<p>Prouzrokovač pepelnice (Blumeria graminis f. sp. tritici) je stalni pratilac proizvodnje p&scaron;enice u agroekolo&scaron;kim uslovima Srbije. Sposobnost seksualne i aseksualne reprodukcije, kao i visok genetski protok patogena, čine da je prouzrokovač pepelnice genetski veoma divergentan, značajnog potencijala za adaptabilnost i promenu u virulentnosti populacije. Do sada je utvrđen znatan broj patotipova ovog patogena, dok se veliki broj konstantno stvara, te je efikasna otpornost p&scaron;enice kratkotrajne prirode. Rad na selekciji na otpornost p&scaron;enice prema prouzrokovaču pepelnice je važan zadatak oplemenjivačkih programa &scaron;irom sveta.&nbsp; Cilj istraživanja je bio utvrđivanje strukture virulentnosti populacije patogena B. graminis f. sp. tritici koja potiče sa teritorije Srbije, kao i dinamike njene promene tokom godina. U polnoj populaciji prouzrokovača pepelnice identifikovana je virulentnost prema svim genima p&scaron;enice za otpornost prema prouzrokovaču pepelnice (Pm geni), tokom ispitivanih godina i u svim ispitivanim lokalitetima. Utvrđene su statistički značajne razlike u virulentnosti gena patogena prema Pm genima domaćina, kao i linearni trend promene frekvencije virulentnosti gena polne populacije B. graminis f. sp. tritici. Najnižu frekvenciju virulentnosti u populaciji tokom ispitivanog perioda ispoljila je kombinacija gena V-5+6, dok je frekvencija virulentnih gena V-6 i V-7 gena bila na konstantno visokom nivou. Najznačajnija promena u populaciji je karakteristična za kombinaciju gena V-2+4b+6. U polnoj populaciji patogena u ispitivanom periodu nijedan izolat nije ispoljio virulentnost prema kombinaciji gena Pm17, Pm2+, Pm2+6 i Pm5+6. Klaster analizom utvrđen je visok stepen genetičkog diverziteta izolata u zavisnosti od godine. Analizom veze između gena avirulentnih lokusa utvrđena je pozitivna avirulentna veza između parova gena virulentnih prema Pm17 i Pm2+6, Pm2 i Pm2+; Pm2+ i Pm3a; Pm2+ i Pm1+2+9; Pm2+ i Pm2+4a+6; Pm3a i Pm8; Pm3a i Pm1+2+9; Pm3a i Pm2+6; Pm8 i Pm17; Pm17 i Pm1+2+9; Pm17 i Pm2+6 i parova gena</p><p><br /><br /><br /><br />Pm1+2+9 i Pm2+6. Piramiding ovih parova gena može biti dobra strategija za produžetak perioda efikasnosti otpornosti određene sorte. Najniža frekvencija virulentnosti polne populacije utvrđena je u lokalitetu Sremska Mitrovica. Najveći koeficijent genetičke udaljenosti utvrđen je između izolata koji potiču sa datog lokaliteta i izolata koji potiču sa ostalih ispitivanih lokaliteta. Između genetičke i geografske udaljenosti izolata prouzrokovača pepelnice za ispitivane lokalitete nije utvrđena statistički značajna linearna veza.&nbsp; Analiza strukture virulentnosti bespolne populacije ukazala je da komplekstnost patotipova prouzrokovača pepelnice raste sa porastom useva. Geni patogena za virulentnost prema genima Pm3a i Pm2+ nisu utvrđeni. Najvi&scaron;u frekvenciju virulentnosti imao je gen za virulentnost prema Mld genu za otpornost p&scaron;enice prema prouzrokovaču pepelnice. Statistički značajne korelacije su utvrđene između polne i bespolne populacije ispitivanog patogena. Istraživanja su imala za cilj i određivanje otpornosti genotipova p&scaron;enice koja je uslovljena promenom u populaciji prouzrokovača pepelnice. Visok nivo parcijalne otpornosti ispoljilo je sedam genotipova koji u svojoj genealogiji imaju roditelja sa kombinacijom gena Pm5+6, kao i kombinacijom gena&nbsp; Pm5+6 i Pm2+4b+6. Na osnovu ispitivanja strukture virulentnosti populacije prouzrokovača pepelnice smatra se da je kombinacija gena Pm5+6 nosioc otpornosti datih genotipova.</p> / <p>Powdery mildew (caused by Blumeria graminis f. sp. tritici) is the common disease of wheat in the agroecological conditions of Serbia. The ability of sexual and asexual reproduction, as well as a high genetic flow of this pathogen, make B. graminis f. sp. tritici genetically very divergent, with a significant potential for adaptability and change in the virulence of its population. So far, a large number of pathotypes of this pathogen have been identified, while a large number is constantly produced and effective resistance of wheat is short-termed. Improving wheat resistance to powdery mildew is an important task of breeding programs worldwide. The objective of this research was to determine and characterize the virulence structure of the B. graminis f. sp. tritici population that originate from the territory of Serbia, as well as the dynamics of its change over the years. During the examined period virulence of sexual stage of B. graminis f. sp. tritici population was identified for all wheat resistance genes (Pm genes) and in all investigated locations. Cluster analysis showed a high degree of genetic diversity of B. graminis f. sp. tritici isolates, depending on the year. Statistically significant differences were found between the virulence genes, as well as the linear trend of change in the virulence frequency of the genes during the investigated period. The lowest frequency of virulence in the population was found for the combination of the V-5+6 gene, while the frequency of the virulent genes V-6 and V-7 was at a consistently high level. The most significant change in the population was characteristic for the combination of the V-2+4b+6.