Resistance of bmr energy sorghum hybrids to sugarcane borer and fall armyworm

The lower lignin content in plants species with energy potential results in easier cellulose breakdown, making glucose available for ethanol generation. However, higher lignin levels can increase resistance to insect attack. The objective of this work was to evaluate the susceptibility of a bmr-6 biomass sorghum (a mutant genotype with a lower concentration of lignin) to important pests of energy sorghum, Diatraea saccharalis and Spodoptera frugiperda. Experiments were performed in the laboratory and greenhouse to evaluate the development of these pests on the biomass sorghum bmr hybrids BR007, BR008, and TX635 and their respective conventional near-isogenic genotypes (without the bmr gene). The lignin content was higher in non-bmr hybrids, but the evaluated insect variables varied between treatments, not being consistent in just one hybrid or because it is bmr or not. The lowest survival of S. frugiperda was observed in the BR008 hybrid, both bmr and non-bmr. The S. frugiperda injury scores on plants in the greenhouse were high (>7) in all treatments. For D. saccharalis, there was no difference in larval survival in the laboratory, but in the greenhouse, the BR007 hybrid, both bmr and non-bmr, provided greater survival. Due the need to diversify the energy matrix and the fact that greater susceptibility of the bmr hybrids to either pests was not found in this study, these results hold promise for cultivation of these biomass sorghum hybrids for the production of biofuels.

Photoperiod Sensitive Energy Sorghum Responses to Environmental and Nitrogen Variabilities

Recently introduced photoperiod-sensitive (PS) biomass sorghum (Sorghum bicolor L. Moench) needs to be investigated for their yield potentials under different cultivation environments with reasonable nitrogen (N) inputs. The objectives of this study were to 1) evaluate the biomass yield and feedstock quality of four sorghum hybrids with different levels of PS ranging from very PS (VPS) hybrids and to moderate PS (MPS) hybrids, and 2) determine the optimal N inputs (0~168 kg N ha−1) under four environments: combinations of both temperate (Urbana, IL) and subtropical (College Station, TX) regions during 2018 and 2019. Compared to TX, the PS sorghums in central IL showed higher yield potential and steady feedstock production with an extended daylength and with less precipitation variability, especially for the VPS hybrids. The mean dry matter (DM) yields of VPS hybrids were 20.5 Mg DM ha−1 and 17.7 Mg DM ha−1 in IL and TX, respectively. The highest N use efficiency occurred at a low N rate of 56 kg N ha−1 by improving approximately 33 kg DM ha−1 per 1.0 kg N ha−1 input. Approximately 70% of the PS sorghum biomass can be utilized for biofuel production, consisting of 58-65% of the cell wall components and 4-11% of the soluble sugar. This study demonstrated that the rainfed temperate area (e.g., IL) has a great potential for the sustainable cultivation of PS energy sorghum due their observed high yield potential, stable production, and low N requirements.

Energy Sorghum Production under Arid and Semi-Arid Environments of Texas

Water availability and supply are critical factors in the production of bioenergy. Dry biomass productivity and water use efficiency (WUE) of two biomass sorghum cultivars (Sorghum bicolor (L.) Moench) were studied in two different climatic locations during 2014 and 2015. The objective of this field study was to evaluate the dry biomass productivity and water use efficiency of two energy sorghum cultivars grown in two different climatic environments: one at Pecos located in the Chihuahuan Desert and a second one located at Weslaco in the Lower Rio Grande bordering Mexico and with a semiarid environment. There were significant differences between locations in dry biomass and WUE. Dry biomass productivity ranged from 22.4 to 31.9 Mg ha−1 in Weslaco, while in Pecos it ranged from 7.4 to 17.6 Mg ha−1. Even though it was possible to produce energy sorghum biomass in an arid environment with saline-sodic soils and saline irrigation, the energy sorghum dry biomass yield was reduced more than 50% in the arid environment compared to production in a semiarid environment with good soil and water quality, and it required approximately twice as much water. Harsh production conditions combined with low energy prices resulted in negative net returns for all treatments. However, a moderate increase in ethanol price could make the semiarid cropland of Texas an economically feasible feedstock production location.