Optimal sample size in citrus progenies considering the degree of homozygosity of their parents and the drought tolerance

Drought tolerance is a fundamental characteristic for the development of citrus rootstock varieties. The leaf curling (reaction to water deficit) and shoot emission (reaction to rehydration) degrees are phenotypic traits that can be used to select superior genotypes. This work aimed to determine the optimal sample size of citrus progenies to concerning these traits. The study was carried out in Cruz das Almas municipality, Bahia State. The progenies studied resulted from the crosses of ‘Sunki da Flórida’ mandarin (TSKFL) with the male parents ‘Swingle’ citrumelo (CTSW), ‘Benecke’ trifoliate orange (TRBK) and the hybrid ‘Rangpur’ lime x trifoliate orange (LCR x TR). The degree of homozygosity of the parents was identified by analysis of SSR (Simple Sequence Repeat) markers, and the modified maximum curvature method was applied to define the optimal sample size. The molecular tests showed that the ‘Sunki da Flórida’ mandarin had the maximum degree of homozygosity (coefficient of endogamy f = 1), and male parents had f-values of 0.615 (TRBK), 0.379 (LCR x TR) and 0.297 (CTSW). The optimal sample size was ten individuals, sufficient to represent the citrus progenies in the evaluations aimed at the mentioned traits, considering parents with similar levels of homozygosis.