Abstract
Good yield and intermediate plant height, ear height, and tassel size characterize the maize population ESALQ-PB1 as an outstanding breeding population. Estimates of genetic parameters are reported for 13 traits: plant height (PH), ear height (EH), ear placement (EP), tassel length (TL), tassel weight (TW), tassel branch number (TB), ear weight (EW), total grain weight (GW), ear length (EL), ear diameter (ED), kernel row number (RN), kernel number per row (KR) and prolificacy (PR). Results refer to one location and one year. Genetic variation was detected for all traits, and the estimates of the additive genetic variance are presented. The coefficients of heritability (individual basis) varied from 0.14 to 0.72 and were considered high for PH, EH and TB; intermediate for EP, TL, TW, EL, EP, ED and RN, and low for EW, GW, KR and PR. The coefficient of heritability (progeny mean basis) showed approximately the same trend and varied from 0.40 to 0.75. The highest expected gain from selection was for TB (27% per cycle) under mass selection and for TW (16.4%) under progeny selection; the lowest expected gain was for ED either for mass selection (1.9%) or progeny selection (2.9%). Additive correlation coefficients (rA) of 0.5<rA<0.6 were found for PH or EH and yield traits (EW and GW) and its components EL and KR, and 0.10<rA<0.44 for PH or EH and tassel traits. For the tassel traits the highest correlation was rA = 0.63 (TB.TW). EP was positively correlated with TB, TW, PH, EH and PR; and negatively correlated with ED and RN. The expected correlated responses in several traits after selection for GW, EH and TB are given.
Highlights
Maize is a typically allogamous species with prevalence of cross pollination
Estimates of genetic parameters are reported for 13 traits: plant height (PH), ear height (EH), ear placement (EP), tassel length (TL), tassel weight (TW), tassel branch number (TB), ear weight (EW), total grain weight (GW), ear length (EL), ear diameter (ED), kernel row number (RN), kernel number per row (KR) and prolificacy (PR)
The highest expected gain from selection was for TB (27% per cycle) under mass selection and for TW (16.4%) under progeny selection; the lowest expected gain was for ED either for mass selection (1.9%) or progeny selection (2.9%)
Summary
Maize is a typically allogamous species with prevalence of cross pollination. The amount of selffertilization in an ordinary field of maize is negligible (Kiesselbach, 1922). The genetic structure of maize populations for quantitative traits has been studied on the basis of statistical parameters (e.g., mean, variance, correlation coefficient, and others). The purpose of this study was to report about parameter estimates of 13 quantitative traits in the maize population ESALQ-PB1 and its potential for breeding. Particular attention was given to tassel branch number and ear height because ESALQ-PB1 was used as a base population for divergent selection of these traits. The 147 half-sib families were evaluated in three 7 × 7 lattice experiments with four replications, at Piracicaba-Brazil (22°39’ S and 47°35’ W, and 597 m of altitude), in 1978/79. The quantitative traits analyzed took only part of the experiments, so that a sample of size five was taken within plots to measure plant, tassel or ear characteristics.
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