Persistence of Ladino white clover ecotypes and its relationship with other agronomic traits

Sixteen landraces and twelve natural populations of Ladino white clover, and six large-leaved control varieties, were assessed in Lodi (southern Lombardy, Italy) under a mowing regime for persistence, defined as ratio between clover dry matter (DM) yield over the last two years and clover DM yield over the five-year crop cycle. Clover content in the sward was on average 35.2% in the fourth year and only 5.5% in the fifth year. Natural populations showed greater persistence and larger variation for this feature than landraces. Six natural populations were more persistent and higher yielding in the long-term than the Italian variety Espanso and one of these populations performed better than the best of the control varieties, namely Lune de Mai and Olwen, at P<0.05. Persistence of the ecotypes was positively associated with stolen density and DM yield assessed in the third year, and to internode length, whilst it was inversely related to seed yield and its components, especially the production of seed heads, so that hardly any ecotype could combine good persistence with high seed yield. This study discusses the potential use of these genetic resources in white clover breeding and suggests stolen density as a low-cost, approximate indicator of long-term yield.