L. A. Schaal

Accumulation of phenolic substances and ascorbic acid in potato tuber tissue upon injury and their possible role in disease resistance

SummaryChlorogenic acid and other o-dihydricphenols were found to accumulate rapidly in the area adjacent to the cut surface of potato tuber slices held at room temperature in a moist chamber.The rate of accumulation was found to be decreased by: (1) holding the slices at lower temperature; (2) dipping the slices in resorcinol solution; (3) dipping slices in sodium bisulfite-sodium chloride solution; (4) immersion of whole tubers in water (room temperature) for 24 hours prior to slicing.The same phenolic substances which accumulated in tuber slices were found to accumulate in necrotic areas of tubers infected with aster yellows.Ascorbic acid was found to accumulate in tuber slices but rapidly decreased after the second day of holding at room temperature.Several ways in which phenolic substances can function in the mechanism of disease resistance are discussed.The possibility that the accumulation of oxidized products of ascorbic acid adjacent to infected tissue may play a role in disease resistance is also discussed.

Comparative Effects of Catechol, Some Related Compounds, and Other Chemicals on Suberization of Cut Potato Tubers

1. This study reports the comparative effects of catechol, eight related compounds, and two other chemicals upon suberization of cut potato tubers. 2. All the ortho-dihydric phenols used except protocatechuic acid stimulated the formation of a thicker suberized layer than was found in the controls. 3. Resorcinol, a meta-dihydric phenol, inhibited suberization, apparently by its effect on tyrosinase. 4. Catechol, an ortho-dihydric phenol, was found to be the most effective compound for stimulating wound-healing actions in Bliss Triumph tubers.

Seed and soil treatment for the control of potato scab

SummaryTreatment of seed and soil with certain chemicals was found to have no value in controlling scab infection in the irrigated, sandy soils of northern Colorado. The soils in which these tests were conducted, produced several crops of heavily scabbed tubers previous to these tests.Treatment of these scabby soils with mercuric chloride, yellow oxide of mercury, sulfamic acid, aluminum sulphate, potassium iodide and sulphur, did not reduce scab infection.Treatment of scab-infected seed with mercuric chloride reduced the number of infected tubers over the infected untreated seed.When sulphur was added with manure to the scabby soil, three weeks previous to planting and to the opened row at planting time, scab infection for the current season or the two following seasons, was not reduced.None of the seed or soil treatments appear to have value for the control of scab in the alkaline soils of northern Colorado. Clean treated seed produced scabby tubers in the scab-infested soil.

Yampa, a new scab-resistant potato

SummaryThe Yampa potato has shown considerable promise as a scab-resistant, good-quality, high-yielding variety. It has shown field resistance to scab, early blight, and to leaf roll and mosaic. It appears best adapted to the lighter mineral soils. It has a relatively tough skin and keeps well. Maturity is approximately 7 to 10 days later than Irish Cobbler or Bliss Triumph.

Osage: A new baking-type potato variety resistant to common scab

During the past few years there has been an increasing demand for potato varieties resistant to common scab, caused by Streptomyces scabies (Thaxt.) Waks. & Henrici). This disease has become a limiting factor in many areas of the country and is a particularly serious problem m some of the productive muck soils of the north-central states. Although resistance to scab has been a primary objective in potato breeding, the important features of yield, market quality, and cooking quality have not been neglected. The need is for a variety equal to Irish Cobbler in yield and cooking quality, but smoother, shallow-eyed and scab-resistant. ~Fhe new variety Osage is offered as an approach to this goal. It is a long potato, known commercially as a baking-type, or long-white. Tubers of Osage are smooth, shallow-eyed and uniform in type (Figure 1). In most localities Osage shows a high degree of resistance to scab.

The reaction of Pawnee and Bliss Triumph potatoes to certain physiologic races ofActinomyces scabies

SummaryBliss Triumph and Pawnee potatoes are commonly infected with scab in Colorado soils; but occasionally Pawnee is found to be free from scab in soils that produce a scabby crop of Bliss Triumph. This suggests that Pawnee is resistant to certain races ofActinomyces scabies that may scab Bliss Triumph severely.Experiments with four isolates ofActinomyces scabies in the greenhouse showed that Pawnee was resistant to two races that caused deep scab on Bliss Triumph; also that a race causing an intermediate type of pustule on Pawnee did not produce scab on Bliss Triumph.

Navajo and Blanca: Two new potato varieties resistant to scab and adapted to Colorado

SummaryNavajo (U.S.D.A. C.S. 13,178) and Blanca (U.S.D.A. C.S. 12,240) are high-yielding, medium-maturing, scab-resistant varieties adaptable to Colorado. Their tubers are smooth, white, and oval to round and slightly flattened. Tests have shown that they are equal to Katahdin in yielding ability and are usually superior in solids content. They are both good bakers. High-quality chips were made from their tubers after harvest and when reconditioned after storage.