Somaclonal variation in seed germination of dallisgrass biotypes

Abstract

Dallisgrass (Paspalum dilatatum Poir.) is an important pasture grass on moist fertile sites in warm climates, however, it is limited in use by periodic low seed quality and resulting erratic availability and establishment difficulties. Due to apomictic reproduction, common pentaploid dallisgrass has not been responsive to traditional plant improvement approaches. Recent research has shown potential for some improvement in forage production and plant persistence with apomictic hexaploid varieties of dallisgrass. Tissue-culture regeneration has been reported to produce somaclonal variation in seed germination of common pentaploid dallisgrass and has recently resulted in availability of potentially useful regenerants of hexaploid dallisgrass. Seed of selected plants from both field and greenhouse environments was evaluated in replicated germination trials to determine whether hexaploid tissue-culture regenerants responded similarly to regenerants from common dallisgrass and to determine whether regenerants expressing potential agronomic usefulness as indicated by preliminary observations differed in germination. The eight germination trials included 299 regenerants with 57 of these being duplicate entries among trials. Germination did not differ among sources of regenerants. Within sources germination differed among regenerants with a few individuals exceeding germination percentage of parent lines in one evaluation of greenhouse-produced seed. Individual regenerants with agronomic potential and high percentage seed germination were identified. The results demonstrate that tissue-culture regeneration can be used to produce improved germination in agronomically useful genotypes of apomictic dallisgrass and suggest that such potential may exist for other recalcitrant plant species.

Variability in germination behaviour ofPaspalum dilatatumPoir. seeds is genotype dependent

“…The monoclonal Chirú biotype, which has been suggested to be genetically related to Virasoro (Speranza, ), often showed high germination percentages and no differences among treatments for any seed lot, resembling the expected behaviour of seeds with little or no dormancy. Evidence of higher germination percentages for this biotype (referred to as ‘Uruguayan’), than in the common biotype, has been reported in the literature (Tischler and Burson, ; Pitman et al ., ). On the other hand, Chirú showed a decreasing germination response to longer dry‐storage times while maintaining a high level of seed viability.…”

“…Morphological and physiological variability has also been reported among P. dilatatum biotypes, including tiller and panicle length (García et al ., ), forage yield and grazing tolerance (Venuto et al ., ), and response to water stress (Couso et al ., ). Similarly, differences have been reported in percentage of spikelets with caryopses and germination rate among some biotypes (Souza‐Chies and Cavalli‐Molina, ; Tischler and Burson, ; Pitman et al ., ). Until recently, however, the available cytogenetic, genetic and morphological information has not been considered for the assemblage of representative germplasm collections for agronomic evaluation.…”