Meiotic Instability of Tall Fescue ✕ Giant Fescue Amphiploids

Publisher Website
Google Scholar
Abstract
Amphiploids of tall fescue (Festuca arundinacea Schreb.) and giant fescue [F. gigantea (L.) Vill.] have high forage quality but are meiotically irregular and have low seed yield. The objective of this study was to evaluate effects of generation advance and cytoplasm on meiotic behavior of tall fescue ✕ giant fescue amphiploid derivatives. Chromosome number and pairing, frequency of micronuclei, and pollen stainability were analyzed in 75 amphiploids developed from reciprocal hybrids of giant fescue ✕ tall fescue (including derivatives of annual ryegrass [Lolium multiflorum Lam.] ✕ tall fescue). Amphiploids represented five generations (C1–C5) of maternal half‐sib progenies in three cytoplasmic backgrounds (annual ryegrass, giant fescue, and tall fescue). Chromosomes were lost and meiotic irregularity increased over generations. Chromosome number at C1 averaged 2n = 83.5 (range 2n = 81 to 84) and at C5 averaged 2n = 74.9 (range 2n = 48 to 84). The frequencies univalents and trivalents increased linearly from C1 to C5 generations, as did the frequency of micronuclei at telophase (T) I and II. Conversely, ring bivalents, frequency of chiasmata, and percentage of daughter cells without micronuclei decreased linearly from C1 to C5 generations. Pollen stainability was relatively constant across generations despite chromosomes loss. Effects of cytoplasm were negligible, as significant differences were detected only for frequency of TII micronuclei. The population will probably regress to the hexaploid level (2n = 6x = 42) where it may be possible to select meiotically regular genotypes for cultivar improvement.