Use of the virus strain group concept to characterize the resistance to PVX and PVYo in the potato cv Allegany

Resistance to the potato viruses X (PVX), Y (PVY) and A (PVA) was examined in the potato cv Allegany released by Cornell University in 1990. Standard potato cultivars from North America and Europe were included for characterization of the resistance response. Allegany was extremely resistant to a strain group 3 isolate of PVX and reacted with hypersensitivity to an ordinary strain isolate of PVY (PVY^o). However, Allegany was susceptible to an isolate of PVY causing necrosis in tobacco (PVY^N), and to an isolate of PVA. No symptoms appeared following infection with PVY^N and PVA. Identification of existing virus strain groups in a geographic area is an important aspect of predicting cultivar response to inoculation in the field.     

Detection of potato spindle tuber viroid in true potato seed by bioassay on Rutgers tomato

Various methods of preparing inoculum from single and composite samples of true potato (TP) seeds and TP seedlings were evaluated by bioassay on Rutgers tomato. An inhibitor of infection was found in concentrated plant sap prepared from composite TP seedlings that could be sequestered with RNasin or purified bentonite. Sap extracts from TP seedlings prepared in buffer containing bentonite were more infectious than nucleic acid extracts from an equivalent fresh weight of tissue. PSTV was detected in single seeds when sap preparations were inoculated on tomato and amplified to levels detectable by polyacrylamide gel electrophoresis.     

Perinatal development of lymphoid tissue and its associated epithelium in the ovine pharyngeal tonsil: A morphological study

The perinatal development of lymphoid tissue and its associated epithelium in the pharyngeal tonsil of sheep was investigated by light and electron microscopy. The lymphoid cells first appeared in the subepithelium in a scattered form at about 92 days gestation. These cells proliferated rapidly during the last trimester of gestation, and had formed many dense aggregates at the time of parturition. At birth, the epithelium overlying the aggregates was extensively infiltrated with lymphocytes and showed early transformation of follicle-associated epithelium. The lymphoid tissue and its associated epithelium did not, however., fully develop until after birth, when well-differentiated follicle-associated epithelium and lymphoid follicles with vigorous lymphopoiesis were present. In l–2 week old lambs, these structures were ultrastructurally similar to those seen in adult sheep although their size was smaller. The results of this study suggest that the lymphoid tissue of the ovine pharyngeal tonsil and its associated epithelium are morphologically ready to cope with antigens in the extra-uterine environment at birth, but that their full development and maturation are dependent on postnatal antigen stimulation.     

The effect of day and night temperatures on the growth,development and yield of glasshouse cucumbers

The responses of January-sown cucumber cvs Farbio and Sandra to day and night temperature during the early post-planting stage (late February to mid-April) were examined in a glasshouse experiment. Three day temperatures (15°, 20° and 25°C) were combined factorially with three night temperatures (10°, 15° and 20°C). Comparisons were also made between two temperature regimes (21°C day: 19°C night and 24°C day: 17°C night) applied during the pre-planting stage (late January to late February) and between two mainstem cropping methods (restriction or retention of mainstem fruits). In the pre-planting stage the 24°C day: 17°C night temperature combination produced plants which were taller, heavier and leafier than those grown at 21°C day: 19°C night. During the first 12 weeks of harvesting the larger plants produced significantly more fruit and higher gross monetary returns than did their smaller counterparts. The difference then diminished and after 20 weeks of harvesting plants from the two pre-planting temperature treatments had produced similar weights of marketable fruit of equivalent value. In the early post-planting period increases in total leaf area and stem length were closely correlated with 24-h mean temperature. Earliness (first harvest) and total weight of fruit after four weeks of harvesting were also linearly related to mean post-planting temperature. Raising the 24-h mean air temperature (within the range 15.2° to 22.6°C) by 1°C during the early post-planting stage increased early (4 week) yield by 0.82 kg m^-2 and total (20 week) yield by 1.17 kg m^-2. There was no effect of day/night temperature amplitude. After 20 weeks of harvest, gross monetary returns and profitability were generally highest when mean temperature in the early post-planting period was high and fell progressively with reduced mean temperature. Restricting stem fruits to oné per leaf node produced no significant difference in either the yield or quality of fruit from plants of any of the temperature treatments. The results are discussed from physiological and practical viewpoints and a cost-benefit comparison of temperature treatments is presented.     

