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 Title: Evaluation of Five Cycles of Selection for Canopy Photosynthesis in Corn Author(s): Nubel, Douglas Stuart Doctoral Committee Chair(s): Alexander, D.E. Department / Program: Agronomy Discipline: Agronomy Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Agriculture, Agronomy Agriculture, Plant Culture Abstract: Photosynthesis is a primary mechanism which determines the total dry matter production and thus economic yield of a plant. Beginning in 1982, half-sib families of maize synthetic RSSSC were monitored for CO$\sb2$ exchange rate, (CER), a common indicator of photosynthesis. The objectives of the study were to determine: (1) the seasonal characteristics of maize canopy CER, (2) heritability of canopy CER, (3) whether selection for canopy CER can be effective in increasing grain yield, (4) how other plant traits might vary with canopy CER, and (5) possible factors which may influence seasonal canopy CER.Estimates of canopy CER were made using mobile transparent chambers set upon tracks bordering 3.06 m$\sp2$ plots. Air samples obtained from sealed plots were pumped from the chamber into infrared gas analyzers during a 35 second time span. Carbon dioxide exchange rates for each plot were measured at least ten times throughout a single day.Using this system, selection for high capacity photosynthetic families was carried out through 1986, one cycle per season. Throughout the selection process there was evidence to indicate: (a) seasonal photosynthetic patterns between high and low CER families remained distinct throughout most of the season, (b) high CER selected families had greater yields than low CER families, and (c) canopy CER was significantly and positively correlated with grain yield and not correlated with above ground vegetative growth.The five selected cycles and their testcrosses to Mo17 were evaluated in 1987. Heritability for canopy CER was low and environment played a key role in CER measurements. With the exception of cycle two, CER for cycles selected for high CER did not differ significantly from CER values of the original population. Grain yields of cycles two, four, and five were significantly higher than that of the original population (yield response was 0.19 Mg ha-1/cycle). All selected cycles had significantly larger kernel weights than cycle 0. The yield and kernel weight increases may indicated some increase in plant photosynthesis which was not detected. Issue Date: 1988 Type: Text Description: 131 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988. URI: http://hdl.handle.net/2142/71658 Other Identifier(s): (UMI)AAI8908792 Date Available in IDEALS: 2014-12-16 Date Deposited: 1988
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