2008 Annual Report
1a.Objectives (from AD-416)
One of the objectives of this research is to identify genes involved in asexual sporulation of wheat-biotype Phaeosphaeria nodorum. The genes that are influenced by near ultra-violet light in their expression and highly expressed and critical for asexual sporulation will be studied. The other objective is to identify the quantitative trait loci (QTL) associated with fungal aggressiveness in wheat-biotype Phaeosphaeria nodorum. The long-term objective of this project is to develop an improved understanding of how specific gene expressions affect asexual sporulation and aggressiveness in Phaeosphaeria nodorum. The knowledge can be applied to develop strategies for Stagonospora nodorum blotch disease (P. nodorum is the sexual stage of S. nodorum) control in wheat and other cereals.
1b.Approach (from AD-416)
Vegetative and sporulative cultures that have spontaneously segregated from a single wheat-biotype P. nodorum colony are isolated. The subtraction technique is used to enrich the differentially expressed gene sequences present in poly (A) RNAs of sporulative culture. The expression of specific genes in vegetative and sporulative samples is studied by Northern hybridization. Genetic transformation of vegetative culture is planned to study the gene(s) involved in asexual conidiation. In order to define the gene(s) responsible for sporulation in wheat-biotype P. nodorum, particular gene(s) are also silenced by the cloning of open reading frame (ORF) of the gene. The genes encoding the transcription factors responsible for asexual sporulation in wheat-biotype P. nodorum can be identified by using a knock-out procedure. All transcription factors gene sequences which can be identified in wheat-biotype P. nodorum will be used for gene knockouts to determine their roles in asexual sporulation in P. nodorum.
The quantitative trait loci (QTL) associated with pathogen aggressiveness in wheat-biotype P. nodorum will be studied by a sexual crossing between two isolates with different aggressiveness levels and analyzing the segregation of molecular markers, functional genes and pathogen aggressiveness in their progeny. Polymorphisms in two parental isolates are detected with RAPD (Figure 1), RFLP, SSR, EST and AFLP techniques. The genetic linkage maps are analyzed and constructed with Joinmap 3.0 version software (www.biometris.nl). The segregation data of pathogen aggressiveness in the population are analyzed and the QTL mapping is produced by using an interval mapping method (MapQTL 5 software, www.biometris.nl).
This research addresses Component 2, Problem Statement 2A (Pathogen Biology, Virulence Determinants and Genetics of the Pathogen) of National Program 303, Plant Diseases, in Objectives by generating new knowledge and technologies to reduce crop loss caused by Septoria diseases in cereals. Genomic sequence diversities of the light responsive genes, white color 1 (WC1) and white color 2 (WC2), in wheat-biotype P. nodorum and other six cereal Phaeosphaeria species were studied. The intron positions in the genes were identified from the messenger RNA.
A unique wheat-biotype P. nodorum isolate (S79-1), which could sporulate spontaneously in the continuous dark, was identified. Sporulation in other wheat-biotype P. nodorum isolates was stimulated only by near-ultraviolet light. The results of biological study would help the identification of numerous genes responsible for asexual sporulation in P. nodorum by the substraction technique.
This research addresses Component 2, Problem Statement 2A (Pathogen Biology, Virulence Determinants and Genetics of the Pathogen) of National Program 303, Plant Diseases, in Objectives by generating new knowledge and technologies to reduce crop loss caused by Septoria diseases in cereals.
5.Significant Activities that Support Special Target Populations
Wang, C., Malkus, A., Zuzga, S.M., Chang, P.L., Arseniuk, E., Ueng, P.P. 2007. Diversity of tri-functional histidine biosynthesis gene (his) in cereal Phaeosphaeria species. Genome. 50:595-609.
Reszka, E., Song, Q., Arseniuk, E., Cregan, P.B., Ueng, P.P. 2007. Use of wheat and rye SSR markers to map QTL controlling partial resistance to Stagonospora nodorum blotch disease in a DH population of winter triticale 'Pinokio' x 'Bogo'. Plant Pathology. 16:161-167.