il riso nell'agricoltura di oggi

Un numero molto  interessante di Nature Outlook parla di agricoltura e in particolare del riso, fornendo dati sulla produzione, il consumo e cosa si fa degli stock invenduti.

Dipendenza giornaliera
Average percentage of daily calories derived from rice 1961–2011, per capita.
Factors that affect the demand of rice include: rapid economic development; increased gross domestic product; and urbanization in developing countries.

consumo giornaliero di alimenti e % di calorie fornite

aumento della domanda negli anni (proiezione fino al 2050)

aumento della produzione di riso negli anni

produzione e consumo

The major rice producers of the world grow more than enough rice to feed their own people. The excess ends up as exports, livestock feed, seed stock or waste (spoiled during transport or storage). Data show the average annual production and consumption from 2007 to 2011, measured in million tonnes (Mt).

spazio richiesto per la coltivazione, riduzione dell'area tra il 1960 e oggi per produrre 1 tonnellata di prodotto

The  average area of land needed to produce 1 tonne.

Improved rice strains and modern agricultural techniques have meant that farmers can produce higher yields on a smaller area of land. 

Un secondo articolo spiega la differenza di geni nelle varietà usate in diverse parti del mondo

• Two farmers in different parts of the world can plant the same species of rice, but their crops may look strikingly different. Rice has enormous genetic diversity, and scientists are now developing the ability to take advantage of it. 
• Makoto Matsuoka at Nagoya University in Japan discovered⁵ that IR8 owed its short stature to a loss-of-function mutation of the semi-dwarf gene sd1. The group found that the genetic impairment led to defects in the biosynthesis and signalling pathways of gibberellin, the plant hormone responsible for controlling cell elongation. The cells were shorter, but in all other respects functioned normally.  
• “There are three key elements in grain yield: panicle size, grain number and grain size,” says Jiayang Li, CAAS project director and a driving force behind the 3,000 Rice Genomes Project. “A rice plant in which these components are great would naturally have high yield.” In 2003, Li and his team identified a gene called MONOCULM 1 (MOC1) that functions as the master control for shoot development⁶. They showed that rice plants that overexpress MOC1 produce more auxiliary stems that branch out from the mother stem than normal, whereas those with a loss-of-function mutation in MOC1 produce only a single, stout stem. Li now aims to find the right expression level for MOC1 to decrease the number of stems while increasing the number of seed-bearing branches, which could lead to even more impressive yields. “Then the grains can become larger and heavier, thus the grain yield further improves,” 
• In 1996, geneticists Pamela Ronald at the University of California, Davis, and David Mackill at IRRI set out to find a wild variety of rice that was particularly tolerant of flooding. 
•  a cluster of three genes was found responsible for submergence tolerance, the ability to survive after being under water for two weeks. Researchers at IRRI — led by David Mackill and plant breeder Abdelbagi Ismail — used precision breeding to introduce the key gene from the cluster into a strain from Bangladesh, where rice is particularly prone to flooding. Early trials showed that the flood-resistant gene improved yield by up to sixfold in some areas.
• “Nowadays, Africans consume much more rice. Burundians eat rice every day. And for some families, especially in cities, rice is eaten three times a day.” A 2013 report by the International Grains Council, based in London, predicted that over the next five years rice imports would increase in sub-Saharan Africa more rapidly than in any other region in the world. Rice takes much less time to prepare and cook than traditional African standbys such as cassava root.
• This newfound taste for rice is understandable, says Gurdev Khush, an agronomist and geneticist at the University of California, Davis. 
• Khush was behind some of the key breeding innovations that helped to ignite the green revolution, an agricultural awakening that brought new strains of rice and farming techniques to Asia in the 1960s.