Resistance of bmr energy sorghum hybrids to sugarcane borer and fall armyworm / Resistência de híbridos de sorgo energia bmr à broca-da-cana-de-açúcar e lagarta-do-cartucho

Abstract 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.

Resumo O menor teor de lignina em espécies de plantas com potencial energético resulta na maior facilidade de quebra da celulose, disponibilizando glicose para geração de etanol. Porém, maiores teores de lignina representa um fator de resistência ao ataque de insetos. O objetivo deste trabalho foi avaliar como importantes pragas do sorgo energia, Diatraea saccharalis e Spodoptera frugiperda, se comportam quanto à alimentação e desempenho em sorgo bmr-6, um genótipo mutante com menor concentração de lignina. Foram realizados experimentos em laboratório e casa de vegetação, avaliando o desenvolvimento destas pragas nos híbridos de sorgo biomassa bmr 007, 008, TX635 e seus respectivos genótipos isogênicos convencionais (sem o gene bmr). O teor de lignina foi maior nos híbridos não bmr, mas nos parâmetros avaliados nos insetos, houve variação entre os tratamentos, não sendo consistente em apenas um híbrido e nem por ser ou não bmr. A menor sobrevivência de S. frugiperda foi verificada no híbrido BR008 tanto bmr quanto não bmr. As notas de injúria por S. frugiperda no sorgo em casa de vegetação foram altas (>7) em todos os tratamentos. Para D. saccharalis, não houve diferença significativa para a sobrevivência larval em laboratório, mas em casa de vegetação o híbrido BR007 tanto bmr quanto não bmr proporcionaram maior sobrevivência. Diante da necessidade de diversificar a matriz energética e o fato de que não foi comprovada neste estudo maior suscetibilidade dos híbridos bmr a ambas as pragas, estes resultados são promissores para o cultivo desses híbridos de sorgo biomassa para produção de biocombustíveis.

Evaluation of fitness in F2 generations of Africa Biofortified Sorghum event 188 and weedy Sorghum bicolor ssp. drummondii

Background: Introgression of transgenes from crops to their wild species may enhance the adaptive advantage and therefore the invasiveness of and weedy forms. The study evaluated the effect of Africa Biofortified Sorghum (ABS) genes from ABS event 188 on the vegetative and reproductive features of the F2 populations derived from crosses with Sorghum bicolor subsp. drummondii. Results: F1 populations were obtained from reciprocal crosses involving ABS event 188 and its null segregant with inbred weedy parents from S. bicolor subsp. drummondii. Four F2 populations and four parental populations were raised in RCBD with 4 replications in a confined field plot for two seasons. Vegetative and reproductive traits were evaluated. The vigour shown in the F2 populations from the reciprocal crosses involving ABS event 188 and S. bicolor subsp. drummondii was similar to that in the crosses involving the null segregant and S. bicolor subsp. drummondii. Differences in vegetative and reproductive parameters were observed between the parental controls and the F2 populations. Examination of the above and below ground vegetative biomass showed lack of novel weedy related features like rhizomes. Conclusions: Therefore, release of crops with ABS 188 transgenes into cropping systems is not likely to pose a risk of conferring additional adaptive advantage in the introgressing populations. The interaction of ABS genes in weedy backgrounds will also not have an effect towards enhancing the weedy features in these populations.

Molecular tagging of gene conferring leaf blight resistance using microsatellites in sorghum [Sorghum bicolor (L.) Moench]

Resistance to leaf blight in sorghum [Sorghum bicolor (L.) Moench] accession G-118 was found to segregate as a single dominant trait in a cross to susceptible cultivar, HC-136. Molecular marker(s) linked to the locus for disease resistance was identified using simple sequence repeat (SSR) markers coupled with bulk segregant analysis. Genomic DNA from the parental cultivars and bulks were screened by PCR amplification with 50 simple sequence repeat primer pairs. Out of these, 38 SSR primers produced polymorphism between parents. After screening of these 38 SSRs with resistant and susceptible bulk, one SSR primer, Xtxp 309 produced a unique band of approximately 700 bp only in resistant parent and resistant bulk and a unique band of 450 bp only in susceptible parent and susceptible bulk. Upon screening with individual resistant and susceptible recombinant inbred lines (RILs), marker Xtxp 309 produced amplification in 23 of the 26 resistant RILs and no amplification was produced in any of the 25 susceptible RILs. The same marker Xtxp 309 produced amplification in 21 of the susceptible RILs and 3 of the resistant RILs of 450 bp band. This was found to be located at a distance of 3.12 cM away from the locus governing resistance to leaf blight which was considered to be closely linked and 7.95 cM away from the locus governing susceptibility to leaf blight. This marker may prove useful in MAS for gene introgression, plant genetic diagnostics and gene pyramiding for resistance via genetic transformation for disease resistance in plants.