Ouro Negro Research Articles

Host Suitability of Lettuce and Bean Germplasm for Meloidogyne incognita and M. javanica Isolates from Spain.

Meloidogyne spp. are an important threat to horticulture and cause substantial yield losses. Plant resistance is an alternative control method for chemical nematicides. This study highlights the host suitability of the lettuces cultivars Grand Rapids and Salinas 88 and the beans cultivars Aporé, Cornell 49242, Macarrão Atibaia and Ouro Negro to four Meloidogyne incognita and seven M. javanica isolates from Spain in a pot experiment. Moreover, the response of these cultivars to increasing M. incognita densities (Pi) was assessed in a plastic greenhouse. The lettuce cultivar Regina 71 and the bean cultivar Bolinha were included as susceptible standards for comparison. It was found that Grand Rapids and Salinas 88 lettuces were resistant to the most nematode isolates in the pot experiment but were classified as slightly and moderately resistant, respectively, in the plastic greenhouse at increasing Pi. Regarding the beans, Aporé was resistant to the majority of the Meloidogyne isolates whereas Macarrão Atibaia and Ouro Negro were slightly resistant and Cornell 49242 was susceptible in the pot experiment. In the plastic greenhouse, Aporé was the only cultivar able to effectively suppress the nematode reproduction irrespective of Pi, while Ouro Negro became less resistant as Pi increased. These results play an important role in enhancing the effective and ecofriendly Meloidogyne management strategies.

Asymbiotic germination, initial development in vitro and acclimatization of Cyrtopodium paludicolum Hoehne, a Brazilian Savanna orchid species

Abstract Cyrtopodium paludicolum is a terrestrial orchid species, native to Brazil, whose natural propagation is jeopardized by the intensive collection from the wild and is threatened by agricultural expansion in Cerrado areas. In light of that, this investigation aimed at studying the in vitro germination and early development of C. paludicolum as influenced by culture medium, sucrose and growth regulators as well as its micropropagation by using dark-grown stem segments. A protocol for its acclimatization is also detailed. The effects of Murashige & Skoog (MS), Knudson C (KC) and Vacin & Went (VW) media on the in vitro germination and initial development were tested. The influence of different concentrations of BA, NAA, and of sucrose on plant multiplication and growth were evaluated. The possibility of using etiolated stem segments for micropropagation was also assessed. Acclimatization was accomplished in two phases by using three different substrates. The results showed that VW was the best medium for germination whereas for seedling formation KC was the most advantageous since they were healthy and vigorous. Sucrose at 2% favored the greatest seedling growth and development. Shoot and root proliferation and development were best promoted in the presence of 2.28/2.28 and 0.57/0.57 µM BA/NAA, respectively. The use of etiolated stem segments for micropropagation was effective. Successful acclimatization was accomplished by initially growing plants in community pots containing a 3:1 (v/v) mix of Bioplant and dried Sphagnum moss followed by their transfer to individual pots containing a 2:1 (v/v) mix of Bioplant and Ouro Negro substrates.

Resistência de linhagens de feijoeiro-comum a isolados de Sclerotinia sclerotiorum em diferentes condições ambientais

Abstract The objective of this work was to evaluate the reaction of common bean (Phaseolus vulgaris) lines to Sclerotinia sclerotiorum, the aggressiveness of the isolates, and the inheritance of resistance to white mold, under two environmental conditions. The experiments were carried out under field and greenhouse conditions. In each one, four isolates were inoculated in 14 common bean lines using the straw-test inoculation method and severity on plants. No common bean line with a high level of resistance to white mold was identified, and most of the lines were moderately resistant to the pathogen. In general, the BRS Campeiro, BRS Radiante, BRSMG Talismã, and Ouro Negro cultivars stand out for resistance. Under field conditions, the UFLA 3 isolate discriminates well the lines, while, under greenhouse conditions, UFLA 26 and UFLA 92 are the most aggressive isolates. Furthermore, according to the genetic study, most of the observed variation can be attributed to horizontal resistance, although a small part is associated with vertical resistance.

