Jacqueline Lee: A late-blight-resistant tablestock variety

Jacqueline Lee has a bright golden skin, yellow flesh, attractive oval shape, and excellent cooking qualities that make it suitable for tablestock use. In addition, it has been determined to have a high level of foliar resistance to the US-8 genotype ofPhytophthora infestans (Mont.) de Bary under Michigan field and greenhouse conditions. It is a full-season variety with vine maturity similar to Snowden. Jacqueline Lee has high yield potential. It has a high set (14–16 tubers/hill) of medium sized tubers that leads to 65%–80% marketable yield. Tubers are low in internal and external defects. It has a scab reaction similar to Atlantic, and the tubers have been observed to have a long dormancy.     

Phase II-Inducing,Polyphenols Content and Antioxidant Capacity of Corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) from Phenotypes of White,Blue, Red and Purple Colors Processed into Masa and Tortillas

White, blue, red and purple corns (Zea mays L.) were lime-cooked to obtain masa for tortillas. The total phenolics and anthocyanins content, antioxidant activity expressed as total reducing power (TRP), peroxyl radical bleaching (PRAC), total antioxidant activity (TAA) and quinone reductase (QR) induction in the murine hepatoma (Hepa 1 c1c7 cell line) as a biological marker for phase II detoxification enzymes were investigated. Among the extracts prepared from raw corn varieties the highest concentration of total phenolics, anthocyanins, antioxidant index and induction of QR-inducing activity were found in the Veracruz 42 (Ver 42) genotype. The nixtamalization process (masa) reduced total phenolics, anthocyanins and antioxidant activities and the ability for QR induction when was compared to raw grain. Processing masa into tortillas also negatively affected total phenolics, anthocyanin concentration, antioxidant activities, and QR induction in the colored corn varieties. The blue variety and its corresponding masa and tortillas did not induce QR. Ver 42 genotype and their products (masa and tortilla) showed the greatest antioxidant activity and capacity to induce QR     

Susceptibility of potato (Solanum tuberosum L.) foliage and tubers to the US8 genotype ofPhytophthora infestans

Late blight is an important disease of potato(Solanum tuberosum L.) worldwide, and therefore, many potato-breeding programs have prioritized the development of late blight-resistant potato cultivars. Although the emphasis has been to enhance foliar resistance, it is also necessary to evaluate tuber late blight resistance in new breeding lines and new sources of late blight resistance. We report here on the assessment of foliar and tuber resistance and the correlation between these aspects of resistance in a sample of Michigan State University potato breeding lines. Two MSU breeding lines had significantly less infected foliage than the susceptible check cultivars. Tuber susceptibility was significantly different (P < 0.05) only between the most susceptible and the least susceptible breeding lines/cultivars. Foliar and tuber susceptibility to potato late blight were not correlated as low tuber susceptibility was associated both with extremely low (e.g., MSG274-3) and high (e.g., MSE202-3Rus) foliar susceptibility.     

Effect of temperature and photoperiod on symptoms associated with resistance toPhytophthora infestans after leaf penetration in susceptible and resistant potato cultivars

The effect of temperature and photoperiod on the expression of resistance against Phytophthora infestans in five potato cultivars with and without resistance (R) genes was investigated. Four experiments were carried out under controlled conditions in growth chambers. Two cultivars (393295.236 and 391046.22) without known R genes from the International Potato Center (CIP) in Lima, Peru, two Mexican cultivars with major R genes (Tollocan and Malinche), and a susceptible cultivar (Atlantic) were used in this study. Plants were grown for 32 days in growth chambers at two temperatures (16 and 24 C) and two photoperiods (12 and 16 h day length), then inoculated with a compatible isolate of P. infestans and incubated in a mist chamber at 18 C. The inoculation efficiency, the percentage of lesions that did not grow beyond the inoculation spot, the sporangia density, and the AUDPC were recorded. The percentage of arrested lesions decreased with temperature in the two most resistant cultivars (393295.236 and Malinche), and the AUDPC was lower at 16 than at 24 C in four of the five cultivars. The inoculation efficiency and the sporangia density were not affected by change in temperature. Sporangia density increased at 16 h photoperiod; however, the final infected leaf area was not affected. Our results demonstrate that the expression of horizontal and vertical resistance was affected by temperature; however, the relative resistance ranking among cultivars was the same in the four experiments with different temperatures and photoperiods. It is assumed that the resistance in the Mexican cultivars may be conferred by minor resistance genes and by the residual effect of defeated R genes. These results emphasize the difficulty in differentiating between horizontal and vertical resistance.     

Michigan Purple: A purple-skinned tablestock variety

Michigan Purple is a purple-skinned tablestock variety. The tubers have an attractive round-ovoid shape and a strong iridescent purple skin. It has a medium set of bright purple-skinned tubers similar in shape to Norland. The tuber flesh is white; it has few internal defects and does not darken after cooking. Under irrigated conditions the yield is high and specific gravity intermediate. Michigan Purple has mid-early vine maturity.     

Beacon Chipper: A round white chip-processing potato variety

‘Beacon Chipper’ is a high-yielding, round white potato for the chip-processing market. This variety has an attractive round appearance with shallow eyes and high percentage of oversize tubers. Specific gravity in Michigan ranges from 1.077 to 1.083. Beacon Chipper may fit a window in raw product requirements between out-of-the-field ‘Atlantic’ crop and a late storage crop. This variety has some tolerance to common scab (Steptomyces scabies Thaxter) in comparison to Atlantic and ‘Snowden’. Beacon Chipper also has good chip-processing storage characteristics (light color and low amount of defects) and better tolerance to pressure bruise than Snowden. Based upon nitrogen and spacing management studies, we recommend that Beacon Chipper be planted at 20-cm within-row spacing with 180 lbs N/acre to maximize U.S. No. 1 yield and quality. The origin and pedigree of Beacon Chipper is currently unknown, despite extensive fingerprint analyses. The name Beacon Chipper was chosen to reflect the common nautical theme of Michigan and Maine.     

Validation of tuber blight (Phytophthora infestans) prediction model

Potato tuber blight caused by Phytophthora infestans accounts for significant losses of tubers in storage. Despite research on infection and management of tuber blight, there is paucity of information on the prediction of the occurrence tuber blight or modelling of tuber infection by P. infestans under field conditions. A tuber blight prediction model was developed in New York in experiments conducted using cultivars Allegany, NY101, and Katahdin in 1998 and 1999. This model was validated using data collected from the potato cultivar Snowden in field experiments in Laingsburg, Michigan from 2000 to 2009. In both New York and Michigan experiments, disease was initiated by artificial inoculation of cultivars with a US-8 isolate of P. infestans. Mean leaf area affected ranged from 0 to 94% at New York, and 0 to 93% at Michigan. At New York and Michigan, mean tuber blight incidences ranged from 1 to 40% and 0 to 15%, respectively. In the validation of the model using data collected at Laingsburg, Michigan, the model correctly predicted tuber blight incidence in 7 out of 9 years. Comparison of observed with predicted values indicated that slopes of the regression line between observed and predicted germination and infection data were not significantly different (P > 0.3547). Correlation coefficient between observed and predicted values was high (r² > 0.65) and the coefficient of variation of the residuals of error was about 12%. Although inoculum availability is assumed in the model, incorporation of relationships of inoculum density, propagule survival in soil, and tuber blight incidence would greatly improve the prediction of tuber blight under field conditions.