Benoit Bizimungu

Characterization of Phytophthora infestans population diversity in Canada reveals increased migration and genotype recombination

Abstract Late blight, caused by Phytophthora infestans, is a devastating disease of potatoes and tomatoes that causes significant crop losses worldwide. Late blight diversity has been increasing since 2009 in many areas of Canada on both potatoes and tomatoes. Although the US-8 genotype of P. infestans has dominated pathogen populations in much of Canada for the past 15 years, novel genotypes have emerged in recent years. A comprehensive survey of late blight samples collected across Canada in 2011 indicated that although the US-8 genotype of P. infestans still dominated pathogen populations in Prince Edward Island, new US-23 and US-24 genotypes had become established in other parts of Canada. The US-11 and US-22 genotypes dominated populations of the pathogen from specific areas of Alberta and Ontario, respectively. Clonal propagation and migration contributed to long-distance transport of P. infestans genotypes and in some situations, both A1 and A2 mating types of the pathogen were found in the same production region. This finding is of concern because it increases the potential for sexual recombination within pathogen populations, leading to the production of oospores that can survive in the absence of host tissue and create new strains of P. infestans. Evidence for recombination in the P. infestans population was detected in Ontario on tomato. Segregation of Gpi allozymes and mating type appeared to occur independently of the RG57 loci, producing several new P. infestans genotypes. Prediction and management of late blight will need to be evaluated and modified to accommodate these new potentially aggressive P. infestans genotypes.

Genotype by Environment Interaction Effects on Starch Content and Digestibility in Potato (Solanum tuberosum L.)

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.

Glycemie index — a review and implications for the Potato industry

Glycemic index (GI) ranks carbohydrate foods according to the postprandial impact on blood glucose. High glycemie index carbohydrates cause a rapid rise in blood glucose and are not recommended for consumption by diabetics, who have inadequate insulin production and are susceptible to hyperglycemia. The clinical value of glycemie index as a tool for controlling diet-induced glycemie response in diabetic patients is endorsed by the World Health Organization, the Canadian Diabetes Association, the European Association for the Study of Diabetes and the Dietitians Association of Australia. Currently the American Diabetes Association considers GI as primarily a tool for researchers. Potato is a carbohydrate food with no fat, rich in vitamin C and potassium and a good source of dietary fibre. However, the starch of cooked potato is rapidly broken down to glucose by amylolitic enzymes, resulting in a rapid elevation of blood glucose, and therefore potato products in general have a moderate to high GI. Glycemie load (GL) takes into account the actual amount of carbohydrate consumed per serving. The GL of potato is generally moderate and seldom high because of potato—s high moisture content. GI and GL provide useful guides for diabetics to control the glycemie response associated with the consumption of carbohydrate sources. GI and GL differ between cultivars and can be modified by processing methods. GI is also influenced by other components of the meal, even a previous meal. More research is required to adequately define GI and GL of potato cultivars and identify the impact of the composition of the starch (amylose/amylopectin ratio), processing techniques that contribute to a lower GI, and the effect of other meal components on the GI of potato.ResumenEl índice glicémico (GI) figura en los alimentos carbohidratados de acuerdo al impacto pos comida sobre la glucosa de la sangre. El alto índice de los carbohidratos glicémicos causa un rápido incremento de glucosa en la sangre y no es recomendado para diabéticos que tienen una inadecuada producción de insulina y son susceptibles a la hiperglicemia. El valor clínico del índice glicémico en pacientes como instrumento para controlar la dieta indujo a una respuesta glicémica en pacientes diabéticos está respaldado por la Organización Mundial de la Salud, la Asociación Canadiense de Diabetes, la Asociación Europea para el Estudio de la Diabetes y la Asociación Dietética de Australia. Actualmente la Asociación Americana de Diabetes considera al GI principalmente como instrumento para investigadores. La papa es un alimento hidrocarbonato sin grasa, rico en vitamina C y potasio y una fuente de fibra, sin embargo, el almidón de la papa cocida se transforma rápidamente en glucosa por acción de enzimas amilolíticas, resultando en una rápida elevación de glucosa de la sangre. Los productos de papa tienen en general un moderado a alto GI. La carga glicémica (GL), toma en cuenta la cantidad Accepted for publication 30 August 2006. Additional Keywords: diabetes, glycemie load, starch, amylose, amylopectin, retrogradation, cultivar, processing real de carbohidratos consumidos por ración, pero la GL de la papa es generalmente moderada y raramente alta debido a su alto contenido de humedad. GI y GL proporcionan guías útiles para el control de la respuesta glicémica asociada con el consumo de fuentes carbohidratadas. GI y GL difieren entre cultivares y pueden ser modificadas por los métodos de procesamiento. El GI está también influenciado por otros componentes del alimento y aún de alimentos consumidos con anterioridad. Se requiere mayor investigación para definir adecuadamente los GI y GL de cultivares de papa, identificar el impacto de la composición del almidón (proporción anulosa/ amilopectina) y las técnicas de procesamiento que contribuyan a disminuir el GI y el impacto de los componentes de otros alimentos sobre el GI de la papa.

