Agrobiodiversity in Cucurbita spp. landraces collected in Rio de Janeiro assessed by molecular markers

Diversity and genetic relationship in forty landraces of Cucurbita spp. collected at small farms in Rio de Janeiro, Brazil, were analyzed by RAPD and ISSR markers, using 20 and 15 primers, respectively. Both markers were efficient to cluster the accessions separating among species, but not so much to the detection of intra-specific variability, considering the event of different pairs of accessions comprising null genetic distances observed for both markers in C. moschata. Low values observed for genetic distance among the C. moschata landraces showed that most likely genetic losses is in progress in that region of cultivation due to anthropic and market pressure, which are stimulating the small farmers to abandon their local varieties in order to use commercial seeds, including hybrids, which is causing risk of genetic erosion

DESCRITORES QUALITATIVOS E MULTICATEGÓRICOS NA ESTIMATIVA DA VARIABILIDADE FENOTÍPICA ENTRE ACESSOS DE PIMENTAS

The use of germplasm in breeding programs is related to the availability of information on the accessions of a collection or germplasm bank. The characterization and the quantification of genetic and phenotypic divergence among accessions were already studied, including many vegetables species. Aiming to quantify the phenotypic divergence among 29 Capsicum spp. accessions, based on morphological and agronomic traits, 37 descriptors were analyzed using principal components, cluster analysis and multicategorical variables. The experiment was carried out in field conditions, at Campos dos Goytacazes, RJ, from March to December, 2004. The data were analyzed using GENES software. The clusters formed using Tocher and nearest neighbor clustering methods showed partial agreement. The use of multicategorical analysis was efficient to quantify the phenotypic divergence.O uso de germoplasma em programas de melhoramento está relacionado à disponibilidade de informações sobre os acessos contidos numa coleção ou banco. A caracterização e a divergência genética e fenotípica entre acessos de bancos de germoplasma têm sido determinadas, e várias espécies de hortaliças já foram objeto de estudos nessa área. Com o objetivo de quantificar a divergência fenotípica entre 29 acessos de Capsicum spp., com base em caracterização morfológica e agronômica, 37 descritores foram analisados utilizando-se técnicas de componentes principais, análise de agrupamento e variáveis multicategóricas. O experimento foi conduzido em condições de campo, em Campos dos Goytacazes, RJ, no período de março a dezembro de 2004. Os dados obtidos foram analisados utilizando-se os recursos computacionais do programa GENES. Os grupos formados pelos métodos de Tocher e do vizinho mais próximo foram parcialmente concordantes. A análise de variáveis multicategóricas foi eficiente na quantificação da divergência fenotípica

Developing an in vitro optimized protocol to sweet potato landraces conservation

This study aimed to develop a protocol for the in vitro conservation of 30 accessions of sweet potato collected in the northern region of Rio de Janeiro State, Brazil, aiming to extend the period between subcultures for this species. An in vitro minimal growth experiment was established with accession UENF 1931 in a factorial arrangement consisting of four concentrations of mineral salts in MS medium and four concentrations of sucrose, at two temperatures. The others accessions were grown in medium containing 100% MS salts and 2% sucrose, which was the medium that allowed the in vitro conservation of accession UENF 1931 for a longer time period. For this second experiment, 30 accessions of sweet potato and two temperatures were used. Plant height, number of leaves, and survival rate were measured every 30 days for 12 months, in both experiments. In the last stage, the sweet potato plantlets originating from in vitro minimal growth were acclimatized and exhibited 100% survival. The recommended in vitro minimal growth conditions for the studied accessions are MS medium with 100% concentration of mineral salts and 2% sucrose, at a temperature of 27±2°C, with subculture performed every 180 days.

NOTE - Meiotic irregularities in Capsicum L. species

Cytogenetic and pollen viability (PV) studies were performed in pepper accessions, Capsicum chinense and Capsicum baccatum. Irregularities such as laggard and univalent chromosomes, bridges, problems in the spindle fibers and cytomixis were observed, especially in C. baccatum which was the most unstable genotype. In the post-meiotic products, irregularities were observed, on average, at 20 % of the microspores in C. baccatum and 17 % in C. chinense. PV in C. baccatum was below 70 %, while in C. chinense, it was above 80 %. Meiotic irregularities in Capsicum, mainly in C. baccatum, considering the low PV estimated, were significant but not impeditive for fertilization

