Testcross Evaluation of Elite Yellow Tropical Maize Inbred Lines

Date

5-2000

Degree

Bachelor of Science in Agriculture

Major Course

Major in Agronomy

College

College of Agriculture and Food Science (CAFS)

Adviser/Committee Chair

Peter S. Guzman

Abstract

Test crossing is essential to assess the merit of elite germplasm in hybrid development. This study was conducted to determine the heterotic grouping of elite tropical yellow maize inbred lines from Centro International de Mejoramiento de Maize Y Trigo (CIMMYT)-Thailand, and to identify single cross hybrids that have potential for release as recommended cultivars.

Thirty-six inbred lines were used in the study.Testcross entries was developed at UPLB by corssing the inbred lines to Pil7 and Pil23. The seventy-two testcrosses and two check hybrids (C818 and P3014) were evaluated at the University of the Philippines Los Baños (UPLB) and Central Mindanao University (CMU), Bukidnon using a rep within set randomized incomplete block design with two replications. The UPLB experiment was discarded due to severe corn borer and stalk rot infestations. Mean yield of Pi23 TC was 26% and 47% greater than the Pi17 TC and checks, respectively. The yield of Pi17 TC was 0.34 ton greater than checks. Analysis of variance showed that there were no significant differences within Pi17 and Pi23 testcrosses for yield.

Means of agronomic traits for Pi17 TC and Pi23 were greater than the mean of the checks. There was no significant difference between Pi17 and Pi23 testcrosses except for days to silking and days to 50% pollen shedding. Comparison between Pi17 and checks showed significant differences in plant height and ear length, while stand count, days to silking, days to 50% pollen shedding, ear diameter and moisture content revealed highly significant differences. Contrast showed that there were highly significant differences between Pi23 TC and checks in all others traits.

Based on grain yield, the top three yielding testcrosses per set were selected. The highest yielding hybrid in each set was a testcross of Pi23. Percentage yield advantage of the hybrids based on the mean of the checks ranged from 30.9% to 175.0%. The percentage yield advantage in terms of the highest yielding checks ranged from 11.4% to 74.5%. The high yielding hybrids will be further evaluated for possible approval as recommended cultivar by the Philippine Seed Board.

Heterotic grouping of the inbred lines was determined by comparing their SCA estimate with a tester. A low SCA estimate of a line with a tester would put the line with the tester group. Pi17 and Pi23 represent A and B heterotic groups, respectively. Line 16 which exhibited the highest testcross performance was group under A (Pil17 heterotic group.) Of the 36 inbred lines evaluated, 17 were grouped under P17, and 19 were assigned to Pi23 heterotic group. Experimental hybrids may be developed by crossing inbred lines between heterotic groups. Breeding populations (F2s, narrow and broad-base synthetics) may be developed within a heterotic group. The synthetic may be subjected to population improvement and inbred lines will be extracted from improved populations.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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