Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

First Advisor

Manjit S. Kang

Abstract

Preharvest infection by Aspergillus flavus Link ex Fries and subsequent aflatoxin contamination of maize (Zea mays L.) grain are major production problems. Ear moisture loss rate (EMLR) is an important component of hybrid performance and maturity, and to some extent determines the suitability of a hybrid for a geographical area. A 10-parent diallel experiment was conducted in 1992 and 1994 to study the genetic nature of both percent kernel infection (PKI) by A. flavus and EMLR. General combining ability (GCA, V$\sb{\rm g}$), specific combining ability (SCA, V$\rm\sb{s}$), and reciprocal mean squares for PKI were significant. The ratio $\rm 2V\sb{g}/(2V\sb{g}+V\sb{s}$) was 0.54, indicating that both GCA and SCA were important. The GCA, SCA, and reciprocal effects for PKI varied across years, which implied that more reliable information could be obtained by conducting multi-year experiments. The EMLR was measured with an electronic probe device. First probe moisture (30DPM) and second probe moisture (51DPM) were recorded in the field at 30 and 51 days after midsilk, respectively. The GCA and reciprocal mean squares were significant, whereas SCA was not significant for EMLR. The 2V$\rm\sb{g}/(2v\sb{g}+V\sb{s}$) ratio was 0.81, indicating that GCA effects were more important than SCA effects for EMLR. inbred lines L108, L605, and L654 showed significant, positive GCA effects for EMLR and Mo17 inbred line showed a negative GCA effect. 30DPM and 51DPM mean squares for F$\sb1$ hybrids were significant. A relatively low Probe1, high EMLR, and positive GCA and reciprocal effects for EMLR were important in lowering 51DPM. Any selection scheme for lowering 51DPM or harvest grain moisture should exploit the extranuclear genetic component(s) for EMLR and use parental lines with significant, positive GCA effects for EMLR, and relatively low 30DPM. No significant correlation exist between PKI and EMLR. However, a significant genotypic correlation was found between PKI and 51DPM, indicating that the breeding goal for lowering both 51DPM and PKI by A. flavus can be achieved simultaneously.

Pages

98

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