Dempsey, Wesley H.
In C. M. Rick's 1959 Planting of F1 lines, a triploid plant was found which had been produced from crossing a Pearson derivative, LA490 (+/+) by Gilbert's G-178 (u/u). Crosses were made between this plant and normal plants of the same origin (+/u) and also to plants which were u/u. Of the thirty-six plants resulting, seven were diploid while twenty-nine were trisomics. Six of the trisomics did not fruit, and two more were trisomic for chromosome 10. Hence fruit-ripening data were available from twenty-eight plants for tests as to whether the male or the female gamete was doubled in the production of this triploid. If the male gamete was diploid, the triploid should be +/u/u; whereas, if the female gamete was diploid, then the triploid would be +/+/u. The Chi Square tests for these two theses are given in the table below.
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Observed Diploid male gamete Diploid female gamete
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Cross +:u Calc. +:u X^2 p Calc. +:u X^2 P
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3n x +/u 8:3 7.3:3.7 0.2 0.70 9.2:1.8 1.0 0.30
3n x u/u 7:10 5.7:11.3 0.4 0.50 11.3:5.7 4.9 0.02-0.05
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The probability that the triploid originated due to a diploid male gamete
appears to be significantly higher than the probability of the alternate
theory.