A Method for Producing Chance Crosses and Polycrosses of Pensacola Bahia Grass, Paspalum Notatum 1

R extensive studies2 of the diploid Pensacola Bahia grass;, Paspalum notatum, have shown that this species is highly selfsterile. Consequently, chance crosses made by pollinating unemasculated florets usually have resulted in less than 5% of selfed seed. Reciprocal chance crosses can be easily made by allowing two plants isolated from other pollen sources to flower in close association. To be effective this method requires that panicles on both plants be flowering at the same time. Small potted plants with their tendency to produce an occasional panicle over a long period of time are not well suited for making such crosses. Several years ago it was discovered that panicles ready to flower would bloom and mature seed in water if a short piece of rooted stolon were left attached to the culm. Keller 3 has shown that a number of other grasses will respond in this manner. This finding has greatly facilitated the production of chance single crosses and potycrosses of Pensacola Bahia. The first step in the production of either chance single crosses or polycrosses consists of collecting in mid-afternoon rooted culms bearing panicles due to. flower the following day. These are labeled with small merchandising tags and are placed in a bucket of water as soon as possible after they are dug. The collected culms are then brought into the laboratory and are arranged systematically so that the desired combinations can be readily found. Two or more culms from each parent entering into a specific single cross are then selected and labeled, as shown in Fig. ~. An effort is always made to chose culms of similar length for each cross in order to facilitate cross pollination. Where several single crosses are to be made, the problem of isolation from other pollen sources can be easily solved by placing each crossing .unit in a separate glassine bag, as shown in the illustration. A number of these may then be placed in one container of water and held together with string or a rubber band. The cans are then placed in a cool, moderately light place in the laboratory where they remain until the seed is mature. Good cross pollination is insured by shaking the bags each morning soon after the panicles have flowered. The polycross has been defined by Tysdal, et al4 as follows: "~I’he name polycross is suggested for the progeny from seed of a line that was subject to outcrossing with the other selected lines in the same