| dc.description.abstract | Warm-season perennial grasses are leading candidates for lignocellulosic biofuel feedstocks because of their relatively high photosynthetic rates, water use efficiency, and nutrient use efficiency. Interspecific F1 hybrids between pearl millet (Pennisetum glaucum [L.] R. Br.) and napiergrass (Pennisetum purpureum Schumach.) (PMN) are “seeded-yet-sterile” triploids (2n=3x=21) with high biomass yield potential that are well adapted to the southern U.S. Similarly, sterile triploid hybrids can potentially be obtained by crossing annual diploid Sorghum bicolor (L.) Moench with perennial tetraploid S. propinquum (Kunth) Hitchcock to produce novel C4 perennial sorghum biofuel feedstocks. The presowing hydration technique solid matrix priming (SMP) was utilized alone and in combination with the elicitor compounds 5-azacytidine (AZA) and chitosan on three PMN hybrids to improve soil emergence, growth, seedling yield, and chlorophyll fluorescence in ambient, heat, and heat plus drought stress environments. Because S. propinquum is a diploid, tetraploid germplasm is needed to produce triploid hybrids with S. bicolor. SMP and a standard moistening protocol were evaluated as techniques of applying colchicine rates with and without dimethyl sulfoxide (DMSO) to S. propinquum seed to induce chromosome doubling.
SMP usually reduced the time to maximum soil emergence in PMN from 4 to 2 d in all three environments. In the heat stress environment, SMP and AZA treatments increased tillering in the elite PMN hybrid 09TX04 relative to the control. The novel chlorophyll fluorescence method developed in this experiment successfully established unstressed, moderate, and severe stress levels. In the heat plus drought stress environment, PMN 09TX04 trended as being less stressed than the other PMN hybrids. Seedling biomass yields for SMP-treated PMN were higher than the control in the ambient (38%) and the heat plus drought (43%) environments.
The treatment using SMP for 5 d with 0.1% colchicine plus 2% DMSO was the only one in which S. propinquum chromosome doubling occurred. Seven of 52 surviving plants in this treatment were tetraploids, a 13% success rate, which is a very high frequency of chromosome doubling. | en |
