Geographical distribution of a specific mitochondrial haplotype of Zymoseptoria tritici

Severity of disease caused by the fungus Zymoseptoria tritici throughout world cereal growing regions has elicited much debate on the potential evolutionary mechanism conferring high adaptability of the pathogen to diverse climate conditions and different wheat hosts (Triticum durum and T. aestivum). Specific mitochondrial DNA sequence was used to investigate geographic distribution of the type 4 haplotype (mtRFLP4) within 1363 isolates of Z. tritici originating from 21 countries. The mtRFLP4 haplotype was detected from both durum and bread wheat hosts with greater frequency on durum wheat. The distribution of mtRFLP4 was limited to populations sampled from the Mediterranean and the Red Sea region. Greater frequencies of mtRFLP4 were found in Tunisia (87%) and Algeria (60%). The haplotype was absent within European, Australian, North and South American populations except Argentina. While alternative hypotheses such as climatic adaptation could not be ruled out, it is postulated that mtRFLP4 originated in North Africa (e.g. Tunisia or Algeria) as an adaptation to durum wheat as the prevailing cereal crop. The specialized haplotype has subsequently spread as indicated by lower frequency of occurrence in the surrounding Mediterranean countries and on bread wheat hosts

Geographical distribution of a specific mitochondrial haplotype of Zymoseptoria tritici

Severity of disease caused by the fungus Zymoseptoria tritici throughout world cereal growing regions has elicited much debate on the potential evolutionary mechanism conferring high adaptability of the pathogen to diverse climate conditions and different wheat hosts (Triticum durum and T. aestivum). Specific mitochondrial DNA sequence was used to investigate geographic distribution of the type 4 haplotype (mtRFLP4) within 1363 isolates of Z. tritici originating from 21 countries. The mtRFLP4 haplotype was detected from both durum and bread wheat hosts with greater frequency on durum wheat. The distribution of mtRFLP4 was limited to populations sampled from the Mediterranean and the Red Sea region. Greater frequencies of mtRFLP4 were found in Tunisia (87%) and Algeria (60%). The haplotype was absent within European, Australian, North and South American populations except Argentina. While alternative hypotheses such as climatic adaptation could not be ruled out, it is postulated that mtRFLP4 originated in North Africa (e.g. Tunisia or Algeria) as an adaptation to durum wheat as the prevailing cereal crop. The specialized haplotype has subsequently spread as indicated by lower frequency of occurrence in the surrounding Mediterranean countries and on bread wheat hosts

Frequency of mutations associated with fungicide resistance and population structure of Mycosphaerella graminicola in Tunisia

The occurrence of fungicide resistance in Mycosphaerella graminicola populations from Tunisia was investigated by examining mutations known to be associated with strobilurin and azole resistance. Few mutations associated with fungicide resistance were detected. No evidence for strobilurin resistance was found among 357 Tunisian isolates and only two among 80 sequenced isolates carried mutations associated with azole resistance. A network analysis suggested that these mutations emerged independently from mutations found in previously described European populations. The population genetic structure of M. graminicola in Tunisia was analyzed using variation at 11 microsatellite loci. Populations in Tunisia were characterized by high gene and genotype diversity. All populations were in gametic equilibrium and mating type proportions did not deviate from the 1:1 ratio expected under random mating, consistent with regular cycles of sexual reproduction. In combination with a high degree of gene flow among sampling sites, M. graminicola must be considered a pathogens with high evolutionary potential. Thus, control strategies against Septoria blotch in Tunisia should be optimized to reduce the emergence and spread of resistant isolate

Durum Wheat Grain Quality Traits as Affected by Nitrogen Fertilization Sources under Mediterranean Rainfed Conditions

Nitrogen application, environmental variation and particularly water deficit and terminal heat that prevail during post grain filling period could significantly affect not only grain yield ability but also quality related traits of durum wheat. A field trial was conducted to evaluate the effect of two nitrogen sources applied at different rates ranging from 0 to 93.8 KgN-1 on yield and grain quality of three durum wheat cultivars. Increased N level from both nitrogen sources (ammonium sulfate nitrate: ASN and urea N) appeared to positively improve yield and grain quality. This effect was particularly significant when for N level superior to 40.2KgNha-1. The average yield increase under maximum N level ranged from 3.23 to 3.37tha-1for urea and ASN respectively. The cultivar Om Rabia appeared to better valorize nitrogen supply and was found associated with higher yielding ability of 1.78tha-1, greater test weight 78.90kg/hl, grain protein content 12.43%, and gluten content 15.20%. This cultivar showed reduced yellow berry of 7.43% under N optimum application. Greater improvements were obtained for ASN than urea for all measured traits. The percentage increases were 6.09% for GY, 2.92% for TW, 4.48% for GP, 5.64% for Gl and 6.88% for CP. These results support that nitrogen derived from ASN and when its application rate is superior to 40.2 KgNha-1 would promote grain yield and quality of durum wheat under rainfall conditions

Frequency of mutations associated with fungicide resistance and population structure of Mycosphaerella graminicola in Tunisia

ISSN:0929-1873ISSN:1573-846