Survey of Tuber pH Variation in Potato (Solanum) Species

Abstract

Variation in tuber pH has been previously reported in cultivated potato and shown to be associated with economic traits. We here report a broad survey of potato germplasm for tuber pH, including wild Solanum species. Cultivar pH ranged from about 5.5 to 6.2, while six wild species were significantly lower. Solanum microdontum had the lowest pH average of the wild species examined at 5.17 with the lowest observed reading of 4.99. This species also exhibited a strong environmental effect, in which field tubers (5.28) were much lower than greenhouse tubers (5.63). Long storage generally did not have a significant effect on wild species tubers, except for S. jamesii, which reduced from 5.78 to 5.54. Various types of sampling were tested. Skins were generally lower than flesh, with a high correlation between the tissues. Samples that were frozen, cooked, or reconstituted from dried powder had different absolute pH values, but these were highly correlated, so germplasm would be ranked for pH similarly regardless of method. Although not tested here, physiological links between pH and economic traits like disease resistance, nutrition and tuber quality are plausible. If so, pH testing might serve as a rapid and inexpensive screening tool in breeding programs. The association of pH and useful traits might also provide clues for exploring underlying genetic and physiological mechanisms in potatoes.Resumen Se ha reportado con anterioridad la variación en el pH del tubérculo en papa cultivada y se ha demostrado su asociación con indicadores económicos. Aquí reportamos un amplio estudio de germoplasma de papa para pH del tubérculo, incluyendo especies silvestres de Solanum. El pH de las variedades fluctuó desde cerca de 5.5 a 6.2, mientras que para seis especies silvestres fue significativamente más bajo. Solanum microdontum tuvo el promedio mas bajo de las especies silvestres examinadas, con 5.17, con la lectura observada mas baja de 4.99. Esta especie también exhibió un efecto ambiental fuerte, en el cual los tubérculos de campo lo tuvieron mas bajo (5.28) que los de invernadero (5.63). El almacenamiento prolongado generalmente no tuvo efecto significativo en tubérculos de especies silvestres, excepto para S. famesii, que lo redujo de 5.78 a 5.54. Se probaron varios tipos de muestreos. La piel fue generalmente más baja que la pulpa, con una alta correlación entre tejidos. Las muestras congeladas, cocinadas, o reconstruidas de polvo deshidratado, tuvieron valores absolutos diferentes de pH, pero altamente correlacionados, de manera que el germoplasma sería clasificado por similitud de pH independientemente del método. Aún cuando no se probó aquí, es posible que existan enlaces fisiológicos entre el pH e indicadores económicos, como resistencia a enfermedades, nutrición y calidad de tubér-culo. De ser así, las pruebas del pH pudieran servir como una herramienta rápida y barata de evaluación en los programas de mejoramiento. La asociación del pH con indicadores útiles pudiera también proporcionar pistas para explotar mecanismo...

Effect of Storage Conditions on the Physicochemical and Processing Qualities of Different Potato Genotypes Grown in Eastern Uganda

“…pH generally ranged from 6.00 to 6.25. This is in agreement with the findings of Kiszonas [23] who reported the pH of raw potatoes to range from 5.5 to 6.2. The increase in reducing sugars makes the potato juice more acidic due to the lactic acid produced in starch break down hence leading to a drop in pH [24].…”

Genome-Wide Identification of Genes Important for Growth of Dickeya dadantii and Dickeya dianthicola in Potato (Solanum tuberosum) Tubers

“…We used potato dextrose broth as an in vitro condition to mimic the nutritional composition of potato tubers more closely. This medium was slightly acidic, reflecting conditions encountered in the tuber or apoplast ( Grignon and Sentenac, 1991 ; Kiszonas and Bamberg, 2010 ). Of the PDB-specific fitness factors, the low affinity potassium transporter Kup was likely required because of its role in ion transport particularly at low pH ( Trchounian and Kobayashi, 1999 ).…”

“…These necrotrophic pathogens rely on numerous traits to survive the various stress conditions encountered in the host, including oxidative stress, osmotic stress, iron starvation, and toxic compounds ( Jiang et al, 2016 ; Reverchon et al, 2016 ). During initial plant colonization, cells encounter a slightly acidic apoplast (pH 5.0–6.5) or tuber (pH 5.5–6.2), and pH levels increase to slightly basic (pH 8) by the late stage of infection ( Grignon and Sentenac, 1991 ; Nachin and Barras, 2000 ; Kiszonas and Bamberg, 2010 ). At high cell densities, the production of plant cell wall degrading enzymes is induced, leading to the maceration of plant tissues and the formation of visible symptoms ( Reverchon et al, 2016 ).…”

Use of Native Potatoes for Research and Breeding

“…This work has not only provided better representation of the species, and insights into collecting techniques and the status and dynamics of genetic diversity, but has also captured germplasm with several novel traits of interest to the potato industry. These include nematode resistance (Brown et al, 2004), extremely high antioxidants (Hale et al, 2008;Nzaramba et al, 2007), extreme tuber dormancy (Bamberg, 2010), antiprostate cancer effects (Nzaramba et al, 2009), and low tuber pH (Kiszonas and Bamberg, 2010).…”