ABSTRACT. The fungus Pseudocercospora griseola, the causal agent of angular leaf spot in the common bean (Phaseolus vulgaris L.), exhibits a broad pathogenic variability that complicates the development of resistant cultivars. For breeding programs to successfully obtain common bean cultivars with durable resistance, knowing the aggressiveness of different strains, as well as the mechanisms of genetic resistance, is important. The aims of this study were to study the variation within race 63.63 by evaluating the aggressiveness of different strains, to analyze the genetic resistance of common bean lines to P. griseola, and to ascertain the implications for genetic improvement in obtaining resistance in this pathosystem. Four strains, collected from different locations, were inoculated in three groups of common bean lines in a greenhouse, and the severity of the disease was subsequently evaluated. Statistical analyses were carried out using the diallel method, which provided information on the vertical and horizontal resistance of host plants, in addition to information 5045 Variability in strains of Pseudocercospora griseola ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (2): 5044-5053 (2015) regarding the aggressiveness of the strains. The aggressiveness of P. griseola differed between the strains of race 63.63. The diallel method proved to be promising for the identification of horizontal and vertical resistance in the common bean-P. griseola pathosystem, with a predominance of horizontal resistance. Gene pyramiding, using marker-assisted selection, may not be the most effective strategy for obtaining durable resistance.
The aim of this study was to develop a diagrammatic scale to evaluate angular leaf spot (ALS) severity in primary leaves of common bean. A diagrammatic scale was developed and validated with nine levels of severity: 0 %; 0.1 to 0.5 %; 0.6 to 4.0 %; 4.1 to 7.0 %; 7.1 to 16 %; 16.1 to 26 %; 26.1 to 32 %; 32.1 to 38 % and 38.1 to 60 %. The use of this scale, associated with the early inoculation method, allowed rating of ALS severity in common bean leaves in the V2 stage of development that is, when the primary leaves are fully open. Validation of the scale was performed by 14 Evaluators. These Evaluators estimated the severity in 40 common bean leaves with different levels of severity, previously measured by the software Quant®. The accuracy and precision of each Evaluator were determined by simple linear regression, by comparing between actual severity, measured electronically, and that estimated by the Evaluator. Without the scale, most of the Evaluators overestimated the severity of the disease. With the scale, the Evaluators obtained better levels of accuracy and precision, with absolute errors less than 5 %. The diagrammatic scale proposed proved to be adequate for early performance of the pathogenicity test.
A common bean (Phaseolus vulgaris L.) breeding program for resistance to Pseudocercospora griseola (Sacc.) Crous & U. Braun (angular leaf spot) using recurrent selection has been conducted since 1998 in Brazil. The selection has been carried out in the field with high natural occurrence of the pathogen. One recurrent selection cycle has been conducted per year. The efficiency of artificial inoculation of P. griseola and early assessment of angular leaf spot severity in common bean progenies of this program were evaluated. For this, 254 and 166 S 0:1 progenies from Cycles XVI and XVIII, respectively, were assessed for angular leaf spot severity in field, with natural occurrence of the pathogen and in greenhouse with artificial inoculation of P. griseola. Most progenies showed a high level of resistance to angular leaf spot, indicating the efficiency of recurrent selection. Artificial inoculation of P. griseola in the greenhouse showed promise for the selection of resistant plants in a recurrent selection program allowing breeders to carry out two cycles per year. A scheme was proposed that combined the advantages of early-generation selection with artificial inoculation of the pathogen in greenhouse with the advantages of selection in field with natural occurrence of P. griseola in the dry season, increasing genetic gain per unit time.
The objective of this study was to examine the molecular and phenotypic variability of 'Prata Anã' banana clones cultivated in northern Minas Gerais State. For the phenotypic and molecular characterization, the clones were collected from five properties. The morphological characterization of 20 clones was accomplished through a qualitative evaluation of 74 descriptors. For the molecular evaluations, 45 clones were collected, and 14 Random Amplified Polymorphic DNA primers were used. Among the 74 morphological descriptors evaluated in the 20 'Prata Anã' banana tree clones, 53 descriptors presented in the same homogeneous class for all clones. The presence of anthocyanin in the pseudostem (ANT) and the shape (BUS) and flexion (FLX) of the bunch clearly differentiated the 'Prata Anã' banana clones from the commercial cultivar. A total of 176 bands were produced from the molecular analysis using the 14 RAPD primers; there were 116 monomorphic and 60 polymorphic bands, with an average polymorphism percentage of 52.2%. The amplification using the OPP 14 primer resulted in the greatest percentage of polymorphic bands at 88%. The dendrogram indicated that each of the 45 'Prata Anã' clones that were evaluated using RAPD markers clustered with the commercial 'Prata Anã' cultivar.Key words: Musa spp., morphological variation, diversity, clonal population, RAPD.Variabilidade genética em clones de bananeira 'Prata Anã' por meio de marcadores fenotípico e molecular Resumo O objetivo do presente estudo foi avaliar a variabilidade fenotípica e molecular de clones de bananeira 'Prata Anã' cultivados no Norte de Minas Gerais. Os clones foram coletados em cinco propriedades. A caracterização morfológica de 20 clones foi realizada por meio da avaliação qualitativa de 74 descritores. Para a avaliação molecular, 45 clones foram coletados e 14 primers RAPD foram utilizados. Dentre os 74 descritores morfológicos avaliados nos 20 clones de bananeira 'Prata Anã', 53 descritores tinham a mesma classe, sendo homogêneos para todos os clones. Dentre os descritores avaliados, a presença de antocianina no pseudocaule (ANT), a forma do cacho (FCA) e a flexão das pencas (FLX) diferenciaram de maneira clara os clones de 'Prata Anã' da cultivar comercial. Por meio da amplificação de 14 iniciadores RAPD foram produzidos o total de 176 bandas, sendo116 monomórficas e 60 polimórficas, média de 52,2% de polimorfismo. O primer OPP14 produziu a maior porcentagem de bandas polimórficas, 88%. Pelo dendrograma observou-se que todos os 45 clones avaliados por meio do uso dos marcadores RAPD agruparam com a cultivar 'Prata Anã'.Palavras-chave: Musa spp., variação morfológica, diversidade, população clonal, RAPD.
