Bioenergy Sorghum Research Articles

Management effects on bioenergy sorghum growth, yield and nutrient uptake

Bioenergy sorghum (Sorghum bicolor L. Moench.) productivity and nutrient uptake may be affected by cropping sequence complexity, fertilization, and residue removal. The goal of this research was to optimize the efficiency of crop management in high biomass (bioenergy) sorghum systems. The two-year field study was conducted in two diverse locations near College Station and Weslaco, Texas. The study utilized a complete factorial design with four replications of the following factors: Rotation: continuous biomass sorghum vs. biannual rotation with corn (Zea mays L.); Stover Return: 0, 25, 50% of the sorghum biomass and all corn stover; and N Rate: 0 vs. non-limiting N. The bioenergy sorghum used was a high-yield photoperiod-sensitive hybrid. Other inputs and practices were those commonly used in the respective areas. Sorghum was harvested for yield, and C, N, P and K, were determined. Rotation, fertilization, and residue return affected yields, plant growth, and nutrient uptake (p < 0.05). Total yields, C, N, P, and K uptake in sorghum were significantly increased by rotation and N fertilization both years, while 25% residue return increased sorghum yield and N uptake at College Station the first year. Uptake of C, N, P and K were increased by N fertilization. Sorghum tissue concentrations of N, P and K declined from the first to the second year although mean yield increased, possibly indicating decreased soil nutrient availability after only two years. A regression equation was developed relating biomass yield and site, rotation, nitrogen rate, and plant physical traits (R2 = 0.67).

Cloning two P5CS genes from bioenergy sorghum and their expression profiles under abiotic stresses and MeJA treatment

Sweet sorghum ( Sorghum bicolor (Linn.) Moench) has promise as a bioenergy feedstock in China and other countries for its use in the production of ethanol as the result of its high fermentable sugar accumulation in stems. To boost biofuel production and extend its range, we seek to improve its stress tolerance. Proline acts as an osmolyte that accumulates when plants are subjected to abiotic stress. P5CS (Δ1-pyrroline-5-carboxylate synthetase) is a key regulatory enzyme that plays a crucial role in proline biosynthesis. We isolated two closely related P5CS genes from sweet sorghum, designated SbP5CS1 (GenBank accession number: GQ377719) and SbP5CS2 (GenBank accession number: GQ377720), which are located on chromosome 3 and 9 and encode 729 and 716 amino acid polypeptides, respectively. The homology between the two sweet sorghum P5CS genes was 76%. Promoter analysis of the two P5CS genes revealed that both sequences not only contained the expected cis regulatory regions such as TATA and CAAT boxes, but also had many stress response elements. Expression analysis revealed that SbP5CS1 and SbP5CS2 transcripts were up-regulated after treatment of 10-day-old seedlings of sweet sorghum with drought, salt (250 mM NaCl) and MeJA (10 μM). The expression levels of the both SbP5CS genes were significantly increased after 3-day drought stress. Under high salt treatment, peak SbP5CS1 expression was detected at 4 h and 8 h for SbP5CS2 in roots, while the trends of expression were nearly identical in leaves. In contrast, under drought and high salt stress, the up-regulated expression of SbP5CS1 was higher than that of SbP5CS2. When the seedlings were exposed to MeJA, rapid transcript induction of SbP5CS1 was detected at 2 h in leaves, and the SbP5CS2 expression level increase was detected at 4 h post-treatment. SbP5CS1 and SbP5CS2 also show different temporal and spatial expression patterns. SbP5CS2 gene was ubiquitously expressed whereas SbP5CS1 was mainly expressed in mature vegetative and reproductive organs. Proline concentration increased after stress application and was correlated with SbP5CS expression. Our results suggest that the SbP5CS1 and SbP5CS2 are stress inducible genes but might play non-redundant roles in plant development. The two genes could have the potential to be used in improving stress tolerance of sweet sorghum and other bioenergy feedstocks.