Dwarf crop discovery no small achievement

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WEST LAFAYETTE, Ind. – A team of Purdue University researchers recently uncovered the genetic mechanism that prevents certain crop plants from growing tall.

The finding has future crop production applications since some grains produce greater yields if plants are kept short.

What controls it? Guri Johal, plant pathologist, identified the process that generates dwarfed corn and sorghum plants, which grow to roughly half the height of their normal counterparts.

This discovery may help in the development of dwarf forms in other crops, which hold the potential to improve food production in certain regions of the world.

Their research also revealed the genetic process behind an unstable variety of sorghum frequently used in commercial production.

Getting answers. Taken together, the findings resolve two questions that have puzzled geneticists since the early 1950s.

Dwarf forms of crops, including wheat, rice and sorghum, are of significant agronomic importance, Johal said.

“Dwarf plants put more of their energy into producing grains, instead of growing tall,” he said.

Prevented starvation. Increased yields of dwarf varieties of wheat, introduced throughout India, Pakistan, and Southeast Asia during the 1960s, prevented massive food shortages in those regions, he said.

A dwarf form of corn called brachytic2 (br2) was recognized in 1951, but until now, scientists have not understood the genetic mechanism underlying the plant’s mutation.

These dwarf mutants are somewhat unusual, as their lower stalks are highly compressed but the upper portions of the plant, including the ears and tassels, are normal.

A related mutant in sorghum called dwarf 3 (dw3) has been put into widespread cultivation because it displays ideal crop characteristics, such as increased grain yield and improved stalk strength and quality, Johal said.

Johal and his colleagues found that loss of a gene product called a p-glycoprotein generates these dwarf corn and sorghum plants by interfering with the movement of auxin, an essential hormone in plant growth and development.

They also have identified the genetic mechanism that causes dwarf sorghum plants to spontaneously revert to a taller form.

They also found that the dwarf mutants, while shorter than their taller counterparts, have more cells per unit area in the stalk, which makes the stalks stronger and perhaps more effective at retaining water.

Dwarf corn. Unlike dwarf sorghum, dwarf corn has not been put into commercial use partly because corn hybrids grown in the United States are not excessively tall.

In addition, br2 tends to produce barren plants when grown at high densities.

Furthermore, the equipment in use in the United States today would not be able to effectively harvest significantly shorter plants, Johal said.

However, he said the discovery of the dwarfing mechanism might renew interest in developing a dwarf corn with improved yield, which could be of particular interest in developing countries.

Dwarf varieties of rice and wheat, introduced during the 1960s throughout the Indian subcontinent and Southeast Asia, were largely responsible for thwarting famine, Johal said.

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