Laboratory Report

By: Robert D Raabe

Robert D Raabe is Professor Emeritus of Plant Pathology at University of California, Berkeley. He introduced a faster method of…

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Perennial Peanut

The rhizomatous perennial peanut (Arachis glabrata) has been the prominent forage crop in the gulf coast area for over fifty years. Used as pasture and hay, it is often called the alfalfa of the south because its protein and mineral content are similar to those of alfalfa. Native to South America, the first introductions in 1930 had limited use because of their slow establishment and low productivity. Introductions by the USDA in the 1980s and 1990s had a higher nutrient value, making the importation of hay (at $90 million per year) less necessary. However, plant improvement through traditional breeding proved difficult because, although the plant produces flowers, little seed is set. Recent searches for new germ plasm in Paraguay resulted in eighty-five accessions of wild and domesticated plants that now are being used to improve the perennial peanut. Agricultural Research 56 (3): 16-17.

A Miniature Bamboo

A French citizen working on the savannah ecology of French Guiana discovered a bamboo that is believed to be the smallest in the world. The mature flowering and fruiting plants are only two centimeters (less than one inch) tall. The fruit and seeds are slightly less than one millimeter (.039 of an inch) in length. Named after the collector, the new species is called Raddiella vanessiae. Other members of the same genus range from three to twelve inches tall. The Plant News, New Series 10 (4): 7.

Resistance to Blue Mold

Blue mold of many fruits results from infection by the fungus Penicillium exspansum. In stored apples, it results in extensive losses worldwide. Because there has been little resistance seen in cultivated apples, plant breeders seldom evaluate new selections on their resistance to the fungus. USDA researchers evaluated a new apple germ plasm collection from the center of apple origin in Kazakhistan, maintained in Geneva, New York. Fruits harvested from eighty-three accessions were inoculated with the fungus under ideal conditions for the disease. An amazing genetic diversity was found: two accessions were classified as immune, four as resistant, fifty-three as moderately resistant, and twenty-four as susceptible. The immune and resistant accessions are now being used in apple breeding programs. Hort Science 43: 420-426.

A Native Weed Killer

For years, it was noticed that western junipers (Juniperus occidentalis) inhibited the growth of plants around them. Although a native plant, its numbers have surged in dry areas of the West, where it is now out-competing native grasses and drying up streams. Researchers in Oregon wondered if something in the juniper chemistry might be killing or inhibiting other plants. Experiments showed that the leaves do inhibit the germination of a number of rangeland plants. Although too soon to tell if the juniper will be developed into a commercial herbicide, the USDA recently granted a large sum of money to further research into the use of dried leaves, juniper tea, and leaf and stem mulch to develop a new type of herbicide. Oregon’s Agricultural Progress 53 (2): 26.

Resistance to Fireblight Bacteria

Fireblight is a bacterial disease that afflicts woody members of the rose family, particularly among the stone fruits. Newly listed plants that have proven resistant to the bacteria include: apples (Malus) ‘Liberty’, ‘Freedom’, ‘Arkansas Black’, ‘Enterprise’; pears (Pyrus) ‘Warren’, ‘Magness’, ‘Moonglow’, ‘Orient’, ‘Ayers’, ‘Sugartime’; crabapples (Malus) ‘Donald Wyman’, ‘Prairiefire’, and ‘Indian Summer’. Horticulture 105 (3): 14

Mycorrhizal Fungi and Rooting

The beach plum (Prunus maritima) colonizes sand dunes along the North Atlantic coast, where soils are low in nutrients and water. It also grows in fertile, well-drained soils. It is regarded as a valuable plant because of its profuse white blossoms in spring, its greenness until late autumn, and its production of edible fruits. Because of these characteristics, it was introduced into China, but a shortage of propagative materials and the fact that it does not root well from cuttings led researchers to experiment with mycorrhizal (arbuscular) fungi in propagating plants from cuttings. Three species of the fungus Glomus were used on both softwood and hardwood cuttings. Hardwood cuttings responded better than softwood, but all cuttings were induced to root and to subsequent growth by the mycorrhizal fungi. All three species of the fungus were successful, though not equally. Journal of Horticultural Science & Technology 82: 863-866.

Tree Labeling

A researcher in Oregon has developed a method using a chemical fingerprint to determine where a plant was grown. This may be important for a number of situations; for example, ten times more “Kona Coffee” is sold than is actually grown on the island of Hawaii. In the research, plant tissues were analyzed to detect ratios of certain micronutrients to one another, including copper, sodium (though not a plant nutrient), potassium, iron, zinc, and possibly others. It also detects the ratios of certain isotopes of carbon and nitrogen. Quantities of these elements will vary from one soil to another, thus making it possible to determine the source of a plant. Idaho potatoes were shown to be distinct from those grown in Maine or Peru. A lawsuit was solved using this technique, which has also been used on blueberries, strawberries, and salmon. Oregon’s Agricultural Progress 53 (3): 28.