Agronomic performance of common bean crops fertigated with treated sewage and mineral fertilizer

ABSTRACT The water deficit in arid and semiarid regions and the high cost of fertilizers are factors for the study of application of sewage on agricultural crops. Therefore, the objective of this study was to evaluate the effect of application of different doses of treated sewage from the tertiary treatment (TS-3), and mineral fertilizer on the yield and production components of common bean plants. The experiment was conducted in Janaúba, MG, Brazil, using a randomized block design, with four repetitions, in a split-plot scheme, with five treatments in the plots consisting of potassium (K2O) applications at the dose required by common bean plants via clear water + 40 kg ha-1 of K2O mineral (Control), and TS-3 applications supplying 20, 40, 60 and 80 kg ha-1 of K2O, and two cultivars in the subplots, BRS-MG-Madreperola and Ouro Negro. The cultivar Ouro Negro was more responsive than the cultivar BRS-MG-Madreperola to the different TS-3 doses and mineral fertilizer regarding their leaf, stem, and shoot dry weights, and their ratios. However, the highest doses of K2O via TS-3 affected negatively the grain yield in common bean plants. The dose of 20 kg ha-1 of K2O via TS-3 is the best dose for common bean plants.

Physiological and antioxidant insights into common bean resistance to common bacterial blight

Common bacterial blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli (Xap) (known also as X. campestris pv. phaseoli and its variant Xap var. fuscans (Xapf)), is the most important bacterial disease of common bean worldwide. Information regarding Xap-common bean interaction and the mechanisms of host resistance involved needs to be elucidated. In the present study, we investigated physiological and biochemical responses in a susceptible (Ouro Negro) and a resistant (Diamante Negro) cultivar of common bean to CBB. To this end, analyses of gas exchange and chlorophyll (Chl) a fluorescence, activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX)) as well as concentrations of photosynthetic pigments, hydrogen peroxide (H2O2), and malondialdehyde (MDA) were performed in cotyledonary leaves that were either infiltrated with a saline solution (control) or with a Xapf suspension. The CBB severity and lesion area were lower in plants from the resistant cultivar than in plants from the susceptible cultivar. The Xapf infection reduced gas exchange parameters and concentration of photosynthetic pigments but such decreases were significantly higher for the susceptible cultivar than for the resistant cultivar. Higher SOD, POX, and APX activities were recorded in the Xapf-infiltrated cotyledonary leaves than in control but greater activities occurred for the resistant cultivar than for the susceptible cultivar. The Xapf-infiltrated cotyledonary leaves, particularly those of the susceptible cultivar, displayed higher concentrations of H2O2 and MDA than plants from the control treatment. Images of Chl a fluorescence showed that changes stemmed from Xapf infection were evident as early as 6 h after inoculation and became more expressive as CBB progressed, mainly for the susceptible cultivar. Area under the curve of Chl a fluorescence parameters was lower for inoculated plants than for plants from the control treatment but it was higher for the susceptible cultivar than for the resistant cultivar. Results of the present study suggest that the antioxidant system played a major role in common bean resistance to CBB limiting Xapf-triggered generation of reactive oxygen species, cellular damage as well as photosynthetic and photochemical dysfunctions.

Technological quality of grain of common bean genotypes of the black commercial class

The technological quality from grains of bean should be evaluated in trials of elite lines to complement the agronomic performance evaluation, ensure the selection and recommendation of new cultivars, and guarantee its greater acceptance by the consumer market. Thus, this study aimed to evaluate the technological quality from selected genotypes of black bean grains. We used 12 elite lines and 4 cultivars from commercial black group constituents of the Value for Cultivation and Use (VCU). The trial was carried out on the Experimental Farm of Federal University of Vicosa-MG, in Coimbra County, in the 2012 crops of autumn/winter seasons. The experimental design was in randomized block, with three replications. The evaluated characteristics were shape, degree of flattening, thousand grains weight, hard-to-cook grains percentage, cooking time, husk percentage and the hydration capacity of the grains. The lines VP 24, VP 25 and VP 29 present the medium level of resistance to cooking similar to the cultivars (controls), and the other evaluated lines have normal resistance to bean cooking. The genotypes CNFP 11977, VP 29 and ‘Ouro Negro’ attain, in shorter time, 50% of the maximum hydration capacity of the grains, and resistance between normal and medium for cooking time. The lines VP 29 and CNFP 11977 also obtained the greatest hydration capacity for most evaluated times. The lines VP 26, VP 29, CNFP 11992, VP 27, VP 28, and CNFP 11977 present the best characteristics associated with technological quality of grains.

