Ajustes metodológicos e seleção de fontes de tolerância à deterioração fisiológica pós-colheita em mandioca

Abstract

One of the problems in the cultivation of cassava is the postharvest physiological deterioration (PPD) that depreciates the roots soon after the harvest. This study aimed to develop a diagrammatic scale and set parameters for evaluation of PPD and to identify cassava genotypes tolerant to PPD. The diagrammatic scale proposal provided better accuracy and determination coefficients (R2) in assessing the PPD. With respect to the definition of parameters for assessing PPD, it was found that the physiological symptoms of PPD and the microbial deterioration (MD) were more pronounced under conditions of low temperatures and high soil humidity. The fungicide treatment significantly of MD but no effects on the expression of the PPD. The storage period of 10 days after harvest was appropriate to assess the PPD. The symptoms of the PPD were similar in average, proximal, medium and distal positions of the roots although ends are more evident to mechanical damage. With respect to the identification of sources of resistance based on the adaptability (Ai) and stability (Si) parameters and the join analyses of genotypic stability and adaptability (Zi), was founded that the variance of genotype (G) x environment (E) interaction, were the most important for the expression of the tolerance to PPD. However, the genetic gain with the selection of the 19 best cassava accessions was very significant for the predicted genotypic values of the interaction G x E, Si, Ai, Zi. These sources of tolerance have high potential to incorporate this feature in commercial cassava varieties.