Environmental induction of high frequency 2n pollen formation in diploid Solanum

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Abstract
Ten genotypes of S. phureja Juz. and Buk. producing 2n pollen via fused (FS) and tripolar (TPS) spindles at the 2nd meiotic division were grown in 2 consecutive years at a cool field site (E1, 8.degree.-22.degree. C) and in a warm greenhouse (E2, 14.degree.-40.degree. C) to examine environmental effects on mean frequency and phenotypic stability of 2n pollen production. Overall frequencies of big pollen (BP) and dyad formation were substantially higher in E1 in both years. The stable standard (154-1) gave almost complete expressions of dyads in E1, with no bud below 99%. Four other genotypes (413, 414, 416, 417) gave a similar response in E1, producing mean dyad frequencies between 93 and 99%, with no bud below 80%. The other 4 genotypes (420, 424, 427, 429) and the variable standard (127-14) produced higher dyad frequencies in E1 vs. E2, but their phenotypes remained variable in E1, showing disparities up to 79% between buds of a single collection. The fidelity of stable and variable phenotypes in E1 was examined by scoring dyad frequencies in putatively stable (413, 414, 415, 416) vs. variable (420, 424, 427, 127-14) genotypes at 4 dates spanning the flowering period in this environment. The stable genotypes showed consistent expression of high dyad frequency (86-99%) at all 4 dates. In contrast, dyad frequencies of the variable genotypes were substantially lower and more variable between and within collections.