Márcia Regina Costa

Characterization of the anthracnose resistance gene present in Ouro Negro (Honduras 35) common bean cultivar

Ouro Negro (Honduras 35) is a highly productive Mesoamerican black seeded bean cultivar that possesses a major dominant gene conferring resistance to anthracnose (causal organism Colletotrichum lindemuthianum). In this work the anthracnose resistance gene present in Ouro Negro was characterized by studying allelic relationships to the following previously characterized anthracnose resistance genes (cultivars): Co-1 (MDRK), Co-12 (Kaboon), Co-13 (Perry Marrow), Co-2 (Cornell 49-242), Co-3 (Mexico 222), Co-4 (TO), Co-42 (SEL 1308), Co-5 (SEL1360), Co-6 (AB 136), and the resistance genes present in PI 207262 and Widusa. In addition, we determined the resistance spectrum of Ouro Negro in relation to 19 pathotypes of C. lindemuthianum. The allelism tests confirmed that the dominant anthracnose resistance gene present in Ouro Negro is positioned at a locus distinct from those with which it was compared. We propose that this new gene be named Co-10. The inoculation of Ouro Negro with the 19 pathotypes of C. lindemuthianum demonstrated that Co-10 confers resistance to pathotypes 23, 64, 67, 73, 81, 83, 87, 89, 95, 102, 117, 119, 343, 453, 1033, 1545 and 1600. The identification of Co-10 is an important contribution to bean breeding programs that are in constant need of new sources of resistance to anthracnose.

Analysis of the abilities of endophytic bacteria associated with banana tree roots to promote plant growth.

A total of 40 endophytic bacterial isolates obtained from banana tree roots were characterized for their biotechnological potential for promoting banana tree growth. All isolates had at least one positive feature. Twenty isolates were likely diazotrophs and formed pellicles in nitrogen-free culture medium, and 67% of these isolates belonged to the genus Bacillus sp. The isolates EB-04, EB-169, EB-64, and EB-144 had N fixation abilities as measured by the Kjeldahl method and by an acetylene reduction activity assay. Among the 40 isolates, 37.5% were capable of solubilizing inorganic phosphate and the isolates EB-47 and EB-64 showed the highest solubilization capacity. The isolate EB-53 (Lysinibacillus sp.) had a high solubilization index, whereas 73% of the isolates had low solubilization indices. The synthesis of indole-3-acetic acid (IAA) in the presence of L-tryptophan was detected in 40% of the isolates. The isolate EB-40 (Bacillus sp.) produced the highest amount of IAA (47.88 μg/ml) in medium supplemented with L-tryptophan and was able to synthesize IAA in the absence of L-tryptophan. The isolates EB-126 (Bacillus subtilis) and EB-47 (Bacillus sp.) were able to simultaneously fix nitrogen, solubilize phosphate and produce IAA in vitro. The results of this study demonstrated that the isolates analyzed here had diverse abilities and all have the potential to be used as growth-promoting microbial inoculants for banana trees.

Endophytic bacterial diversity in banana ‘Prata Anã’ (Musa spp.) roots

The genetic diversity of endophytic bacteria in banana ‘Prata Anã’ roots was characterized. Two hundred and one endophytic bacteria were isolated, 151 of which were classified as Gram-positive and 50 as Gram-negative. No hypersensitivity response was observed in any of the isolates. The rep-PCR technique generated different molecular profiles for each primer set (REP, ERIC and BOX). Fifty readable loci were obtained and all of the fragments were polymorphic. Amplified ribosomal DNA restriction analysis (ARDRA) of the isolates based on cleavage with four restriction enzymes yielded 45 polymorphic bands and no monomorphic bands. PCR amplified the nifH gene in 24 isolates. 16S rDNA sequencing of the 201 bacterial isolates yielded 102 high-quality sequences. Sequence analyses revealed that the isolates were distributed among ten bacterial genera (Agrobacterium, Aneurinibacillus, Bacillus, Enterobacter, Klebsiella, Lysinibacillus, Micrococcus, Paenibacillus, Rhizobium and Sporolactobacillus) and included 15 species. The greatest number of isolates belonged to the genus Bacillus. The bacteria identified in this study may be involved in promoting growth, phosphate solubilization, biological control and nitrogen fixation in bananas.

Adaptability and stability of sweet sorghum cultivars

The objective of this study was to evaluate the phenotypic stability and adaptability of 25 sweet sorghum cultivars of Embrapa Maize and Sorghum. The experiments were conducted in five Brazilian environments, three in the state of Minas Gerais, and the others in Sinop, Mato Grosso and Pelotas, Rio Grande do Sul. Fresh biomass yield (FBY), and total soluble solids (TSS) of the juice were evaluated in a randomized complete block design with three replications. Analysis of variance showed significant genotype by environment interaction for both traits. According to the Annicchiarico methodology analysis, genotypes CMSXS634, BRS506, and CMSXS646 were the most stable and adapted for FBY and TSS concomitantly; CMSXS634 being more adapted to favorable environments and CMSXS646 being more adapted to unfavorable environments.

