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

The causal organism of late blight of potato is phytophthora infestans (a fungus). It is carried through tubers. Symptoms appear first as water soaked areas along the margins and tips of lower leaflets. The spots enlarge rapidly, become necrotic, turn brown and then blackish or blighted.

The pathogen responsible for black rot of crucifer is a bacteria; Xanthomonas campestris. It lives on the plant residue in the soil or in the seed. In a germinating seed, the bacterium enters through the stomata and first spreads intercellularly in the substomatal region and then systemically into the vascular bundle. First sign of the disease appears near leaf margin, characterized by chlorosis, which progresses towards the centre of leaf blade. In the affected portions, the vein and veinlets turn brown and finally black.

Black rust of wheat is caused by Puccinia graminis tritici, a fungus which belongs to basidiomycota. It is an internal obligate parasite. The uredial pustules occur on stem, leaf sheath and leaves. The pustules of black rust are reddish brown in colour and elongated in shape. The rust spreads and by the time crop matures, dark, black, elongated tellal pusules are formed.

Thomas fairchild was the first English nurseryman to experiment with hybridization of plants. He was the author of "The City Gardener" (1728). He made history in 1717 by taking pollen from a carnation and inserting it into a sweet william in his nursery, thereby producing a new variety that was known as "Fairchilds's Mule". 

Jaya and Ratna are semi-dwarf varieties of rice which are developed in India.

Three varieties of maize namely Shakti, Rattan and Protina have been developed, evaluated and released for cultivation based on being rich in amino acid lysine. Generally, cereal and millet proteins are deficient in lysine and tryptophan amino acids which are called essential amino acids.

Saccharum barberiwas originally grown in North India but has poor sugar content and yield. However, Saccharum officinarum had higher sugar content and thicker stems but did not grow well in North India. These two species were crossed to have sugarcane varieties combining the desirable qualities of high sugar, high yield, thick stems and ability to grow in the sugarcane belt of North India.

High protein genes of Atlas 66 have been successfully incorporated into commercial variety Lancota to make it rich in proteins.

Germplasm is the sum total of all the alleles of the genes present in a crop and its related species The germplasm of any crop species consists of the following types of materials: cultivated improved varieties, improved varieties that are no more in cultivation, old local or 'desi' varieties, pure lines produced by plant breeders, and wild species related to the crop species.

Germplasm collection is the first important step in breeding a new genetic variety of crop.

Tobacco mosaic is caused by Tobacco Mosaic Virus. The infection causes characteristic pattern, such as "mosaic" - like mottling and discolouration on the leaves. Turnip Mosaic Virus causes turnip mosaic. Chlorotic lesions, mosaic and mottling are the common symptoms of this disease.

Insect resistance in host crop plants is due to morphological, biochemical or physiological characters. Hairy leaves of many plants are associated with resistance to insect pestes. For example, resistance to jassids in cotton and cereal leaf beetle in wheat.

High aspartic acid, low nitrogen and sugar content in maize leads to resistance against maize stem borers.

Smooth leaved nectar-less cotton varieties do not attract bollworms.

The process of mutation breeding involves inducing mutations artifically through use of chemicals or radiations (like gamma radiations)and selecting plants that have the desirable character as a source in breeding. In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations.

Resistance to yellow mosaic virus in bhindi (Abelmoschus esculentus) was transferred from a wild species (Abelmoschus manihotland) and resulted in new variety of A. esculentus called 'Parbhani kranti'.

Breeding of crops with higher levels of vitamins and minerals or higher and healthier fats is called biofortification. Breeding for improved nutritional quality is undertaken with objectives of improving protein, oil and vitamin content and quality, along with micro nutrient and mineral content.

Hilsa, sardines and pomphrets are marine fishes. Cryopreservation is storing substances at very low temperature (-196ºC) in liquid nitrogen.

Pusa Komal is a hybrid variety of cowpea. This variety is resistant to bacterial blight disease Pusa Komal has been developed by hybridization of P-85-2 and P-426 cowpea strains It is widely adapted, flower early, bears good quality pods and gives higher yield.