Inheritance of growth habit and phosphoglucoisomerase isozymes in Pennisetum alopecuroides (L.) spreng

Abstract

Fountain grass, Pennisetum alopecuroides (L.) Spreng., is a C4 bunch type perennial typically 90-125 cm tall with numerous purple or mauve spike-like inflorescences. It has been grown as an ornamental in the U.S. since the early 1940's, yet only one form is readily available in the trade. Evaluation of germplasm from several sources resulted in the identification of four growth habits classified as prostrate (p), upright (u), mound (m), and dwarf (d). No reports of breeding improvements or basic genetics could be found for fountain grass. On that basis, three areas of research were selected: inheritance of growth habit, isozyme variation and inheritance, and pollen viability. Selected plants of the four growth habits were crossed in a complete diallel in 1990 and 1991. F1 and F2 progeny evaluations support the conclusion that the dwarf and upright forms appear to share similar genetic backgrounds, as do the mound and prostrate forms. The dwarf and prostrate forms appear to be controlled by one or two recessive genes. The upright and mound appear to be dominant traits. Progeny from four crosses, d x p; p x d; m x d; and d x m, exhibited heterosis in culm length, exceeding either parent. Ten isozymes were screened for variation. Polymorphism was found only in phosphoglucoisomerase at one locus, PGI-2, and appeared to be associated with growth habit. The dwarf form exhibited one slow band, SS; extracts from the mound and prostrate forms yielded one fast band, FF, and the upright formed as triple bands, FS, a heterodimer. Hybrids between FF and SS parents could be detected as triple bands, FS. Three generations followed expected segregation ratios for this isozyme. In vitro pollen germination (in a 25 g kg sucrose and 100 mg ml boric acid solution) ranged from a low of 4% for the F1 mound progeny to a high of 47% for the upright parent. Fountain grass appears to have sufficient genetic diversity for future selection and improvement as an ornamental.