Evaluation of nutritional profiles of starch and dry matter from early potato varieties and its estimated glycemic impact.

To identify healthier potatoes with respect to starch profiles, fourteen early varieties were evaluated for their dietary fiber, total starch, rapidly digestible (RDS), slowly digestible (SDS), and resistant (RS) starch for nutrition and with regard to estimated glycemic index (eGI) and glycemic load (eGL). While all these profiles were highly dependent on the potato variety, eleven out of fourteen varieties were classified as low GL foods (p<0.05). A strong positive correlation was observed with eGI and RDS (r=0.975-1.00, 0.96-1.00 and 0.962-0.997 for uncooked, cooked and retrograded varieties, respectively), whereas a strong negative correlation was observed between eGI and RS (r=-0.985 to -0.998, -0.96 to -1.00 and -0.983 to -0.999 for uncooked, cooked and retrograded varieties respectively, p<0.05). For the cultivars examined, the present study identified RDS and RS as major starch factors contributing to eGI.

Marker Assisted Selection of Potato Clones that Process with Light Chip Color

Development of cultivars with acceptable chip color is a major but challenging objective of breeding programs world-wide. Currently clones with suitable chip color are identified by including breeding populations in several storage environments over multiple crop seasons. Chip color involves several factors associated with the accumulation of reducing sugars including temperature. The availability of molecular markers associated with the genes controlling chip color would greatly reduce the time required to identify clones with this trait in breeding populations and advance our understanding of this critical carbohydrate characteristic. Polymorphisms in a sucrose synthase allele provided an excellent marker associated with chip color that could assist in selecting for genotypes with acceptable Agtron scores.ResumenEl desarrollo de cultivares con color aceptable de hojuelas es el objetivo principal y un desafío en los programas de mejoramiento a nivel mundial. Generalmente los clones con color conveniente de hojuelas se identifican mediante la inclusión de poblaciones de mejoramiento en varios ambientes de almacenamiento sobre múltiples campañas de cultivo. El color de las hojuelas involucra diferentes factores asociados con la acumulación de azúcares reductores, incluyendo la temperatura. La disponibilidad de marcadores moleculares asociados con los genes que controlan el color de las hojuelas reduciría enormemente el tiempo el tiempo requerido para identificar los clones con esta característica en las poblaciones de mejoramiento. Los polimorfismos en el alelo de sacarosa sintasa proporcionan un excelente marcador asociado con el color de las hojuelas que podría ayudar en la selección de genotipos con aceptables puntajes Agtron.

Northstar: A high-yielding, white cold-storage chipping potato cultivar with attractive oval tubers resistant to late blight

