Powdery mildew (PM) is a common disease caused by Blumeria graminis, which affects cereals and has recently adapted to triticale. Adult‐plant resistance (APR) genes provide durable protection of crops from the disease. Quantitative trait loci corresponding to the APR effects were mapped in an F2 population of “Lamberto” (susceptible) × “Moderto” (resistant). A genetic map of winter triticale was constructed based on the segregation of 863 DArT, 38 microsatellite and 10 resistance gene analogue markers. Composite interval mapping (CIM) was applied to identify three QTLs for maximum disease severity (MDS) and two for the area under disease progress curve (AUDPC) conferring resistance to the powdery mildew on chromosomes: 6A, 7A, 1B and 4R. The 39% variation in AUDPC was explained by the main QTL localised on chromosome 4R. Genes coding TRIUR3 proteins, serine/threonine protein kinase and cell wall associated kinases were localised in silico within the QTL and alternative DNA markers were proposed for flexible use in laboratories of diversified throughput.
Przedmiotem badań było 35 genotypów pszenżyta ozimego o zróżnicowanym podłożu genetycznym oraz dwie odmiany, które analizowano pod względem odporności na fuzariozę kłosów powodowaną przez Fusarium culmorum oraz akumulacji toksyn fuzaryjnych w ziarnie. Genotypy pszenżyta zostały wysiane na poletkach doświadczalnych w dwóch lokalizacjach: Cerekwica i Radzików. Kłosy poszczególnych genotypów były inokulowane mieszaniną trzech szczepów Fusarium culmorum. Określono indeks fuzariozy kłosów (IFK) oraz procent uszkodzonych ziarniaków (FDK). Ziarniaki były analizowane pod względem zawartości trichotecen z grupy B (deoksyniwalenol [DON] i pochodne, niwalenol) oraz zearalenonu. Indeks fuzariozy kłosów w obu lokalizacjach był zbliżony, średnio w Cerekwicy 7,8% a w Radzikowie 10,2%, jednakże średnie IKF różniły się statystycznie istotnie. Procent ziarniaków uszkodzonych przez Fusarium był wyższy w Cerekwicy niż Radzikowie, odpowiednio średnio 43,0% i 28,7%. Stwierdzono wysokie stężenie toksyn w ziarniakach badanych genotypów pszenżyta. Zawartość DON w dwóch lokalizacjach wahała się od 1,528 do 7,613 mg/kg — średnio 3,994 mg/kg. Stwierdzono również wysokie stężenie niwalenolu od 1,673 do 19,735 mg/kg — średnio 7,213 mg/kg. Wykazano istotną statystycznie korelację pomiędzy sumą trichotecen i FDK (r = 0,706) oraz sumą trichotecen a redukcją masy ziarna z kłosa (r = 0,407). Zawartość niwalenolu i zearalenonu również istotnie korelowała z FDK (r = 0,697 i r = 0,339. Analiza k-średnich pozwoliła na wyróżnienie trzech grup genotypów pszenżyta. Grupa pierwsza — obejmująca 15 genotypów charakteryzowała się średnim IFK oraz niskim uszkodzeniem ziarniaków i niską zawartością toksyn fuzaryjnych. Redukcja plonu ziarna oraz MTZ była na średnim poziomie, natomiast najniższa w tej grupie była redukcja liczby ziarniaków w kłosie. Grupa druga zawierająca 11 genotypów, charakteryzowała się najniższym średni porażeniem kłosa, czemu towarzyszyło wyższe niż w grupie pierwszej uszkodzenie ziarniaków. Wyższa też była w tej grupie zawartość toksyn w ziarnie. Redukcja plonu i liczby ziarniaków nie różniła się wyraźnie od tej dla grupy pierwszej. Niższa była natomiast redukcja MTZ. W grupie trzeciej obejmującej 11 genotypów znalazły się genotypy o najwyższej podatności na porażenie kłosa, uszkodzenie ziarniaków i akumulację toksyn. W grupie tej najwyższe były też redukcje komponentów plonu.