Development and characterization of common black bean lines resistant to anthracnose, rust and angular leaf spot in Brazil

Anthracnose, rust and angular leaf spot caused by Colletotrichum lindemuthianum, Uromyces appendiculatus and Pseudocercospora griseola, respectively, are economically important diseases affecting the common bean production in Brazil. The BIOAGRO/UFV bean breeding program developed Rudá-R, a dry bean line with ‘carioca’ seed type, containing the following disease resistance genes: Co-4, Co-6 and Co-10 (anthracnose); Ur-ON (rust) and Phg-1 (angular leaf spot). To transfer this combination of disease resistance genes present in Rudá-R to a black-seeded bean, a backcrossing program aided by molecular markers was conducted, involving Rudá-R (donor genitor) and Diamante Negro (recurrent genitor). Forty black-seeded BC3F3:6 lines were obtained with combinations of at least three markers linked to the indicated disease resistance genes. The lines were evaluated for resistance to the three mentioned pathogens. Eight of the lines were homozygous and resistant to all four evaluated races of C. lindemuthianum, but susceptible to race 2047. Four of the lines were homozygous and resistant to two races of U. appendiculatus. Twenty of the lines were homozygous and resistant to the two races of P. griseola tested. Grain yield of the BC3F3:6 lines was evaluated during the ‘winter’ season of 2006 and the ‘dry’ season of 2007. All lines had statistically equal or higher yields than Rudá-R and Diamante Negro. Lines were identified that not only were high yielding but also resistant to the three pathogens tested. These lines are potential genotypes for further testing and for release as new black common bean varieties.

Potential use of endophytic bacteria to promote the plant growth of micropropagated banana cultivar Prata Anã

Endophytic bacteria isolated from shoot tip cultures of banana ‘Tropical’ and ‘Galil 18’ were identified at the genera and species levels by means of the profile of fatty acids test through gas chromatography and the potential of plant growth promotion of micropropagated ‘Prata Ana’ banana plantlets was evaluated. A completely randomized experimental design in a factorial scheme 2 × 9, with two immersion periods (30 and 60 min), eight isolates (endophytic bacteria) plus control (saline solution; 0.85% sodium chloride) with seven replications was used. The plantlets were cultured under greenhouse conditions and the evaluations were performed at 24 (DAP1) and 48 (DAP2) days after planting. The isolates of endophytic bacteria affected significantly pseudostem height, number of leaves and pseudostem diameter. Five isolates: 03, 05, 06, 07 and 08 showed percentages of increment index over 20% for pseudostem height. Among them, the isolate 07, Klebsiella pneumoniae pneumoniae showed the highest increment indices: 27.48, 13.68 and 13.55% for pseudostem height, number of leaves and pseudostem diameter, respectively. The results show the potential use of K. pneumoniae pneumoniae (Isolate 07) for growth promotion in micropropagated ‘Prata Ana’ banana plantlets. Keywords: Musa sp., Klebsiella pneumoniae pneumoniae , plant growth promoting bacteria African Journal of Biotechnology Vol. 12(31), pp. 4915-4919

Genetic diversity in sugar apple (Annona squamosa L.) by using RAPD markers

A diversidade genetica da colecao de 64 acessos de pinheira, coletados em diferentes cidades, no norte do Estado de Minas Gerais, foi avaliada por meio do uso de marcadores RAPD. Foram selecionados 20 primers RAPD que geraram 167 fragmentos, dos quais 48 foram polimorficos (28,7%), produzindo uma media de 2,4 fragmentos polimorficos por primer. Baixa percentagem de polimorfismo foi obtida com o conjunto de primers (< 29%), indicando baixa variacao genetica entre os 64 acessos avaliados. As distâncias geneticas foram estimadas, utilizando-se o coeficiente de similaridade de Jaccard. Acessos de diferentes cidades foram agrupados em um mesmo grupo, indicando que nao ha correlacao entre os agrupamentos moleculares e origem geografica. O dendrograma revelou cinco grupos. O primeiro grupo reuniu os acessos C19 e G29, coletados nas cidades de Verdelândia e Monte Azul, respectivamente. O segundo grupo reuniu os acessos G16 e B11, coletados nas cidades de Monte Azul e Coracao de Jesus, respectivamente. Os acessos remanescentes foram agrupados em tres grupos, com oito, 15 e 37 acessos, respectivamente. O marcador RAPD apresentou baixo nivel de polimorfismo entre os acessos avaliados.

Genetic diversity and molecular characterization of physic nut genotypes from the active germplasm bank of the Agricultural Research Company of Minas Gerais, Brazil

Three in vitro experiments were conducted to study the effect of different concentrations of carbon source, salinity and gelling agent on number of new shoots, shoot length, fresh weight, and dry weight of fig (Ficus carica L.) to develop an efficient in vitro propagation method. The results show that there were no significant differences between the three carbon sources regarding number of newly formed shoots and their shoot lengths. However, there were some differences regarding fresh and dry weights. On the other hand, increased salinity concentrations reduced the number of the newly formed shoots, as well as, their shoot lengths. In addition, liquid media produced more shoots compared with the three solidifying agents used. However, there were significant differences among the concentrations of solidifying agents used.