Cattle-Breeding Valley Plains and C4 Spontaneous Grasses in North Patagonia

The climate of North Patagonia (Argentina) is semiarid and the region periodically suffers severe droughts that may lastseveral years, decreasing forage offer and consequently cow livestock and productivity. In most of the cattle fields extensive grazing isusually continuous through the year-long. The absence of pasture rotational schemata affects rangeland health changing thecomposition of plants communities in detriment of the valuable species. When under a severe drought, the appreciated forageLeptochloa crinita (= Trichloris crinita) stopped reproduction and the population became scarce, a grazing schedule was designed in acattle farm to avoid foraging during spring and summer in a paddock located in the valley plains, where the species was disappearing.Besides L. crinita populations, the sympatric presence of the Poaceae Aristida mendocina, Distichlis spicata and Distichlis scoparia isexpected, each one in slightly different patches within the same area. The forage value differs between species but all of them are eatenby bovines. For ten years the plant communities were studied with the aims of determining the incidence of the patches on the paddockcarrying capacity in early autumn and estimating the contribution of the four C4 species to bovine diet by microhistology. Free ofgrazing during its growing period, L. crinite enhanced the area of its patches and the biomass production of its good quality forage andwas consumed preferently. A. mendocina is not prized by cattle but contributed to the diet at the end of the foraging period. Distichlisspp. is important component of the cows’ diet, especially in dry years. Management actions to preserve a valuable species may haveside effects involving other community members.

The application of Fourier transform mid-infrared(FTIR) spectroscopy to identify variation in cell wall composition of Setaria italica ecotypes

Cell wall composition in monocotyledonous grasses has been identified as a key area of research for developing better feedstocks for forage and biofuel production.Setaria viridis and its close domesticated relative Setaria italica have been chosen as suitable monocotyledonous models for plants possessing the C4 pathway of photosynthesis including sorghum,maize,sugarcane,switchgrass and Miscanthus×giganteus.Accurate partial least squares regression（PLSR）models to predict S.italica stem composition have been generated,based upon Fourier transform mid-infrared（FTIR）spectra and calibrated with wet chemistry determinations of ground S.italica stem material measured using a modified version of the US National Renewable Energy Laboratory（NREL）acid hydrolysis protocol.The models facilitated a high-throughput screening analysis for glucan,xylan,Klason lignin and acid soluble lignin（ASL）in a collection of 183 natural S.italica variants and clustered them into classes,some possessing unique chemotypes.The predictive models provide a highly efficient screening tool for large scale breeding programs aimed at identifying lines or mutants possessing unique cell wall chemotypes.Genes encoding key catalytic enzymes of the lignin biosynthesis pathway exhibit a high level of conservation with matching expression profiles,measured by RT-q PCR,among accessions of S.italica,which closely mirror profiles observed in the different developmental regions of an elongating internode of S.viridis by RNASeq.

Characterization of novel Brown midrib 6 mutations affecting lignin biosynthesis in sorghum

The presence of lignin reduces the quality of lignocellulosic biomass for forage materials and feedstock for biofuels. In C4 grasses, the brown midrib phenotype has been linked to mutations to genes in the monolignol biosynthesis pathway. For example, the Bmr6 gene in sorghum （Sorghum bicolor） has been previously shown to encode cinnamyl alcohol dehydrogenase （CAD）, which catalyzes the final step of the monolignol biosynthesis pathway. Mutations in this gene have been shown to reduce the abundance of lignin, enhance digestibility, and improve saccharification efficiencies and ethanol yields. Nine sorghum lines harboring five different bmr6 alleles were identified in an EMS-mutagenized TILLING population. DNA sequencing of Bmr6 revealed that the majority of the mutations impacted evolutionarily conserved amino acids while three-dimensional structural modeling predicted that all of these alleles interfered with the enzyme＇s ability to bind with its NAPPH cofactor. All of the new alleles reduced in vitro CAD activity levels and enhanced glucose yields following saccharification. Further, many of these lines were associated with higher reductions in acid detergent lignin compared to lines harboring the previously characterized bmr6-ref allele. These bmr6 lines represent new breeding tools for manipulating biomass composition to enhance forage and feedstock quality.

Linkages between woody plant proliferation dynamics and plant physiological traits in southwestern North America

Aims Woody plant encroachments in arid and semiarid ecosystems are widely reported but the physiological mechanisms still need to be further revealed.In the current study,we aim to determine whether differences in leaf physiological traits help explain grassland susceptibility to woody plant encroachment and whether distinctive physiological adaptations allow some shrub species to invade grasslands.Methods We compared physiological traits(photosynthesis,leaf water status,pigment compositions and leaf antioxidant capacities)of six species representing three functional groups:woody encroachers(Prosopis velutina,Larrea tridentata),woody non-encroachers(Acacia greggii,Lycium fremontii)and C4 grasses(Bouteloua curtipendula,Bouteloua barbata)which are naturally growing in a botanical garden in University of Arizona,USA.Important Findings We infer that P.velutina(encroacher)but not A.greggii or L.fremontii(non-encroachers)is encroaching in grasslands because the former species has higher water and light utilization efficiencies(instantaneous water use efficiency,instantaneous light use efficiency,and Fv/Fm).The extremely high carotenoid and total antioxidant capacity in its leaves appears to help the shrub L.tridentata(encroacher)survive high ambient oxidative damage caused by both drought and high light stresses in this grassland.The two C4 grass species,B.curtipendula and B.barbata,grow well in the arid ecosystem but may be susceptible to disturbances.