Three triticale cDNAs encoding inhibitors of cysteine endopeptidases, belonging to phytocystatins, have been identified and designated as TrcC-1, TrcC-4 and TrcC-5. Full-length cDNAs of TrcC-1 (617 bp) and TrcC-4 (940 bp), as well as a fragment of TrcC-5 cDNA (369 bp), were obtained. A high-level identity of the deduced amino acid sequence of TrcCs with other known phytocystatins, especially with wheat and barley, has been observed. Moreover, the presence of conserved domain, containing the G and W residues, the sequence of QxVxG and the sequence of LARFAV, characteristic for plant cysteine endopeptidase inhibitors, has been noted. The profiles of TrcC-1 and TrcC-5 mRNA levels in the developing seeds of two triticale cultivars that differ in their resistance to preharvest sprouting (Zorro and Disco) were similar. However, the expression of TrcC-4 was, higher in the developing seeds, and in the scutellum of germinating seeds of a cultivar more resistant to preharvest sprouting (Zorro) than in the less resistant (Disco). Additionally, the expression of TrcC-4 remained longer in developing seeds of Zorro as compared to Disco. The performed studies suggest that TrcC-4 might have an influence on the higher resistance of Zorro cultivar to preharvest sprouting.
Cytoplasmic male sterility (CMS) phenomenon is widely exploited in commercial hybrid seed production in economically important crop species, including rye, wheat, maize, rice, sorghum, cotton, sugar beets, and many vegetables. Although some commercial successes, little is known about QTLs responsible for the trait in case of triticale with sterilizing Triticum timopheevii (Tt) cytoplasm. Recombinant inbred line (RIL) F6 mapping population encompassing 182 individuals derived from the cross of individual plants representing the HT352 line and cv Borwo was employed for genetic map construction using SNP markers and identification of QTLs conferring pollen sterility in triticale with CMS Tt. The phenotypes of the F1 lines resulting from crossing of the HT352 (Tt) with HT352 (maintainer) × Borwo were determined by assessing the number of the F2 seeds per spike. A genetic map with 21 linkage groups encompasses 29,737 markers and spanned over the distance of 2549 cM. Composite (CIM) and multiple (MIM) interval mappings delivered comparable results. Single QTLs mapped to the 1A, 1B, 2A, 2R, 3B, 3R, 4B, and 5B chromosomes, whereas the 5R and 6B chromosomes shared 3 and 2 QTLs, respectively. The QTLs with the highest LOD score mapped to the 5R, 3R, 1B, and 4B chromosomes; however, the QRft-5R.3 has the highest explained variance of the trait.
Abscisic acid (ABA) is a phytohormone involved in the acquisition of primary dormancy during seeds maturation as well as dormancy maintenance in imbibed seeds. After imbibition, the ABA content decreased to a much lower level in embryos of freshly harvested triticale grains of the Leontino cultivar, which is more susceptible to pre-harvest sprouting (PHS) than embryos of the Fredro cultivar. Lower ABA content in the Leontino cultivar resulted from increased expression of TsABA8'OH1 and TsABA8'OH2, which encode ABA 8'-hydroxylase and are involved in ABA catabolism. Higher ABA content and maintenance of dormancy in Fredro grains were correlated with intensified ABA biosynthesis, which resulted from higher expression of TsNCED1, which encodes 9-cis-epoxycarotenoid dioxygenase. These results suggest that grains of triticale cultivars with different resistance to PHS vary in their ability to metabolize ABA after imbibition. After-ripening did not affect the ABA content in embryos of dry grains of either triticale cultivar. However, after-ripening caused dormancy release in Fredro grains and significantly affected the ABA content and the rate of its metabolism after imbibition. A more rapid decline in ABA content in imbibed Fredro grains was accompanied by decreased transcript levels of TsNCED1 as well as increased expression of TsABA8'OH1 and TsABA8'OH2. Thus, after-ripening may affect dormancy of grains through reduction of the ABA biosynthesis rate and intensified ABA catabolism. Overexpression of TsNCED1 in tobacco increases ABA content and delays germination, while overexpression of TsABA8'OH2 decreases ABA content, accelerates germination, and reduces the sensitivity to ABA of transgenic seeds compared to seeds of wild-type plants. Therefore, these genes might play an important role in the regulation of triticale grain dormancy, thus affecting susceptibility to PHS.
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