The critical value of soil Olsen-P (mg Olsen-P kg-1) is the value of soil Olsen-P above which the probability of crop response to P fertilization is small or null. The aim of the present study was to determine the critical value of soil Olsen-P for potato tuber yield in volcanic soils. The data used in this study were taken from 41 experiments of P fertilization conducted in southern Chile from 1977 to 2015 by the National Potato Center at the Instituto de Investigaciones Agropecuarias (INIA). To identify the critical values of soil Olsen-P, relationships between relative yields and initial soil P-Olsen were assessed using three models (linear-plateau, boundary and Mitscherlich function). Across experiments, the average fresh tuber yield was 41.9 Mg ha-1 and varied between 4 and 89 Mg ha-1. Fresh tuber yield decreased up to 92% by P deficiency; however, yield reduction was concentrated between 20 and 40%. The critical Olsen P values determined were 41, 33 and 11 mg Olsen-P kg-1 obtained (P < 0.01) with linear-plateau, boundary function and Mitscherlich function, respectively. However, linear-plateau and Mitscherlich functions showed lower coefficient of determinations (R 2 = 0.23-0.31) than the boundary function (R 2 = 0.97). Therefore, we suggest that the critical Olsen-P value of 33 mg P kg-1 determined with the boundary function is more appropriate for potato growers than the critical value determined with the other models. This information will be valuable for optimizing strategies for P fertilizer management in potato production systems aimed at achieving optimal crop yield and minimizing potential environmental risk.

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The critical value of soil exchangeable potassium (K) (mg K kg −1) is a valuable tool for an efficient K fertilization management in potato production systems. The aim of the present study was to determine the critical value of soil exchangeable K for potato crops grown in different environments and differing availabilities of initial exchangeable K. The data used in this study were taken from 34 experiments on K fertilization conducted in southern Chile from 1977 to 2017 by the National Potato Center at the Instituto de Investigaciones Agropecuarias (INIA). Yield responses to K fertilization rates were assessed with linear-plateau and Mitscherlich models in order to determine the critical soil exchangeable K across environments. Across experiments, the average fresh tuber yield ranged between 18 and 91 Mg ha −1. Fresh tuber yields decreased by up to 70% when no K fertilization was applied. Yield reduction was concentrated around 25% in response to K deficiency. Relative yields were described as significant by both linear-plateau and Mitscherlich models. However, relative yields were better described by the linear-plateau model (p < 0.01, R 2 = 0.62; SEE = 0.11). The critical soil exchangeable K value identified with the linear-plateau model was 224 mg K kg −1. This critical K value will be useful for potato farmers that produce their crops in volcanic soils, such as Andisols. Moreover, this critical K value will help to increase K use efficiency through better K fertilization management strategies aimed at building and/or maintaining K levels in soils.

Twenty-two colored-flesh potatoes and three commercial noncolored-flesh varieties-which were all raw as they were microwaved (800 W, 8 min) and fried (180 °C, 5 min)-were characterized in terms of functional, sensory aspects and suitability for use. Twelve genetic samples were more suitable for frying (> 20% dry matter), four for boiling (~15-18% dry matter) and nine for preparing puree or roasting (~18 to 20% dry matter). The total polyphenol content (TPC) of the raw colored-flesh potatoes contained between 1.10 to 3.68 g of gallic acid equivalent kg-1 in fresh weight (FW), which was between two-and threefold higher than the measured values in noncolored-flesh varieties. The total antioxidant capacity (TAC) was between 1.00 to 4.71 g of Trolox equivalent kg-1 FW, which was also lower in noncolored-flesh potatoes. The cooking process (frying and microwave) did not affect the TPC in most of the genetic samples analyzed, but it reduced the TAC by 40-75% (fried) and 30-90% (microwaved). According to sensory evaluation results, the genetic samples R2, R19, R3 and R5 were suitable for frying, while R16, R21, R9, R15 and R22 were suitable for microwaving. Colored-flesh potatoes are an interesting alternative for consumers due to their greater phytochemical content.

The potato breeding program of Instituto de Investigaciones Agropecuarias (INIA) Chile has developed and released 11 commercial varieties of potato. It is estimated that these varieties have 50% of the Chilean potato market and are being evaluated in seven foreign countries. The aim of this work is to summarize the current importance and scope of biotechnology in breeding in Chile, by presenting a program that has generated widespread material among farmers and consumers. The germplasm bank is the source of genetic diversity for controlled crosses. Techniques to introduce the material to in vitro conditions and thermotherapy to obtain pathogen-free in vitro plants are applied. The material is characterized by SSR markers. There is a flow of material from gene bank to the annual scheme of controlled crosses and selection in the plant breeding program. In the selection plots, molecular markers associated with one or few genes that have a large and heritable effect in important traits are used: golden nematode resistance, virus resistance, and late blight resistance. Then, in the early stages of seed production, all the material of the new varieties is checked by fingerprint and molecular and ELISA test for pathogen, to assure the identity and pathogen-free status of the starting seed material.