Abstract
BackgroundCrop production practices and industrialization processes result in increasing acidification of arable soils. At lower pH levels (below 5.0), aluminum (Al) remains in a cationic form that is toxic to plants, reducing growth and yield. The effect of aluminum on agronomic performance is particularly important in cereals like wheat, which has promoted the development of programs directed towards selection of tolerant forms. Even in intermediately tolerant cereals (i.e., triticale), the decrease in yield may be significant. In triticale, Al tolerance seems to be influenced by both wheat and rye genomes. However, little is known about the precise chromosomal location of tolerance-related genes, and whether wheat or rye genomes are crucial for the expression of that trait in the hybrid.ResultsA mapping population consisting of 232 advanced breeding triticale forms was developed and phenotyped for Al tolerance using physiological tests. AFLP, SSR and DArT marker platforms were applied to obtain a sufficiently large set of molecular markers (over 3000). Associations between the markers and the trait were tested using General (GLM) and Multiple (MLM) Linear Models, as well as the Statistical Machine Learning (SML) approach. The chromosomal locations of candidate markers were verified based on known assignments of SSRs and DArTs or by using genetic maps of rye and triticale.Two candidate markers on chromosome 3R and 9, 15 and 11 on chromosomes 4R, 6R and 7R, respectively, were identified. The r2 values were between 0.066 and 0.220 in most cases, indicating a good fit of the data, with better results obtained with the GML than the MLM approach. Several QTLs on rye chromosomes appeared to be involved in the phenotypic expression of the trait, suggesting that rye genome factors are predominantly responsible for Al tolerance in triticale.ConclusionsThe Diversity Arrays Technology was applied successfully to association mapping studies performed on triticale breeding forms. Statistical approaches allowed the identification of numerous markers associated with Al tolerance. Available rye and triticale genetic maps suggested the putative location of the markers and demonstrated that they formed several linked groups assigned to distinct chromosomes (3R, 4R, 6R and 7R). Markers associated with genomic regions under positive selection were identified and indirectly mapped in the vicinity of the Al-tolerant markers. The present findings were in agreement with prior reports.
Highlights
Crop production practices and industrialization processes result in increasing acidification of arable soils
The present study aimed to identify molecular markers associated with Al tolerance among plants randomly selected from advanced triticale breeding materials
Al tolerance test Out of 232 individual plants representing 232 breeding forms, the roots of 76 plants were irreversibly damaged by aluminum and did not continue to grow after the test, and 35 showed little regrowth ability (transformed value of regrowth below 0.2 (Table 1))
Summary
Crop production practices and industrialization processes result in increasing acidification of arable soils. Little is known about the precise chromosomal location of tolerance-related genes, and whether wheat or rye genomes are crucial for the expression of that trait in the hybrid. Hexaploid triticale (X Triticosecale Wittmack) is a hybrid of tetraploid wheat and diploid rye with genome composition AA, BB and RR. It is cultivated in Poland mainly as a fodder cereal, and its area of cultivation doubled during the last 10 years [1]. Tolerant plants can be identified by physiological tests [3,4,5,6,7,8,9]. More direct methods based on DNA markers [10,11,12,13] and saturated genetic maps or, preferentially, consensus maps of the species are needed to overcome these issues
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