Genetic structure of annual ryegrass (Lolium multiflorum) populations estimated by RAPD

Abstract

Annual ryegrass is a temperate climate annual foraging grass, grown mostly in the South of Brazil, especially in the state of Rio Grande do Sul. Despite its importance, little is known about its genetic diversity, both within and among the populations cultivated. This knowledge is of fundamental importance for developing breeding and conservation strategies. The aim of this study was to characterize the genetic diversity and structure of four populations of annual ryegrass. Three of the populations were located in Rio Grande do Sul and the fourth in Uruguay. RAPD markers were used to study the genetic diversity and structure of these populations. Analysis of 375 individuals sampled from the populations, using six RAPD primers, generated a total of 82 amplified bands. They included 73 polymorphic bands (89,02%). The value of the total genetic diversity index obtained, species H (0,71) was high, indicating the presence of wide genetic diversity in the four populations. Genetic structure analysis revealed that 98% of total diversity is intrapopulational, whereas interpopulational genetic diversity was only 2%. These results suggest that before these populations separated, they had gone through a period of gene exchange and, even after the separation event, gene frequency stayed at levels similar to the original levels, with no differential selection for these genes in the different cultivation areas. Key words: foraging, genetic diversity, molecular markers ESTRUTURA GENÉTICA DE POPULAÇÕES DE AZEVÉM ANUAL (Lolium multiflorum) ESTIMADA POR RAPDRESUMO: O azevém anual é a gramínea anual forrageira de clima temperado de maior utilização no sul do Brasil, particularmente no Estado do Rio Grande do Sul. Apesar de toda a importância que a espécie apresenta, pouco se conhece a respeito da diversidade genética presente entre e dentro das populações cultivadas. Este conhecimento é de fundamental importância para o estabelecimento das estratégias de melhoramento genético e de conservação destes materiais. O objetivo deste estudo foi caracterizar a diversidade genética e a estrutura genética de quatro populações de azevém anual, sendo três populações do Estado do Rio Grande do Sul e uma do Uruguai. O nível de diversidade e a estrutura genética destas populações foram estudados com marcadores RAPD. A análise de 375 indivíduos amostrados nas populações, com seis iniciadores, gerou um total de 82 bandas que foram utilizados nas análises, dentre as quais 73 (89,02%) foram polimórficas. O valor do índice de diversidade genética total obtido, species H (0,71) foi elevado evidenciando a presença de uma grande diversidade genética nas quatro populações. A análise da estrutura genética revelou que 98% da diversidade total esta contida dentro das populações, enquanto que a diversidade genética entre as populações representou somente 2%. Sugere-se que antes da separação destas populações, as mesmas tenham passado por um período de troca de genes e que mesmo após o evento de separação elas mantiveram a freqüência destes em nívei...

Genetic diversity of six arable plants in relation to their Red List status

“…This is in partial contrast to many other studies which reveal an at most moderate within-population differentiation for annual selfing taxa; e.g., 55% in Medicago trunculata (Bonnin et al 1996), 61% in Senecio vulgaris (Müller-Schärer and Fischer 2001) and 66% in Senecio gallicus (Comes and Abbott 2000). Our species showed high genetic variation within populations, indicating more similarity to the annual and allogamous Lolium multiflorum (Vieira et al 2004) with 98% variation within populations.…”

High degree of genetic diversity among genotypes of the forage grass Brachiaria ruziziensis (Poaceae) detected with ISSR markers

“…Guaberto (2009) and Ambiel et al (2010) worked with RAPD markers in different species of Brachiaria and found similar results, which confirms the predominance of genetic variability within species. Higher variation within groups was also observed in cross-pollinating species such as Buffalo grass (Huff et al, 1993), Lolium multiflorum (Vieira et al, 2004), Bromus innermis (Diaby and Casler, 2005); Bromus riparius Rehm (Ferdinandez et al, 2001), B. auleticus (Rivas, 2001), Chloris gayana K. (Ubi et al, 2003), Pascopryum smithii (Larson et al, 2003) and Eucalyptus globulus (Nesbitt et al, 1995). In Napier grass, RAPD analysis found 35% variation between and 65% within groups based on geographical origin (Lowe et al, 2003).…”

Assessment of genetic diversity in Cattleya intermedia Lindl. (Orchidaceae)

“…In some allogamous species such as Bromus inermis and B. riparius (Ferdinandez and Coulman, 2002) variability among populations is higher than within population. On the other hand, in Lolium multiflorum, these values can reach 98% within populations (Vieira et al, 2004). RAPD has been used to study the genetic variability among populations for different number of species, independent of the strategy of reproduction, with success in autogamous (Diniz et al, 2005) or allogamous plants (Ferrão et al, 2009, Shaw et al, 2009, Ferreira et al, 2008.…”