Alexandre Siqueira Guedes Coelho

Biochemical and metabolic profiles of Trichoderma strains isolated from common bean crops in the Brazilian Cerrado, and potential antagonism against Sclerotinia sclerotiorum

Some species of Trichoderma have successfully been used in the commercial biological control of fungal pathogens, e.g., Sclerotinia sclerotiorum, an economically important pathogen of common beans (Phaseolus vulgaris L.). The objectives of the present study were (1) to provide molecular characterization of Trichoderma strains isolated from the Brazilian Cerrado; (2) to assess the metabolic profile of each strain by means of Biolog FF Microplates; and (3) to evaluate the ability of each strain to antagonize S. sclerotiorum via the production of cell wall-degrading enzymes (CWDEs), volatile antibiotics, and dual-culture tests. Among 21 isolates, we identified 42.86% as Trichoderma asperellum, 33.33% as Trichoderma harzianum, 14.29% as Trichoderma tomentosum, 4.76% as Trichoderma koningiopsis, and 4.76% as Trichoderma erinaceum. Trichoderma asperellum showed the highest CWDE activity. However, no species secreted a specific group of CWDEs. Trichoderma asperellum 364/01, T. asperellum 483/02, and T. asperellum 356/02 exhibited high and medium specific activities for key enzymes in the mycoparasitic process, but a low capacity for antagonism. We observed no significant correlation between CWDE and antagonism, or between metabolic profile and antagonism. The diversity of Trichoderma species, and in particular of T. harzianum, was clearly reflected in their metabolic profiles. Our findings indicate that the selection of Trichoderma candidates for biological control should be based primarily on the environmental fitness of competitive isolates and the target pathogen.

Intrapopulation fixation index dynamics in finite populations with variable outcrossing rates

The intrapopulation fixation index ( f ) is inversely related to the outcrossing rate (t). Results obtained from data on molecular markers of natural populations have shown that these values are highly variable, even when measured in the same group of individuals. It is thus suggested that factors besides those described in Wrights genetic equilibrium must be operating. Using simulated data sets this study shows that the finite size condition of a population is sufficient to spread the estimated f values along a range at equilibrium, as opposed to keeping them at the theoretical equilibrium point. The variation in outcrossing rates can amplify this range considerably. Correlation between estimated f values obtained from different loci in this condition showed to be negatively related to the outcrossing rates, and positively related to the variance of these rates along generations. The finite size of populations associated to small fluctuations in t mean values over time may explain the usually reported high variation among estimated f values of different loci.

Isolation and characterization of microsatellite loci in Cabralea canjerana (Meliaceae).

PREMISE OF THE STUDY Microsatellite primers were developed in the native Neotropical tree species Cabralea canjerana (Vell.) Mart. (Meliaceae) to study population genetics in some Atlantic Forest fragments of Brazil. This species is suitable for use in reforestation and is commercially important due to its high-quality wood. METHODS AND RESULTS In this study, eight microsatellite loci were isolated from an enriched C. canjerana genomic library. These are the first microsatellite loci described for this genus. Genetic diversity analyses were carried out using 30 individuals and six polymorphic loci. An average of 11.2 alleles was found, and the observed heterozygosity was 0.65. CONCLUSIONS The microsatellite markers described here are valuable tools for further population genetic studies of the species.

Mitochondrial and chloroplast localization of FtsH-like proteins in sugarcane based on their phylogenetic profile

A phylogenetic analysis of plant FtsH-like proteins was performed using protein sequences from the GENEBANK database and five groups of plant FtsH-like proteins were identified by neighbor-joining analysis. Prediction of the subcellular location of the proteins suggested that two (FtsH-m1 & FtsH-m2) were mitochondrial and three (FtsH-p1, FtsH-p2, FtsH-p3) were plastid targeting. The phylogenetic profile of plant FtsH-like proteins was used to search sugarcane expressed sequence tag (EST) clusters in the SUCEST database. Initially, 153 clusters presenting homology with FtsH-like proteins were recovered, of which 23 were confirmed by a BLAST search in the GENEBANK database and by comparison of their hidropathy index with that of previously described FtsH-like proteins. Sugarcane presented EST clusters in all phylogenetic groups. In silico expression analysis showed that the groups are differentially expressed in sugarcane tissues, with FtsH-p2 and FtsH-m1 presenting increased levels of expression.

VARIANCE ADDITIVITY OF GENETIC POPULATIONAL PARAMETER ESTIMATES OBTAINED THROUGH BOOTSTRAPPING

O estudo da estrutura genetica de populacoes naturais e muito importante para a conservacao e o uso da variabilidade genetica disponivel na natureza. Esta pesquisa relaciona-se com a analise da estrutura genetica de populacoes a partir de dados moleculares reais e simulados. Visando estimar variâncias de estimativas de parâmetros pertinentes, o metodo de reamostragem bootstrap foi aplicado levando em conta diferentes unidades amostrais, a saber: individuos dentro de populacoes (I), populacoes (P) e individuos e populacoes concomitantemente (I, P). Os parâmetros considerados foram: o indice de fixacao total (F ou FIT), o indice de fixacao intrapopulacional (f ou FIS) e a divergencia interpopulacional (q ou FST). O trabalho objetivou estimar a variância amostral das estimativas destes parâmetros para verificar se as variâncias de , e , obtidas pela reamostragem de individuos e populacoes concomitantemente (I, P) sao equivalentes as obtidas pela soma (I+P) das variâncias estimadas reamostrando-se I e P separadamente. A equivalencia foi verificada em todos os casos investigados, mostrando ser possivel estimar as variâncias das estimativas de , e , para cada fonte de variacao (unidade amostral) somando-as depois para estimar a variância total. O procedimento facilita o uso do metodo bootstrap em dados com estrutura hierarquica e permite mensurar a importância relativa de cada fonte de variacao sobre a variância amostral total das estimativas dos parâmetros.O estudo da estrutura genetica de populacoes naturais e muito importante para a conservacao e o uso da variabilidade genetica disponivel na natureza. Esta pesquisa relaciona-se com a analise da estrutura genetica de populacoes a partir de dados moleculares reais e simulados. Visando estimar variâncias de estimativas de parâmetros pertinentes, o metodo de reamostragem bootstrap foi aplicado levando em conta diferentes unidades amostrais, a saber: individuos dentro de populacoes (I), populacoes (P) e individuos e populacoes concomitantemente (I, P). Os parâmetros considerados foram: o indice de fixacao total (F ou FIT), o indice de fixacao intrapopulacional (f ou FIS) e a divergencia interpopulacional (q ou FST). O trabalho objetivou estimar a variância amostral das estimativas destes parâmetros para verificar se as variâncias de , e , obtidas pela reamostragem de individuos e populacoes concomitantemente (I, P) sao equivalentes as obtidas pela soma (I+P) das variâncias estimadas reamostrando-se I e P separadamente. A equivalencia foi verificada em todos os casos investigados, mostrando ser possivel estimar as variâncias das estimativas de , e , para cada fonte de variacao (unidade amostral) somando-as depois para estimar a variância total. O procedimento facilita o uso do metodo bootstrap em dados com estrutura hierarquica e permite mensurar a importância relativa de cada fonte de variacao sobre a variância amostral total das estimativas dos parâmetros.