heterosis or hybrid vigor the term was coined by Shull in 1912 however heterosis was first studied by Cole Reuter in 1763 followed by Darwin in 1876 let us understand how cross hybridization is done by breeders it is done by a process called artificial hybridization artificial hybridization is the production of hybrids by cross pollinating two separate plants under controlled conditions under the supervision of the plant breeder this process of artificial hybridization in plants involves very steps these are as follows selection of parents with desired characters care is taken while selecting parents for hybridization program all the desired characters should be present in parents which are required in the new crop variety emasculation anthers are male parts of the flowers are removed now flower contains only female parts this is done to prevent self pollination among flowers bagging and tagging soon after emasculation the couples are covered Politan bags to prevent contamination of stigma by foreign pollen collection of pollen grains at maturity the pollen grains are collected from desired parent plant in dry plastic bags artificial pollination when the stigma of the emasculated flower matures the polythene bag is removed and with the help of a brush fresh poland from selected plants is dusted over the receptive stigma of the female tagging a tag is with relevant information attached to the plant the tag bears the information like date of emasculation date of crossing and detail of male and female parents etc desirable combination of variations seeds obtained after crossing are sown and evaluated for desirable and undesirable traits and are screened properly back crossing if desired traits are absent in the progeny then they are back crossed again till the desired traits are obtained limitations cross hybridization is a very time-consuming and tedious process the cross hybrids may not combine the desirable characters usually only one in few hundred to a thousand crosses show the desirable combination step for selection and testing of superior recombinants the hybrid obtained is scientifically checked for desired characters if the test is fast the plants are self pollinated for several generations since the f1 hybrid has both dominant as well as recessive alleles at every next generation we will get wide variety of combinations some will be desirable and some will be undesirable at each generation the undesirable plants are eliminated and the process is continued for seven to eight generations until uniformity or homozygosity is obtained this will create a pure line where characters do not segregate this pure line is called as cultivar cultivar is plant with desirable characters that can be maintained by propagation to evaluate these cultivars the cultivars are grown in research fields and the performance is recorded under ideal fertilizer application irrigation and other crop management practices in India Indian Council of agricultural research ICA are at New Delhi carries out these evaluations after evaluations the plants are again tested in farmer's fields for at least three growing seasons the testing is done at several locations throughout the country representing all the agro climatic zones where these crops are usually grown using the test results the cultivars are evaluated by comparing it with the best available local crop cultivars in the farms if the new cultivar is far better than the existing cultivar it is selected for seed multiplication step 5 multiplication of improved seed the seeds of the approved cultivars are multiplied by growing them in suitable conditions a large quantity of seeds is obtained the seed are then tested for quality and certified by national seed corporation NSC such tested seeds are called as to fight seeds now the seeds can be distributed to farmers and licensed seed sellers