The intensity of and recovery from photoinhibition under drought in a thermotolerant common bean compared to drought tolerant genotypes

The chlorophyll a fluorescence parameters of four Phaseolus vulgaris L. genotypes were evaluated under drought in two greenhouse experiments. Under severe water stress, the thermotolerant genotype 'Diplomata' maintained significantly higher values of predawn leaf water potential (Ψw), maximum Fv/Fm and effective (ΦPSII) quantum yield of photosystem II , and non-photochemical quenching than 'Ouro Negro', in the first experiment, and 'A 285' and 'A 222', in the second one. Among these parameters, Fv/Fm showed more differences that discriminated between the genotype responses even when measured at night. Next, a difference between Fv/Fm after sundown and Fv/Fm at dawn on the same day (day ∆Fv/Fm), i.e., the intensity of photoinhibition, and a difference between Fv/Fm at dawn and Fv/Fm after sundown on the day before (night ∆Fv/Fm), i.e. the photoinhibition recovery, were evaluated. Day ∆Fv/Fm and night ∆Fv/Fm were significantly higher for 'Diplomata' under severe water stress in both experiments. In addition, 'Ouro Negro' in the first experiment and all the genotypes in the second showed negative values of night ∆Fv/Fm on the last day of drought when their Ψw were also minimal indicating no recovery from photoinhibition and the need for rehydration. At maturation, stressed plants of 'Diplomata' showed a significantly higher yield than 'Ouro Negro' in the first experiment and the same as 'A 285' in the second. Therefore, the thermotolerant genotype 'Diplomata' also showed drought tolerance, and the use of day ∆Fv/Fm and night ∆Fv/Fm fluorescence analysis was able to discriminate between the tolerances of these genotypes and to indicate the need for rehydration.

Identification of resistance sources of common bean (Phaseolus vulgaris L.) to angular leaf spot (Pseudocercospora griseola)

Common bean (Phaseolus vulgaris L.) is the most important edible legume in the world and is an important source of income for farmers and food for millions of families. Angular Leaf Spot (ALS), caused by the fungus Pseudocercospora griseola (Sacc.) Ferraris, is one of the most important diseases in the production of common bean with the potential to cause significant seed yield losses. An effective and environmentally friendly alternative to control this disease is the use of improved varieties that combine resistance genes of Andean and Mesoamerican origin. In this study, the response of 181 bean genotypes (coming from different breeding programs of several countries including the USA, Puerto Rico, Honduras, Ecuador, Colombia, Tanzania, Malawi, and Angola) to two angular spot isolates (races 61:11 and 63:51, prevalent in Isabela and Juana Díaz, Puerto Rico) were evaluated. Many of these genotypes contained resistant genes to different biotic and to abiotic stress. A total of 16 lines were identified to have resistance to both races. The resistant lines include the Andean breeding lines CAL 143, 277 and the Mesoamerican cultivar ‘Ouro Negro’ that possess the resistance genes Phg-5, Phg-1, Phg-3, respectively. This information can help common bean breeding programs to pyramid genes from the Andean and Mesoamerican gene pools to generate varieties with long-lasting resistance to this disease.

