what do you mean by crop improvement ? how is it done in India? what is the necessity for improvement of Crop plants?
Answers
Crop improvement, the engineering of plants for the benefit of humanity, is as old as agriculture itself. Some 10,000 years ago, primitive people made the transition from hunting and foraging to cultivating crops. With that switch began the continuous process of improving the plants on which we depend for food, fiber, and feed.
Throughout the milennia, two techniques have been used to improve crops, according to Lawrence Bogorad, a plant molecular biologist at Harvard University. The first is selection, which draws on the genetic variation inherent in plants. The earliest farmers selected plants having advantageous traits, such as those that bore the largest fruit or were the easiest to harvest. Perhaps through some rudimentary awareness that traits were passed from one generation to the next, the choicest plants and seeds were used to establish the next year's crop. Natural selection, which determines the survival of species, was now augmented by artificial selection. By selecting and isolating choice plants for cultivation, the early farmers were in essence influencing which plants would cross-pollinate. Through selection and isolation, they were narrowing, yet controlling, the available gene pool for each crop.
Plant remains found in ancient Egypt and Mesopotamia indicate that plant cultivation was already widespread by that time. In earlier ruins of pre-Incan indian villages in Peru, archeologists have uncovered Lima beans that have seeds nearly 100 times larger than those of wild Limas in the area. This suggests that the Incans obtained their beans from still earlier plant breeders who left no record.
The second technique was breeding. The farmers selected two plants and then crossed them to produce offspring having the desired traits of both parents. The process was hit or miss, however, since early plant breeders did not understand the genetic transmission of traits and could not predict the likely outcome of a particular cross. Nonetheless, valuable traits did arise that could be selected and maintained in the population.
The physical basis of inheritance—or what actually happens when two plants are crossed—was not understood until the early 1900s. The key was Gregor Mendel's breeding experiments in the 1860s, though the importance of his work was not recognized until after his death. Working with peas in his monastery garden in Austria, Mendel deduced that hereditary information is stored in discrete units that we now call genes. Moreover, he reasoned that each trait, such as color, is controlled by two genes, one from the male parent and one from the female parent.
Soon after, other researchers found that genes are transmitted in blocks of 5,000 or so, rather than independently as Mendel had surmised. What Mendel did not know was that genes do not exist separately in the cell; rather, they are linked together on long chromosomes in the cell nucleus. Thus, while the gene is the unit of heredity, the chromosome is the unit of transmission. Each parent contributes half of the chromosome complement to the offspring; in humans, for instance, each parent contributes 23 chromosomes.
In the early 1900s, biologists learned how chromosomes are assorted during cell division—and how that determines the properties of the offspring. They learned how to locate genes on chromosomes, because chromosomes break and rejoin, or cross over, fairly regularly during cell division, leading to new genetic combinations. They also learned that sometimes chromosomes are present in multiple copies, or in reduced number, and that this particular dosage affects gene expression.
Crop improvement:
Crop improvement is nothing but plant breeding to fulfill human needs.
• Crop improvement is done by using a selective breeding technique and genetic engineering technique in India.
• Crop improvement is necessary for plants because farmers can get high yielding crops by using HYC crops.
• This can be done by using breeding techniques like cross-breeding and hybridization.