The potato () tuber is a swollen stem. Sprouts growing from the tuber nodes represent loss of apical dominance and branching. Long cold storage induces loss of tuber apical dominance and results in secondary branching. Here, we show that a similar branching pattern can be induced by short heat treatment of the tubers. Detached sprouts were induced to branch by the heat treatment only when attached to a parenchyma cylinder. Grafting experiments showed that the scion branches only when grafted onto heat- or cold-treated tuber parenchyma, suggesting that the branching signal is transmitted systemically from the bud-base parenchyma to the grafted stem. Exogenous supply of sucrose (Suc), glucose, or fructose solution to detached sprouts induced branching in a dose-responsive manner, and an increase in Suc level was observed in tuber parenchyma upon branching induction, suggesting a role for elevated parenchyma sugars in the regulation of branching. However, sugar analysis of the apex and node after grafting showed no distinct differences in sugar levels between branching and nonbranching stems. Vacuolar invertase is a key enzyme in determining the level of Suc and its cleavage products, glucose and fructose, in potato parenchyma. Silencing of the vacuolar invertase-encoding gene led to increased tuber branching in combination with branching-inducing treatments. These results suggest that Suc in the parenchyma induces branching through signaling and not by excess mobilization from the parenchyma to the stem.

SummaryAcrylamide is produced in a wide variety of carbohydrate-rich foods during high-temperature cooking. Dietary acrylamide is a suspected human carcinogen, and health concerns related to dietary acrylamide have been raised worldwide. French fries and potato chips contribute a significant proportion to the average daily intake of acrylamide, especially in developed countries. One way to mitigate health concerns related to acrylamide is to develop potato cultivars that have reduced contents of the acrylamide precursors asparagine, glucose and fructose in tubers. We generated a large number of silencing lines of potato cultivar Russet Burbank by targeting the vacuolar invertase gene VInv and the asparagine synthetase genes StAS1 and StAS2 with a single RNA interference construct. The transcription levels of these three genes were correlated with reducing sugar (glucose and fructose) and asparagine content in tubers. Fried potato products from the best VInv/StAS1/StAS2-triple silencing lines contained only one-fifteenth of the acrylamide content of the controls. Interestingly, the extent of acrylamide reduction of the best triple silencing lines was similar to that of the best VInv-single silencing lines developed previously from the same potato cultivar Russet Burbank. These results show that an acrylamide mitigation strategy focused on developing potato cultivars with low reducing sugars is likely to be an effective and sufficient approach for minimizing the acrylamideforming potential of French fry processing potatoes.

Potato is an economically important agro-industrial crop that is conventionally propagated, however; its potential transmission of viruses through seed tubers from generation to generation is a major limitation of potato yield production. In order to produce potato virus-free and sufficient amount of potato seed tubers, several approaches of in vitro methods for virus elimination have been developed. Meristem culture has been used alone or combined with techniques such as thermotherapy, electrotherapy, cryotherapy and chemotherapy as the best alternative method for treating potato infected by viruses. Recent literature has shown that to eliminate potato virus significantly depends upon the potato cultivar, antiviral agents, type of virus, the duration of heat treatment. Appropriate duration for efficiency elimination is still under investigation. Viral elimination rate can be detected through serological methods such as enzyme-linked immunosorbent assay (ELISA) and molecular biology technique such as real time reverse transcriptase polymerase chain reaction (real time RT-PCR) that are used for pre and post elimination virus detection to evaluate the efficiency and the accuracy of virus elimination method. The purpose of this review is to highlight virus elimination methods in potato and recommending the most effective tool for virus detection in order to ensure the production of potato plantlet free of viruses. Resumen La papa es un cultivo de importancia económica agro-industrial que se propaga de manera convencional, no obstante, la potencial transmisión de virus a través del tubérculo-semilla de generación en generación es una limitación mayor en la producción del rendimiento. Con el fin de producir papa libre de virus y suficiente cantidad de tubérculo-semilla de papa, se han desarrollado varias estrategias de métodos in vitro para la eliminación de los virus. El cultivo de meristemos se ha usado solo o combinado con técnicas tales como termoterapia, electroterapia, crioterapia y quimioterapia, como el mejor método alternativo para tratar papa infectada por virus. La literatura reciente ha demostrado que para eliminar virus significativamente se depende de la variedad de papa, agentes antivirales, tipo de virus, la duración del tratamiento térmico. Aun esta bajo investigación la duración apropiada para la eliminación eficiente. El nivel de la eliminación del virus puede detectarse por métodos serológicos, tales como el inmunoensayo con enzimas conjugadas (ELISA) y técnica de biología molecular, como la reverso-transcripción de reacción en cadena de la polimerasa en tiempo real (RT-PCR) que se usan para la detección del virus pre y post eliminación para evaluar la eficiencia y la precisión del método de eliminación del virus. El propósito de esta revisión es resaltar los métodos de eliminación de virus en papa y en la recomendación de la herramienta más efectiva para la detección de virus para asegurar la producción de plántulas de papa libres de virus.