Comparative analysis of infected cassava root transcriptomics reveals candidate genes for root rot disease resistance.

Cassava root-rot incited by soil-borne pathogens is one of the major diseases that reduces root yield. Although the use of resistant cultivars is the most effective method of management, the genetic basis for root-rot resistance remains poorly understood. Therefore, our work analyzed the transcriptome of two contrasting genotypes (BRS Kiriris/resistant and BGM-1345/susceptible) using RNA-Seq to understand the molecular response and identify candidate genes for resistance. Cassava seedlings (resistant and susceptible to root-rot) were both planted in infested and sterilized soil and samples from Initial-time and Final-time periods, pooled. Two controls were used: (i) seedlings collected before planting in infested soil (absolute control) and, (ii) plants grown in sterilized soil (mock treatments). For the differentially expressed genes (DEGs) analysis 23.912 were expressed in the resistant genotype, where 10.307 were differentially expressed in the control treatment, 15 DEGs in the Initial Time-period and 366 DEGs in the Final Time-period. Eighteen candidate genes from the resistant genotype were related to plant defense, such as the MLP-like protein 31 and the peroxidase A2-like gene. This is the first model of resistance at the transcriptional level proposed for the cassava × root-rot pathosystem. Gene validation will contribute to screening for resistance of germplasm, segregating populations and/or use in gene editing in the pursuit to develop most promising cassava clones with resistance to root-rot.

Genome-wide association study and selection for field resistance to cassava root rot disease and productive traits.

Cassava root rot disease is caused by a complex of soil-borne pathogens and has high economic impacts because it directly affects the tuberous roots, which are the main commercial product. This study aimed to evaluate cassava genotypes for resistance to root rot disease in a field with a previous history of high disease incidence. It also aimed to identify possible genomic regions associated with field resistance based on genome-wide association studies. A total of 148 genotypes from Embrapa Mandioca and Fruticultura were evaluated over two years, including improved materials and curated germplasms. Analysis of phenotypic data was conducted, as well as a genomic association analysis, based on the general linear model, mixed linear model, and fixed and random model circulating probability unification. The observed high disease index (ω) was directly correlated with genotype survival, affecting plant height, shoot yield, and fresh root yield. The genotypes were grouped into five clusters, which were classified according to level of root rot resistance (i.e., extremely susceptible, susceptible, moderately susceptible, moderately resistant, and resistant). The 10 genotypes with the best performance in the field were selected as potential progenitors for the development of segregating progenies. Estimates of genomic kinship between these genotypes ranged from -0.183 to 0.671. The genotypes BGM-1171 and BGM-1190 showed the lowest degree of kinship with the other selected sources of resistance. The genotypes BGM-0209, BGM-0398, and BGM-0659 showed negative kinship values with most elite varieties, while BGM-0659 presented negative kinship with all landraces. A genome-wide association analysis detected five significant single nucleotide polymorphisms related to defense mechanisms against biotic and abiotic stresses, with putative association with fresh root yield in soil infested with root rot pathogens. These findings can be utilized to develop molecular selection for root rot resistance in cassava.

Genetic variability in populations of Agave sisalana perrine detected by inter simple sequence repeats / Variabilidade genética em populações de Agave sisalana perrine detectada pela técnica inter simple sequence repeats

The aim this work was to evaluate the genetic variability within and among populations grown on sisal region of Bahia. The genetic diversity of 140 population of sisal was analyzed using ISSR molecular markers. Samples were collected in six counties in Bahia. Eighteen primers of ISSR were used, in which nine of them were effective in the amplification of DNA samples to yield 143 polymorphic loci. The average percentage of polymorphism found in the population was 64%. The average heterozygosis (He) and Shannon-Wiener index (I) were 0.180 and 0.279, respectively. 73% of the molecular variance can be due to intrapopulation differences. The populations were divided into two groups according to their geographical location, showing a structure of genetic variability in space. The GST 0.235, enough to avoid that there is a strong population differentiation. The genetic structure of sisal can be exploited for the creation of gene banks for conservation in situ and ex situ to obtain individuals of good commercial quality. There is genetic variability among sisal genotypes. ISSR molecular markers are efficient to analyze the divergence between sisal genotypes, assisting improvement work.

O objetivo deste trabalho foi avaliar a variabilidade genética existente entre e dentro das populações cultivadas na região sisaleira baiana. A diversidade genética de 140 indivíduos de sisal foi analisada por meio de marcadores moleculares ISSR. As amostras foram coletadas em seis municípios baianos. Utilizando-se dezoito primers de ISSR, dos quais, nove foram eficientes na amplificação do DNA das amostras analisadas, obtendo-se 143 locos polimórficos. O percentual médio de polimorfismo encontrado nas populações foi de 64%. A média de heterozigosidade (He) e do índice de Shannon-Wiener (I) foram de 0,180 e 0,279, respectivamente. 73% da variância molecular pode ser atribuída às diferenças intrapopulacionais. As populações foram divididas em dois grupos, de acordo com sua localização geográfica, evidenciando uma estruturação da variabilidade genética no espaço. O GST de 0,235 foi suficiente para evitar que exista uma forte diferenciação populacional. A estruturação genética do sisal pode ser explorada para a criação de bancos de germoplasma, visando à conservação in situ e ex situ, para a obtenção de indivíduos de boa qualidade comercial. Há presença de variabilidade genética entre os genótipos de sisal. Marcadores moleculares ISSR são eficientes para analisar a divergência entre os acessos de sisal, auxiliando trabalhos de melhoramento.