Abstract‘Northstar’ (V0123-25) is a white-skinned, white-flesh, mid-season maturing potato cultivar suitable for cold storage chipping. It was selected from a cross made at the Lethbridge Research Centre of Agriculture and Agri-Food Canada between ‘Niska’ and ND860-2. In trials across western Canada, full season marketable yields of Northstar were 6% to 31% greater than ‘Snowden’ and 11% greater than ‘Norchip’. Specific gravity of Northstar has averaged 0.009 and 0.012, less than Snowden and ‘Atlantic’, respectively. Chip color was superior to Norchip, Snowden and Atlantic. Northstar showed an excellent potential for direct chipping out of a 6 C storage. Tubers of Northstar are uniform, oval, smooth to slightly flaky in texture, with shallow eyes. The incidence of hollow heart and internal necrosis was lower than Atlantic, Norchip and Snowden. Deformed tubers occurred at levels less than Norchip and Snowden. Northstar is resistant to tuber late blight infection, moderately resistant to common scab, Verticillium wilt and Fusarium wilt, and moderately susceptible to foliar late blight. It is susceptible to early blight and shows clear tuber and foliar symptoms when infected with bacterial ring rot.Resumen‘Northstar’ (VO123-25) es un cultivar de papa de piel blanca, pulpa blanca que madura a media estación, adecuado para hojuelas de almacenamiento frío. Fue seleccionado de un cruzamiento entre ‘Niska’ y ND860-2 en el Centro de Investigación Agrícola Lethbridge and Agri-Food Canada. En pruebas a través del Oeste canadiense, los rendimientos comerciables de estación completa de Northstar fueron de 6% a 31% más altos que ‘Snowden’ y 11% mayores que ‘Norchip’. La gravedad específica de Northstar ha promediado 0.009 y 0.012 menos que Snowden y ‘Atlantic’, respectivamente. E1 color de hojuela fue superior que Norchip, Snowden y Atlantic. Northstar mostró un excelente potencial para hacer hojuelas de tubérculos directamente extraídos de almacenamiento de 6 C. Los tubérculos de Northstar son uniformes, ovales, lisos a ligeramente escamosos, con ojos superficiales. La incidencia de corazón vacío y necrosis interna fue menor que en Atlantic, Norchip y Snowden. Los tubérculos deformes se presentan a menores niveles que en Norchip y Snowden. Northstar es resistente a la infección de tizón tardío al tubérculo, moderadamente resistente a sarna común, marchitez por Verticillium y Fusarium y moderadamente susceptible a tizón tardío foliar. Es susceptible al tizón temprano y muestra claros síntomas al tubérculo y al follaje cuando se infecta con pudrición bacteriana en anillo.

Differences between the Bud End and Stem End of Potatoes in Dry Matter Content, Starch Granule Size, and Carbohydrate Metabolic Gene Expression at the Growing and Sprouting Stages

Potatoes usually have the tuber bud end dominance in growth during tuber bulking and in tuber sprouting, likely using carbohydrates from the tuber stem end. We hypothesized that the tuber bud end and tuber stem end coordination in carbohydrate metabolism gene expression is different between the bulking dominance and sprouting dominance of the tuber bud end. After comparing the growing tubers at harvest from a green vine and the stage that sprouts just started to emerge after storage of tubers at room temperature, we found the following: (1) Dry matter content was higher in the tuber stem end than the tuber bud end at both stages. (2) The starch granule size was larger in the tuber bud end than in the tuber stem end. (3) The tuber bud end had higher gene expression for starch synthesis but a lower gene expression of sucrose transporters than the tuber stem end during tuber growing. (4) The tuber stem end at the sprouting stage showed more active gene expression in both starch degradation and resynthesis, suggesting more active export of carbohydrates, than the tuber bud end. The results indicate that the starch accumulation mechanism in the tuber bud end was different between field growing and post-harvest sprouting tubers and that tubers already increased dry matter and average starch granule sizes in the tuber bud end prior to the rapid growth of sprouts.

Alta Crown: A New Russet Potato Cultivar with Resistance to Common Scab and A Low Incidence of Tubers Deformities

