User:Erica Liu/sandbox

Article evaluation
chosen article: Green revolution

notes: The first entry "technologies" of the second subsection "Agricultural production and food security" is not sufficient. I think I can add more sources to this entry and talk about more about green revolution technologies' characteristics.

Technologies
The Green Revolution spread technologies that already existed, but had not been widely implemented outside industrialized nations. These technologies included modern irrigation projects, pesticides, synthetic nitrogen fertilizer and improved crop varieties developed through the conventional, science-based methods available at the time.

The novel technological development of the Green Revolution was the production of novel wheat cultivars. Agronomists bred cultivars of maize, wheat, and rice that are generally referred to as HYVs or "high-yielding varieties". HYVs have higher nitrogen-absorbing potential than other varieties. Since cereals that absorbed extra nitrogen would typically lodge, or fall over before harvest, semi-dwarfing genes were bred into their genomes. A Japanese dwarf wheat cultivar Norin 10 developed by a Japanese agronomist Gonjiro Inazuka, which was sent to Orville Vogel at Washington State University by Cecil Salmon, was instrumental in developing Green Revolution wheat cultivars. IR8, the first widely implemented HYV rice to be developed by IRRI, was created through a cross between an Indonesian variety named "Peta" and a Chinese variety named "Dee-geo-woo-gen".

With advances in molecular genetics, the mutant genes responsible for Arabidopsis thaliana genes (GA 20-oxidase, ga1, ga1-3 ), wheat reduced-height genes (Rht) and a rice semidwarf gene (sd1) were cloned. These were identified as gibberellin biosynthesis genes or cellular signaling component genes. Stem growth in the mutant background is significantly reduced leading to the dwarf phenotype. Photosynthetic investment in the stem is reduced dramatically as the shorter plants are inherently more stable mechanically. Assimilates become redirected to grain production, amplifying in particular the effect of chemical fertilizers on commercial yield.

HYVs significantly outperform traditional varieties in the presence of adequate irrigation, pesticides, and fertilizers. In the absence of these inputs, traditional varieties may outperform HYVs. Therefore, several authors have challenged the apparent superiority of HYVs not only compared to the traditional varieties alone, but by contrasting the monocultural system associated with HYVs with the polycultural system associated with traditional ones.

Draft the article
topic picked: the Green Revolution

Technology
The Green Revolution spread technologies that already existed, but had not been widely implemented outside industrialized nations. Two kinds of technologies were used in the Green Revolution and aimed at cultivation and breeding area respectively. The technologies in cultivation are targeted at improving the growing conditions, which included modern irrigation projects, pesticides, synthetic nitrogen fertilizer. The others of breeding aimed at improving the crop varieties developed through the conventional, science-based methods available at the time. These technologies included hybrid, combining modern genetics with selections.

High-Yielding Varieties
The novel technological development of the Green Revolution was the production of novel wheat cultivars. Agronomists bred cultivars of maize, wheat, and rice that are generally referred to as HYVs or "high-yielding varieties". HYVs have higher nitrogen-absorbing potential than other varieties. Since cereals that absorbed extra nitrogen would typically lodge, or fall over before harvest, semi-dwarfing genes were bred into their genomes. A Japanese dwarf wheat cultivar Norin 10 developed by a Japanese agronomist Gonjiro Inazuka, which was sent to Orville Vogel at Washington State University by Cecil Salmon, was instrumental in developing Green Revolution wheat cultivars. IR8, the first widely implemented HYV rice to be developed by IRRI, was created through a cross between an Indonesian variety named "Peta" and a Chinese variety named "Dee-geo-woo-gen". In the 1960s, when a food crisis happened in Asia, the spread of HYV rice was aggravated intensely.

Dr. Norman Borlaug, who is usually recognized as the "Father of the Green Revolution", bred rust-resistant cultivars which have strong and firm stems, preventing them falling over under extreme weather at high levels of fertilization. CIMMYT(Centro Internacional de Mejoramiento de Maiz y Trigo -- International Center for Maize and Wheat Improvement) conducted these breeding programs and helped spread high-yielding varieties in Mexico and countries in Asia like India and Pakistan. These programs successfully led the harvest double in these countries.

Plant scientists figured out several parameters related to the high yield and identified the related genes which control the plant height and tiller number. With advances in molecular genetics, the mutant genes responsible for Arabidopsis thaliana genes (GA 20-oxidase, ga1, ga1-3 ), wheat reduced-height genes (Rht) and  a rice semidwarf gene (sd1) were cloned. These were identified as gibberellin biosynthesis genes or cellular signaling component genes. Stem growth in the mutant background is significantly reduced leading to the dwarf phenotype. Photosynthetic investment in the stem is reduced dramatically as the shorter plants are inherently more stable mechanically. Assimilates become redirected to grain production, amplifying in particular the effect of chemical fertilizers on commercial yield.

HYVs significantly outperform traditional varieties in the presence of adequate irrigation, pesticides, and fertilizers. In the absence of these inputs, traditional varieties may outperform HYVs. Therefore, several authors have challenged the apparent superiority of HYVs not only compared to the traditional varieties alone, but by contrasting the monocultural system associated with HYVs with the polycultural system associated with traditional ones.

Disease-Resistant Varieties
In order to prevent crops from the threat of diseases, plants pathologists bred and cultivated DRVs or "Disease-Resistant Varieties". DRVs have special genes which can produce related molecules. When the parasites ate DRVs, the molecules could hamper the functions of parasite enzymes and toxins successfully realizing. DRVs breeding technologies can be divided into traditional methods, cellular-level methods and molecular-level methods. Traditional DRVs breeding technologies refer to cultivating mixtures within and between species to protect crops against stresses. In the 18th century, the mixtures of wheat and oats were found less infected by rust fungi by Tozzetti and his record of this fact was usually seemed as the earliest record of the valuable result of crop heterogeneity for disease control.

Cellular-level breeding technologies include using phytotoxins as tools to breed and select DRVs. Scientists found out that there was a correlation between toxin tolerance and resistance to pathogens. According to this find, phytotoxins were used as tools for the in vitro selection of novel resistant genotypes. Using phytotoxins as possible selective factors was first tested by Carlson in 1973, with the haploid cell lines of Nicotiana tabacum.

Molecular-level methods refer to genetic engineering, in which recombinant DNA technology is a common tool.Genetic engineering doesn't limit the source of transferred gene in plant anymore. The specific gene from totally unrelated species can be transferred to plant's cell. Accordingly, after gene transformation, the plant is called transgenic plant. Scientists identified and isolated the gene of a valuable trait and then selected a proper vector as a tool to transport. For example, Ti plasmid is a small circular strand of DNA in bacterial cells, which usually appears in Agrobacterium tumefaciens. Agrobacterium tumefaciens is a bacterium that can cause the crown gall disease in plants. After inserting the desired gene into Ti plasmid, when the plant was attacked by Agrobacterium tumefaciens, the desired gene can be transported to the nucleus of the plant cells. Crop with Bt (Bacillus thuringiensis) gene was an example of the transgenic plant which can produce the protein with insecticidal properties. Bt gene has been transferred into more than 50 crop plants including corn, cotton, and potato. This technology not only brought the economic benefit that it saved 50% to 70% cost of pesticides but also brought the environmental benefit that it lessened the pollution of using pesticides.