Strategies for Enhancement in Food Production Test 7

Late blight caused by the oomycete, Phytophthora infestans is the most destructive disease in potato cultivation worldwide. New, more virulent P. infestans strains have evolved which overcome the genetic resistance that has been introgressed by conventional breeding from wild potato species into commercial varieties. R genes (for single-gene resistance) and genes for quantitative resistance to late blight are present in the germplasm of wild and cultivated potato. The species Solanum demissum proved to be an important source of resistance, and by conventional plant breeding (crossing and back-crossing) in the 1940s and 1950s this resistance was bred into commercial potato cultivars. Four major resistant genes (termed R genes) were discovered and were introduced successively into commercial cultivars. Thus, the correct answer is option A.

Herbicides, also commonly known as weed killers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets, while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic mimics of natural plant hormones. Herbicides interfere with photolysis of water, inhibits O2 evolution and also inhibits translocation of organic solutes. Thus, option D is correct.

A biofertilizer is a suspension of the living organism which remains in close association with the soil and increases the fertility of the soil. It is applied to plant surfaces, or soil colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Blue-green algae is a free living nitrogen fixing bacteria. So, BGA has been recommended as a biofertilizer. VAM plays a great role in inducing plant growth. VAM are symbiotic entophytic soil fungi, which colonize the roots of approximately 80% plants. VAM also is used as biofertilizer. 

So, the correct answer is option C.

Bacillus thuringiensis (Bt) is a bacteria that can infect and kill insects and thus, it is used as an insecticide. Alfalfa webworms killed by Bacillus thuringiensis. The insecticidal activity of Bt was first discovered in 1911. However, it was not commercially available until the 1950s. In recent years, there has been tremendous renewed interest in Bt.

Meristematic tissue is present at the tips of shoot so it is easy to regenerate it.

Anabaena-Azollae is a small filamentous phototrophic cyanobacteria generally seen as a multicellular organism with two distinct, interdependent cell types. It is a small, circular, photoautotrophic vegetative cell that performs oxygenic photosynthesis and is typically blue green in color. Since it is a phototrophic cyanobacteria, it derives energy for N2 fixation by performing photosynthesis. Thus, option A is correct.

A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). Pyrethroids now constitute the majority of commercial household insecticides. In the concentrations used in such products, they may also have insect repellent properties and are generally harmless to human beings in low doses but can harm sensitive individuals. Pyrethroids are axonic excitoxins, the toxic effects of which are mediated through preventing the closure of the voltage-gated sodium channels in the axonal membranes. The sodium channel is a membrane protein with a hydrophilic interior. This interior is a tiny hole which is shaped precisely to strip away the partially charged water molecules from a sodium ion and create a favorable way for sodium ions to pass through the membrane, enter the axon, and propagate an action potential. When the toxin keeps the channels in their open state, the nerves cannot repolarize, leaving the axonal membrane permanently depolarized, thereby paralyzing the organism. So, pyrethroids are largest group of insecticides of plant origin. Thus, option C is correct.

A biofertilizer is a living microorganism or made up of dried microorganisms. It is applied to plant surfaces, or soil colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers such as Rhizobium, Azotobacter, Azospirilium, mycorrhiza and blue-green algae have been in use for a long time. 

• Rhizobium inoculant is used for leguminous crops. Azotobacter can be used with crops like wheat, maize, mustard, cotton, potato, and other vegetable crops. 
• Blue-green algae belonging to a general Cyanobacteria genus fix atmospheric nitrogen and are used as inoculations for paddy crop grown both under upland and lowland conditions. 
• Mycorrhiza is a symbiotic association between a fungus and a plant. The Mycorrhiza plays a key role in selective absorption of immobile (P, Zn, and Cu) and mobile (S, Ca, K, Fe, Mn, Cl, Br, and N) elements to plants. These are available to plants in less amount.
• Anabaena in association with water fern Azolla contributes nitrogen up to 60 kg/ha/season and also enriches soils with organic matter. 
• Algae-fungi symbiosis is not used as biofertilizer because their symbiotic association forms lichens. 

So, the correct answer is option B.

Jojoba is a native shrub of the Sonoran, Mojave and Baja California deserts of Arizona, California, and Mexico as well as the southernmost portion of the California Floristic Province. It is the sole species of the family Simmondsiaceae, placed in the order Caryophyllales. Jojoba is grown commercially for its oil, a liquid wax ester, extracted from its seed. Parthenium argentatum Gray, commonly known as the Guayule is a flowering shrub in the aster family, Asteraceae, that is native to the southwestern United States and northern Mexico. Leucaena leucocephala is a small, fast-growing mimosoid tree native to southern Mexico and northern Central America (Belize and Guatemala), but is now naturalized throughout the tropics. Common names include white leadtree, jumbay, and white popinac. So, all the three are examples of new crops. Thus, option D is correct and other options are wrong.

Recalcitrant seeds (sometimes known as unorthodox seeds) are seeds that do not survive drying and freezing during ex-situ conservation. Moreover, these seeds cannot resist the effects of drying or temperatures less than 10^oC thus, they cannot be stored for long periods like orthodox seeds because they can lose their viability. Plants that produce recalcitrant seeds include avocado, mango, mangosteen, lychee, tea, cocoa, rubber tree, some horticultural trees, and several plants used in traditional medicine such as species of Virola and Pentaclethra. 

Thus, the correct answer is option C.

Azospirillum inoculations are recommended mainly for sorghum, millets, maize, sugarcane and wheat.
Mycorrhizal biofertilizers can be used for pine trees.
Rotenone is an odourless, colourless, crystalline ketonic chemical compound used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the seeds and stems of several plants, such as the jicama vine plant and the roots of several members of Fabaceae.
VAM is a biofertilizer and not a mycoherbicide. 

So, the correct answer is option C.

Biopesticides are the type of pesticides in which the living organisms are used for the destruction of the pests. They are used in the methods of pest management. This method focuses on the control of pests  by using predators or pathogens or enemies of the pests and insects. Biopesticides are the pesticides derived from natural materials. Bioinsecticides and bioherbicides come under the category of biopesticides. Bioinsecticides are used for the killing of pests and insects. Bioherbicides are used for the elimination of unwanted weeds and herbs. 

Thus, the correct answer is option C.