Ames, Iowa
USDA-ARS
Phenotypic characterization of inbred lines and their o2 conversions --Scott, MP Peter Loesh was a plant breeder at Iowa State University from 1971 to 1980. During this time, he worked extensively with the o2 mutation in an effort to improve the nutritional quality of maize. Unfortunately, he passed away suddenly, and this work was not brought to a conclusion. Some of his effort was devoted to developing o2 back-cross conversions of public domain inbred lines. Because Dr. Loesh’s field books have been lost, the extent of recovery of the recurrent parent phenotype is not known.

The objective of this study was to characterize Dr. Loesh’s o2 converted lines relative to their recurrent parents and to verify that they have the o2 genotype. To accomplish this, I planted one row of each line adjacent to one row of the corresponding recurrent parent at the Iowa State University Agronomy Farm in the summer of 2001. The resulting plants were characterized phenotypically on the basis of their plant height, ear height and pollination date (see Table). With the exceptions noted in the table, the inbreds were phenotypically similar to their recurrent parents.

In order to verify that the Loesh inbreds carried the o2 mutation, each of these lines was crossed to an o2 mutant tester from the Maize Co-op Stock Center (701D). In all cases, the o2 genotype was confirmed.

These lines will be valuable for comparing the effect of different genetic backgrounds on the o2 mutation, and may also be useful to breeding programs aimed at improving nutritional quality with the o2 mutation. Seed of these lines has been sent to the Maize Co-op Stock Center for maintenance and distribution.

Table. Phenotypic characterization of inbred lines and their o2 conversions.
 
Pedigree plt hta ear ht pol dateb comments
A257 NS NS -1  
A619 ** NS -3  
B14A ** NS -2 o2 small kernels
B45 NS * 0  
B46 * NS 2 O2 red cob, o2 white cob
B57 NS NS -6  
B66 NS NS 0  
M14 NS * -9  

aPlant and ear height measurements are the average of the first five plants in the row. NS indicates the difference between the inbred line and its o2 conversion is not significant, ** significant to P=0.05, * significant to P=0.1

bPollen date = (number of days after planting when half the plants in the O2 row first shed pollen) — (number of days after planting when half the plants in the o2 row first shed pollen)
 
 


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