Marcadores RAPD e caracteres morfoagronômicos na determinação da diversidade genética entre acessos de pimentas e pimentões RAPD markers and morphoagronomic traits in determining genetic diversity among chili peppers and sweet peppers

A diversidade genética existente em coleções e bancos de germoplasma pode ser estimada por meio de diversos métodos, sendo que a escolha destes depende da disponibilidade dos recursos e da precisão desejada pelo pesquisador. Neste trabalho, marcadores RAPD e caracteres morfoagronômicos foram usados para estimar a divergência genética entre 52 acessos de Capsicum spp. Um total de 57 variáveis binárias geradas pela caracterização morfoagronômica e 84 bandas polimórficas obtidas a partir da análise por RAPD foram analisadas separadamente e em conjunto, permitindo a construção de três dendrogramas. Observou-se a formação de dois grupos principais, tanto na análise morfoagronômica e molecular separadamente, quanto na análise conjunta dos dados. O agrupamento dos acessos pela análise conjunta seguiu o mesmo padrão verificado para a análise molecular, que se constituiu em um grupo formado por acessos de C. baccatum e outro grupo formado pelos acessos de C. chinense, C. frutescens e C. annuum. Esse agrupamento segue a proposta vigente para a classificação de Capsicum spp. em complexos gênicos. A associação dos métodos permitiu uma melhor distinção entre os acessos, o agrupamento desses em nível de espécie e a conclusão de que não há duplicatas na coleção, demonstrando a importância do uso de diferentes técnicas na caracterização de um banco de germoplasma.The genetic diversity within collections and banks of germplasm can be estimated by different methods and their choice is dependent of the available resources and the desired precision from the researcher. In the present work, RAPD markers and morph-agronomic traits were used to estimate the genetic divergence among 52 Capsicum spp. accessions. Fifty-seven binary variables from morph-agronomic characterization and 84 polymorphic markers from RAPD analysis were both separately and jointly evaluated and three dendrograms were generated. Two major groups were formed in all analyses. The clusters from the joint analysis were similar to the ones from molecular analysis. One group was formed with only C. baccatum accessions and the other one with C. chinense, C. frutescens and C. annuum accessions. These results were in agreement with the gene pool complexes proposal. The association of these methods allowed a better distinction among the accessions, a cluster formation at species level and a conclusion that there is no duplicates in the collection, showing how important is the use of different methods to characterize a germplasm bank

COLETA, CARACTERIZAÇÃO E DIVERGÊNCIA FENOTÍPICA DE FRUTOS DE FAVA-D'ANTA

This paper aimed to collect, to characterize and to estimate the phenotypic divergence of Dimorphandra spp. from different regions of Brazil. Dimorphandra species are sources of rutin, quercetin and rhamnose for pharmaceutical industry. Fruits at mature stage were collected from 21 areas, totaling 84 trees in cities of Minas Gerais, Maranhão and Tocantins states. The following descriptors were used to characterize the collected fruits: mean fruit fresh weight; mean seed fresh weight; fruit length and diameter; length, diameter and thickness of seed; seed color; number of viable and unviable seeds per fruit, and boron content in mesocarp and endocarp. The data were analyzed using a standardized average Euclidian distance matrix. The areas were clustered based on Neighbor Joining algorithm. Phenotypic variability among areas was detected. The clustering of the groups was consistent with geographic region of the collection and the species were separated in different groups. The D. wilsonii Rizz. species was the most divergent considering the three studied species. However, for germplasm conservation, more expeditions to collect samples are needed to increase the effective population number and to ensure an adequate accuracy to assure the occurrence of minimal genetic erosion

A comparison of RAPD and ISSR markers reveals genetic diversity among sweet potato landraces (Ipomoea batatas (L.) Lam.)

Small farmers have played an important role in maintaining genetic resources of traditional varieties. Collecting and characterizing germplasm, especially landraces and heirloom varieties, are strategic activities that would create a knowledge base describing the traditional varieties of a given region and reduce the risk of genetic erosion. The objectives of this work were as follows: collect sweet potato roots from rural properties and local markets in Rio de Janeiro State, Brazil; characterize the accessions using RAPD and ISSR molecular markers, comparing the efficiency in discrimination of these two types of molecular markers; and estimate the genetic variability of the population. Fifty-nine samples from rural properties and 19 from local markets were studied. A matrix of binary data was developed to analyze the molecular data using the Jaccard index to estimate genetic differences among accessions, and clusters were made using the UPGMA method. The molecular techniques detected genetic variability among the accessions, with cophenetic correlation coefficients (CCC) of 0.80 for RAPDs and 0.89 for ISSRs. The RAPD and ISSR marker results corresponded well, with a correlation of 0.55. All of the accessions were considered distinct, which demonstrates that traditional farmers maintain sweet potato genotypes that have good genetic diversity

