Bulk method selection with grazing treatments on segregating populations from Avena sativa × A. sterilis hybrids

Abstract

Seven F₅ populations derived from Avena sativa × Avena sterilis hybrids were bulked and then sheep grazing and simulated grazing (lawn mowing) were imposed from F₅ up to F₁₀. After the 5 year, on 1100 F₁₀ plants per treatment, determinations were performed on the following traits: growth habit at early and late tillering; number of tillers and height of young plants; height of headed plants; number of headed tillers per plant. After five generations under grazing treatments the frequency of prostrate young plants was significantly higher in sheep grazing and in lawn-mowing treatments compared to the control. Moreover, plants from both grazing treatments were found to be lower and more tillered. These results were confirmed at the end of tillering. No difference in final plant height and number of headed tillers was observed. In only five generations, sheep grazing changed the frequency of the different plant habits. A similar result, but to a lesser extent, was induced by simulated grazing. Both treatments heavily penalized the erect habit. Through this bulk method repeated for five generations integrated with two types of grazing we were able to split the start population into nine lots of F₁₁ seeds corresponding to the 3 × 3 combinations of treatment (sheep grazing, simulated grazing, control) and juvenile growth habit (prostrate, erect, intermediate).