Biochemical markers of cardiac injury in normal, surviving septic, or nonsurviving septic neonatal foals

The cardiac biomarkers cardiac troponin T (cTnT) and I (cTnI) and the cardiac isoenzyme of creatine kinase (CKMB) are used extensively in human medicine to diagnose and provide valuable prognostic information in patients with ischemic, traumatic, and septic myocardial injury. We designed a study to establish normal values for these markers in healthy, neonatal foals and to compare them with values obtained from septic neonates in a referral hospital population. The 25th, 50th, 75th, and 95th percentiles for cTnI and CKMB in the healthy-foal population were 0.08, 0.14, 0.25, 0.49 ng/mL and 1.4, 2.3, 4.0, 7.4 ng/mL, respectively. The values obtained for cTnT were frequently (43/52 foals; 83%) below the lower limit of detection of the assay (0.009 ng/mL), but the median and range were 0.009 and 0.009-0.041 ng/mL, respectively. In the septic foal population, the 25th, 50th, 75th, and 95th percentile values for cTnI and CKMB were 0.05, 0.12, 0.22, and 1.10 ng/mL and 2.0, 4.4, 7.8, and 24 ng/mL, respectively. The values obtained for cTnT were less frequently below the lower limit of detection (23/38 foals; 60%) compared with the healthy foal population, and the median and range were 0.009 and 0.009-0.20 ng/mL, respectively. Significantly higher values were observed for cTnT and CKMB in septic foals compared with the healthy neonatal foal population, but there were no differences among septic foals in survivors compared with nonsurvivors. These findings suggest that myocardial injury occurs during septicemia in neonatal foals but that the injury is not associated with survival among septic foals.     

Pike: A full season scab and golden nematode resistant chipstock variety

Pike is a chipstock variety released jointly by the Cornell and Pennsylvania Experiment Stations in March 1996. Pike has a specific gravity comparable to Atlantic and the ability to produce light-colored chips after 7 C storage. Most of the chip color data were taken in December, January, and February. It has scab resistance comparable to that of Superior and is golden nematode resistant. It is a full season variety, somewhat earlier than Snowden. In 23 trials in New York, internal necrosis and hollow heart of Pike was 5% compared to 18% for Atlantic. When grown at high temperatures, Pike is susceptible to a unique expression o f heat necrosis that is net-like in appearance which is different from the internal brown spot of Atlantic. The yield has been about 95% of the yield of Atlantic.     

Evaluation of flusulfamide for the control of bacterial ring rot of potato

The potential of flusulfamide (2’, 4-dichloro- α, α, α, trifluoro-4’-nitro-m-toluenesulfonanilide) as a control agent for bacterial ring rot of potato was evaluated by testing the bactericidal activity of this compound against the causal agent,Clavibacter michiganensis subsp.sepedonicus inin vitro tests, followed by greenhouse and field trials involving treatment of inoculated seed tubers. In thein vitro tests, significant reduction in the size and number ofC. m. sepedonicus colonies was observed with complete inhibition of growth occurring at flusulfamide concentrations of 100 mg/1 or greater. In the greenhouse and field trials, tubers of potato cultivar Russet Burbank were inoculated with the causal organism of bacterial ring rot,C. m. sepedonicus, in one of three different ways (cutting, dipping, injection) and subsequently treated by dipping in an aqueous solution containing varying concentrations of flusulfamide. The “dip” and “cut” methods of inoculation were intended to simulate transmission that would occur during normal production practices, while the “inject” treatment was intended to assess the effect of flusulfamide on existing infections. In both the greenhouse and field experiments, foliar disease incidence and infection rates were reduced, but not eliminated, in plants that were inoculated by cutting or dipping and treated with flusulfamide, whereas plants that had been inoculated by injection showed little effect of treatment with flusulfamide. Based on the results of these experiments, flusulfamide appears to have protective rather than curative properties againstClavibacter michiganensis subsp.sepedonicus.