Usefulness of temperate-adapted maize lines developed by doubled haploid and single-seed descent methods.

KEY MESSAGE: Spontaneous haploid genome doubling is not associated with undesirable linkage drag effects. The presence of spontaneous doubling genes allows maximum exploitation of variability from the temperate-adapted BS39 population Tropical non-elite maize (Zea mays L.) germplasm, such as BS39, provides a unique opportunity for broadening the genetic base of U.S. Corn Belt germplasm. In vivo doubled haploid (DH) technology has been used to efficiently exploit non-elite germplasm. It can help to purge deleterious recessive alleles. The objectives of this study were to determine the usefulness of BS39-derived inbred lines using both SSD and DH methods, to determine the impact of spontaneous as compared with artificial haploid genome doubling on genetic variance among BS39-derived DH lines, and to identify SNP markers associated with agronomic traits among BS39 inbreds monitored at testcross level. We developed two sets of inbred lines directly from BS39 by DH and SSD methods, named BS39_DH and BS39_SSD. Additionally, two sets were derived from a cross between BS39 and A427 (SHGD donor) by DH and SSD methods, named BS39 × A427_DH and BS39 × A427_SSD, respectively. Grain yield, moisture, plant height, ear height, stalk lodging, and root lodging were measured to estimate genetic parameters. For genome-wide association analysis, inbred lines were genotyped using genotype-by-sequencing and Diversity Array Technology Sequencing (DArTSeq). Some BS39-derived inbred lines performed better than elite germplasm inbreds and all sets showed significant genetic variance. The presence of spontaneous haploid genome doubling genes did not affect performance of inbred lines. Five SNPs were significant and three of them located within genes related to plant development or abiotic stresses. These results demonstrate the potential of BS39 to add novel alleles to temperate elite germplasm.

A novel triple amino acid substitution in the EPSPS found in a high-level glyphosate-resistant Amaranthus hybridus population from Argentina.

BACKGROUND: The evolution of herbicide-resistant weeds is one of the most important concerns of global agriculture. Amaranthus hybridus L. is a competitive weed for summer crops in South America. In this article, we intend to unravel the molecular mechanisms by which an A. hybridus population from Argentina has become resistant to extraordinarily high levels of glyphosate. RESULTS: The glyphosate-resistant population (A) exhibited particularly high parameters of resistance (GR50 = 20 900 g ai ha-1 , Rf = 314), with all plants completing a normal life cycle even after 32X dose application. No shikimic acid accumulation was detected in the resistant plants at any of the glyphosate concentrations tested. Molecular and genetic analyses revealed a novel triple substitution (TAP-IVS: T102I, A103V, and P106S) in the 5-enol-pyruvylshikimate-3-phosphate synthase (EPSPS) enzyme of population A and an incipient increase on the epsps relative copy number but without effects on the epsps transcription levels. The novel mechanism was prevalent, with 48% and 52% of the individuals being homozygous and heterozygous for the triple substitution, respectively. In silico conformational studies revealed that TAP-IVS triple substitution would generate an EPSPS with a functional active site but with an increased restriction to glyphosate binding. CONCLUSION: The prevalence of the TAP-IVS triple substitution as the sole mechanism detected in the highly glyphosate resistant population suggests the evolution of a new glyphosate resistance mechanism arising in A. hybridus. This is the first report of a naturally occurring EPSPS triple substitution and the first glyphosate target-site resistance mechanism described in A. hybridus. © 2018 Society of Chemical Industry.

Herdabilidades e correlações entre caracteres de linhagens de feijão obtidas em monocultivo e em consórcio com o milho

Hybrids from 'Ouro 1919' x 'Ouro Negro 1992', 'Ouro 1919' x Raça D and 'Ouro 1919' x Phaseolus aborigineus 283, beans were obtained to study heritability and genetic correlations between some yield responses, in two crop systems namely monocropping and intercropping with maize during both dry and rainy seasons. All estimates were obtained through field data of F1, F2 and F3 populations as well as those of their original parents. Main populations were defined by the Single Seed Descent (SSD) method. Heritabilities estimated under intercropping conditions were often higher than those under monocropping system. Among all studied responses the highest heritabilities corresponded to the number of legumes per plant. Genetic correlation coefficients within systems suggest that the selection procedure should mainly consider the number of legumes per plant when selecting under monocropping system aiming further intercropping use.

Foram realizados os cruzamentos entre 'Ouro 1919' x 'Ouro Negro 1992', 'Ouro 1919' x Raça D e 'Ouro 1919' x Phaseolus aborigineus 283, com o objetivo de estimar as herdabilidades, no sentido amplo e as correlações fenotípica e genotípica da produtividade de grãos e seus componentes de rendimento, nos sistemas de monocultivo e de consórcio com a cultura do milho nas épocas de semeadura das "águas" e da "seca'. Para obtenção dessas estimativas, utilizaram-se, no ensaio de campo, as populações, F1, F2 e F3 e seus genitores. As populações segregantes foram conduzidas pelo método de melhoramento "Single Seed Descent" (SSD). De modo geral, os coeficientes de herdabilidade foram maiores no sistema de consórcio do que no monocultivo. Entre os caracteres estudados, as maiores herdabilidades foram, de modo geral, obtidas para o número de vagens por planta. Os coeficientes de correlação entre os caracteres avaliados, em cada sistema de cultivo, mostraram que, no caso de seleção no monocultivo visando semeadura no consórcio, o número de vagens por planta é o caráter com maior potencial a ser utilizado no processo seletivo.

Herdabilidades e correlações entre caracteres de linhagens de feijão obtidas em monocultivo e em consórcio com o milho

Hybrids from 'Ouro 1919' x 'Ouro Negro 1992', 'Ouro 1919' x Raça D and 'Ouro 1919' x Phaseolus aborigineus 283, beans were obtained to study heritability and genetic correlations between some yield responses, in two crop systems namely monocropping and intercropping with maize during both dry and rainy seasons. All estimates were obtained through field data of F1, F2 and F3 populations as well as those of their original parents. Main populations were defined by the Single Seed Descent (SSD) method. Heritabilities estimated under intercropping conditions were often higher than those under monocropping system. Among all studied responses the highest heritabilities corresponded to the number of legumes per plant. Genetic correlation coefficients within systems suggest that the selection procedure should mainly consider the number of legumes per plant when selecting under monocropping system aiming further intercropping use.

Foram realizados os cruzamentos entre 'Ouro 1919' x 'Ouro Negro 1992', 'Ouro 1919' x Raça D e 'Ouro 1919' x Phaseolus aborigineus 283, com o objetivo de estimar as herdabilidades, no sentido amplo e as correlações fenotípica e genotípica da produtividade de grãos e seus componentes de rendimento, nos sistemas de monocultivo e de consórcio com a cultura do milho nas épocas de semeadura das "águas" e da "seca'. Para obtenção dessas estimativas, utilizaram-se, no ensaio de campo, as populações, F1, F2 e F3 e seus genitores. As populações segregantes foram conduzidas pelo método de melhoramento "Single Seed Descent" (SSD). De modo geral, os coeficientes de herdabilidade foram maiores no sistema de consórcio do que no monocultivo. Entre os caracteres estudados, as maiores herdabilidades foram, de modo geral, obtidas para o número de vagens por planta. Os coeficientes de correlação entre os caracteres avaliados, em cada sistema de cultivo, mostraram que, no caso de seleção no monocultivo visando semeadura no consórcio, o número de vagens por planta é o caráter com maior potencial a ser utilizado no processo seletivo.