HERITABILITY, GENETIC AND PHENOTYPIC CORRELATIONS, AND PREDICTED SELECTION RESPONSE OF QUANTITATIVE TRAITS IN PEACH - II - AN ANALYSIS OF SEVERAL FRUIT TRAITS

Thirteen peach [Prunus persica (L.) Batsch] fruit characteristics were investigated for 3 years, 1993, 1994, and 1995, in College Station, T exas, to determine heritability, genetic and phenotypic correlations, and predicted response to selection. Seedlings of 108 families resulti ng from crosses among 42 peach cultivars and selections were used in t he evaluations. A mixed linear model, with years treated as fixed and additive genotypes as random factors, was employed to analyze the data . Best linear unbiased prediction (BLUP) was used to estimate fixed ef fects. Restricted maximum likelihood (REML) was used to estimate varia nce components, and a multiple trait model was used to estimate geneti c and phenotypic covariances between traits. Genetic and phenotypic co rrelations greater than or equal to 0.65 and <0.30 were considered str ong or very strong and weak, respectively. Date of ripening, fruit dev elopment period (FDP) and date of full bloom had the highest heritabil ity (h(2)) estimates, 0.94, 0.91, and 0.78, respectively. Fruit cheek diameter and titratable acidity (h(2) = 0.31) were the traits with the lowest estimates. Fruit development period, fruit blush, and date of ripening had the highest predicted selection responses, whereas fruit suture, fruit cheek, L/W12 (ratio fruit length to average fruit diamet ers), and fruit tip had the lowest values. Most genetic correlations w ere greater than or equal to 0.30 and were, in general, much higher th an the corresponding phenotypic correlations. All four measures of fru it size were genetically and phenotypically very strongly correlated. Important genetic correlation estimates were also observed for date of ripening with FDP (r(a) = 0.93), date of ripening and FDP with fruit blush (r(a) = -0.77, r(a )= -0.72), SS (percent soluble solids) (r(a) = 0.63, r(a) = 0.62) and TA (r(a) = 0.55, r(a )= 0.64), and SS with TA (r(a) = -0.56). Direct selection practiced solely for early ripening and short FDP is expected to have a greater effect on correlated trait s than direct selection for early bloom and large fruit mass.