Narrative Persuasion and Social Norms in Entertainment-Education: Results from a Radio Drama in Mozambique

ABSTRACT Narrative persuasion and social norms are part of the most recent theorizing behind the health communication strategy known as entertainment-education. There is little research, however, that compares these theoretical constructs from Mozambique, a setting that has not been researched to the same extent as other EE practice locations. This study uses mixed methods data from the midline evaluation of Ouro Negro (English translation: Black Gold), an EE radio program for individual health and social change in Mozambique to answer two research questions: what is the relationship between exposure to Ouro Negro and narrative persuasion?, and what is the relationship between narrative persuasion with Ouro Negro and social norms? Quantitative results related to the first question indicated that exposure significantly predicted three narrative persuasion constructs in multivariate regression models, results confirmed by a storytelling activity in focus groups. Quantitative results for the second question, which utilized propensity score matching, were not significant, and findings from a qualitative 2 × 2 table activity confirmed that behaviors were not normative in the directions promoted by the radio drama. Implications and recommendations for future entertainment-education research are discussed.

Sowing time and physiological potential of bean seeds of different growth types

This work was carried out in order to evaluate the physiological quality of common bean seeds of different types of growth, according to the sowing seasons. The treatments were arranged in 2 x 4 factorial scheme, involving two sowing seasons (dry and winter) and four genotypes (Ouro Vermelho, Ouro Negro, BRSMG Madrepérola e Manteigão Vermelho), in randomized blocks design . The seeds were initially evaluated as for water content, thousand seeds weight and physiological potential by the germination and vigor tests (first germination count, plantlets emergence in sand, emergence speed Index and electrical conductivity). The seeds of the prostrate genotypes, with type of growth III (Ouro Negro and BRSMG Madrepérola) or semi-prostate with type of growth II/III (Ouro Vermelho) present better physiological potential, regardless of the sowing season. In the crop of Summer/autumn, the sowing of bean is more suitable for producing seeds with high physiological quality in the conditions of cultivation of the north of Minas Gerais.

High-resolution mapping reveals linkage between genes in common bean cultivar Ouro Negro conferring resistance to the rust, anthracnose, and angular leaf spot diseases.

Co-segregation analysis and high-throughput genotyping using SNP, SSR, and KASP markers demonstrated genetic linkage between Ur-14 and Co-3 4 /Phg-3 loci conferring resistance to the rust, anthracnose and angular leaf spot diseases of common bean. Rust, anthracnose, and angular leaf spot are major diseases of common bean in the Americas and Africa. The cultivar Ouro Negro has the Ur-14 gene that confers broad spectrum resistance to rust and the gene cluster Co-3 4 /Phg-3 containing two tightly linked genes conferring resistance to anthracnose and angular leaf spot, respectively. We used co-segregation analysis and high-throughput genotyping of 179 F2:3 families from the Rudá (susceptible)×Ouro Negro (resistant) cross-phenotyped separately with races of the rust and anthracnose pathogens. The results confirmed that Ur-14 and Co-3 4 /Phg-3 cluster in Ouro Negro conferred resistance to rust and anthracnose, respectively, and that Ur-14 and the Co-3 4 /Phg-3 cluster were closely linked. Genotyping the F2:3 families, first with 5398 SNPs on the Illumina BeadChip BARCBEAN6K_3 and with 15 SSR, and eight KASP markers, specifically designed for the candidate region containing Ur-14 and Co-3 4 /Phg-3, permitted the creation of a high-resolution genetic linkage map which revealed that Ur-14 was positioned at 2.2cM from Co-3 4 /Phg-3 on the short arm of chromosome Pv04 of the common bean genome. Five flanking SSR markers were tightly linked at 0.1 and 0.2cM from Ur-14, and two flanking KASP markers were tightly linked at 0.1 and 0.3cM from Co-3 4 /Phg-3. Many other SSR, SNP, and KASP markers were also linked to these genes. These markers will be useful for the development of common bean cultivars combining the important Ur-14 and Co-3 4 /Phg-3 genes conferring resistance to three of the most destructive diseases of common bean.

