Controlled Hybridization Technique for Switchgrass

Abstract

Controlled hybridizations of plants are necessary for genetic studies, including those that use molecular markers. A hybridization technique for grass species such as switchgrass, Panicum virgatum L., with indurate floral bracts has not been previously reported. The objective of this study was to develop a technique for emasculating and hybridizing switchgrass. Emasculations were successful when the top of the stigmas could be seen through the translucent tips of the lemma and palea. Panicle branches containing 25 to 50 fertile florets were emasculated at this stage after removing excess panicle branches. Both sessile staminate florets and the fertile florets of a spikelet were emasculated because removal of the sessile floret damaged the upper fertile floret. Emasculations and hybridization were completed before natural pollen shed, which occurs after 1000 h in the greenhouse. Panicle branches with emasculated rioters were covered with glassine bags. Anthers from florets of male parents at a similar stage of development were collected in petri dishes and shaken to induce pollen shed. Pollen in petri dishes was applied directly to stigmas of florets emasculated previously the same morning. The average percentage of crossability [(seed/floret emasculated and fertilized) 100] for crosses that produced seed was 27%, with a range of 4 to 86%. The procedure was successfully used to make controlled crosses in a greenhouse between plants of ’Summer’, an upland tetraploid, and ‘Kanlow’, a lowland tetraploid switchgrass.