Potato virus Y (PVY) is one of the most important of the potato viruses, but little is known about the impact on yield of seedborne infection levels below 100%. Blending infected and healthy seed from different seed lots introduces the variable of performance differences between the seed lots, which may obscure the effect of virus alone. Seed lots containing various levels of seedborne PVY (0, 2, 10, 20, and 50% incidence of infected tubers) were created by combining in different proportions seed pieces from healthy and infected tubers from the same seed source. These seed lots were planted in replicated field plots at the University of Idaho Parma R & E Center in Parma, ID from 1995 to 1997. Regression analyses on data from the three consecutive seasons indicate that seedborne PVY has virtually the same negative impact on yield for all three cultivars.

Processing quality has become increasingly important to the potato industry. A serious defect in product quality is the physiological disorder known as sugar ends, also referred to as dark ends, jelly ends, translucent ends, and/or glassy ends. Symptoms of the most common type of sugar end include relatively low starch and high sugar content in the basal end of the tuber. Tubers with the sugar end disorder produce French fries that are dark on one end, making the fries unacceptable to consumers. Sugar end potatoes cause time and profit losses at the processing plant and may require blending of loads to meet product specifications, along with the need to change processing protocols. Sugar end can be costly to growers if the tubers have insufficient quality and the crop is rejected for processing. Conditions conducive to the development of sugar ends include high soil temperatures, transitory soil moisture deficits, and insufficient or excess nitrogen fertilization. Tubers are most sensitive to these stresses during early bulking. Historically, several theories have been proposed concerning the mechanism of sugar end development. Research shows that stressed plants produce adequate amounts of assimilate to support continued tuber growth, but accumulate large amounts of sucrose in the basal tissues of the tuber immediately following stress. Accumulated evidence suggests that heat stress and water deficit induce changes in the activities of certain key carbohydrate metabolizing enzymes shifting the tuber from a starch synthesizing function to one of starch mobilization. Genetic resistance to sugar end development is known and the identified traits are highly heritable. This review summarizes sugar end investigations to-date, and presents a list of research-based crop management recommendations that assist potato producers in minimizing the potential for sugar end development in the field.Resumen La calidad de procesamiento de papa se ha vuelto cada vez más importante para la industria. Un defecto serio en la calidad del producto es el desorden fisiológico conocido como punta azucarada, referido también como punta oscura, punta translúcida y/o punta vítrea. Los síntomas de los tipos más comunes de punta azucarada incluyen bajo contenido relativo de almidón y alto contenido de azúcar en el extremo basal del tubérculo. Los tubérculos con punta azucarada producen papas fritas que tienen un extremo oscuro, haciendo la fritura inaceptable para los consumidores. Las papas con extremo azucarado causan pérdida de tiempo y ganancias a la planta procesadora y puede requerir la mezcla de lotes de papa para satisfacer las especificaciones del producto, además de de la necesidad de cambiar los protocolos de procesamiento. La punta azucarada Am. puede ser costosa para los productores si los tubérculos son de calidad insuficiente y el cultivo es rechazado para procesamiento. Las condiciones que conducen al desarrollo de este desorden incluyen altas temperaturas del suelo, deficiencia transitoria de agua e insuficiencia o exceso de ...

Zebra chip disease (ZC) is an emerging disease of potato in which tubers are produced with striped necrotic patterns that make them unmarketable. ZC is associated with the bacterium "Candidatus Liberibacter solanacearum" (Lso), which is transmitted by the potato psyllid, Bactericera cockerelli (Šulc; Hemiptera: Triozidae). First found in Idaho during 2011, ZC now contributes to increased production costs each season via additional insecticide sprays. To clarify the extent and severity of the threat of ZC in Idaho, we sampled potato psyllids in commercial potato fields across the state over four growing seasons (2012-2015). All life stages of psyllids were sampled using a combination of methods (yellow sticky traps, vacuum samples, and leaf samples), and adult psyllids were tested for the presence of Lso by Polymerase Chain Reaction (PCR). Abundance of potato psyllids initially increased gradually over each growing season, then exhibited a sharp late-season rise and a sharp decline as most fields were being harvested. Abundance of psyllids was higher at warmer, lower elevation sites, but infestation onset did not differ between growing regions. Fewer psyllids were collected in vacuum samples than in sticky trap samples. Nymphs and eggs were found only late season and during years with high abundance of adults. Overall incidence of Lso was similar among all years but one. The results presented here clarify our understanding of the seasonal phenology of potato psyllids and Lso in Idaho potato fields and will aid in developing integrated management strategies against this important pest of potato.

Rhizoctonia solani may affect potato growth, yield and grade through lesions on stems and stolons and through development of black scurf on daughter tubers. R. solani inoculum can be found on seed potatoes and in the soil, although the relative importance of each inoculum source is unknown. Field studies at Parma and Aberdeen, Idaho, were conducted in 2004 and 2005 to evaluate the importance of each source of inoculum on the subsequent development of this disease. Seed of cultivars Ranger Russet (2004) and Russet Burbank (2005) was washed and sorted into three (2004) and two (2005) levels of black scurf. Prior to planting, the plots were inoculated with R. solani cultures mixed with vermiculite at low, medium and high rates. Each level of seed inoculum was planted at each level of soil inoculum. Significantly greater levels of disease on stems and stolons was consistently found on plants grown from high inoculum seed compared to low inoculum seed. However, significant effects of soil inoculum level on stem and stolon disease were rarely seen. In contrast, both seed and soil inoculum level influenced the development of black scurf on daughter tubers. The largest response to soil inoculum level was seen when seed inoculum was low.Resumen Rhizoctonia solani puede afectar el crecimiento de la papa, el rendimiento y calidad a través de lesiones en tallos y estolones y por el desarrollo de costras negras en los tubérculos producidos. El inoculo de R. solani se puede encontrar en tubérculo semilla y en el suelo, aunque se desconoce la relativa importancia de cada fuente de inoculo. Durante 2004 y 2005 se condujeron estudios de campo en Parma y Aberdeen, Idaho, para evaluar la importancia de cada fuente de inoculo en el desarrollo subsecuente de esta enfermedad. A semilla de los cultivares Ranger Russet (2004) y Russet Burbank (2005) se les lavó y agrupó en tres (2004) y dos (2005) niveles de costra negra. Antes de plantar, los lotes se inocularon con cultivos de R. solani mezclados con vermiculita a niveles bajo, medio y alto. Cada nivel de inoculo a la semilla se plantó en cada uno de los niveles de inoculo al suelo. Se encontraron consistentemente niveles significativamente mayores de enfermedad en tallos y estolones de plantas que crecieron en altos niveles de inoculo en la semilla comparados con los de niveles bajos. No obstante, raramente se vieron los efectos significativos de los niveles de inoculo en el suelo sobre la enfermedad en tallo y estolón. En contraste, ambos niveles de inoculo en semilla y suelo, influenciaron el desarrollo de la costra negra en los tubérculos generados. La mayor respuesta al nivel de inoculo en el suelo se observó cuando el nivel de inoculo a la semilla era bajo.

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