Hypertriploid Plants in Barley (Hordeum VulgareL.)

Abstract

Four hypertriploid plants were obtained: two plants were found in the progeny of the primary trisomic for chromosome 4 (Robust) in the F₂ population of the cross between Robust x KM 200 (a short-awned mutant). The F₁ hybrid of Robust x zebra Colorado (zb_c) and Robust x light green (lg4) contained one plant each. All the four hypertriploids studied were larger than their diploid sibs in various plant organs. The frequency of trivalents was predominantly high with an average 4.91 per cell followed by bivalents (2.06), univalents (1.73), and quadrivalent (0.35). The presence of a quadrivalent indicated the presence of one chromosome four times. Since hypertriploids were morphologically similar to Robust trisomic for chromosome 4 and all occurred in its progenies, it is assumed that chromosome 4 is repeated four times. The quadrivalent sometimes dissociated into two bivalents at MI, thus increased the number of bivalents, eventually increasing the total number of trivalents plus bivalent (6III + 2II, 4III + 4II, 3III + 5II, 2III + 6II) more than 7, which is generally found in autotriploids. Hypertriploids showed poor pollen fertility compared to diploid sibs. No seed was obtained after selfing of hypertriploid plants. Artificial pollination with pollen of diploid plants resulted in 7.72%, 6.96%, and 4.12% seed set for hypertriploid plants, No. 1, 2, and 3, respectively. One hypertriploid x diploid cross yielded nearly 81% aneuploid progeny. Of these, 56.3% were primary trisomies and 25% were 16-chromosome plants. Primary trisomies were for chromosome 1 (Bush), 3 (Pale), 4 (Robust), 5 (Psuedonormal), 6 (Purple), and 7 (Semierect).