Describing the Tradeoffs Between Persistence and Productivity in Alfalfa

Abstract

Substantial plant loss is a commonly accepted phenomenon in commercial alfalfa production. Frequently less than 2% of the seeds originally sown are present in productive mature stands. Optimum yields may not be achieved if the small proportion of plants that survive do not represent the most productive individuals in the original population. We began a study in 1989 to describe the relationships between survival (persistence) and productivity in alfalfa. Sixty 5 yr-old plants were dug from a field of CUF -101 in Pinal Co. (= "Persistent population "). Field performance of progenies of these plants were compared with those of 60 greenhouse -grown CUF-101 plants (= "Random population ") in a 2-yr study in Tucson. In the second year of production spring and fall forage yield and average rate of stem elongation were significantly lower in the Persistent population than in the Random population. These data suggest that plants that are able to persist for the average life of a stand may represent a subset of the original sown population which exhibit more conservative growth patterns. This indicates that simultaneous selection for traits associated with productivity and persistence may be necessary in alfalfa breeding.