Alta Crown (CV92028-1) is a new russet potato cultivar with resistance to common scab and a low incidence of tuber deformities. It was selected at the Lethbridge Research Centre of Agriculture and Agri-Food Canada, from a cross made at Colorado State University, San Luis Valley Research Center between breeding clones AC83172-1RU and C086030-1RU. Alta Crown has semi-erect, short, and compact vines. The cultivar has uniform, oblong to long, medium to large tubers with a medium to dark russet skin, cream- colored flesh and shallow eyes. In trials across western Canada and Ontario, Alta Crown produced similar or lower total yields than did Russet Burbank and Shepody, but a higher percentage of marketable tuber yield at maincrop harvest, and at early harvest. The average weight of marketable tubers was superior to that of Russet Burbank at all sites, and to that of Shepody at some sites. Alta Crown exhibited resistance to tuber deformities, hollow heart and internal necrosis defects. Specific gravity of Alta Crown in western Canadian regional trials was similar to that of Shepody and Russet Burbank. Fry colour was also similar to Russet Burbank and Shepody in product quality evaluations. Alta Crown was identified as having resistance to common scab and was moderately resistant to late blight tuber rot and foliar early blight, but was susceptible to foliar late blight. It shows moderate foliar and tuber symptoms when infected with bacterial ring rot. A post-harvest laboratory testing is recommended to complement visual inspection.ResumenAlta Crown (CV92028-1) es una nueva variedad de papa tipo russet con resistencia a la roña común y con baja incidencia de deformaciones del tubérculo. Se seleccionó en el Centro de Investigación en Agricultura y de Agroalimentos de Canadá, de una cruza hecha en la Universidad Estatal de Colorado, en el Centro de Investigación del Valle de San Luis, entre los clones AC83172-1RU y C086030-1RU. Alta Crown tiene tallos semi-erectos, cortos y compactos. La variedad tiene tubérculos uniformes, de oblongos a largos, de tamaño de medio a grande, con piel rugosa de intermedia a oscura, pulpa color crema y ojos superficiales. En ensayos a lo largo del oeste de Canadá y Ontario, Alta Crown produjo rendimientos similares o más bajos que Russet Burbank y Shepody, pero con un porcentaje mayor de rendimiento de tubérculo comercial en la cosecha de cultivo principal y en cosecha temprana. El peso promedio de tubérculos comerciales fue superior al de Russet Burbank en todos los sitios, y al de Shepody en algunos. Alta Crown exhibió resistencia a deformaciones de tubérculo, corazón hueco, y a defectos de necrosis interna. La gravedad específica de Alta Crown en los ensayos regionales del oeste de Canadá fue similar a la de Shepody y de Russet Burbank. El color del freído también fue similar al de Russet Burbank y Shepody en las evaluaciones de calidad del producto. Alta Crown se identificó como con resistencia a la roña común y fue moderadamente resistente a la pudrición del tubérculo por tizón tardío y al tizón temprano foliar, pero fue susceptible al tizón tardío en las hojas. Muestra síntomas moderados en hoja y tubérculo cuando se infecta con la pudrición anular bacteriana. Se recomienda una prueba de laboratorio en postcosecha para complementar la inspección visual.

Verticillium dahliae Disease Resistance and the Regulatory Pathway for Maturity and Tuberization in Potato

Verticillium wilt resistance is linked to control of tuberization in potato. The StCDF1 tuberization gene is epistatic to the Ve2 resistance gene. eQTL can be used to examine gene networks for complex traits.

Effectiveness of the field selection parameters on potato yield in Atlantic Canada

Abstract: Cultivated potatoes (Solanum tuberosum L.) are the 4th most important crop feeding the world. Therefore, yield is a crucial trait for potato breeding and germplasm enhancement. The analysis of phenotype data of potato plants enables the extraction of crucial phenotypic characters for potato yield breeding. Using data collected from 179 advanced breeding clones that were planted in evaluation trials over three years at the Benton Ridge breeding substation in Atlantic Canada, we deciphered the dynamic properties of trait expression over the growth period based on nine parameters used in Agriculture and Agri-Food Canadas potato breeding program. The analysis of breeding data provided valuable information to understand the factors that contribute to the phenotypic performance of potato and potato tuber yield. Linear mixed model fit by maximum likelihood and principal component analysis (PCA) were employed as complementary analysis tools to analyze these characters to try to uncover the relationship of complex agronomic traits. Our results showed that the majority of the selection parameters effectively contributed to the improvement of potato tuber yield. The first five principal components (PCs) accounted for 74.9% of the phenotypic variation observed from 2012 to 2014. The maturity, early vigor, eye depth, and top vigor are the most important phenotypic parameters affecting potato tuber yield selection. Based on the results, these selection parameters are yet highly independent variables which also displayed some degree of interrelationship.