Fenologia e produtividade do amendoim em diferentes épocas de semeadura no recôncavo sul baiano / Phenology and yield of peanut in different sowing seasons in southern bahia recôncavo

O trabalho foi feito com o objetivo de avaliar a fenologia e a produtividade de duas cultivares de amendoim (Arachis hypogaea L.) em diferentes épocas de semeadura na região do Recôncavo sul Baiano. A primeira época de semeadura foi julho-outubro e a segunda abril-julho. Para cada época, foi instalado um experimento no delineamento em blocos casualizados no esquema fatorial 2 x 2 (cultivares x época) com quatro repetições, em parcelas de 5,0 m de comprimento e largura de 4,0 m, constituídas de oito linhas cada, nas quais foram observados, a cada três dias, os estádios de desenvolvimento das plantas das cultivares Vargem Lisa e BRS Havana. Avaliou-se a fenologia (germinação, aparecimento das primeiras folhas tetrafoliadas, aparecimento dos primeiros ramos, início da floração, aparecimento do ginóforo, início da formação da vagem, final da floração e maturação completa da vagem) e a produtividade de vagens e grãos (kg ha-1). A época de semeadura e a cultivar influenciam diretamente na fenologia das plantas de amendoim. A cultivar Vagem Lisa teve um maior rendimento de vagens e grãos na segunda época de semeadura.

The goal of this research was to assess the phenology and productivity of two peanut cultivars (Arachis hypogaea L.) in different sowing seasons in the region of southern Bahia Recôncavo. The first sowing season was from July to October and the second season from April to July. For each season, an experiment was conducted carried out in randomized block design in a factorial scheme 2 x 2 (cultivars x sowing season) with four replicates. Each in plot was consisted of eight lines with 5.0 m in length and 4.0 m in width. The assessments were done every three days during the plant development stages of Vargem Lisa and BRS Havana cultivars. We evaluated the phenology (germination, emergence of first leaves tetrafoliadas, onset of the first branches, beginning of flowering, emergence of gynophore, beginning of pod formation, ending of flowering and full pod maturity) and yield of pods and grains (kg h-1). The sowing season and cultivar directly influence the peanut phenology. The cultivar Vagem Lisa had a highergreater pod lat and grain yield in the second sowing season planting.

Toxicidade do alumínio e efeito do ácido giberélico em linhas quase isogênicas de trigo com o caráter permanência verde e maturação sincronizada / Aluminum toxicity and effect of giberellic acid on stay-green and synchronized maturation wheat near-isogenic lines

O objetivo deste trabalho foi avaliar linhas quase isogênicas de trigo com o caráter permanência verde e de maturação sincronizada quanto à tolerância ao alumínio e à sensibilidade ao ácido giberélico (AG3). O experimento foi conduzido no Laboratório de Duplo-haplóides e Hidroponia da FAEM/UFPel, em delineamento de blocos ao acaso, com parcelas subdivididas com três repetições, através do teste simultâneo utilizando solução nutritiva com concentrações de 10mg L-1 de Al3+ e 100mg L-1 de AG3. Foram determinados: a inserção da 1ª folha, o comprimento da 1ª folha, a inserção da 2ª folha, comprimento da 2ª folha, diferença da inserção entre a 1ª e 2ª folha, estatura de plântula, estatura de planta, área foliar, área radicular e o crescimento de raiz. Os caracteres estatura da plântula, inserção da 1ª folha e comprimento da 2ª folha foram os mais expressivos para a seleção de indivíduos com estatura reduzida através da reação do AG3. O grupo do caráter permanência verde apresentou maior insensibilidade à ação do AG3, enquanto o grupo de plantas sincronizadas proporcionou maior tolerância ao Al3+. Contudo, existe possibilidade de selecionar linhas quase isogênicas dentro do grupo permanência verde com tolerância ao Al3+ e insensibilidade ao AG3 através da técnica de cultivo hidropônico com solução nutritiva em ambiente controlado.

The objective was to evaluate wheat near-isogenic lines differing from the trait stay-green and synchronized maturation regarding their alluminum tolerance and sensibility to the giberellic acid (GA3). The experiment was conducted in the Double-haploids and Hydroponics Laboratory of FAEM/UFPel, in random block with split plot design with three replications, using the simultaneous test in nutrient solutions with 10mg L-1 of Al3+ and 100mg L-1 of GA3. The following characters were evaluated: insertion of the 1st leaf, length of the 1st leaf, insertion of the 2nd leaf, length of the 2nd leaf, difference between the 1st and 2nd leaf insertion, seedling stature, plant stature, leaf area, root area and root growth. The characters seedling stature, insertion of the 1st leaf and length of the 2nd leaf were the most expressive for the selection of individuals with reduced stature caused by the GA3. The group stay-green presented higher insensibility to GA3 compared to the group of synchronized plants showed larger tolerance to Al3+. However, it is possible to select near-isogenic lines within the stay-green group with Al3+ tolerance using hydroponic culture under controlled environmental conditions.