Assessing How the Aluminum-Resistance Traits in Wheat and Rye Transfer to Hexaploid and Octoploid Triticale.

The mechanisms of aluminum (Al) resistance in wheat and rye involve the release of citrate and malate anions from the root apices. Many of the genes controlling these processes have been identified and their responses to Al treatment described in detail. This study investigated how the major Al resistance traits of wheat and rye are transferred to triticale (x Tritosecale Wittmack) which is a hybrid between wheat and rye. We generated octoploid and hexaploid triticale lines and compared them with the parental lines for their relative resistance to Al, organic anion efflux and expression of some of the genes encoding the transporters involved. We report that the strong Al resistance of rye was incompletely transferred to octoploid and hexaploid triticale. The wheat and rye parents contributed to the Al-resistance of octoploid triticale but the phenotypes were not additive. The Al resistance genes of hexaploid wheat, TaALMT1, and TaMATE1B, were more successfully expressed in octoploid triticale than the Al resistance genes in rye tested, ScALMT1 and ScFRDL2. This study demonstrates that an important stress-tolerance trait derived from hexaploid wheat was expressed in octoploid triticale. Since most commercial triticale lines are largely hexaploid types it would be beneficial to develop techniques to generate genetically-stable octoploid triticale material. This would enable other useful traits that are present in hexaploid but not tetraploid wheat, to be transferred to triticale.

Quantification of Pseudocercospora fuligena in Tomato Lines Carrying Introgressions from Solanum habrochaites Using a qPCR Assay.

Black leaf mold (BLM), caused by Pseudocercospora fuligena, is a major plant growth- and yield-limiting factor for tomato production in the humid tropics. A library of 90 introgession lines (ILs), the BLM-resistant donor Solanum habrochaites, and the BLM-susceptible recurrent S. lycopersicum parent (RP) were visually phenotyped under natural infection conditions in a nethouse in central Thailand. ILs showing no and severe BLM symptoms were among the phenotypes. Because visually classifying different phenotypes of BLM symptoms can lead to erroneous results due to the similarity of BLM symptoms to other abiotic and biotic problems, a SYBR Green-based quantitative polymerase chain reaction (qPCR) assay for fungal DNA was developed. Correlation of the results from visual phenotyping of plants grown in Thailand under natural infection conditions with qPCR test-based quantities of the tomato leaf fungal DNA content, while significant, explained only 39% of the relationship across the library population. Based on this phenotyping in Thailand, selected ILs were artificially infected in a growth chamber in Germany with a P. fuligena isolate from Thailand. The results of the natural infection could be verified for the selected ILs in the growth-chamber experiment. A close correlation (R2 = 0.87) existed between the visual disease rating and fungal DNA content in leaves in the latter experiment. Three lines without visual symptoms and very low amounts of P. fuligena-specific rDNA shared an overlapping introgression on chromosome one that may be associated with BLM resistance.