Repeatability analysis of guava fruit and leaf characteristics

Psidium guajava L. (guava) is an important species that presents high genetic variability due to its mixed reproductive system, which is desired in breeding programs. Repeatability is an important tool for the selection of genotypes in pre-breeding studies. When genetic variability is present, the knowledge regarding the number of samples to be used in repeatability studies is indispensable. This study aims to determine the number of necessary measures while optimizing resources and maintaining the reliability of the results for the variables evaluated in P. guajava. The experiment was carried out with genotypes from three Brazilian States: Espírito Santo, São Paulo, and Minas Gerais, and a total of 79 P. guajava genotypes were collected. The following characteristics were evaluated: young leaf length and width; developed leaf length and width; fruit length; fruit diameter and fruit cavity diameter; and fruit weight and pulp weight. For the evaluated characteristics, deviance, permanent phenotypic and temporary environment variance, coefficients of repeatability and determination, accuracy and the number of estimated measurements required were determined. We established that the number of measurements required in repeatability analysis for a coefficient of repeatability with a reliability of 80% is four, for the measurements of developed leaf width, pulp weight, fruit diameter, and fruit cavity diameter.