Dalea pupurea Crossing Exploration

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My first goal of the crossing attempt was to determine the rate of floret emergence. The second major challenge was to isolate individual florets so that I could control pollination. I first found suitable plants without any emerged florets, then covered the terminal spike with a mesh bag that was secured to the stem using a twist-tie. Stems were supported by tying them loosely to a pin-flag. Then, I marked the pin-flag with labeled fluorescent orange flagging. I followed this procedure for each of ten haphazardly selected plants at the Nice Island remnant.

To examine the rate of floret emergence, I visited plants every two to three days. The first burst of flowering occurred during hot days in mid-July. Following the first 2-3 rows of opened florets, I secured a length of embroidery floss around the spike to demarcate emerged florets from the still closed floral buds. I then immediately replaced the mesh bags following belt application. I determined that florets opened at the rate of one to two rows per day, progressing from the bottom to the top of the spike.

This species is primarily outcrossing. Pollination was attempted using haphazardly collected pollen at the same site with fresh toothpicks. Pollen was stored into new microfuge tubes in the freezer. I later applied this random donor pollen to floret stigmas at ten plants.

This crossing protocol had some challenges. First, the close organization of florets on the inflorescence made individual crosses impractical. Second, a relatively delicate stem did not allow for snug closure of the mesh bag and twist-tie, resulting in insects inside the mesh. Third, the size of the mesh (aperture size) was such that most stamens poked out through the mesh. It was concluded that crosses of this species will require a different approach.

For pictures, visit the Dalea page at The Echinacea Project

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