Potato blight, caused by the Phytophthora infestans (Mont.) de Bary, is one of the most devastating potato diseases (Schepers 2000), causing serious problems in countries with high relative humidity, cool nights and warm days in summer. Damaged potato foliage reduces the assimilation surface which results in reduced yield. Resistance to the blight is controlled by major R genes and an unknown number of genes expressing quantitative parameters of the resistance (Lara et al. 2006). Solanum demissum is characterized by the highest efficiency of polygenes (Ballvora et al. 2012). Resistance of potato varieties to P. Infestans is one of the most important breeding objectives. Potato varieties relatively resistant to P. infestans have been developed, but their resistance may weaken due to changes in pathogen race composition. Furthermore, as only a limited gene pool is used for breeding for potato blight resistance, the disease can affect large groups of varieties at the same time in different years. According to Hansen et al. (2005), in Europe, varieties initially classified as resistant are being severely infected by the disease as a result of shifts in pathogen populations.

In a two year study conducted at Agricultural Research Station, Kota a hot spot for potato stem necrosis disease, the observations on incidence and index of disease confirmed resistance in cultivars Kufri Anand, Kufri Sindhuri, JN-189, JW-96, JX-214, JN-1530, OP-1 and PS/F-220 and hybrid TPS population HPS 25/13 as compared to susceptible control variety Kufri Bahar. The study indicated that these cultivars/hybrids along with the parents of TPS population HPS 25/13 can be utilized in breeding potato varieties resistant to stem necrosis disease of potato.

International Potato Center (CIP), Lima, Peru has developed germplasm with improved horizontal resistance to late blight free of R genes. Nineteen germplasm accessions were imported from CIP and evaluated for their late blight resistance and adaptability under hill conditions in India. Six germplasm accessions had high yield and resistance to late blight. Use of these accessions as parents in the late blight breeding programme will help in combating this dreaded disease besides broadening the genetic base of future potato cultivars.

Abstract. A local potatoes selection was evaluated, under field condition, for its resistance to potato blight (Phytophthora infestans). Data obtained during 2011-2013 assessments suggest that this selection is highly resistant to potato blight (AD = 0,03%) and could be used as a source for breeding new varieties genetically resistant to this disease. Since there were no reliable data concerning the origins of this selection, it was named MB-1.

Bacterial soft rot is a serious disease in potato (Solanum tuberosum L.), causing rapid tuber tissue maceration and, consequently, marketable yield loss. Soft rot bacteria, including Pectobacterium carotovorum subsp. carotovorum (Pbc), are favored by moist conditions, which are prevalent in large potato storage facilities. However, although most potatoes in North America are stored before use, there are no published surveys of soft rot resistance in cultivars exposed to long-term storage conditions. Thus, we tested 65 cultivars and 13 breeding lines for soft rot resistance after 6 months of storage. There was a significant effect of cultivar and production environment on soft rot resistance score. During 6 months of storage, tuber soft rot resistance in resistant clones did not change, while it changed in susceptible clones. The three most resistant cultivars to soft rot were Freedom Russet, Anett, and Alaska Red Eye.

A new cultivar Jeseo was bred in the potato breeding program of Jeju Special Self-governing Province Agricultural Research and Extension Services. It was originated from two backcrosses made in 1999 and 2001 between somatic hybrid as a female and Dejima as a male parents. The Jeseo was evaluated as a seedling for tuber characteristics, disease resistance, growth and yielding ability from 2001 to 2005. This clone was evaluated in the regional yield trials at 4 locations for 2 years. The tuber characteristics of this cultivar have a round, shallow eye depth, yellow-skinned, and short dormant period. And also, it showed high resistant to potato common scab (Streptomyces scabies, S. turgidiscabie and S. acidiscabie), soft rot, and Potato leaf roll virus (PLRV). However, it was susceptible to Potato virus Y (PVY) and late blight (Phytophthora infastans). The mean tuber yield of Jeseo according to the spring and fall cropping during the 2012 was 38.8 ton per hectare, which was lower than that of Dejima

Biochemically, starch is composed of amylose and amylopectin but can also be defined by its digestibility rates within the human intestinal tract, i.e., rapidly digested (RDS), slowly digested (SDS), or resistant (RS). The relative ratio of these starch components is the main contributor to differences in the glycemic index (GI) of carbohydrate sources. This study evaluated the digestible starch profile of 12 potato genotypes comprising elite breeding lines and commercial varieties in six environments, with the optimal profile defined as low RDS and high SDS. Genotype by environment interaction (GEI) analysis found significant (p = 0.05) genotypic and environmental effects for all digestibility rate components; however, interaction effects were only significant for SDS. Optimal starch profiles were identified for two genotypes, CV96044-3 and Goldrush. The desirable starch profile in these potato cultivars can be exploited in breeding programs for the improvement of starch profile and other important characteristics such as high yields and disease resistance.

The main aim of this research was to evaluate foliar resistance of the potato varieties of Dutch breeding company Agrico to find those most resistant to late blight in order to diminish the number of fungicide sprays required while obtaining a high yield in North-East European conditions. In the trial at the Einola Farm in 2010 and 2011, 10 potato varieties and 2 breeding lines were included. The disease scores of different varieties varied from 2.1 to 7.6 points. Nine of the varieties grown were susceptible and two varieties very susceptible to late blight. The most resistant variety was Toluca (foliar blight estimated mean value 5.9), which is immune to foliar blight in its land of origin. On the basis of two years data, we can conclude that most of the tested varieties are too susceptible to late blight to be grown without chemical control against this pathogen in North-East European conditions.

Standard area diagrams (SADs) to assess the severity of potato early blight (Alternaria grandis) on leaves of potato (Solanum tuberosum L.) were developed and validated. The proposed SADs include images of leaves with 10 distinct disease severities (0.1, 1, 3, 5, 10, 20, 40, 60, 80 and 100 %). The SADs were validated by 12 raters who had no previous experience in evaluating plant disease. Lin’s concordance correlation analysis of estimated vs. actual disease severity (based on image analysis) showed that precision and accuracy improved for most raters using the SADs, compared to assessments made without the SADs. The SADs improved accuracy (coefficient of bias, C b = 0.97 and 0.99, without and with SADs, respectively) and agreement (Lin’s concordance correlation coefficient, ρ c = 0.91 and 0.98 without and with SADs, respectively) of the estimates of severity. Severity estimates were more reliable when using SADs (coefficient of determination, R ² = 0.80 unaided and R ² = 0.95 with SADs, and the intra-class correlation ρ = 0.86 without SADs and ρ = 0.97 using the SADs). The SADs improved raters’ ability to accurately, precisely and reliably estimate potato early blight severity, and as such can be used to assess severity for several purposes, including breeding for resistance, fungicide screening, and pathotype characterization.