Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

First Advisor

Manjit S. Kang

Abstract

Parenchyma cell death (PCD) in stalk internodes of maize (Zea mays L.) is related to stalk rot. Spread of stalk rotting fungi is restricted by living parenchyma cells. A previously reported correlation coefficient of 0.70 between leaf midrib cell death (LMCD) and PCD indicated that selection for LMCD might result in low PCD, thus improving stalk quality. Inheritance of PCD and LMCD in maize possessing the leafy (Lfy) gene needs to be investigated. Experiments were conducted in three environments to estimate general (GCA) and specific combining ability (SCA) effects for PCD and LMCD via a diallel cross among seven Lfy synthetics and to determine the effect of Lfy gene on PCD and LMCD. Eight weeks after planting, five consecutive leaves per plant, beginning with the sixth leaf from the base of a plant, were visually rated for LMCD. Twenty one days after mid silk, the first four stalk internodes above brace roots of 10 leafy and 10 non-leafy plants in each of the 21 F$\sb1$ crosses were split longitudinally and visually rated for PCD. The PCD of third stalk internode and LMCD of third leaf were reliable in differentiating genotypes. SCA was more important than GCA for PCD, whereas GCA was more important than SCA for LMCD. A632 syn, B73 syn, Mo17 syn, and Wf9 syn showed negative GCA effects for PCD, whereas A632 syn, B73 syn, and Hy syn showed negative GCA effects for LMCD. The Lfy plants had significantly lower PCD and LMCD than the non-Lfy plants, suggesting that extra leaves in the Lfy plants probably produced supplemental photosynthate and thus had a favorable effect on PCD and LMCD. The current knowledge of inheritance of maize seed quality traits, though important to breeders, is limited. Seed from the 21 F$\sb1$ crosses were evaluated for seven seed quality traits. SCA was more important than the GCA for most seed quality traits. Significant additive genetic correlations (r $\ge$ 0.84) among seed weight, dry matter, and vigor index suggested that selection for heavier seed may result in improved seedling vigor. Results revealed superiority of Hy syn and Hy syn x Mo17 syn cross for seed quality.

Pages

96

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