Fertilizer application methods for Irish potatoes compared

This study was conducted in eastern Virginia on a Sassafras fine sandy loam soil to determine whether fertilizer for Irish potatoes could be broadcast before planting instead of band-placed at planting. Band placement is considered the most efficient method; however, use of the broadcast method involves less labor and speeds up the planting process. Two rates of fertilizer were used, 100 and 150 pounds per acre (112 and 169 Kg/Ha) of N, P₂O₅ and K₂O (43.7 and 65.6 pounds of P and 84.0 and 124.5 pounds of K) in a commercial material. The two rates were applied broadcast after plowing and disced in, on the rye cover before plowing, on the rye cover in January and band-placed at planting. Pungo and Superior varieties were compared, and responses varied from year to year and between varieties. The yields of Pungo potatoes were not significantly influenced by the two fertilizer rates or methods and time of application. Thus, for the Pungo variety, 100 pounds per acre (112 Kg/Ha) each of N, P₂O₅ (43.7 pounds P) and K₂O (83 pounds K) were adequate, either broadcast or band-placed. The Superior variety was less tolerant of adverse growing conditions than the Pungo and when stunted produced higher yields with band-placed fertilizer. The Superior variety under more optimum conditions (1968) produced higher yields with the broadcast fertilizer application.     

Fertilizer injury to potatoes as affected by fertilizer source,rate and placement

To investigate fertilizer injury to potatoes under field conditions, a three year study from 1979 to 1981 was undertaken in Central New York. The study was carried out on a well drained Howard gravelly silt loam; pH 6.6–6.8 with high organic matter (6.1–6.4%) and cation exchange capacity (CEC) of 13.4–14.9. When applied at a normal rate equivalent to 1,685 kg/ha of 10-15–15-1.2 the blended fertilizer containing urea N did not significantly reduce the tuber yield compared to ammoniated fertilizer and blended fertilizer containing ammonium nitrate (AN). However, when it was placed in contact with the seedpiece, the urea delayed emergence and early growth of the plant. Fertilizers containing urea-diammonium phosphate (DAP) and ureatriple superphosphate (TSP), applied at higher than normal rates and placed in contact with the seedpiece, significantly delayed emergence and reduced tuber yield.     

Composition of sulfited potatoes: Comparision with fresh and frozen potatoes

The content in moisture, fat, protein, carbohydrate, fibre and vitamin C was analyzed in three commercial types of potatoes: sulfited (treated with E223), frozen potatoes (pre-fried) and fresh potatoes (not processed). The composition of sulfited potatoes does not usually appear in food composition tables. Our results showed significant differences in the content of carbohydrates and fibre between sulfited and fresh potatoes. The content of vitamin C in sulfited potatoes, which is similar to that of frozen potatoes, was shown to be approximately half of that found in fresh potatoes.     

Harvesting potatoes with minimum damage

Temperature, tuber condition and harvester operation must be considered if potatoes are to be harvested with minimum damage. In general, total damage increased as temperature decreased; however, the type of damage resulting from impact was influenced by temperature and tuber condition. The data indicate that a tuber turgidity level occurs wherein total damage susceptibility level is minimal for a given tuber temperature and that the proper tuber turgidity level changes as temperature changes. A tuber hydration level which produces little damage when bruised at a flesh temperature of 65–70 F results in severe damage (shatter bruise) when subjected to the same force at 45–50 F. Conversely, a hydration level which results in severe blackspot at 65–70 F may result in slight to moderate total damage when subjected to the same impact at 50–55 F. Data from several commercial harvester studies indicate that damage may increase rather than decrease with a reduction of harvester speed. The ratio of chain speeds to forward speed was found to be more important than forward speed alone. The optimum ratios varied and were dependent on potato yield. Theoretical ratios based on the volume of tubers at different yield levels and harvester chain capacities were calculated and compared with actual ratios of commercial harvest operation. Harvesters operated with chain speed to forward speed ratios near the theoretical ratios resulted in low tuber damage (25%) with forward speed ranges of 1.60 to 3.25 mph. Harvesters operating with ratios differing considerably from theoretical ratios resulted in a high level of damage (66%). The catechol test identified shatter bruise damage which ruptured the skin, but did not detect internal blackspot. Therefore, the catechol test should be used with discretion when attempting to determine the total damage level. Lye peeling and abrasive peeling identified both blackspot and severe shatter bruise damage and should be used when determining harvester operation speeds when both types of damage occur.     

Transgenic potatoes expressing anErwinia pectate lyase gene — results of a 4-year field experiment

Summary Four potato lines of cv. Désirée that express the pectate lyase (PL) isoenzyme 3 ofErwinia carotovora subsp.atroseptica were examined in a 4-year field experiment with respect to plant development, tuber yield and resistance of tuber tissue toErwinia soft rot. The PL3 degrades plant cell wall pectin into unsaturated oligogalacturonates eliciting plant defence responses. In one line, enzyme expression was controlled by the CaMV 35S promoter (C) and in three lines it was driven by the potato patatin B33 promoter (D). Plant development of the D-lines in field plots was not distinguishable from that of the non-transgenic counterpart. Also tuber yield was not too different. By contrast, plants of the C-line were smaller than those of the nontransformed counterpart and also showed reduced tuber yield. There were no significant differences in dry mass, starch and protein content of tuber tissue between PL transgenic and non-transgenic potatoes. But compared with the latter, field-grown tubers expressing the PL displayed an enhanced resistance toErwinia soft rot. Thus, average rotting caused byEc-bacteria was diminished in tubers of PL-transgenic lines by 34.1%. The resistance of tubers toEc soft rot was significantly correlated with the PPO activity in tuber tissue.     

马铃薯转基因研究进展

简要介绍马铃薯转基因技术方法,着重对已获得的转抗真菌病基因、抗病毒基因、抗虫基因、改良品质基因的马铃薯的特征特性,以及将马铃薯作为植物生物反应器来生产有用蛋白质和疫苗等方面的研究成果进行了综述,同时还对转基因马铃薯的生物安全性作了评价和展望。