Hybrid Lethality in Crosses between Emmer Wheats and <i>Aegilops squarrosa</i>, II Synthesized 6x Wheatis Employed as Test Varieties

Abstract

Crosses of four strains of synthesized 6x wheats with 20 varieties of Emmer wheats were made to test necrosis or growth abnormality in the resulting F1 hybrids. These abnormalities are attributable to complementary genes, one of them belonging to A and/or B genome of Emmer wheat, and the other to D genome of Aegilops squarrosa. Crossability, on an average, was about twice or more effective in comparison with the Emmer wheat×autotetraploid squarrosa crosses. The viability spectra of ABD No. 1×Emmer wheat crosses (Group 1) was similar to that of Emmer wheat ×autotetraploid squarrosa crosses. The viability spectra, however, varied depending upon the synthesized 6x wheat used as the female parent, except that ABD No. 3× Emmer wheat crosses (Group 3) and ABD (Sears) ×Emmer wheat crosses (Group 4) showed similar spectra, resulting in three kinds of viability spectra. Thus, three strains of synthesized 6x wheats, ABD No. 1, ABD No. 2 and ABD (Sears) were found to be useful as test strains for hybrid necrosis or growth abnormality genes.Two types of necrosis were found in some of synthesized 6x wheat×Emmer wheat crosses. The one designated as Type 1 occurred in crossing ABD No.1, ABD No. 3 or ABD (Sears) with T. dicoccum Khapli, T. dicoccoides kotschyanum and straussianum. The genotype for Type 1 necrosis was estimated to be ne1ne2Ne3/Ne1Ne2 and Ne1ne2Ne3/Ne1Ne2, which is in agreement with the three gene hypothesis presented by Hermsen (1959). The other, designated as Type 2, was a late appearing type of necrosis; it was found in the majority of crosses between ABD No.1 and dicoccum-and durum-varieties. The assumed genotype for Type 2 necrosis, Ne1ne2Ne3/Ne1n2, requires further direct proofs.Dwarfishness observed in the crosses between ABD No.1 and dicoccum Vernal, durum melanopus, pyramidale or persicum varieties are also attributable to complementary genes different from those for necrosis.On the basis of viability spectra, 20 varieties of Emmer wheat can be divided into four groups as illustrated in Table 3.