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Performance Level as Criterion for the Choice of Maize Testers 1
Author(s) -
Rawlings J. O.,
Thompson D. L.
Publication year - 1962
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1962.0011183x000200030012x
Subject(s) - geneticist , library science , crop , agricultural science , operations research , mathematics , computer science , biology , agronomy , genetics
IT HAS been generally accepted that broad gene base testers are more efficient than narrow gene base testers for the evaluation of general combining ability in inbred lines of maize (Matzinger (7), Grogan and Zuber (4), and others). The importance of performance level or, by inference, gene frequency of the tester as a criterion for choice of testers, however, has never been as clearly established. Hull (5) stated that theoretically the most efficient tester would be homozygous recessive at all loci and that homozygosity for the dominance alleles at any locus should be avoided. These conclusions were based on considerations of the constant parent regression method of analysis of single crosses. The regression of performance of offspring on the performance of the variable parents for a particular constant parent was shown to be largest when the gene frequency of the character for the constant parent was zero. The regression was zero when the gene frequency was at one for complete dominance or at equilibrium gene frequency for overdominance. A strong positive regression would be desirable as this would allow more discrimination among the variable parents. Green (2) tested Hull's hypothesis with respect to lodging resistance. A lodging resistant double cross and a lodging susceptible open-pollinated variety were used as testers for the F2 progenies of three single crosses. When considerable lodging occurred, there was little difference between the testers. With little lodging, however, the lodging susceptible tester gave a much greater range for standability within all the F;2 progenies than the lodging resistant tester. Keller (6) reasoned that if Hull's hypothesis were correct, the component of variance due to the interaction of lines with testers would be less for high combining testers than for low combining testers. Separate estimates of the line X tester component of variance were obtained for the high and low yielding groups in 22 single cross experiments. The averages of these estimates were essentially the same for the two groups. It was concluded that the data disagreed with Hull's hypothesis. The purposes of the study reported herein were to consider further the role of average gene frequency of the