In Imperial County, alfalfa ranks second in gross agricultural earnings and occupies approximately one third of all agricultural acreage.
Selection is based on a simple index of both number of immature whiteflies and stickiness.
One cycle of among and within half-sib family selection is completed each year. Estimates of genetic variance produced from OP seed were then utilized to estimate genetic gain. These estimates Predicted that it would require 3 to 5 cycles of selection to develop populations with economic levels of resistance. Following 5 cycles of selection, the resulting populations were evaluated in comparison with susceptible check materials to determine selection progress. UC-356 and CUF 101 are both highly susceptible with ASI's for index of 3.50 and 3.40, respectively.