Meiotic behaviour and pollen fertility of F₁, F₂ and BC₁ progenies of Iris dichotoma and I. domestica

Pollen characteristics are very important for Iris interspecific hybridisation. In this study, the pollen viability and male meiosis were studied in yellow-flowered Iris dichotoma (Y2), I. domestica (S3) and their hybrids F₁, F₂ and BC₁ (BC₁-Y and BC₁-S). The BC₁-Y hybrids showed higher pollen viability than that of F₁, F₂ and BC₁-S hybrids, which were between I. dichotoma (26.1%) and I. domestica (35.1%). Two sterile hybrids, F₂-1 and BC₁-S-1, exhibited more meiotic abnormalities (57.3% and 58.7%) than other individuals. During the first meiotic division, a diffuse diplotene stage was observed for the first time in the genus Iris. The meiotic abnormalities included non-congressed chromosomes, chromosome bridges, lagging chromosomes, unequal division, abnormally oriented spindle fibres, nonsynchronous division and polyad, and resulted in reduced pollen fertility. The relatively high frequency of 2n pollen grains was found in hybrids of BC₁-Y-2, BC₁-Y-1, BC₁-S-2, BC₁-S-3 and BC₁-S-4. Our research provides a new resource for meiotic behaviour and pollen fertility of the genus Iris.