Variability of nodulation traits in Andean and Mesoamerican common bean gene pools

Abstract: The objective of this work was to evaluate the genotypic diversity for nodulation in common bean (Phaseolus vulgaris) genotypes of Andean and Mesoamerican gene pools present in the core collections of Embrapa, in Brazil. Evaluations were carried out in two stages: the first one with 879 genotypes, taking the cultivar 'Ouro Negro' as reference; and the second one with 116 genotypes with greater nodulation, to identify those showing stability in nodulation in the two stages. Rhizobium strains were inoculated in pre-germinated common bean seed. Plants received weekly a nutrient solution without N, and nodulation was evaluated 35 days after planting. The percentage of genotypes that exceeded the reference cultivar was 22% for number of nodules, 46% for nodule dry weight, and 33% for one nodule dry weight. The combined analysis of data from the two evaluation phases showed wide differences among genotypes, and significant interactions between genotypes and stages. By the orthogonal contrasts analysis, the Mesoamerican genotypes showed a greater nodulation than the Andean ones. In both stages, twenty-six more stable genotypes were identified, most of them belonging to the Mesoamerican gene pool. There is a large variability in nodulation traits among the common bean genotypes present in the core germplasm collections of Embrapa, which suggests that there are genotypes with improved nodulation.

Molybdenum supply and biological fixation of nitrogen by two Brazilian common bean cultivars

ABSTRACT The common bean has been considered to have low biological nitrogen fixation capacity; however, this process can be made more effective with molybdenum (Mo) supplementation. The objective of this study was to evaluate the influence of Mo rates on the growth and biological nitrogen fixation by two Brazilian common bean cultivars using the 15N isotope dilution technique. The experiment was performed in 2014 in a completely randomized design arranged in a 5 x 3 factorial scheme, corresponding to 5 rates of Mo (control, 40, 80, 120 and 240 g ha-1), the common bean cultivars Aporé, Ouro Negro and NORH-54 (a non-nodulating common bean cultivar), and three replicates. The application of Mo and the inoculation with rhizobia strains contributed to improving nitrogen fixation and grain weight. The cultivar Ouro Negro showed a higher number and weight of nodules and a higher amount of nitrogen derived from the atmosphere than the cultivar Aporé. The biological nitrogen fixation of Aporé was more dependent on the application of Mo. These results indicated that inoculation with Rhizobium strains and Mo supply effectively contributed to biological nitrogen fixation and improving grain production.

English

Uganda is the second largest producer of dry beans (Phaseolus vulgaris L.) in Africa, but common bean rust caused by Uromyces appendiculatus (Pers. Unger), is negatively impacting the production of the crop. There is little information on the occurrence and identity of the rust pathotypes present in the country. Consequently, a field survey was carried out during the 2015 second planting season in fifteen districts, representing the areas of high beans production in Uganda. High common bean rust incidence and severity were observed in the low altitudes and the South-Western Highlands of Uganda. Wakiso and Hoima districts had the highest rust disease incidence 72 and 76% respectively and severity rates of 6 and 5.5, respectively. Rust disease incidence was uniformly high on commercial genotypes and landraces. Similarly, high rust disease incidence and severity were observed in the bean-maize–groundnut cropping system. Twenty-three single rust isolates were collected in Uganda and inoculated on 11 bean rust differentials and Ouro Negro (Ur-14) genotypes. Six rust pathotypes were identified and these included 2-0, 4-0, 50-0, 5-1, 4-33 and 63-19. Five of the pathotypes were of Andean origin and only pathotype 4-33 was of Mesoamerican origin. The rust pathotype 63-19 showed similar pathogenic characteristics with the Puerto Rico rust race 19-63. This study provides critical baseline information to integrate breeding and crop protection in the efforts to develop an overall strategy for the management of common beans in Uganda. Key words: Phaseolus vulgaris, Uromyces appendiculatus, rust differentials, co-evolution, disease severity.

