Ten institutions in nine countries joined together to test the stability of resistance of 14 potato genotypes to the oomycete pathogen Phytophthora infestans in three separate trials. Seven of the genotypes were tested in one trial involving seven locations, and all 14 were tested in two subsequent trials, each involving eight locations. Stability of resistance was tested with nonparametric tests and with an additive main effects and multiplicative interaction (AMMI) model. Overall, resistance to P. infestans was robust; resistant genotypes were consistently resistant in all locations and trials. The nonparametric analysis indicated that specific genotypes were basically stable across sites for resistance. In trial 3, the Z statistic for overall stability was significant at 0·05%, indicating a significant level of interaction across the trial, but there were no significant interactions for specific genotypes in this trial. The genotype by environment (G × E) effect of the AMMI model was highly significant in both trials, but the mean square of G × E was less than 10% of the genotype effect in each trial. The first two principal components (PCA1 and PCA2) of the AMMI analyses together explained 75 and 80% of the interaction effects in trials 2 and 3, respectively. Based on both nonparametric and AMMI analyses, Ecuador and Argentina were locations of relatively high interaction effects for both trials 2 and 3, although in Ecuador this interaction was not associated with any particular potato genotype. Other locations also had high interaction effects, but these occurred in only one trial. The genotypes Chata Blanca and, to a lesser extent, Torridon were relatively unstable in trials 2 and 3, but in the case of Torridon, resistant, this did not represent a significant loss of resistance.

Late blight is the main disease of potatoes around the world. Because of the difficulties in applying effective control methods, the introduction of resistant cultivars represents a safe strategy. The potato species Solanum tarijense represents an attractive resistance source as its adaptation to long days is promissory, producing tubers of good size and aspect. Deposition of structural compounds like lignin and callose were described as a non-specific resistance mechanism. In this work, we measured polyphenoloxidases (PPO) and peroxidases (POX) activities and the accumulation of phenols, lignin and callose and their correlation with the resistance levels of S. tarijense. Clones Oka 6320.9 and Oka 5632.11 showed low infection rates and these were correlated with a higher accumulation of phenols, lignin and callose and a strong induction of PPO and POX activities. However, in highly infected clones, a lower or no accumulation of these compounds was observed. These results demonstrate a correlation between the amount of defence molecules and the resistance levels according to the detached-leaf assay. However, more field experiments are required to validate these results.

This chapter covers integrated pest, disease and weed management (biological, cultural and chemical methods) in cotton (against Anthonomus grandis and Alabama argillacea), potato (against viruses, Phytophthora infestans, Rhizoctonia solani, plant parasitic nematodes, insect pests and weeds), and apple and pear (insects and diseases) in Argentina.

No abstract

La sequía es una importante limitación que ejerce el medio ambiente sobre la producción de papa en las áreas tradicionales de cultivo. Ante la creciente influencia del cambio climático y debido a que la actual base genética de la papa presenta escasa variabilidad, se hace necesario identificar materiales genéticos con resistencia o tolerancia a sequía. Con el objetivo de desarrollar material genético tolerante se evaluó el comportamiento de variedades cultivadas y especies silvestres de papa. Se emplearon ocho variedades nativas cultivadas de papa y dos genotipos de Solanum tarijense (trj). Se adaptó el protocolo de ensayo de sequía propuesto por la red Latinpapa. Se realizaron tres tratamientos: Control, las plantas siguieron un esquema de riego normal; Sequía con Déficit, a partir del día 45 después de plantación (ddp) se aplicó riego con déficit, y Sequía Severa, a partir del día 45 ddp, no se aplicó riego. Hubo un efecto significativo del genotipo y del tratamiento sobre la altura de las plantas y sobre el número y el peso de tubérculos. En cuanto a número de tallos solo hubo efecto significativo sobre el genotipo. Natin Suito presentó mayor vigor en los tratamientos de sequía. Las variedades presentaron poca senescencia hasta los 87 ddp. La variedad Yema de Huevo no presentó signos evidentes de senescencia hasta los 97 ddp. Existe variabilidad entre los genotipos evaluados con respecto a su comportamiento bajo estrés hídrico. Las variedades Sipancachi, Unknown y ClS 1802 norte produjeron tubérculos bajo estrés hídrico y la variedad Unknown fue la de mayor peso de tubérculo.