ITEMS FROM GERMANY

 

INSTITUT FÜR PFLANZENGENETIK UND KULTURPFLANZENFORSCHUNG (IPK)

Corrensstraße 3, 06466 Gatersleben, Germany.

 

A. Börner, U. Freytag, U. Sperling, K.F.M. Salem, and E.K. Khlestkina.

Sixty years disease-resistance screening. [p. 58]

During a 60-year period, 10,348 accessions belonging to 21 species (hexaploid, tetraploid, and diploid) of the genus Triticum and 489 accessions of the genus Aegilops were scored for disease resistance. Tests were made at the seedling stage for powdery mildew, leaf rust, stripe rust, and eyespot, and at the adult-plant stage for powdery mildew, leaf rust, stripe rust, eyespot, and S. nodorum. Not all accessions were analyzed for all diseases at all different growth stages, however, for most of the material, scoring data for several diseases are available. For a certain number of accessions, repeated tests were made in different years. About 125,000 disease scores, recorded on index cards using different scoring scales, were computerized, converted into a 1-9 scale, and used to summarize the results. About 20 % of the material analyzed was classified as heterogeneous. For accessions without detectable segregation, a large variability for resistance/susceptibility was detected. At the adult-plant stage, resistant accessions without visible infections were identified for all diseases. The percentage of resistant accessions at that growth stage always was higher than those found in the material tested at the seedling stage. About 90 % of the accessions identified to be resistant at the seedlings stage were resistant or only slightly infected as adult plants. The probability for finding resistant material was shown to be highest in Aegilops and diploid species of the genus Triticum (> 50 %) but decreased with increasing ploidy level to about 10 % in the hexaploid wheats. Highly resistant accessions can be identified within the hexaploid gene pool but with a much lower efficiency. The higher input needed here for screening will be compensated by a lower effort necessary for using this material in the breeding process. The data obtained for the individual accessions are available via the internet at http://www.ipk-gatersleben.de.

 

Stem-reserve mobilization. [p. 58-59]

A selection of 28 Egyptian wheat varieties was grown in the greenhouse and evaluated for the ability to mobilize stored stem reserves under drought stress. For the investigation, we used a method for chemical desiccation of the plant canopy. Two weeks after anthesis in one replication of the experiment, the canopies were sprayed with potassium iodide (0.5 %). In order to calculate the rate of reduction in grain weight caused by the treatment, the 1,000-kernel weight of the treated plants was compared with that of controls after harvest. The percentages of reduction ranged between 16.97 % for Seds 3 and 33.83 % for Sakha 8 (Table 1). Sakha 8 was already known to be drought resistant. Further candidates for increased drought insensitivity are the varieties Gemmiza 7 and Gemmiza 9.

Table 1. Percentage of grain weight reduction after chemical desiccation of the plant canopy of wheats originated from Egypt.
 Variety  % grain weight reduction  Variety  % grain weight reduction
 Sakha S  33.83  Gemmiza 5  22.96
 Gemmiza 7  31.98  Seds 2  22.41
 Gemmiza 9  31.76  Giza 164  21.29
 Seds 4  29.19  Gemmiza 3  21.09
 Giza 155  28.11  Sakha 69  21.02
 Sakha 92  27.54  Giza 163  20.49
 Seds 7  27.52  Gemmiza 1  20.40
 Seds 9  26.69  Sahel 6  19.15
 Seds 5  25.19  Giza 144  17.48
 Sahel 1  24.59  Giza 160  18.85
 Sakha 61  24.28  Giza 157  18.66
 Seds 8  23.75  Seds 3  16.97
 Seds 6  23.73  Giza 167  15.68
 Giza 139  23.05    

 

Geographical distribution of red-coleoptile color genes. [p. 58-65]

A collection of 254 wheat accessions of the Gatersleben gene bank was scored for coleoptile color determined by anthocyanin pigmentation. Fifteen seeds/accession were placed on filter paper and kept for 36 hours at 4°C to synchronize germination. The temperature was increased to 15°C and the color of the coleoptiles was scored after 5-8 days of growth at a photoperiod of 14-h light/10-h darkness. The results obtained are given in Table 2. About 71 % (181) of all tested varieties had noncolored coleoptiles. Red and dark red coleoptiles were detected in 22 % (56) and 7 % (17) of the plants, respectively, One accession was heterogeneous. A high percentage of red coleoptiles was detected in T. macha lines from Georgia and T. spelta from Germany and Switzerland.

 

Publications.