Potato Petiole Research Articles

Effect of blasticidin S on hypersensitive death of potato leaf petiole cells caused by infection with an incompatible race of Phytophthora infestans

The effect of an inhibitor of protein synthesis, blasticidin S, on the infection process of an incompatible race of Phytophthora infestans was studied in cut surface cells of potato leaf petiole tissue. Ten parts/10 6 of blasticidin S applied to the host tissue 0·5, 1·0 and 1·5 h before inoculation did not affect the time required for penetration of the host cell wall by the parasite and the growth rate of intracellular hyphae. The time elapsing from penetration to the hypersensitive death of the infected host cell was not affected by treating the potato cells with 10 parts/10 6 of blasticidin S 1·5 h before inoculation. Incorporation of 3H-leucine into the acid insoluble fraction of potato petiole tissue showed that protein synthesis was strongly inhibited by the blasticidin S treatment. These results suggested that de novo protein synthesis does not play an important rôle in the processes leading to hypersensitive death of potato cells caused by infection with an incompatible race of P. infestans.

Speckle leaf of potato as affected by fertilizer and water management

Studies involving the effect of irrigation and fertilizer management on speckle leaf of potato, S. tuberosum, were conducted in Montcalm and Monroe Counties in 1970–71. The first symptoms of speckle leaf at the Montcalm location were observed 73 days after planting in plots without N fertilizer. Ninety-four days after planting, all fertilizer treatments showed speckle leaf; however, potatoes receiving 336 kg N/ha were the last to show the symptoms. In Monroe County, symptoms were directly related to rate of nitrogen and irrigation levels. Excessive irrigation resulted in nitrogen loss and an increasing severity of speckle leaf. The Norchip variety showed considerably more resistance than the Haig variety. Potato petiole analysis showed that the stage of maximum N uptake by the potato plant corresponded very closely with the initiation and development of speckle leaf. Nitrogen deficient leaves at this stage of growth are the most susceptible to speckle leaf injury. Speckle leaf injury in 1971 was minimal under dry-weather conditions and could not be consistently related to any of the fertilizer treatments.

Urea nitrogen for potatoes

1. The source of nitrogen influenced the total yield of potato tubers, the nutrient concentrations in the potato petiole and the appearance of growing plants, especially in fields of low available phosphorus. 2. Urea resulted in higher nitrate-nitrogen, calcium, and magnesium concentrations in the plant petiole, but in lower phosphate-phosphorus concentrations as compared with ammonium sulfate. 3. Urea application in soils of neutral and alkaline reaction resulted in lower total yields than did ammonium sulfate at equal rates of nitrogen. In acid soils, urea appeared equal to ammonium sulfate. 4. Potatoes from urea-fertilized plants grown on soils of low available phosphurus exhibited symptoms of phosphorus deficiency during early season but outgrew these symptoms as the plants approached maturity. 5. Increasing the biuret content in the urea material from 0.2 to 1.3 per cent had no effect on yield or plant appearance. 6. In neutral and alkaline soils, ammonium sulfate was more efficient than urea as a nitrogen source for potatoes. In acid soils, indications were that urea equaled ammonium sulfate in efficiency for potatoes.

The influence of a pre-infectional heat treatment on the resistance of potato plant to Phytophthora infestans.

1. Tissues of a potato petiole and slices of potato tuber were heated at 45°-53.5°C for five minutes, and then inoculated with Phytophthora infestans. The resistance of them to P. infestans was reduced remakably.2. No influence of the heat-treatment on the time required for penetration of the fungus into the host cell, nor on the growth rate of the intracellular hypae was found by microscopical observations on the cortex cells of the petioles.3. The necrogenous reaction of potato-plant tissue to infection by incompatible race of Phytophthora infestans was delayed remarkably by pre-infectional heat-treatment. The delay of the hypersensitive death of an infected cell was ascertained by microscopical observation on the cortex cells of the petioles.4. The appearance of protoplasmic strands, in the cut-surface cell of a petiole was reduced remarkably by the heat-treatment.5. The R.Q. of the potato tuber slice was not affected by the heat-treatment, but the respiratory rate was depressed remarkably by the same treatment. The rate of respiratory depression seems to go along with that of the reduction of resistance.6. Basis was found for the supposition that the metabolic activity in the cell is closely associated with the hyper-sensitive death of infected cell.

INVESTIGATIONS ON FUNGICIDES. I. FUNGICIDAL AND SYSTEMIC FUNGICIDAL ACTIVITY IN CERTAIN ARYLOXYALKANECARBOXYLIC ACIDS

Fifty‐four aryloxyalkanecarboxylic acids have been examined as systemic fungicides. Of these, four which produced negligible damage in broad‐bean seedlings yet conferred systemic fungicidal protection to broad beans against Botrytis fabae and to tomatoes against Alternaria solanixvere studied in detail. The direct fungicidal activity of twenty compounds was assessed against B. fabae and Pythium ultimum. No correlation between fungicidal and systemic fungicidal action toward B. fabae was established. Other possibilities regarding their mode of action as systemic fungicides are discussed. The systemic fungicidal activity of a‐phenoxyziobutyric and 2:4:6‐trichlorophenoxyacetic acids in beans and of the latter compound in tomato plants was found to depend upon seasonal factors, but for 3‐phenoxybutyric and 5‐phenoxycaproic acids such variation was not observed. Results obtained in the bean test by two methods of assessment were found to correlate. The potato petiole test (van Raalte) for assessing systemic fungicidal activity was studied and modified. Evidence was obtained that the results might be unreliable owing to toxic effects produced by the compounds on the petiole tissue. Attempts were made to avoid this complication, but when phytotoxicity was eliminated, little fungicidal activity was shown.