Graduate Thesis Or Dissertation
 

Physiological and agronomic response of potato periderm russeting to measures for control of common scab

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/mg74qq62t

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  • Management factors used for studies on potato scab control were evaluated for their effect on tuber russeting and related biochemical and anatomical parameters during 1971 and 1972. Russet Burbank potatoes were irrigated in 1971 to maintain high available soil moisture (between 90% and field capacity) for 0, 3, 6 and 9 weeks, beginning one week after plant emergence. Soil moisture was maintained between 60% and field capacity during the time it was not held above 90%. In 1972, plots for four soil-moisture treatments were irrigated to maintain minimum levels of 90%, 75%, 60% and 45%, respectively, throughout the season beginning one week after emergence. Subplot treatments in 1971 were soil compaction, pentachloronitrobenzene (PCNB) at 28 kg/ha, Super-X (mixture of PCNB and 5-ethoxy-3 trichlornmethyl 1, 2, 4 thiadiazole) at 28 kg/ha, sulfur at 896 kg/ha, and Nserve [2 chloro, 6 (dichloromethyl) pyridinel at 1.7 kg/ha, and an untreated check. In 1972, subplots were PCNB at 28, 22 and 17 kg/ha; sulfur at 896, 672 and 448 kg/ha, and an untreated check. Reduction of tuber russeting (net) resulted from increased length of high-moisture period in 1971, and increased available soil-moisture percentage in 1972. Soil compaction at the high-moisture level reduced net in 1971. PCNB, Super-X and N-serve did not change net significantly, but sulfur increased net. In 1972, PCNB reduced net, and sulfur with low soil moisture reduced net. Net was found to consist of collapsed, lignified, unsuberized cork cells above columnar layers of slightly flattened, suberized cork cells. Together these form the periderm of Russet Burbank tubers. Periderm areas with net had more layers of suberized cork cells below the net than did areas without net. The number of cork-cell layers increased with visual estimates of the amount of net. Histological stains showed that lignin content was highest in net tissue, lower in suberized cork, and absent beneath the cork. Suberin was present in cork cells below the net and absent in other tissue. Pectins were evident beneath the cork, but were found only in small amounts in cork tissue. Histochemical stain tests for cellulose were negative in walls of suberized cork, presumably due to a suberin covering. Histochemical evidence thus indicates that lignin is responsible for intercellular adhesion in net tissue. Thin-layer chromatography of tuber periderm extracts showed a predominance of chlorogenic acid, caffeic acid and coumarin. Other unidentified phenols were found in smaller amounts. The concentration of phenolic acids was reduced by high soil-moisture treatments and PCNB. It is suggested that reduced tuber net was due to reduced lignin in net cells. Reduced net from high soil-moisture treatments and from compaction was probably due to inhibition of lignin synthesis in the net as a result of low soil oxygen. Water extraction of phenolic precursors from periderm may be a contributing factor. Reduction of net by PCNB is apparently due to inhibition of lignin synthesis. On the basis of these results, soil moisture, sulfur and PCNB may generally be used in pathogen control programs without seriously reducing net if excesses are avoided.
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