Friday, September 23, 2016

Hybrid Vigor

World food security has generally kept pace with the world population explosion of the last 200 years. Regional famines have occurred since man appeared on Planet Earth. A widespread famine involving billions of Earth residents, however, has been averted as the planet population inexorably headed from one billion to over seven billion in the past two centuries. Gifted and inspired agriculturalists have avoided disastrous worldwide food shortages with food crop initiatives—among them vigorous application of hybridization.

The history of hybridization is a food production success story. We are reminded of God’s Genesis mandate to “subdue the earth.” The Creator provided Earth’s raw materials and its living things. He also provided the intellectual ability to discover and apply the potential of living things—how to develop and manage methodology to engage plant and animal life in the service of human needs. Nutritional requirements have been at the forefront.

Gregor Mendel in 1865 published “Experiments in Plant Hybridization.” His ideas did not receive much attention until the early 20th century. George Harrison Shull first described the term “hybrid vigor” in 1908. He described the phenomenon that plant crosses (hybrids) outperform their parents. An Italian scientist, Nazareno Strampelli, performed early work on wheat hybrids from 1904 to World War II. He laid the groundwork for the Green Revolution of the 1960s. Our previous posts on Norman Borlaug describe his work on intense development of artificially selected and hybridized wheat and rice during the heyday of the Green Revolution, said by some analysts to have saved one billion people from starvation.

Hybridization is the cross-breeding of two true-breeding varieties. A true breeding plant produces vegetation of the same variety when they self-pollinate. Many old varieties raised in our grandparents’ day were true-breeding varieties. Their plants were able to produce seed for planting on their farms the following year, but yields were static year after year. The purchase and use of hybrid seeds removed the difficult problem of saving and planting self-raised seed, provided new vigor, and increased production dramatically. 

Widespread hybridization is a relatively new agricultural practice. Corn hybrids were responsible for increasing productivity from 30 bushels/acre in the 1940s to 150 bushels/acre in the 2010s. This year, 2016, US farmers will harvest an all-time record of 175.1 bushels/acre. That is a productivity increase five times greater than 1940 and a yield increase six or seven times greater than 1940. US production of corn (maize) is almost double the next largest world producer, China. 

The other main US grain crop is soybeans. The US narrowly outproduces Brazil in annual world production of soybeans. Since 1940 US soybean production per acre has increased almost two and one half times. Worldwide production of soybeans has increased enormously since 1940; it is now a far more important crop than in former years. From the SOYINFO website comes this quote: “The dramatic and sustained exponential growth in world soybean production is unequalled by any other crop in the world.” By weight, soybeans supply 36% protein. Animal feed is produced by the majority of soybean and corn crops worldwide. In wheat production, the US ranks fourth worldwide. Hybridization has also dramatically increased worldwide wheat production.

One wonders about past world population growth if artificial selection and hybridization had not impressively increased plant productivity, the foundation of human food supply. Beyond population growth we conjecture on the current health of our teeming millions had hybridization practices not been applied in the past century.

Along with the blessings wrought by hybridization of crops, valid concerns also exist. The potential for environmental harm exists in the resulting widespread monoculture of agricultural crops. Monoculture is the “cultivation of a single crop in a given area.”  In the Midwestern “breadbasket” states vast stretches of farmland produce but a single crop. No longer is there a natural reseeding pattern of native plants in the present era of widespread hybrid seed purchases, heavy application of fertilizers, and novel technologies. Runoff of dissolved chemical fertilizers into our waterways is a serious problem. Much natural plant diversity no longer exists. Soil erosion and adequate water supply is a constant challenge. Scientists are laboring to solve these problems.  

Along with our ability to produce food at record levels we must prudently address related problems with the help of divine wisdom. Plant scientists must continue to apply their creative gifts to balance the benefits of artificial selection and hybridization with diligent efforts to maintain the health of Earth’s agricultural legacy. We are thankful that scientists are working to achieve this balance.