&nbsp; Data were analyzed for associations among pairs of avirulence genes, and a positive avirulent relationship was established between the pairs of genes virulence to Pm17 and Pm2+6, Pm2 and Pm2 +; Pm2 + and Pm3a; Pm2 + and Pm1+2+9; Pm2+ and Pm2+4a+ 6; Pm3a and Pm8; Pm3a and Pm1+2+9; Pm3a and Pm2+6; Pm8 and Pm17; Pm17 and Pm1+2+9; Pm17 and Pm2 6 and gene pairs Pm1+2+9 and Pm2+6.</p><p><br /><br /><br /><br />Pyramiding these gene pairs can be a good strategy for extending the period of effectiveness of the resistance of a particular variety of wheat. The lowest frequency of virulence of the sexual stage of population was determined at the location of Sremska Mitrovica. The highest coefficient of genetic distances is established between isolates originating from a given location and isolates originating from other investigated locations. Between the genetic and geographical distance of B. graminis f. sp. tritici isolates a statistically significant linear relationship was not found. Virulence structure of the asexual population indicated that the complexity of the powdery mildew pathotypes grows with the crop growth. In this part of population the genes virulence to Pm3a and Pm2 + have not been found. The highest frequency of virulence had gene virulence to Mld resistance gene. Statistically significant correlations were found between the sexual and asexual population of the examined pathogen. The research was also aimed at determining the resistance of wheat genotypes to powdery mildew. High level of partial resistance was found in seven tested wheat genotypes whose parents have combination of the Pm5+6 gene, as well as a combination of the Pm5+6 and Pm2+4b+6 genes. Based on the study of the virulence structure of the powdery mildew population in this research, it is considered that the combination of the Pm5+6 gene is the carrier of the resistance of the given genotypes</p>

Powdery mildew, caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici E'm. Marchal (syn. Erysiphe graminis f. sp. tritici), is one of the major diseases of wheat (Triticum aestivum L.) worldwide. The use of cultivars with resistance to powdery mildew is an efficient, economical and environmentally safe way to control powdery mildew. Race-specific resistance has been extensively used in breeding programs; however, it is ephemeral. Adult plant resistance (APR) to powdery mildew is more durable as demonstrated by the cultivar Massey, which has maintained its APR to powdery mildew since its release in 1981. To develop an efficient breeding strategy, it is essential to understand the genetic basis of APR. The objectives of this study were to identify molecular markers associated with APR to powdery mildew in common wheat Massey and to verify their association using recombinant inbred (RI) lines. A cross was made between the powdery mildew susceptible cultivar Becker and Massey. One hundred and eighty F2:3 lines were rated for disease severity under natural pressure of powdery mildew in field. Using both restriction fragment length polymorphism (RFLP) and microsatellite markers, three quantitative trait loci (QTL), designated as QPm.vt-1B, QPm.vt-2A and QPm.vt-2B, were identified in the Becker x Massey F2:3 generation. These loci are located on chromosomes 1B, 2A and 2B, respectively, and explained 17%, 29% and 11% of the total variation among F2:3 lines for powdery mildew resistance, respectively. Cumulatively, the three QTLs explained 50% of the phenotypic variation among F2:3 lines in a multi-QTL model. The three QTLs associated with APR to powdery mildew were derived from Massey and displayed additive gene action. QPm.vt-2B also fits a recessive model for APR to powdery mildew. In the second part of this study, 97 RI lines were developed from the Becker x Massey cross. The RI lines were evaluated for APR to powdery mildew under natural disease pressure for three years. Both single marker analysis and interval mapping confirmed the presence of the three QTLs identified in the F2:3 generation. The three QTLs, QPm.vt-1B, QPm.vt-2A and QPm.vt-2B, accounted for 15%, 26% and 15% of the variation of mean powdery mildew severity of the RI lines over three years. In a multi-QTL model, the three QTLs explained 44% of the phenotypic variation of the RI lines. The RI lines were grouped according to the genotype of the three QTLs, represented by markers GWM304a, KSUD22 and PSP3100, respectively. The RI lines with Massey alleles at all three loci had a mean disease severity of 3.4%, whereas the RI lines with Becker alleles at all three loci had a mean disease severity of 22.3%. These severity values are similar to those of the corresponding parents. The molecular markers identified and verified as to their association with APR to powdery mildew in Massey have the potential for use in marker-assisted selection for resistance to powdery mildew and in pyramiding powdery mildew resistance genes, as well as facilitating a better understanding of the molecular basis of APR to powdery mildew. / Ph. D.

