Resumen En muchos tejidos vegetales, se ha utilizado el acondicionamiento a baja temperatura (LTC) para inducir respuestas adaptativas poscosecha para superar las consecuencias del daño por frío (CI). Este estudio tuvo como objetivo investigar si el LTC es eficaz para reducir la incidencia de daño por frío (CI) en cultivares de batata. Las raíces de batata BRS Cuia y BRS Rubissol se sometieron a almacenamiento en frío (6 °C o 13 °C) y LTC (10 °C durante 7 días, seguido de un segundo almacenamiento a 6 °C). El LTC aumentó la tolerancia de las raíces de la batata al IC mediante la activación del sistema antioxidante, principalmente en el cv. BRS Rubissol, que se asoció notablemente con un mayor contenido de fenoles solubles totales y prolina, así como una mayor actividad de la fenilalanina amonio liasa. Además, no se observaron lesiones externas ni internas en las raíces de LTC, manteniendo la calidad para el procesamiento, lo que indica que el LTC es eficaz para mitigar el daño por frío en los cultivares brasileños de batata.

Abstract In many plant tissues, low-temperature conditioning (LTC) has been used to induce postharvest adaptive responses to overcome chilling injury (CI) consequences. This study aimed to investigate whether LTC is effective in reducing the incidence of chilling injury (CI) in sweet potato cultivars. Sweet potato roots BRS Cuia and BRS Rubissol were submitted to cold storage (6 °C or 13 °C) and LTC (10 °C for 7 d, followed by second storage at 6 °C). LTC increased the tolerance of sweet potato roots to CI via antioxidant system activation, mainly in cv. BRS Rubissol, which was markedly associated with higher content of both total soluble phenolics and proline, as well as increased activity of phenylalanine ammonium lyase. Moreover, no either external or internal injuries were observed in the LTC roots, maintaining the quality for processing, which indicates that the LTC is effective in mitigating chilling injury in Brazilian sweet potato cultivars.

ABSTRACT High incidence of sprouts and loss of quality of sweet potato is one of the negative aspects that compromises the commercialization most, and the methods of sprout control are still very limited. The appearance of sprouts promotes the wilting of sweet potato roots, reducing their commercialization period. The main objectives of this study were to evaluate sprout control and physiological and biochemical changes, in addition to the impact on the quality of postharvest chips in sweet potato roots cultivar BRS Cuia treated with methyl jasmonate (MeJa) and nonanoic acid (NA). Roots were fogged with 10 μmol·L–1 MeJa or 5 μmol·L–1 NA applied at first sprout initiation and control. Physiological and biochemical alterations such as fresh weight loss assessment, sprouting incidence and sprout length, total soluble sugars, reducing sugars, nonreducing sugars, enzymatic peroxidase and polyphenol oxidase, chips quality after frying were then assessed. Besides that, to determine the influence of treatments and storage periods, multivariate analysis was also performed using the main components. The MeJa reduced the incidence of sprouting and maintained the root quality during storage at room temperature. Notably, such events led to an increased both shelf life and potential of commercialization. Moreover, MeJa-treated chips displayed lighter color appearance after frying than control and NA-treated roots. Roots fogged with NA did not suppress the growth of sprouts, which consequently triggered a higher browning intensity in fried sweet potato chips.

Abstract One of the major problems affecting potatoes quality on stored is the susceptibility to enzymatic browning, which occurs mainly after wounds during the harvest, at postharvest handling and by aging, leading to the development of dark color compounds. Enzymatic browning is associated with the action of polyphenoloxidases (PPO) and peroxidases (POD), which use phenolic compounds and oxygen as substrates. The products of these enzymes cause undesirable changes of color and flavor of processed potato products. The present study aimed to evaluate some kinetic properties based to optimum pH and reaction temperature, and to determine changes on activity of potato tubers PPO and POD treated with sprouting suppressors compounds menthol and eugenol. For each treatment, samples were collected in six different periods, before application (day 0) and 10, 20, 30, 40, and 50 days after the treatments to determine the influence of sprout inhibitors on the activity of PPO and POD. Changes in pH and temperature affected drastically the activity of both enzymes. The use of eugenol and menthol as sprouting suppressors decreased enzymatic activity on the treated tubers compared to control with an inverse relationship between enzymes activity and content of phenolic compounds.

RESUMEN En condiciones de cultivo que favorezca el crecimiento de la parte aérea de la planta, la adopción de prácticas de manejo que reduzca el tamaño de las plantas puede ser una alternativa para aumentar el rendimiento de los tubérculos. El objetivo de este trabajo fue evaluar el efecto del paclobutrazol sobre el crecimiento vegetativo y la partición de la materia seca de la planta de papa cv. Markies cultivado en verano en el estado de Minas Gerais, Brasil. Los tratamientos fueron 0,1; 1,0; 10 y 100 mg L-1 de paclobutrazol (PBZ) aplicado a las semillas germinadas antes de plantar y um control tratado con agua. PBZ fue eficiente em la reducción de la altura de la planta. Los tratamientos con dosis de 10 y 100 mg L-1 de PBZ retrasaron la aparición de la parte aérea y el comienzo de la tuberización de la planta. PBZ a 0,1 mg L-1 redujo la longitud del tallo en un 18%, pero no difirió con el control en relación al contenido de masa fresca y seca, la producción total, la gravedad específica y el contenido de almidón de los tubérculos. El tratamiento de tubérculos de papa con PBZ a 0,1 mg L-1 presentan plantas más pequeñas y compactas, que podrían ser adecuadas para una plantación más densa para maximizar la población de plantas y aumentar el rendimiento económico por unidad de área.

ABSTRACT Under cultivation conditions that favor the growth of plant shoots, the adoption of management practices that reduce the size of potato plants can be an alternative for increasing tuber yield. The objective of this study was to evaluate the effect of paclobutrazol on vegetative growth and dry matter partitioning in the potato plant cv. Markies, cultivated under summer conditions in the state of Minas Gerais. The treatments were 0.1, 1.0, 10 and 100 mg L-1 of paclobutrazol (PBZ), applied to sprouted seeds before planting and control with water. PBZ was efficient in reducing plant height. The PBZ treatments with doses of 10 and 100 mg L-1 delayed the emergence of shoots and the beginning of plant tuberization. PBZ at 0.1 mg L-1 reduced the lengh of the stem by 18% but did not differ from the control for the fresh and dry mass content, total production, specific gravity and starch content of tubers. The treatment with seed potatoes and PBZ at 0.1 mg L-1 resulted in smaller, more compact plants, which could be suitable for more densely planted cultivations in order to maximize plant populations and increase economic return per unit of area.