Correlation between historical data of the germination test and of the tetrazolium test in coffee seeds by GAMLSS

Abstract

In the Brazilian National System of Seeds and Seedlings, coffee seeds are evaluated by the germination or tetrazolium test. However, differences have been observed between the results of these tests in various studies, especially when the seeds have a lower level of quality. Given this situation, the aim of this study was to evaluate the correlation between historical data of results of the germination test and of the tetrazolium test in samples of coffee seeds using Generalized Additive Models for Location, Scale and Shape (GAMLSS). Historical data of results of the germination test and of the tetrazolium test of coffee seeds originating from different cultivars and different crop seasons were used. The zero-or-one inflated beta GAMLSS is suitable for fitting data from the germination test and from the tetrazolium test. The estimate of viability by the tetrazolium test varies according to the germination percentage class. There are greater GAMLSS correlations between the percentages of normal seedlings and of viability in the tetrazolium test for germination values above 70%, and low correlations below this value, showing that evaluation of coffee seeds based only on the tetrazolium test may not correspond to actual physiological performance.