Inheritance of photosynthesis in a diallel among eight maize inbred lines from Iowa Stiff Stalk Synthetic

Abstract

INDEX WORDSZea mars L . . maize . CO 2 -exchange rate, combining ability, heterosis . SUMMARY Photosynthesis is a trait that should be improved in a selection program for yield potential of maize (Zea mat's L .) . We measured leaf CO 2 -exchange rate (CER), an estimate of photosynthetic efficiency, of a complete diallel (parents, F, crosses, and their reciprocals) among eight inbred lines (4 with low and 4 with high CER) from the Iowa Stiff Stalk Synthetic maize population . Measurements were made during vegetative (CER 1) and grain filling (CER 2) stages of growth, and the experiment was conducted two years at one location . We measured large differences among crosses and significant heterosis for high CER at CER 1(0 .0 to 25 .1 %) and CER 2 (0 .0 to 53 .8%) . Several crosses exhibited overdominant phenotypes for high CER at both growth stages . and one cross showed significant overdominance for low CER at CER 1 . General combining ability effects (gca) were the largest components of among-cross variation at both CER I and CER 2 . Specific combining ability (sea) also was significant at both growth stages, but gca effects were 9 .4 and 4 .8 times larger than sea effects at CER I and CER 2, respectively . Furthermore, high CER lines showed positive gca effects . and low CER lines showed negative gca effects at each stage. Maternal and reciprocal effects were not significant ; thus, CER in these crosses was controlled largely by additive effects of nuclear genes . A high positive genotypic correlation (r = 0 .74) between CER I and CER 2 suggested that selection at either growth stage would improve CER throughout the growing season .

Physiological observations of maize (Zea mays L.) hybrids differing in photosynthetic capability

“…These cultivars have consistently maintained these CER differences in previous field studies (Crosbie et al, 1978;Part I above). Interpre tation of a photosynthetic influence on leaf area and dry weight accumulation patterns at varying N levels depends upon the assumption of different reducing power and carbon skeleton availability based on CO^ uptake differences.…”

“…The variations from this pattern that occurred suggest an interaction between leaf CER, N fertility, and experimental environments. Leaf CER of the high selections were somewhat lower than previously ob served in field-grown plants (Crosbie et al,, 1978;Part I above). This suggests that CER may have been more limited in this experiment by environmental factors than genotypic char acteristics.…”

“…Six experimental maize hybrids were selected based on their previously reported unit leaf area CER (Crosbie et al, 1978 (June 6, 1978;June 6, 1979) followed the first planting (May 6, 1978;May 5, 1979) in both years.…”

“…Four experimental maize hybrids were selected based on previously reported leaf CER (Crosbie et al, 1978). Two hybrids, BSSS166 x BSSS187 (H^) and BSSS173 x BSSS187 (Hg),…”

Changes in physiological traits associated with grain yield improvement in single-cross maize hybrids from 1930 to 1970

“…Tanaka and Yamaguchi (1972) previously concluded that sink size as determined by number of kernels per unit field area was a limitation to increased grain yields. Significant correlations between sink strength and grain yield also have been reported by El-Lakany and Russell (1971), Obilana and Hallauer (1974), Hallauer (1971), Crosbie et al (1978a) and Crosbie and Mock (1980). Different sink strength traits were correlated with grain yield in dif ferent maize populations, however.…”