Characterization and Mapping of Anthracnose Resistance Gene in Mesoamerican Common Bean Cultivar Crioulo 159

The common bean cultivar Crioulo 159 provides a valuable source of resistance to Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara. The objective of this study was to characterize the genetic resistance of Crioulo 159 to C. lindemuthianum races 2, 64, 73, and 2047 through inheritance, allelism testing, and molecular analysis. Populations were obtained from crosses between Crioulo 159 and cultivars possessing anthracnose resistance genes. Inheritance tests performed in the F2 population and F2:3 families derived from Crioulo 159 (R, resistant) × Cornell 49–242 (S, susceptible) and inoculated with races 2047 and 73 showed segregation that fit ratios of 3R:1S and 1RR:2RS:1SS, respectively, indicating the action of a dominant resistance gene in Crioulo 159. The absence of recombination between two identical sets of F2:3 families inoculated with C. lindemuthianum race 2047 and 73, respectively, allowed the conclusion that a single dominant gene controls the resistance of Crioulo 159 to both races. Allelism tests revealed the independence of the gene in Crioulo 159 from those previously characterized for anthracnose resistance genes. Based on the results, we propose naming this newly discovered anthracnose resistance gene in Crioulo 159 as Co‐16. Molecular analyses revealed that sequence‐tagged site marker g2467900/800 is linked in coupling phase at 4.8 cM from the Co‐16 locus on chromosome Pv04. Additionally, molecular markers g2303, BARCPVSSR04561 and BARCPVSSR04570, which are linked to the Co‐34 allele in Ouro Negro, were not linked to the Co‐16 gene in Crioulo 159.

English

Conilon coffee is a highly heterozygous diploid plant that is also allogamous, producing seeds through cross-fertilisation. Due to their allogamy, plants of seminiferous origin are highly heterogeneous, exhibiting high morphological and genetic diversity. However, propagation through cutting guarantees the maximum homogeneity of fields, particularly in grain maturation, among other desirable characteristics. Currently, the majority of commercial Conilon coffee is planted using seedlings propagated by cuttings. Studying the juvenile behaviour of different clonal genotypes of the Conilon coffee plant represents an important tool to assist with the establishment of this crop. The objective of this study was to assess the growth, development and genetic diversit y in several promising genotypes of the Conilon coffee plant based on the morphological characteristics of seedlings propagated by cutting. We used seedlings Conilon coffee of 33 genotypes selected by coffee growers, and with great productive potential, and genotype 02 of the Emcapa 8111 variety. Based on morphological characteristics linked to the growth and development of the aboveground and root systems of the genotypes, their phenotypic correlations were estimated, along with the genetic diversity among genotypes, using Tocher’s optimisation method and the unweighted peer group method with arithmetic mean. Genotypes A1, P2, Z39, Ouro Negro, Tardio C, Cheique, and Z29 exhibited a higher Dickson quality index (between 0.40 and 0.56). Genetic variability exists among the seedlings of the 34 genotypes of Conilon coffee studied. The most dissimilar genotypes were CHR, 18, and Z39, which remained in isolated groups in all experiments.

Genetic Characterization and Mapping of Anthracnose Resistance of Common Bean Landrace Cultivar Corinthiano

ABSTRACTThe objectives of this study were to characterize the genetic resistance in the Andean common bean (Phaseolus vulgaris L.) cultivar Corinthiano to races 8, 65, 89, and 2047 of Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara through inheritance and allelism tests and to map the source of resistance. Corinthiano was crossed with cultivars Michelite, Michigan Dark Red Kidney (MDRK), Cornell 49‐242, Mexico 222, PI 207262, TO, TU, AB 136, G 2333, Jalo Listras Pretas (JLP), Jalo Vermelho (JV), BAT 93, Ouro Negro, AND 277, Pitanga, SEL 1308, H1 line, and Crioulo 159 to generate F2 populations. Inheritance tests conducted in F2 population and F2:3 families from the cross Corinthiano (resistant [R]) × Cornell 49‐242 (susceptible [S]) inoculated with race 2047 showed segregation that fit ratios of 3R:1S and 1RR:2Rr:1rr, respectively, indicating the action of a dominant resistance gene in Corinthiano. Allelism tests demonstrated that the gene in Corinthiano is independent from those previously characterized genes: Co‐1, Co‐14, Co‐2, Co‐3, Co‐33, Co‐34, Co‐35, Co‐4, Co‐5, Co‐52, Co‐42, Co‐6, Co‐11, Co‐12, Co‐13, Co‐14, and Co‐16 that are present in the genotypes tested. The symbol Co‐15 was assigned to this newly discovered anthracnose resistance gene in Corinthiano. Molecular analyses revealed that the sequence‐tagged site (STS) marker g2685 is linked in coupling phase at 5.6 cM from the Co‐15 locus. This marker was also polymorphic in the mapping population BAT 93/Jalo EEP 558, which confirmed the location of this marker and the Co‐15 gene on Pv04. Corinthiano has shown to be an important source of resistance to anthracnose, possessing a new gene that should be valuable in breeding for anthracnose resistance in common bean.

