© 2003 Plant Management Network.
Resistance to Take-all is Not Expressed in Wheat-Alien Chromosome Addition and Substitution Lines
Yong-Ki Kim, Bernd Friebe, and William W. Bockus, Department of Plant Pathology, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS 66506
Corresponding author: William W. Bockus. firstname.lastname@example.org
Kim, Y. K., Friebe, B., and Bockus, W. W. 2003. Resistance to take-all is not expressed in wheat-alien chromosome addition and substitution lines. Online. Plant Health Progress doi:10.1094/PHP-2003-1124-01-HN.
Take-all (Figs. 1, 2), caused by the fungus Gaeumannomyces graminis (Sacc.) Arx & D. Olivier var. tritici J. Walker, is regarded as the most damaging root disease of cereals including wheat (Triticum aestivum L.) and is widely distributed worldwide. In spite of its importance, little progress has been made in breeding for resistance. The absence of useful levels of resistance to G. graminis var. tritici in wheat has turned the attention of breeders and pathologists to the possibility of transferring resistance from related species (2). Haynaldia villosa Schur has been reported to possess a high level of resistance (1). Similarly, Jensen and Jorgensen (3) identified useful levels of resistance in barley (Hordeum spp.).
A greenhouse bioassay was developed that consistently ranked four small grains in their correct order of susceptibility to take-all in the field (wheat > barley > rye = oat) (4). This assay was used to evaluate several wheats that carry alien chromosomes. Single plants were grown in a 1:1 (v:v) mixture of pasteurized soil (Kennebeck silty clay loam) and vermiculite in plastic tubes (2.5 cm in diameter and 12.5 cm long). Experiments included 10 tubes per entry-treatment (inoculated or non-inoculated) per replication and 4 replications. The experimental design was a randomized split-plot with the accessions as main-plot treatments and presence or absence of inoculum as sub-plot treatments (Fig. 3). Inoculated tubes each received three oat kernels colonized by G. graminis var. tritici introduced 1 cm below seed level (Fig. 4). After 4 weeks at 20±5°C, fresh weights of plant parts (10 plants per treatment per replication) above the soil level were measured and losses in fresh weight calculated.
Four sets of wheat-alien chromosome addition and substitution lines of species with resistance to take-all were obtained from the Wheat Genetics Resource Center, Kansas State University. The sets were: (i) wheat (cv. Chinese Spring)-Hordeum vulgare (cv. Betzes) disomic addition lines; (ii) wheat (cv. Chinese Spring)-Hordeum chilense disomic addition lines; (iii) wheat (various lines)-H. villosa disomic addition and substitution lines; and (iv) wheat (cv. Chinese Spring)-H. villosa disomic addition lines. Three of the four sets were not complete. Cytogenetic analysis revealed that two addition lines of Set i (chromosomes 1H and 7H) and two addition lines of Set ii (2Hch and 3Hch) had only 42 chromosomes. For Set iii, addition and substitution lines for 1V, 2V, and 7V were not available. Parental lines and "Don" oats were used as controls.
Each set of addition and substitution lines, along with the appropriate controls, was evaluated in its own experiment. Within an experiment, 80 seeds of each entry (line or control) were used (10 in non-inoculated tubes and 10 in inoculated tubes in each of 4 replications). All five wheat-barley disomic chromosome addition lines were more susceptible [82 to 90% loss in fresh weight, LSD (P = 0.05) = 10.1] than the barley parent (Betzes = 36%) and two of them (2H and 3H) had significantly more loss (90%) than the wheat parent (Chinese Spring = 78%). In another experiment, there were no differences among all five wheat-H. chilense disomic chromosome addition lines [77 to 88%; LSD (P = 0.05) = 13.7] and they were as susceptible as the wheat parent (79%). In a third experiment (Set iii), H. villosa [30%; LSD (P = 0.05) = 8.16] was more resistant than barley (Betzes = 47%); however, all four wheat-H. villosa disomic chromosome addition and two substitution lines (4V and 5V) were more susceptible (85 to 93% loss) than the wheat check (76%). Substitution lines 3V and 6V were as susceptible (75 to 80%) as wheat. In a fourth experiment involving the complete set of wheat-H. villosa disomic chromosome addition lines (Set iv), improved levels of resistance over that of the wheat parent [77% loss; LSD (P = 0.05) = 14.9] were not detected in any of the chromosome addition lines (74 to 90%).
In summary, the bioassay used in this study was a rapid, accurate way for screening accessions for susceptibility to take-all in the greenhouse. None of the addition or substitution lines had improved levels of resistance even though their resistant parents had significantly less take-all than wheat. In the cases where a complete set of lines was not available, any genes that might confer resistance may be on a chromosome missing from the set. Alternatively, take-all resistance in these species may be polygenic with genes on different chromosomes or it may be masked by the wheat genome. Therefore, transfer of take-all resistance from H. vulgare, H. chilense, or H. villosa to wheat may not be easily accomplished.
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