GENETIC PARAMETER ESTIMATES AND EFFICIENCY OF 3 SELECTION PROCEDURES IN CARROT BREEDING VARIETY CAMPINAS

The potential for genetic breeding of the carrot variety ''Campinas'' was assessed through estimates of the genetic-statistical parameters o f 16 traits of agronomic importance. The parameters were obtained from 102 half-sib progenies, harvested in a seed production field. Two exp eriments were carried out in Randomized Complete Blocks in the fall-wi nter and spring-summer planting periods. To compare the three selectio n methods, usually employed in population breeding genetics the expect ed genetic gains were estimated considering each block or plot as stra ta, and mass selection between and within the half-sib progenies. Samp les of 15 marketable roots per plot were evaluated at the individual l evel for the characters root length (RL) and root shape index (SI). A joint analysis of variance, weighted for the differences in number of replications between the experiments was performed for the six common traits. The results of the genetic parameter estimates of the single v ariance analysis indicated that the variety Campinas was best adapted to the fall-winter planting period. Heritabilities greater than 60% we re observed for the majority of traits assessed at the plot level. The selecction against the trait premature flowering (PF) may result in s atisfactory genetic gain in the two environmental conditions because o f the high genetic variability coefficients obtained. The percentage o f marketable cylindrical rods (MCR) demonstrated an expected genetic g ain per cycle of only 4.82% in the fall-winter period, probably becaus e it had already been selected, for various cycles, under these enviro nmental conditions. On the other hand, in the spring-summer planting p eriod, the genetic gain was estimated to be 14.44%. Total and marketab le yields were high in the fall-winter period and low in the spring-su mmer period. For the traits RL and SI, assessed at the individual leve l, the stratified mass selection, considering each plot as strata, was less efficient in relation to the other proposed selection methods. T herefore it is concluded that breeding of the variety Campinas, based on the performance of the half-sib progenies for root quality and yiel d is fairly promising within each planting period, but simultaneous se lection for both periods is difficult.