Test: Plant Breeding (Old NCERT) - Grade 12 MCQ

Triticale (×Triticosecale) is the intergeneric hybrid between the female parent wheat and the male parent rye. 

Mutations can be induced by several methods. The three general approaches used to generate mutations are radiation, chemical and transposon insertion. The first induced mutations were created by treating Drosophila with X-rays. Using this a pproach Mueller to induce lethal mutations. In addition to X-rays, other types of radiation treatments that have proven useful include gamma rays and fast neutron bombardment. These treatments can induce point mutations (changes in a single nucleotide) or deletions (loss of a chromosomal segment).

Heterosis, also called hybrid vigour, the increase in such characteristics as size, growth rate, fertility, and yield of a hybrid organism over those of its parents. Plant and animal breeders exploit heterosis by mating two different pure-bred lines that have certain desirable traits.

Heterozygosity and its related gene interactions are the primary genetic basis for explanation of heterosis because the hybrid is heterozygous across all genetic loci that differ between the parents.

Origin of many of our most important cultivated plants was through polyploidy. A polyploid plant has more than two sets of chromosomes (genomes) in somatic cells. There are two kinds of polyploids, viz., autopolyploid and allopolyploid. In the autopolyploid each set of chromosomes, is identical or at least very closely similar to each other. On the other hand, in allopolyploid the basic sets of chromosomes, making up the multiple sets of chromosomes are differentiated from each other. Allopolyploid is the plant derived from hybridization between two differentiated species followed by doubling of the genomes. In sonic cases cultivated varieties have arisen by autopolyploidy. This is true of timothy, Phleum pratense. The 42 chromosomes in this species are all derived from the 14 chromosomes occurring in the small semi-wild pasture timothy, Phleum nodosum (Nordenskiold, 1949). Similar spontaneous autopolyploid origin is known for a large number of ornamental plants, potato, banana, apples, etc. A large proportion of cultivated plants are allopolyploids. Prominent among these are wheat, cotton, tobacco, and many forage grasses, Evolution of cultivated varieties of wheat is via allopolyploidy. In wheat and Aegilops only allopolyploid species have been found in nature, while no autopolyploids have been ever known (Kihara, 1966). According to Kihara (1966) the common wheat, Triticum aestivum, which is hexaploid (i.e. possesses six sets of chromosomes per somatic cell) has arisen from hybrids between the cultivated emmer i.e.( a tetraploid wheat, such as Tritiriun dicoccum) and Aegilops squarrosa, The evidence suggests that amphidiploid between the einkorn, Triticurn urariu (possessing 14 chromosomes or two sets of chromosomes, AA ) and a species presumably of sitopsis section of Aegilops, gave rise to wild emmer wheat, T. dicorcoids with genomic constitution AABB, which in turn gave rise to most cultivated hexaploid wheats (Jain, 1989).
Haploids are with a single set of chromosomes. The haploids are gametic cells formed after meiotic division. Diploids are with double set of chromosomes. They are formed after the fusion of male and female gametes. The resulted cell is called as zygote and it further divides mitotically.
Some cells have an abnormal number of chromosomes that is not a whole multiple of the haploid number. This condition is called aneuploidy. Most aneuploids arise by nondisjunction, a failure of homologous chromosomes to separate at meiosis. When a gamete of this type is fertilized by a normal gamete, the zygotes formed will have an unequal distribution of chromosomes. 

This germplasm includes: wild collected seeds, virus and viroid tested plants growing in greenhouses or screenhouses, in vitro cultures, and cryogenically preserved pollen and meristems. The tissue culture collection is composed of primarily the core collection of pathogen-tested cultivars and wild collected species. The cryopreserved clonal collection was established from tissue-cultured plants and includes 90 accessions stored using the controlled rate cooling or encapsulation-dehydration techniques.

All crops have been derived from wild plant species that were selected by the pre-historic humans for growing them under human supervision. The process of bringing wild plant species under human management is called domestication. Domestication began over 12,000-10,000 years ago at Fertile Crescent and elsewhere. Cereals and legumes were among the first to be domesticated. 

Saccharum barberi is a strong-growing species of grass in the genus Saccharum, the sugarcanes. It originates from northern India and has been exported to other countries and grown for the production of sugar.

The correct option is Option D.

Mankombu Sambasivan Swaminathan (born 7 August 1925) is an Indian geneticist and administrator, known for his role in India's Green Revolution, a program under which high-yield varieties of wheat and rice were planted. He is the founder of the MS Swaminathan Research Foundation. He is called as the father of Indian Green Revolution. He has introduced high-yielding varieties of wheat and rice in India. He has contributed towards the strengthening of agriculture and improving food security

The biggest constraint of the plant breeding is the availability of limited number of disease resistance genes that arc present and identified in various crop varieties or wild relatives. 

Colchicine is a toxic chemical that is often used to induce polyploidy in plants.  Basically, the colchicine prevents the microtubule formation during cell division, thus the chromosomes do not pull apart like they normally do.  

Introduction of high yielding varieties leads to elimination/minimal of cultivation of the rest of the species and the high yielding variety then takes over by pollination and various other cultivation processes. So, the genetic diversity cannot be observed due to the dominance of high yielding varieties.

Intensive use of fertilizers degrades the soil quality by depleting the nutrient content in the soil. 

Intensive intercropping does not affect genetic diversity. It increases the yield due to the synergism between the crops and reduces the incidence of disease spread.

Biopesticides degrade the soil quality and compromise the natural defence mechanism of crops against pesticide attack.

Hence, Option B.

Cryopreservation is a long-term storage technique with very low temperatures to preserve the structurally intact living cells and tissues for an extended period of time at a relatively low cost. Cryopreservation is to preserve and store the viable biological samples in a frozen state over extended periods of time.Technology and prospects of cryopreservation of germplasm , medium periodically; the freeze storage would suppress cell division and thus the need cells are in a non-metabolic state, which delays or virtually stops the 'ageing' process.

Emasculation is the process of removal of anther from bisexual flower before maturity to prevent self pollination. After emasculation, it is possible to make selective hybridisation of anther of selected flower with emasculated flower by overcoming self pollination.

Bio-fortification: It is the most practical means to improve public health. In bio-fortification breeding of crops with higher levels of vitamins and minerals or higher protein and healthier fats. In 2000, maize hybrids were developed that had twice the amount of amino acid lysine and tryptophan (MALT). Atlas 66 (Wheat variety), having high protein content has been used as a donor for improving cultivated wheat. Iron fortified rice variety contains over 5 times much Fe.