L’utilisation de molécules stimulatrices des défenses des plantes (SDP), également appelées inducteurs de résistance, constitue une alternative potentielle aux traitements fongicides conventionnels pour combattre les maladies dues à des champignons phytopathogènes. Trois SDPs, le tréhalose (TR), l’acide salicylique (SA) et l’heptanoyl d’acide salicylique (HSA), un dérivé fonctionnel du SA, protègent le blé (Triticum aestivum L.) contre l’oïdium (Blumeria graminis f.sp. tritici), lorsqu’ils sont utilisés de façon préventive. La protection obtenue n’est pas liée à un effet fongistatique direct sur la germination des spores du champignon, mais à l’induction chez le blé de défenses qui diminuent le développement de la maladie. Notre travail consistait à caractériser les mécanismes de défense mis en jeu après applications foliaires de TR, de HSA et de SA chez un cultivar de blé sensible à l’oïdium. Un suivi de l’expression de gènes marqueurs de défense, réalisé par RTqPCR, a été mené en cinétique,depuis le traitement par les SDPs jusqu'à 4 jours après infection. Les activités enzymatiques correspondantes ont été également mesurées, et l’influence indirecte des SPDs sur le processus infectieux a été observé en microscopie in planta. Ainsi, les réactions de défense déclenchées par le TR, le SA et le HSA ralentissent l’évolution de l’infection, jouant respectivement sur la germination des conidies, structures infectieuses de Bgt, sur la germination du tube germinatif appressorial (AGT) et sur la proportion d’AGTs qui parviennent à pénétrer dans les tissus foliaires. Le TR est à l’origine d’une augmentation de l’expression des gènes codant pour une lipoxygénase, une protéine de transfert des lipides et une phospholipase C, impliquées dans le métabolisme lipidique et la signalisation, et de gènes codant pour des protéines PR comme les chitinases et PR1, tous connus comme marqueurs de défense. Ainsi, les réactions déclenchées par le TR correspondent à un effet inducteur de défenseplutôt qu’à une réaction de stress osmotique. Le HSA modifie particulièrement le métabolisme lipidique, en induisant fortement et pendant toute la cinétique, l’expression du gène codant pour la LOX et l’activité correspondante, aussi bien hors contexte infectieux qu’en contexte infectieux. Cette augmentation de l’activité LOX n’est pas retrouvée chez des feuilles traitées au SA et caractérise donc le HSA. L’importance des réactions observées avec le TR, le SA et le HSA, hors contexte infectieux et en présence de Bgt amène à discuter les effets éliciteurs et potentialisateurs de ces 3 SDPs. / The use of plant elicitors, also known as resistance inducers, is an alternative to conventional fungicides to control diseases caused by phytopathogenic fungi. Three resistance inducers, trehalose (TR), salicylic acid (SA) and heptanoyl salicylic acid (HSA), a functional derivative of SA, protect wheat (Triticum aestivum L.) against powdery mildew (Blumeria graminis f . sp. tritici) when applied prior to infection. The protection obtained is not linked to any direct fungistatic effect on the fungal spore germination, but to the induction of wheat defences that impair the development of the disease. Our work aimed at characterizing the defence mechanisms triggered after foliar applications of TR, HSA and SA in a wheat cultivar susceptible to powdery mildew. Monitoring of defence markers genes expression by RTqPCR was conducted during a time-course experiment from the treatment time until 4 days after infection. Corresponding enzyme activities were also measured, and the indirect influence of elicitors on the infectious process was observed by microscopy in planta. Thus, defence responses triggered by TR, SA and HSA slow the progression of the infection, respectively altering the germination of infectious structures such as conidia, the differentiation of appressorial germ tube (AGT) and the proportion of AGTs that manage to penetrate the epidermis. TR causes an increase in the expression of genes encoding a lipoxygenase, a lipid transfer protein and a phospholipase C, which are involved in lipid metabolism and signaling, and genes encoding for PR-proteins such as chitinases and PR1, all known as markers of defence. Thus, the reactions triggered by TR match with the ones triggered during induced defence rather than during osmotic stress response. HSA specifically targeted lipid metabolism, inducing strongly and throughout the time-course, the expression ofthe gene encoding LOX and the corresponding enzyme activity, both in infectious and non-infectious contexts. This increase in LOX activity was not found in leaves treated with SA and thus characterizes HSA mode of action. The importance of the reactions observed with TR, SA and HSA, in non-infectious conditions and in the presence of Bgt have to be considered regarding either elicitation or potentiation.