Can the critical temperature for photochemical damage in common bean plants be changed after a drought event?

Low water availability and high temperatures occur under field conditions and we hypothesize that the critical temperature for photochemical damage (T C ) in common bean (Phaseolus vulgaris L.) plants is increased by the occurrence of previous water deficit in a genotype-dependent manner. Five common bean cultivars A320, A222, Carioca, BAT477 and Ouro Negro were evaluated. Thirty days after seedlings emergence, one group of plants was exposed to water deficit for ten days and rehydrated and another one was maintained well hydrated during the experimental period. The minimum chlorophyll fluorescence ( F O ) was monitored in leaf discs exposed to temperatures ranging from 25 to 45 o C and the T C values estimated. The previous water deficit did not

English

For adapting well to various soil and climatic conditions in Brazil and the tradition of high consumption, bean plays a key role in feeding the population. Despite the different environmental conditions, there are few specific cultivars for each planting season, particularly when aimed at the production of quality seeds. The objective of this study was to evaluate the physiological potential of bean seeds from five population densities, under the edafoclimatic conditions of Janauba, northern Minas Gerais. The experiment was conducted on winter crop season, with planting in August 2011. The experimental design was a randomized block in 3 x 5 factorial, with four replicates. The treatments consisted of three cultivars of common bean with different growth types (Ouro Vermelho, Ouro Negro and BRSMG Madreperola, and five densities (100, 200, 300, 400 and 500 thousand plants ha -1 ). Seeds were evaluated for water content, germination and vigor (tests of first count, seedling emergence, emergence speed and accelerated aging). From the results, it can be concluded that the bean seeds of the cultivar Ouro Negro present superior physiological potential in relation to the cultivars Ouro Vermelho and BRSMG Madreperola. Increasing the sowing density up to 300 thousand plants ha -1 is suitable for the production of bean seeds on winter crop season, representing a good alternative for cultivation in the region.

Endophytic fungi from the genus Colletotrichum are abundant in the Phaseolus vulgaris and have high genetic diversity.

To evaluate the diversity of endophytic fungi from the leaves of the common bean and the genetic diversity of endophytic fungi from the genus Colletotrichum using IRAP (inter-retrotransposon amplified polymorphism) and REMAP (retrotransposon-microsatellite amplified polymorphism) analyses. The fungi were isolated by tissue fragmentation and identified by analysing the morphological features and sequencing the internal transcribed spacer (ITS) regions and the rDNA large subunit (LSU). Twenty-seven different taxa were identified. Colletotrichum was the most commonly isolated genera from the common bean (32.69% and 24.29% of the total isolates from the Ouro Negro and Talismã varieties, respectively). The IRAP and REMAP analyses revealed a high genetic diversity in the Colletotrichum endophytic isolates and were able to discriminate these isolates from the phytopathogen Colletotrichum lindemuthianum. Fungi from the genus Colletotrichum are abundant in the Phaseolus vulgaris endophytic community, and the IRAP and REMAP markers can be used to rapidly distinguish between C. lindemuthianum and other Colletotrichum members that are frequently found as endophytes. This is the first report of the diversity of endophytic fungi present in the common bean and the use of IRAP and REMAP markers to assess the genetic diversity of endophytic fungi from the genus Colletotrichum.