Divergent Phenotypic Recurrent Selection for Nitrate Reductase Activity and Correlated Responses in Maize

Dunand, Richard Thomas

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Description

Title

Divergent Phenotypic Recurrent Selection for Nitrate Reductase Activity and Correlated Responses in Maize

Author(s)

Dunand, Richard Thomas

Issue Date

1980

Department of Study

Agronomy

Discipline

Agronomy

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Biology, Plant Physiology

Language

eng

Abstract

• Divergent phenotype recurrent selection for post anthesis nitrate reductase activity (NRA) in maize was conducted through three cycles. The original material (C(,0)) was the maize (Zea mays L.) synthetic, Super Stiff Stalk Synthetic. The primary objectives were to determine: the selection response of NRA and the correlated responses in grain yield, grain protein, dry matter production and related parameters. The correlative responses were obtained by growing C(,0) and the four composites from selection under comparable single season environments. Auxiliary studies determined: the relationship between seedling and post anthesis NRA of individual plants; the NRA and plant productivity of S1 progeny from high and low NRA plants; the effect of supplementary nitrogen fertilization on yield and plant constituents of the composites selected for high and low NRA and the accuracy with which seasonal NRA can be used to estimate plant nitrogen content.
• Divergent selection for NRA was successful as the high NRA composites had higher levels of NRA than the low NRA composites, and the difference in NRA between the high and low NRA composites from the first cycle of selection was twice that between the high and low NRA composites from the second cycle of selection.
• A concurrent comparison (single season) of all composites produced from two cycles of recurrent selection showed a significant linear increase in NRA with selection for high NRA and a significant linear decrease in NRA with selection for low NRA. Plant productivity was not altered by selection for high NRA, but grain dry weight, grain reduced nitrogen, aerial plant dry weight, aerial plant total and reduced nitrogen and stover nitrate were significantly reduced with selection for low NRA. Plant productivity was negatively correlated with NRA in the high NRA composites while the correlation was positive with the low NRA composites.
• Determination of NRA using different assays and at different growth stages in individual C(,0) plants showed in vivo (+NO(,3)) and in vitro NRA were significantly correlated at the seedling stage and after anthesis with the highest correlation at the seedling stage.
• Two field tests with S1 progeny of high and low NRA plants showed Sl's from high NRA plants had significantly higher NRA than S1's from low NRA plants. Parent-offspring regressions were not significant. In one of the tests S1 progeny from high NRA plants averaged significantly higher grain yield and nitrogen harvest indices.
• Addition of supplemental nitrogen to already high nitrogen fertility plots resulted in an initial increase in composite midrib nitrate and a decrease in NRA with NRA recovery to presupplemental nitrogen levels ten days later. Midrib nitrate decreased exponentially through the period 62-99 days after planting, and pre anthesis NRA in the composites exhibited divergence identical to that noted post anthesis. It was postulated that changes in root absorption and end product regulation could be responsible for the variations in midrib nitrate and leaf NRA.
• High NRA composites and their S1 progeny from the second cycle of selection had lower leaf fresh weight than their counterparts. In addition, low stover glucose and high stover nitrate were found in the S1 progeny. It appears carbon and nitrogen metabolism are closely related and that high NRA in conjunction with high nitrogen fertility may adversely affect plant growth.
• Seasonal NRA was higher in S1 progeny from high NRA plants with NRA highest early in the seedling stage and during the reproductive stage and declining with grain maturation and plant senescence. Calculations of plant reduced nitrogen based on seasonal NRA closely approximated Kjeldahl nitrogen determinations.
• Selection on the basis of post anthesis NRA and grain yield is discussed as a means of gaining additional information on the role physiological processes play in determining plant productivity.

Graduation Semester

1980

Type of Resource

text

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