The purpose of this work was to identify hybrids in intraspecific crosses between sugar apple accessions and interspecific crosses between sugar apple and atemoya accessions by using RAPD markers. Four sugar apple accessions were selected: Seedless P 1 , P 2 , P 3 and P 4 and the atemoya cultivar Gefner (G1). In the pre-female phase the flowers were adequately protected and reciprocal crosses were performed. In crosses where the sugar apple accession Seedless P 1 was used as the male parent, the fruits contained seeds, indicating that the pollen grains of Seedless P 1 are viable. The fruits of reciprocal crosses where Seedless P 1 was used as a female parent contained no seeds. The percentage of true hybrids in the crosses P 4
Diversidade genética de 20 clones de 'Prata-Anã Gorutuba', quatro clones de 'Prata-Rio', quatro clones de 'Prata-Catarina' e as cultivares Caipira, Thap Maeo, Tropical, Maçã e Prata-Anã Comum foi avaliada por meio de marcadores moleculares Simple Sequence Repeats. De um total de 19 pares de primers SSRs utilizados, 57,8% deles amplificaram bandas polimórficas e distintas, 26,3% não produziram produtos específicos e 15,7% apresentaram falhas na amplificação de alguns indivíduos. O dendrograma indicou a formação de dois grupos. O primeiro grupo com a cultivar triploide Caipira, genoma exclusivamente A; enquanto o segundo (formado por sete subgrupos) agrupou todas as cultivares resultantes da hibridação natural ou artificial entre Musa acuminata e M. balbisiana, o subgrupo II, Tropical (AAAB) e o subgrupo III, Maçã (AAB). Os subgrupos IV, V, VI e VII foram formados, respectivamente, por: 'Prata-Catarina' clones 1 e 2; 'Prata-Rio' clones 1 e 2; 'Prata-Catarina' clone 3; 'Prata-Gorutuba' clones 12 e 17, 'Prata-Catarina' clone 4, 'Prata-Rio' clone 4, 'Thap Maeo' e 'Prata-Anã'. O subgrupo VIII foi formado exclusivamente pelos clones de' Prata-Anã Gorutuba'. Os resultados indicam a eficiência dos marcadores microssatélites na discriminação e na caracterização dos clones da 'Prata-Anã Gorutuba' da cultivar Prata-Anã.
The expression of HaHB4 ® transcription factor reduces soybean sensitivity to abiotic stresses, such as water deficit. Studies that quantify the tolerance of HaHB4 ® soybean to the soil water content in comparison with cultivars currently sown in Brazil are lacking.The objective of this study was to determine the level of drought tolerance of soybean genotypes expressing the HaHB4 ® transcription factor (TS18-6-610108 and TS18-6-610084) and commercial cultivars (TMG 7063 IPRO and BS IRGA 1642 IPRO) subjected to water deficit during the vegetative phase. We used the fraction of transpirable soil water (FTSW) approach. Parameters related to leaf transpiration, dry matter accumulation, water use efficiency (WUE), and transpiration coefficient (TC) were evaluated in the four soybean genotypes and two treatments (T1-100% replacement of transpired water and T2-without replacement of transpired water). The FTSW threshold for the decline in transpiration was evaluated to identify the onset of water stress in soybean. TS18-6-610108 and BS IRGA 1642 IPRO maintains potential transpiration at low FTSW values. The TS18-6-610108 genotype has 14% higher WUE than the sensitive cultivar under water deficit. Under well-irrigated conditions, the HaHB4 ® genotypes showed the highest TC values, which indicate well-functioning physiological processes.
Angular leaf spot (ALS), a typical disease in common beans (Phaseolus vulgaris), is caused by the fungus Pseudocercospora griseola (Singh & Schwartz, 2010). Conidia are mainly spread by wind; however, water droplets, agricultural implements and contaminated seeds also facilitate pathogen transmission. The optimum conditions for infection include humidity and a temperature of 24°C. The conidia can germinate in about 3 h, penetrating the leaves through the stomata within 2 days. The whole tissue is colonized by the pathogen after 3-7 days and lesions can be observed 8-15 days after infection. Symptoms of ALS appear primarily on leaves and pods (Liebenberg & Pretorius, 1997). The lesions may coalesce, causing premature defoliation that compromises pod
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