Genetic differentiation and gene flow in Colletotrichum sublineolum in Ethiopia, the centre of origin and diversity of sorghum, as revealed by AFLP analysis

Abstract

Isolates of Colletotrichum sublineolum were collected from different sorghum-producing regions of Ethiopia and divided into five groups based on their geographic origin. The growth rate of 50 isolates showed considerable variation: 1AE7-5AE8 mm day )1 , mean 3AE3 mm day )1 . However, the isolates displayed little variation in colony colour and colony margin, except for isolates from the north, which were different from the others. Amplified fragment length polymorphism analysis of 102 isolates revealed much greater variations among the different groups. Dice similarity coefficients ranged from 0AE32 to 0AE96 (mean 0AE78). Cluster analysis and principal coordinate analysis revealed a differentiation of the isolates according to their geographic origin, and both methods clearly indicated a genetic separation between the southern, the eastern and the other isolates. Analysis of molecular variance (AMOVA) indicated a high level of genetic variation both among (42%) and within (58%) the C. sublineolum sampling sites in Ethiopia. The AMOVA also indicated a high level of genetic differentiation (F ST = 0AE42) and limited gene flow (Nm = 0AE343). The results of this study confirmed the presence of a highly diverse pathogen, which is in agreement with the existence of diverse host genotypes and widely ranging environmental conditions in sorghum-producing regions of the country. Such diversity should be taken into account in future breeding programmes to achieve an effective and sustainable disease management strategy.

Genetic diversity and pathotype determination of Colletotrichum sublineolum isolates causing anthracnose in sorghum

“…Valèrio et al (2005) studied molecular diversity of 37 C. sublineolum isolates collected from four distinct regions of Brazil by using RAPD and RFLP-PCR markers. Chala et al (2011) studied genetic differentiation and gene flow in C. sublineolum isolates using AFLP analysis and confirmed the presence of a highly diverse pathogen, which was attributed to the existence of diverse host genotypes and widely ranging environmental conditions in sorghum-producing regions of Ethiopia.…”

Evaluation of Ethiopian sorghum accessions for resistance against Colletotrichum sublineolum

“…1) and this might have been one possible cause for the variation in the response of the accessions. C. sublineolum is a highly variable pathogen (Rosewich et al 1998;Chala et al 2011). This might have been also another possible reason for the differential reaction of the sorghum accessions to anthracnose.…”

“…To-date considerable variations in resistance to anthracnose are reported among sorghum genotypes in different parts of the world (Casela et al 2001;Erpelding and Prom 2006;Chala et al 2010b). Nonetheless, the high variability of the pathogen (Rosewich et al 1998;Chala et al 2011) and differential reaction of sorghum genotypes under different environmental conditions (Hess et al 2002) call for a greater effort to continuously look for potential sources of resistance from diverse gene pools.…”

Utilização de multilinhas dinâmicas para o manejo da antracnose do sorgo

“…Entretanto, seu uso é dificultado pela elevada variabilidade patogênica apresentada por C. sublineolum, que determina a rápida adaptação do patógeno a cultivares resistentes (Casela & Frederiksen, 1994;Lima & Menezes, 2002;Chala et al, 2011;Costa et al, 2011;Pereira et al, 2011). Nos últimos anos, grande ênfase tem sido dada à busca por alternativas que permitam ampliar a durabilidade da resistência do sorgo à antracnose.…”