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Kernel Number Determination in Argentinean Maize Hybrids Released between 1965 and 1993

^a INTA Balcarce-Universidad Nacional de Mar del Plata, CC 276, 7620 Balcarce, Argentina
^b Facultad de Agronomía, UBA, Av. San Martín 4453
^c Dep. of Plant Agriculture, Crop Science Building, Univ. of Guelph, Guelph, ON, Canada, N1G 2W1

View larger version (39K): [in a new window]   Fig. 1. Relationship between kernel number per uppermost ear (KN1) or per plant (KNP) and plant growth rate during a period bracketing silking (PGRs) in five maize hybrids released in Argentina in different decades. Curves are the fitted Model 1. Triangles represent kernel number of prolific plants (kernel number of the topmost and second ear). Other symbols represent KN1 at low (2–4 plants m–2; solid circles), intermediate (8 plants m–2; squares), and high plant densities (16–30 plants m–2; white circles).

View larger version (27K): [in a new window]   Fig. 2. Frequency distributions (%) of kernel number per plant for plants growing at (a) 0.5 > PGRs > 1 g d–1 and (b) at 1 > PGRs > 1.5 g d–1 in four maize hybrids released in Argentina at different decades (data from Exp. 1).

View larger version (29K): [in a new window]   Fig. 3. (a) Mean growth rate of the topmost ear (EGRs) vs. 1.5-g d–1 intervals of plant growth rate during a period bracketing silking (PGRs) and (b) relationship between kernel number of the topmost ear and ear growth rate during a period bracketing silking of an older (DKF880) and a newer hybrid (DK752) in Exp. 2. In Fig. 3a values at the x axis indicate the upper limit of the interval. Bars indicate standard error. Number of individuals ranged from 10 to 100 depending on the range of PGRs. **indicates significant differences between hybrids within the range of PGRs at P < 0.05. In Fig. 3b, curves are the fitted Model 2 for DKF880 (gray line) and DK752 (black line). Fitted regression were: DKF880, KN1 = 1807 ± 189.9 x (EGRs – 0.028 ± 0.01)/[1 + 2.77 ± 0.464 x (EGRs – 0.028 ± 0.01)] if EGRs xt and KN1 = 0 if EGRs < xt, R2 = 0.78; DK752, KN1 = 1191 ± 89.5 x (EGRs – 0.007 ± 0.019)/[1 + 0.76 ± 0.12 x (EGRs – 0.007 ± 0.019)] if EGRs xt and KN1 = 0 if EGRs < xt, R2 = 0.89. The regressions were significant at P < 0.05.

View larger version (26K): [in a new window]   Fig. 4. (a) Mean kernel number per uppermost ear (KN1) vs. 1.5-g d–1 intervals of plant growth rates during a period bracketing silking (PGRs), (b) mean growth rate of the topmost ear (EGRs) vs. 1.5-g d–1 intervals of PGRs in an older (DKF880) and newer hybrid (DK752) in Exp. 3. Values at the x axis indicate the upper limit of the interval unless indicated otherwise. Bars indicate the standard error. Number of individuals in each treatment ranged from 10 to 40 depending on the range of PGRs. **indicates significantly different from the control at P < 0.05.