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2003 Plant Management Network.
Accepted for publication 6 October 2003. Published 24 November 2003.


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. bockus@plantpath.ksu.edu


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.).


     
 

Fig. 1. Prematurely-ripe culms due to take-all in a commercial wheat field.

 

Fig. 2. Root rot and basal stem discoloration of a wheat plant due to take-all.

 

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 205C, fresh weights of plant parts (10 plants per treatment per replication) above the soil level were measured and losses in fresh weight calculated.


 

Fig. 3. Bioassay to screen for reaction of small grain entries to take-all. An entry within each replication had two rows (non-inoculated and inoculated) of ten plastic tubes, each with one plant. The pair of rows on the left show a typical susceptible entry (74 to 93% loss) and the pair of rows on the right show a typical resistant entry (30 to 47% loss). Note that several of the plants in the inoculated row of the left-hand pair show disease escape, hence the need for averaging all 10 plants in a row to get a value for one replication.

 

Fig. 4. Wheat seedling in a plastic tube showing discoloration of the basal stem due to take-all.


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.


Literature Cited

1. Foex, E. 1935. Quelques observations sur les maladies du pied des cereals. C. R. Hebd. Seances Acad. Agric. France 21:501-505.

2. Friebe, B., Jiang, J., Raupp, W. J., McIntoch, R. A., and Gill, B. S. 1996. Characterization of wheat-alien translocations conferring resistance to disease and pests: Current status. Euphytica 91:59-87.

3. Jensen, H. P., and Jorgensen, J. H. 1976. Screening of barley varieties for resistance to the take-all fungus, Gaeumannomyces graminis. Z. Pflanzenzucht 76:152-162.

4. Rothrock, C. S. 1988. Relative susceptibility of small grains to take-all. Plant Dis. 72:883-886.