Neste trabalho, marcadores moleculares de RAPD foram utilizados para acessar a variabilidade genética e estudar as relações interespecíficas e intraespecífica em um grupo de 37 espécies, compreendendo 56 plantas individuais. Um total de 15 primers foram selecionados para amplificação do DNA. De um total de 221 bandas analisadas, 209 (95%) foram polimórficas. O nível de similaridade genética interespecífica variou de 37% entre Catasetum complanatum e Catasetum laminatums a 83% entre Catasetum triodon e Catasetum uncatum. A similaridade genética intraespecífica variou de 88% entre os indivíduos de Catasetum triodon a 93% entre os indivíduos de Catasetum atratum e Catasetum macrocarpum. Os resultados deste trabalho contribuem para o entendimento das relações interespecíficas no gênero Catasetum, para definir estratégias para o estabelecimento de um banco de germoplasma e para dar suporte a programas de melhoramento.

In this work, RAPD molecular markers were used to access the genetic variability and to study the inter and intraespecifc relationship in a group of 37 species, including 56 individuals. A total of 15 RAPD primers were selected for DNA amplification. From a total of 221 bands analyzed, 209 (95%) were polymorphics. The level of interespecifc genetic similarity ranged from 37% between Catasetum complanatum and Catasetum laminatum to 83% between Catasetum triodon and Catasetum uncatum. The intraspecifc genetic similarity varied 88% for the individuals of Catasetum triodon to 93% between the individuals of Catasetum atratum and Catasetum macrocarpum. These results would contribute to understand the genetic relationship in Catasetum, to define the strategies to establish a germplasm core collection for the genus and to provide support for breeding programs.

The genetic relationships among 81 maize accessions consisting 79 landraces and two improved varieties, maintained by farmers in southern Brazil were investigated using Random Amplified Polymorphic DNA (RAPD). Thirty-two highly informative primers amplified 255 markers of which 184 (72.2%) were polymorphics. Based on the RAPD markers, a dendrogram was constructed using the UPGMA method. The range of genetic similarity was from 0.78 to 0.91. The molecular data grouped the accessions into two main clusters, which were correlated according to kernel colors. Small clusters were seen associated to characteristics, such as kernel morphology. The analysis of the molecular data revealed that maize management adopted by small-scale farmers has contributed to the maintenance of genetic variability and since field isolation is a regular practice, variety identities have been preserved. These results will be useful to establish and maintain a germplasm collection of landrace maize and may guide us in designing strategies that maximize the utility of maize genetic resources.

Macrophomina phaseolina é considerado como um dos fungos mais prevalecentes em infecções radiculares de soja, no Brasil. Nenhuma fonte de resistência genética foi ainda encontrada. Além disso, nenhuma informação foi obtida quanto à variabilidade genética deste patógeno, em regiões tropicais. Cinqüenta e cinco isolados de raízes de soja (Glycine Max), obtidos de diferentes regiões geográficas, foram analisados por RAPD para avaliação da diversidade genética. Análise de agrupamento (UPGMA), utilizando 74 loci, permitiu identificar três grupos, com uma média de 99%, 92% e 88% de similaridade genética, respectivamente. Os três grupos correspondem a 5,45%, 59,95% e 34,6% de todos os isolados utilizados. Apenas uma planta estava infetada por três diferentes haplotipos, enquanto 10,9% de todas as plantas estavam infetadas por haplotipos pertencentes a dois diferentes grupos. Em outro estudo a similaridade genética foi determinada entre isolados originários de diferentes hospedeiros [soja, sorgo (Sorghum bicolor), girassol (Helianthus annuus), caupi (Vigna unguiculata), milho (Zea mays) e trigo (Triticum aestivum)] e de duas amostras de solo de áreas virgens. Os resultados mostraram que isolados mais divergentes são oriundos de áreas com monocultura. Amplificação da região ITS produziram apenas um fragmento com 620 pb. Nenhum dos isolados foi diferenciado quando o produto amplificado por PCR foi digerido com enzimas de restrição. Os resultados demonstram a existência de variabilidade genética entre os isolados brasileiros de M. phaseolina e mostram que uma única raiz pode ter mais de um haplotipo. Além disso, a rotação de cultura induz menos diversidade genética entre os isolados. O conhecimento dessa variabilidade pode ser útil na seleção de genótipos resistentes à podridão de carvão.

Macrophomina phaseolina has been considered one of the most prevalent soybean (Glycine max) pathogens in Brazil. No genetic resistance has been determined in soybean and very little is known about the genetic diversity of this pathogen in tropical and sub-tropical regions. Fifty-five isolates from soybean roots were collected in different regions and analyzed through RAPD for genetic diversity. The UPGMA cluster analysis for 74 loci scored permitted identification of three divergent groups with an average similarity of 99%, 92% and 88%, respectively. The three groups corresponded to 5.45%, 59.95% and 34.6%, respectively of all isolates used. A single plant had three different haplotypes, while 10.9% of the analyzed plants had two different haplotypes. In another study the genetic similarity was evaluated among isolates from different hosts [soybean, sorghum (Sorghum bicolor), sunflower (Helianthus annuus), cowpea (Vigna unguiculata), corn (Zea mays) and wheat (Triticum aestivum)] as well as two soil samples from native areas. Results showed that more divergent isolates originated from areas with a single crop. Isolates from areas with crop rotation were less divergent, showing high similarity values and consequently formed the largest group. Amplification of the ITS region using primers ITS1 and ITS4 produced only one DNA fragment of 620 bp. None of the isolates were differentiated through PCR-RFLP. Our results demonstrated genetic variability among Brazilian isolates of M. phaseolina and showed that one single root can harbor more than one haplotype. Moreover, cultivation with crop rotation tends to induce less specialization of the pathogen isolates. Knowledge of this variation may be useful in screening soybean genotypes for resistance to charcoal rot.

Inter-simple sequence repeat (ISSR) markers were used to evaluate genetic divergence among eight Coffea species and to identify the parentage of six interspecific hybrids. A total of 14 primers which contained different simple sequence repeats (SSR) were used as single primers or combined in pairs and tested for PCR amplifications. Two hundred and thirty highly reproducible fragments were amplified, which were then used to estimate the genetic similarity and to cluster the Coffea species and hybrids. High levels of interspecific genetic variation were revealed. The dinucleotide motif (GA)9T combined with other di- tri- and tetra-nucleotides produced a greater number of DNA fragments, mostly polymorphics, suggesting a high frequency of the poly GA microsatellite motifs in the Coffea genomes. The genetic similarity ranged from 0.25 between C. racemosa and C. liberica var. dewevrei to 0.86 between C. arabica var. arabica and Hybrid N. 2. The C. arabica species shared most of its markers with five of the six hybrids suggesting that it is the most likely candidate as one of the progenitors of those hybrids. These results revealed that ISSR markers could be efficiently used for genetic differentiation of the Coffea species and to identify the parentage of Coffea interspecific hybrids.