No abstract

Potato virus Y (PVY) is a serious threat to potato production due to effects on tuber yield and quality, in particular, due to induction of potato tuber necrotic ringspot disease (PTNRD), typically associated with recombinant strains of PVY. These recombinant strains have been spreading in the United States for the past several years, although the reasons for this continuing spread remained unclear. To document and assess this spread between 2011 and 2015, strain composition of PVY isolates circulating in the Columbia Basin potato production area was determined from hundreds of seed lots of various cultivars. The proportion of nonrecombinant PVYO isolates circulating in Columbia Basin potato dropped ninefold during this period, from 63% of all PVY-positive plants in 2011 to less than 7% in 2015. This drop in PVYO was concomitant with the rise of the recombinant PVYN-Wi strain incidence, from less than 27% of all PVY-positive plants in 2011 to 53% in 2015. The proportion of the PVYNTN recombinant strain, associated with PTNRD symptoms in susceptible cultivars, increased from 7% in 2011 to approximately 24% in 2015. To further address the shift in strain abundance, screenhouse experiments were conducted and revealed that three of the four most popular potato cultivars grown in the Columbia Basin exhibited strain-specific resistance against PVYO. Reduced levels of systemic movement of PVYO in such cultivars would favor spread of recombinant strains in the field. The negative selection against the nonrecombinant PVYO strain is likely caused by the presence of the Nytbr gene identified in potato cultivars in laboratory experiments. Presence of strain-specific resistance genes in potato cultivars may represent the driving force changing PVY strain composition to predominantly recombinant strains in potato production areas.

Crop loss assessment after an event of hailstorm can be inaccurate, subjective, inconsistent, and time consuming with the conventional method. Low-altitude, high-resolution aerial imaging using an unmanned aerial vehicle can be utilized for rapid assessment of target crops in a large scale, which can potentially improve the evaluation procedure. The goal of this study was to evaluate the feasibility of rapid and accurate assessment of crop damage due to simulated hailstorms using aerial multispectral imaging. Field experiments were conducted during two seasons in two potato varieties (Russet Norkotah, Ranger Russet) with three levels of mechanical defoliation (33%, 66%, and 99%) at three growth stages (tuber initiation, early bulk, and late bulk). All defoliation treatments were compared to the non-treated control plots (0% defoliation). Aerial multispectral images were collected between 77 and 108 days after planting (0 to 60 days after damage). Vegetation indices such as green normalized difference vegetation index (GNDVI), normalized difference vegetation index, and soil-adjusted vegetation index were calculated from replicate plots of different treatments. Results from two seasons showed similar trends in GNDVI values, with maximum effect of hail damage observed in tuber initiation stages. The mean GNDVI value was significantly lower in crops with the severe damage (99%

Iron deficiency in humans occurs in all regions of the world. Potatoes are a modest source of iron. The purpose of this study was to determine if genetic variation for potato tuber iron content exists. Iron content in unpeeled potato was measured in 33 clones, including varieties and advanced breeding selections, in three trials (Tri-State, Western Regional Russet, Western Specialty/Red) which in total were grown in twelve environments. In two trials significant genotype × environment interaction occurred. Thirteen clones contributed significantly to this genotype × environment interaction, making them unstable across environments, including the variety Russet Burbank. Broad-sense heritabilities and their 95% confidence intervals (in parentheses) in the Tri-State, Western Regional Russet and Western Specialty/Red Trials were 0.00 (0.00, 0.38), 0.64 (0.17, 0.87), and 0.73 (0.25, 0.90), respectively. Overall the range of mean iron content on a clonal basis was 17 to 62 ug per gram dry weight. The upper limit is three times higher than generally reported values of potato. The five highest values were found in the Western Specialty/Red trial and were red-skinned, white-fleshed clones. These results suggest that genetic variation for tuber iron content exists and that breeding for enhanced iron content would be feasible.Resumen La deficiencia de hierro en humanos se presenta en todas las regiones del mundo. Las papas son una fuente modesta de hierro. El propósito de este estudio fue determinar si existe variación genética del contenido de hierro en el tubérculo de papa. Se midió el contenido de hierro en papa sin pelar de 33 clones, incluyendo variedades y selecciones avanzadas, en tres ensayos (TriState, Russet Regional del Oeste, Especialidades Rojas del Oeste) que en total se cultivaron en doce ambientes. En dos ensayos se presentó una interacción significativa clon × ambiente. Trece clones contribuyeron significativamente a esta interacción clon × ambiente, haciéndolas inestables en los ambientes, incluyendo la variedad Russet Burbank. Las heredabilidades en un amplio sentido y su intervalo de confianza de 95% (en paréntesis) en Tri-State, Russet Regional del Oeste y Especialidades Rojas del Oeste fueron 0.00 (0.00, 0.38), 0.64 (0.17, 0.87), y 0.73 (0.25, 0.90), C. R. Brown (*) respectivamente. En general, la amplitud de la media en el contenido de hierro con base clonal fue de 17 a 62 ug por gramo de peso seco. El límite superior es tres veces más alto que lo que generalmente se reporta en valores de papa. Los cinco valores más altos se encontraron en el ensayo de Especialidades Rojas del Oeste, en clones de piel roja y pulpa blanca. Estos resultados sugieren que existe la variación genética para el contenido de hierro en el tubérculo y que pudiera ser posible el mejoramiento para aumentar el contenido de hierro.

The effects of soil temperature during tuber development on physiological processes affecting retention of postharvest quality in low-temperature sweetening (LTS) resistant and susceptible potato cultivars were investigated. 'Premier Russet' (LTS resistant), AO02183-2 (LTS resistant) and 'Ranger Russet' (LTS susceptible) tubers were grown at 16 (ambient), 23 and 29 °C during bulking (111-164 DAP) and maturation (151-180 DAP). Bulking at 29 °C virtually eliminated yield despite vigorous vine growth. Tuber specific gravity decreased as soil temperature increased during bulking, but was not affected by temperature during maturation. Bulking at 23 °C and maturation at 29 °C induced higher reducing sugar levels in the proximal (basal) ends of tubers, resulting in non-uniform fry color at harvest, and abolished the LTS-resistant phenotype of 'Premier Russet' tubers. AO02183-2 tubers were more tolerant of heat for retention of LTS resistance. Higher bulking and maturation temperatures also accelerated LTS and loss of process quality of 'Ranger Russet' tubers, consistent with increased invertase and lower invertase inhibitor activities. During LTS, tuber respiration fell rapidly to a minimum as temperature decreased from 9 to 4 °C, followed by an increase to a maximum as tubers acclimated to 4 °C; respiration then declined over the remaining storage period. The magnitude of this cold-induced acclimation response correlated directly with the extent of buildup in sugars over the 24-day LTS period and thus reflected the effects of in-season heat stress on propensity of tubers to sweeten and lose process quality at 4 °C. While morphologically indistinguishable from control tubers, tubers grown at elevated temperature had different basal metabolic (respiration) rates at harvest and during cold acclimation, reduced dormancy during storage, greater increases in sucrose and reducing sugars and associated loss of process quality during LTS, and reduced ability to improve process quality through reconditioning. Breeding for retention of postharvest quality and LTS resistance should consider strategies for incorporating more robust tolerance to in-season heat stress.