Estimates of repeatability and path coefficients on grapes
Patrícia Coelho de Souza Leão and João Gomes da Costa
Abstract: The objective ofthis study was to estimate the repeatability coefficient, the minimum number of evaluations towhich a trait should be subjected and the effect ofthe inter-relationships offive characters on grapevine (Vitis spp.) yield, aiming at getting useful information for breeding strategies ofthis fruit crop. Repeatability coefficients were estimated for the following characters: total soluble solids (TSS); total titrable acidity (TTA); TSS/TTA ratio;berry length, diameter and weight; bunch length, width and weight, and number and yield ofbunches per plant on eleven seedless grape varieties in five yield cycles (1997 and 1998) in Petrolina-PE. The repeatability estimates were obtained by the main components method from the correlation matrix. The simple correlation coefficients were calculated and they were partitioned into direct and indirect effects by the path analysis. The estimated repeatability coefficients ranged from 0.4750 to 0.8372 associated to the coefficients ofdetermination from81.9% to 96.26%.The traits TSS, TTA and bunch length presented 10w repeatability coefficients, meaning a low regularity of performance from one measurement to another. The other characters showed regularity on therepetition ofthe behavior ofthe genotypes. The results ofthe path analysis showed that the studied variables satisfactorily explain the character yie1d per plant.