The most important disease of Coffea arabica is coffee leaf rust caused by the fungus Hemileia vastatrix. The purpose of this study was to characterize the inheritance of coffee resistance gene(s) to race II of this pathogen and to identify and map molecular markers linked to this trait. Different populations were used: F 2 (160 plants), BCr (20), and BCs (135), derived from a cross between the resistant genotype Híbrido de Timor UFV 427-15 and the susceptible cultivar Catuaí Amarelo UFV 2143-236 (IAC 30). The segregation analysis showed that the resistance of Híbrido de Timor to race II of the H. vastatrix is conferred by a single dominant gene. The amplification of 176 AFLP (Amplified fragment length polymorphism) primer combinations using bulked segregant analysis (BSA) allowed the identification of three molecular markers linked to the resistance gene. Genetic mapping of these three markers in the F 2 population indicated that they are distributed on both sides, flanking the resistance gene. The markers E.CTC/M.TTT405 and E.CGT/M.TGT 300 were found linked to the resistance gene at 8.69 cM (LOD 18.91) and 25.10 cM (LOD 5.37), respectively, while E.CCT/M.TTC230 was localized on the other side of the gene, at 20.50 cM (LOD 6.15). These markers are the first rust resistance markers identified in Híbrido de Timor and can be useful for marker assisted selection in coffee breeding programs.
Pasture is the main food source for more than 200 million cattle heads in Brazil. Although Brazilian forage breeding programs have successfully released well-adapted, high-yielding cultivars over the years, the use of genomic tools in these programs is currently limited. These tools are required to tackle the main challenges for tropical forage breeding in Brazil. In this context, this note lists the main research priorities raised at the workshop "Breeding Forages in the Genomic Era", which are necessary to accelerate the use of genomic tools for next-generation breeding of tropical forages and allow breeders to increase genetic gains. Additionally, an online discussion forum (hosted at http://www. cnpgl.embrapa.br/genfor) has been launched to strengthen collaborations among research groups. The research priorities and more synergistic collaborations will assist researchers and decision-makers in delivering a sustainable increase in production of animal products, especially beef and milk, which are required to feed a rising world population.
Coffee leaf rust caused by the fungus Hemileia vastatrix causes considerable economic losses for coffee producers. Although agrochemical products can provide sufficient disease control, the use of resistant cultivars is a safer alternative. This resistance may be constrained by one or a few genetic factors, mainly those found in material originating from interspecific hybrids. In this study, the genetic analysis of an F 2 population consisting of 224 plants derived from a crossing of Híbrido de Timor UFV 427-15 (resistant) with Catuaí Amarelo IAC 30 (susceptible) showed that a dominant gene confers the resistance of coffee to race II of H. vastatrix. From a genetic map saturated with 25 amplified fragment length polymorphism (AFLP) markers linked to the resistance gene, we developed a high-density genetic map with six sequence-characterized amplified region (SCAR) markers delimiting a chromosomal region of 9.45 cM and flanking the dominant gene at 0.7 and 0.9 cM. This is the first saturated and high-density genetic map obtained from this region containing the resistance gene. The results of this study are of great importance for the introduction of molecular markers for marker-assisted selection; they will also facilitate studies related to the cloning, structure, and function of race-specific genes involved in the resistance of coffee trees to H. vastatrix.
ABSTRACT. The objective of this study was to identify physiological traits that could distinguish between cotton genotypes that were tolerant or sensitive to water deficits. The experiment was conducted in a completely randomized design through a factorial combination to analyze four genotypes (BRS 187 8H and ACALA SJ-4 -water deficit tolerant; CNPA 7H and SU-0450/8909 -water deficit sensitive) and two water regimes (watered/always irrigated and stressed/with a water deficit imposed at flowering). Irrigation was suspended for the plants in the water deficit treatment groups when their first flowers appeared. Leaf water potential (ψpd) was monitored until the plants reached -3.0 MPa predawn, at which point leaf samples were collected for analysis. The plants were reirrigated and monitored for a recovery to 50% of leaf water potential. The maximum photochemical efficiency (Fv/Fm), chlorophyll content (SPAD index), relative water content (RWC), disruption of the cell membrane via membrane leakage, carbon isotope composition (δ 13 C), seed cotton yield and fiber quality were evaluated. The trends in membrane leakage and carbon isotope composition were different between the tolerant and sensitive genotypes under a water deficit, which makes these physiological traits suitable for screening for tolerance to water deficits in cotton.Keywords: abiotic stress, Gossypium, water deficit.RESUMO. Traços fisiológicos para fenotipagem de algodoeiro sob seca. Objetivou-se identificar variáveis fisiológicas para distinguir genótipos de algodoeiro tolerantes e sensíveis ao déficit hídrico. O experimento foi conduzido no delineamento inteiramente casualizado em arranjo fatorial, sendo testados quatro genótipos (BRS 187 8H e ACALA SJ-4 -tolerante ao déficit hídrico; CNPA 7H e SU-0450/8909 -sensíveis ao déficit hídrico) e dois regimes hídricos (controle -sempre irrigado e com déficit hídrico imposto na emissão da primeira flor. Na emissão da primeira flor, a irrigação foi suspensa para o grupo a ser submetido ao déficit hídrico. O potencial hídrico foliar foi monitorado na antemanhã até que as plantas dos cultivares em estudo atingissem -3,0 MPa, ponto no qual coletaram-se amostras foliares para análises fisiológicas. Após, irrigou-se as plantas até a obtenção de valor superior a 50% do potencial hídrico foliar (-1,50 MPa). Avaliaram-se a eficiência fotoquímica máxima (Fv/Fm), o conteúdo de clorofila via índice SPAD, o conteúdo relativo de água (CRA), o extravasamento de eletrólitos, a composição isotópica do carbono (δ 13 C), o rendimento de algodão em caroço por planta e a qualidade da fibra. A disruptura de membrana via extravasamento de eletrólitos e a δ 13 C apresentaram-se como potenciais indicadores fisiológicos visando a seleção de genótipos de algodoeiro tolerantes ao déficit hídrico.Palavras-chave: estresse abiótico, Gossypium, déficit hídrico.
BackgroundDrought is by far the most important environmental factor contributing to yield losses in crops, including soybeans [Glycine max (L.) Merr.]. To address this problem, a gene that encodes an osmotin-like protein isolated from Solanum nigrum var. americanum (SnOLP) driven by the UBQ3 promoter from Arabidopsis thaliana was transferred into the soybean genome by particle bombardment.ResultsTwo independently transformed soybean lines expressing SnOLP were produced. Segregation analyses indicated single-locus insertions for both lines. qPCR analysis suggested a single insertion of SnOLP in the genomes of both transgenic lines, but one copy of the hpt gene was inserted in the first line and two in the second line. Transgenic plants exhibited no remarkable phenotypic alterations in the seven analyzed generations. When subjected to water deficit, transgenic plants performed better than the control ones. Leaf physiological measurements revealed that transgenic soybean plants maintained higher leaf water potential at predawn, higher net CO2 assimilation rate, higher stomatal conductance and higher transpiration rate than non-transgenic plants. Grain production and 100-grain weight were affected by water supply. Decrease in grain productivity and 100-grain weight were observed for both transgenic and non-transgenic plants under water deficit; however, it was more pronounced for non-transgenic plants. Moreover, transgenic lines showed significantly higher 100-grain weight than non-transgenic plants under water shortage.ConclusionsThis is the first report showing that expression of SnOLP in transgenic soybeans improved physiological responses and yield components of plants when subjected to water deficit, highlighting the potential of this gene for biotechnological applications.
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