RESUMO O armazenamento adequado dos tubérculos é muito importante para manter o equilíbrio da oferta de batata no mercado e para a obtenção de tubérculos-semente em adequado estádio fisiológico no momento do plantio. O objetivo deste trabalho foi determinar o efeito de diferentes temperaturas de armazenagem no envelhecimento fisiológico de tubérculos de três clones de batata produzidos durante o outono e a primavera. O experimento foi desenvolvido em um fatorial de três clones (Asterix, SMIJ461-1 e SMINIA793101-3) por quatro temperaturas de armazenamento (4, 8, 12 e 25 ºC) e duas épocas de plantio (outono e primavera) no delineamento experimental inteiramente casualizado, com quatro repetições. As avaliações foram em intervalos de 30 dias, do início até os 180 dias de armazenamento. O armazenamento refrigerado prolongou a dormência dos tubérculos, reduzindo o número de brotos e evitando o apodrecimento; as temperaturas de 4 e 8 o C impediram a brotação dos tubérculos produzidos no outono. A perda de massa fresca e a respiração dos tubérculos aumentaram com o tempo e a temperatura de armazenamento. A época de plantio altera o comportamento fisiológico dos tubérculos durante o armazenamento. O armazenamento à baixa temperatura (4 e 8 ºC) é eficaz para retardar o envelhecimento fisiológico.Palavras-chave: Solanum tuberosum L., temperatura de armazenamento, perdas pós-colheita, respiração, batata-semente. ABSTRACT PHYSIOLOGICAL AGING OF POTATO TUBERS PRODUCED DURING FALL AND SPRING GROWING SEASONS AND STORED UNDER DIFFERENT TEMPERATURESAdequate tuber storage is necessary to maintain a good availability of potato tubers in the market and to get seeds with adequate physiological age at planting. The objective of this work was to determine the effect of different storage temperatures on tuber physiological aging of three potato clones produced during fall and spring growing seasons. The experiment was carried out as factorial of three clones (Asterix, SMIJ461-1 and SMINIA793101-3) by four storage temperatures (4, 8, 12 and 25 ºC) and two growing seasons (fall and spring) in a random design with four replications. At 30-day intervals, tubers were evaluated from the beginning to 180 days of storage. Cold storage increased dormancy period, reduced sprout number and kept health tubers. Tubers produced during fall season did not sprout at the storage temperatures of 4 and 8 o C. Tuber fresh weight loss and respiration increased with storage period and temperature. Crop growing season changes tuber physiological aging during storage. Storage in low temperature (4 and 8 ºC) conditions is efficient to slow down tuber aging.

Palavras-chave: Solanum tuberosum, sobrevivência ex vitro, produção de mudas, propagação vegetativa. ABSTRACTMS salt and sucrose concentrations in the in vitro multiplication and acclimatization of potato

The effect of the nutrient solution concentration on potato plant growth and minituber yield were determined in a sand closed hydroponic system. Minitubers and micropropagated plantlets of the cv. 'Macaca' were used. Treatments were five nutrient solution concentrations at electrical conductivities (EC) of 1.0 (T1), 2.2 (T2), 3.4 (T3), 4.7 (T4) and 5.8dS m-1 (T5). The split plot randomised experimental design was used with three replications. Plants from minitubers produced higher fresh and mean weight of minitubers, shoot dry mass and leaf area index than the micropropagated ones. However, higher dry mass of minitubers was found with micropropagated plantlets compared to minitubers. The concentration of the nutrient solution did not affect minituber number. Increasing the nutrient solution concentration decreased total and minituber dry mass production of micropropagated plantlets and plant growth and minituber production of minituber-originated plants. Low concentration of nutrient solution at an EC of about 1.0dS m-1 can be used in the hydroponic production of potato minitubers of both micropropagated and minituber-originated plants.

The production of mini-tubers under soilless cultivation system increased the availability of pathogen-free seed potatoes. The objective of this study was to evaluate the rooting capability of mini-cuttings of potato clones as a function of the irrigation solution and the physiological age of the mother plant, under soilless cultivation system. Potato mini-cuttings were collected from young and mature plants of the cultivars Asterix and Macaca and the advanced clone SMINIA 793101-3. The young plants were newly acclimatized individuals and the mature plants were at the stage of producing mini-tubers. In the first experiment, mini-cuttings originating from summer pruning of mature plants were grown under closed soilless cultivation system irrigated with a nutrient solution developed for the production of potato mini-tubers and a solution comprised of tap water only. The experiment was conducted in a 3 × 2 factorial arrangement (clones and irrigation solutions) in the complete random design with four replicates of 15 mini-cuttings. In the second experiment, the young and mature mini-cuttings were established under a closed soilless cultivation system irrigated with nutrient solution. The experiment was conducted in a 3 × 2 factorial arrangement (clones and physiological age of the mother plant) in the complete random design with four replicates of 15 mini-cuttings. In both experiments, the percentage of rooting and survival of mini-cuttings, number of roots and length of the longest root were assessed at 21 days of cultivation. Potato mini-cuttings can be rooted under closed soilless cultivation system irrigated with nutrient solution or tap water. Mini-cuttings of young plants have higher rooting capability compared to the ones taken from mature plants. The loss of rooting capability depends upon the potato cultivar.

The objective of this paper was to study plot size variation among potato clones to increase experimental precision of yield performance trials. The experiment was carried out at the experimental area of the Horticulture Dept., UFSM, Santa Maria, Rio Grande do Sul State, Brazil. Tubers of five potato clones were planted in two rows of 60 hills in August 2004. For all ten experimental rows, combined plots were formed adding a different number of adjacent hills of the same row. Soil heterogeneity index and optimum plot size were estimated for each row. Real differences between treatment means for each clone and all clones were estimated using the Hatheway technique. The experimental precision of potato yield trials varied with the evaluated clone because of different optimum plot sizes. Eight-hill plots are the optimum size to quantify yield of potato clones, but experimental precision depends upon adjustments of the number of treatments and replications to the availability of experimental area. Genetic diversity indeed decreases experimental precision and justifies the use of different plot sizes. Practical applicattions and strategies to increase experimental precision of yields performance trials of potato clones are discussed.