Selection for Tolerance to Frequent Cutting Regimes in Alfalfa1

Abstract

A study was conducted on alfalfa (Medicago sativa L.) to evaluate the effects of two cycles of phenotypic recurrent selection for tolerance to frequent harvest on persistence, dry matter, and crude protein yield. One hundred and eight clones (72 from selected and 36 from control materials) were established in plant nursery in April 1982. An experimental design was used, which subjected the 108 clones to the following harvest treatments during 1983 and 1984 growing seasons: very frequent (14 cuts from April 1983 to September 1984); frequent (12 cuts from April 1983 to September 1984); and infrequent (9 cuts from May 1983 to September 1984). The results can be summarized as follows: i) selection increased persistence of alfalfa materials and both dry matter and crude protein yield within each harvest treatment; ii) the selected materials, even if more persistent and productive than the controls, showed a depression in dry matter and crude protein yield when submitted to frequent and very frequent harvest treatments compared to the infrequent harvest treatment. In general, the selection for tolerance to frequent cutting regimes seems more suitable for improving the average persistence of alfalfa than in synthetizing new cultivars able to overcome the decrease in yield potentialities connected to the increase of harvest frequency.