Download or read book Evaluation of Tolerance to High Plant Densities and Plant Efficiency of Maize Breeding Population Developed by Recurrent Selection of Grain Yield written by T.M. Crosbie and published by . This book was released on 1978 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several recurrent relection schemes are being used to improve grain-yield performance of several maize (Zea mays L.) populations at the Iowa Agriculture and Home Economics Experiment Station. Three cycles of reciprocal full-sib selection in Iowa Two-ear Synthetic [BS10(FR)] and Pioneer Twc-ear Composite [BS11(FR)], seven cycels of reciprocal recurrent selection in Iowa Stiff Stalk Synthetic [BSSS(R)], Iowa Corn Borer Synthetic #1 [BSCB1(R)], and five cycels of half-sib recurrent selection in Lancaster Surecrop 9LANC) with maize inbred, Hy, as tester have been completed. I grew testcrosses of unimproved and improved populations of BS10(FR), BS11(FR), BSSS(R), BSCB1(R) And LANC, plus population crosses (i.e., CO X CO, CN X CN) of BS10(FR) X BS11(FR) and BSSS(R) X BSCB1(R) at three plant densities in three environments. Testers were maize inbreds Mo17, B77, and B79, My research was conducted: (1) to evaluate respones to plant densities of the CO and CN populations, (2) to study changes in several morphological and physiological traits associated with recurrent selection for increased grain yield, and (3) to caompare results obtained for testcrosses and populations crosses to evaluate combining ability for grain yield, density tolerance, and physiological traits. Reciprocal full-sib selection did not improve the response to plant densities of testcrosses and population crosses of BS10(FR) and BS11(FR). Furthermore, selection did not increase grain yield of BS10(FR) X BS11(FR) at 39.5 and 79.0 M plants/ha or of (...).