Review : Holistic pest management against early blight disease towards sustainable agriculture

Alternaria species are well-known aggressive pathogens that are widespread globally and warmer temperatures caused by climate change might increase their abundance more drastically. Early blight (EB) disease, caused mainly by Alternaria solani, and brown spot, caused by Alternaria alternata, are major concerns in potato, tomato and eggplant production. The development of EB is strongly linked to varieties, crop development stages, environmental factors, cultivation and field management. Several forecasting models for pesticide application to control EB were created in the last century and more recent scientific advances have included modern breeding technology to detect resistant genes and precision agriculture with hyperspectral sensors to pinpoint damage locations on plants. This paper presents an overview of the EB disease and provides an evaluation of recent scientific advances to control the disease. First of all, we describe the outline of this disease, encompassing biological cycles of the Alternaria genus, favorite climate and soil conditions as well as resistant plant species. Second, versatile management practices to minimize the effect of this pathogen at field level are discussed, covering their limitations and pitfalls. A better understanding of the underlying factors of this disease and the potential of novel research can contribute to implementing integrated pest management systems for an ecofriendly farming system.</p

Genetic divergence among Dimorphandra spp. accessions using RAPD markers Divergência genética entre acessos de Dimorphandra spp. usando marcadores RAPD

The genus Dimorphandra has distinguish relevance considering either medicinal or biodiversity aspects because it includes two species that are economically important flavonoids sources for pharmachemical industry (D. mollis Benth. and D. gardneriana Tul.), and species endemic to Brazil, such as D. jorgei Silva and D. wilsonii Rizz., threatened by extinction. In order to evaluate variability among accessions of D. mollis (fava-d'anta), D. gardneriana and D. wilsonii, it was collected fruit from individual plants from three Brazilian states in a total of 57 accessions, which were analyzed with RAPD markers. It was used 20 seeds per progeny; the DNA was extracted from fully-formed young leaves, which were collected in bulk. The data were analyzed using a binary matrix, in which the score one represented presence of a band and zero, absence. The similarity matrix was developed by using the arithmetic complement of the Jaccard index, later grouped based on the Neighbor Joining algorithm. It was found considerable intra and inter specific variability in Dimorphandra spp., which were separated into four groups. Though genetic variability was found, the collecting trips showed that most of these areas are subject to loss of genetic resources of fava-d'anta due to the following factors: continuous anthropic activity, propensity for natural fires, and loss of natural seed dispersers (large fruit-eating mammals). Therefore, protections of these areas and ex situ conservation are essentials for the maintenance of genetic variability of these species.O gênero Dimorphandra tem grande relevância, sobretudo nos aspectos medicinais e de biodiversidade, por incluir duas espécies que são importantes economicamente como fontes de flavonoides para indústria farmacoquímica (D. mollis Benth. e D. gardneriana Tull.), e espécies endêmicas do Brasil, como a D. jorgei Silva e D. wilsonii Rizz., sendo esta ameaçada de extinção. Objetivando avaliar a variabilidade entre acessos de D. mollis, D. gardneriana e D. wilsonii, foram realizadas coletas de frutos separados por planta em três estados brasileiros em um total de 57 acessos que foram analisados por meio da técnica RAPD. Utilizaram-se vinte sementes por progênie e o DNA, extraído de folhas definitivas, jovens, e coletadas em bulk. Os dados foram analisados utilizando-se uma matriz de dados binários. Para formação da matriz de dissimilaridade, foi utilizado o complemento aritmético do Índice de Jaccard e posteriormente o agrupamento pelo algoritmo de Neighbor Joining. O estudo revelou que existe variabilidade entre e dentro das espécies de Dimorphandra spp., o qual formou quatro grupos. Apesar da variabilidade genética constatada, as expedições de coleta demonstraram que a maioria das áreas amostradas está sujeita a perdas de recursos genéticos de fava-d'anta devido aos seguintes fatores: ocorrência de ação antrópica contínua; propensão a incêndios naturais; e diminuição dos dispersores naturais de sementes (grandes mamíferos frugíveros). Assim, a proteção destas áreas e a conservação ex situ, são primordiais para manutenção da variabilidade genética dessas espécies