Masters Theses

Date of Award

12-1978

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

L.M. Josephson

Committee Members

V.H. Reich, F.L. Allen

Abstract

Two populations of corn, a white endosperm and a yellow endosperm, were selected for prolificacy in a low plant population of 13,069 plants per acre and in a high plant population of 26,138 plants per acre. The lines developed from the two populations were sib-mated and testcrossed to single-ear inbreds in order to obtain seed for evaluation. The selections were evaluated as lines and in hybrids at Knoxville and Crossville, Tennessee, in both low and high plant populations.

A randomized complete block design was used for all evaluations which were replicated three times at both locations. Data were obtained on the number of ear shoots, total ears, and nubbin ears produced per plant. The weight of total ears and the weight of nubbin ears per plant were also obtained along with ear height data.

It was found that lines selected at a plant population of 26,138 plants per acre tended to have a greater degree of prolificacy than lines selected at a plant population of 13,069 plants per acre. The high density selection group averaged a greater degree of prolificacy along with having more individual selections significantly greater than the means of the evaluations. However, the increased prolificacy observed from the high density selections was due largely to an increased number of small ears.

The data obtained would suggest that selection for prolificacy was more effective in the yellow endosperm selections than in the white endosperm selections. This may be due to the poorer comparative response of inbred T232 than T115 under the conditions of evaluation.

Ear weight per plant of the white endosperm selections was greater when selected in the high density while the opposite was true for the yellow endosperm selections. Individual white selections producing the greatest number of ear shoots also produced the most total ears and had the highest ear weight. Among the yellow endosperm selections, those producing the most ear shoots did not necessarily have the most number of ears.

Generally, selections that were superior when evaluated at the low plant population were also superior when evaluated at the high plant population.

Evaluation of the selections in crosses generally did not differentiate the low and high density selections.

Selections from the white endosperm population had a higher ear placement when selected in low density while the yellow endosperm selections had a higher ear placement when selected in high density.

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