Genetic diversity analysis of common beans based on molecular markers

A core collection of the common bean (Phaseolus vulgaris L.), representing genetic diversity in the entire Mexican holding, is kept at the INIFAP (Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias, Mexico) Germplasm Bank. After evaluation, the genetic structure of this collection (200 accessions) was compared with that of landraces from the states of Oaxaca, Chiapas and Veracruz (10 genotypes from each), as well as a further 10 cultivars, by means of four amplified fragment length polymorphisms (AFLP) +3/+3 primer combinations and seven simple sequence repeats (SSR) loci, in order to define genetic diversity, variability and mutual relationships. Data underwent cluster (UPGMA) and molecular variance (AMOVA) analyses. AFLP analysis produced 530 bands (88.5% polymorphic) while SSR primers amplified 174 alleles, all polymorphic (8.2 alleles per locus). AFLP indicated that the highest genetic diversity was to be found in ten commercial-seed classes from two major groups of accessions from Central Mexico and Chiapas, which seems to be an important center of diversity in the south. A third group included genotypes from Nueva Granada, Mesoamerica, Jalisco and Durango races. Here, SSR analysis indicated a reduced number of shared haplotypes among accessions, whereas the highest genetic components of AMOVA variation were found within accessions. Genetic diversity observed in the common-bean core collection represents an important sample of the total Phaseolus genetic variability at the main Germplasm Bank of INIFAP. Molecular marker strategies could contribute to a better understanding of the genetic structure of the core collection as well as to its improvement and validation

Métodos de controle de plantas daninhas no cafeeiro afetam os atributos químicos do solo Effects of weed control methods on coffee crop on soil chemical attributes

Nos ecossistemas agrícolas sob cafeeiro, nos quais o manejo do solo se resume, basicamente, à aplicação de corretivos, fertilizantes e controle de plantas daninhas, faz com que alternativas de manejo que preservam ou aumentam os teores de matéria orgânica no solo, a exemplo de alguns métodos de controle de plantas daninhas, sejam consideradas, quando se busca a sustentabilidade da cultura. Neste estudo o objetivo foi avaliar o efeito de alguns métodos comumente utilizadas na cultura do cafeeiro sobre os atributos químicos de um Latossolo Vermelho distroférrico sob cafeeiro, durante 15 anos. Os tratamentos avaliados consistiram de sete métodos de controle, envolvendo o uso de roçadora (RC), grade (GR), enxada rotativa (ER), herbicida de pré-emergência (HPRE), herbicida de pós-emergência (HPOS), capina manual (CM) e uma testemunha sem capina (TEST). Foram determinados, nas profundidades de 0-0,15m e 0,15-0,30m, os teores de P, K+, Ca2+ + Mg2+, soma de bases (SB), saturação por bases (V), CTC efetiva (t) e potencial (T). Os resultados mostraram que o tratamento sem capina (TEST) influenciou, positivamente, os teores de P, K+, Ca2+ + Mg2+, valores de CTC efetiva, potencial e V, enquanto o HPRE exerceu um efeito contrário, ou seja, de redução nos valores das variáveis analisadas. Demais métodos RC, GR, ER, HPOS e CM apresentam um comportamento intermediário entre os métodos TEST e HPRE sobre as condições de fertilidade do solo.<br>In agricultural ecosystems under coffee cultivation, soil management is based on liming, fertilizers and weed control. Alternatives that preserve or increase soil organic matter content are considered when the sustainability is the goal. This study was conducted to evaluate the chemical attributes of a dystroferric Red Latosol (Oxisols) under coffee cultivation submitted to 15 years of weed control methods. Seven interrows coffee plant weed control methods were used; a mower (RC), tanden disk harrow (GR), rotative hoe (ER), pre-emergence herbicide (HPRE), post-emergence herbicide (HPOS), hand hoe (CM) and no interrows control (TEST). The P, K+, Ca2++ Mg2+, sum of bases (SB), base saturation (V), effective (t) and potential (T) cation exchange capacity (CEC) were determined in soil depth from 0-0.15m and 0.15-0.30m. TEST treatment affected positively the P, K+, Ca2+ + Mg2+ content, and effective and potential CEC and V values, while the HR inversely reduced analyzed variable values. Others interrows methods RC, GR, ER, HPOS e CM presented an intermediary conduct among the TEST and HPRE methods on soil fertility

Construção de uma coleção nuclear de arroz para o Brasil Constructing a rice core collection for Brazil

A coleção de germoplasma de arroz da Embrapa consiste aproximadamente de 10.000 acessos. O objetivo desse trabalho foi estabelecer a Coleção Nuclear (CN) dessa coleção utilizando as informações e dados disponíveis sobre seus acessos. A estratégia CN foi introduzida no manejo de recursos genéticos vegetais com o principal objetivo de ampliar e sistematizar o uso desses recursos. Uma CN deve ser selecionada procurando reter a variabilidade genética existente na coleção inteira (CI) com um mínimo de redundância. Os acessos da coleção de arroz foram classificados em três estratos: a) variedades tradicionais do Brasil (VT); b) linhagens/cultivares melhoradas do Brasil (LCM); e c) linhagens/cultivares introduzidas (LCI). As variedades tradicionais foram ainda classificadas segundo o sistema de cultivo (terras altas, várzeas e facultativo). Os três estratos foram representados na Coleção Nuclear, mas ênfase maior foi dada às variedades tradicionais, que constituíram 308 acessos. Os acessos foram alocados para cada sistema de cultivo, proporcionalmente ao produto do logarítmo do número de variedades tradicionais pelo índice de Shannon (medida de diversidade) de cada um deles. A seleção dos acessos foi feita com o auxilio do Sistema de Informação Geográfica (SIG). A CN brasileira de arroz está formada por 550 acessos.<br>The Rice Germplasm Collection of Embrapa consists of approximately 10,000 accessions. This study aimed to establish a core collection using the currently available information data for those accessions. The strategy Core Collection (CN) was introduced in the management of plant genetic resources with the main purpose of improving the use of these resources. CN should be selected in order to preserve the genetic variability of the whole collection (CI), with minimum redundancy. The accessions within the rice collection were classified into three strata: a) landraces from Brazil (VT); b) breeding materials from Brazil (LCM); and c) introductions (LCI). The landraces were further classified according to crop system (uplands, lowlands and facultative). These three strata were represented in the Core Collection, but more emphasis was considered in representing the landraces, which are represented by 308 accessions. The accessions were allocated, for each crop system, proportionally to the product of the logarithm of the number of landraces by the Shannon Diversity Index (a measure of genetic diversity) within each crop system. Curators and breeders, supported by a Geographical Information System (GIS) made the selection of the accessions. The final Brazilian rice Core Collection consists of 550 accesses