ITEMS FROM BULGARIA

"K.MALKOV" INSTITUTE FOR PLANT GENETIC RESOURCES

4122 Sadovo, Plovdiv, Bulgaria.

Black point of grains in bread winter wheat: 1. N-fertilization influence on the black point of grain in some Bulgarian bread wheat cultivars.

Z. Dachev, Ch. Fylipov, V.I. Vassilev, and S. Stoyanova.

The effect of five different levels of nitrogen fertilization was investigated in the experimental field of IPGR­Sadovo in 1996 and 1997. Ten winter bread wheat cultivars were used. Significant variation in the percent of black-pointed grain was observed, related to both the wheat cultivar and the level of nitrogen fertilization (Table 1).

The differences between wheat cultivars were greater in the unfertilized and lowest nitrogen level treatments (60 kg/ha). The most sensitive wheat cultivars at these levels of fertilization were LC 318, Zlatostrui, Perla, and Sadovo 1. A moderate percent of black-pointed grains were found in the cultivars No 301, Sadovo 552, and Pobeda. The cultivars Slavianka 196, Momchil, and Katia were slightly affected. Black-pointed grains were significantly reduced under levels of nitrogen, especially over the critical point (about 120 kg/ha).

We have observed the same corelation between N-fertilization influence on the black point of grain in most of bread wheat cultivars, but the differences were mainly in quantity of the effect in the second year.

Table 1. The effect of nitrogen levels on the black-pointed grains (%) in several Bulgarian wheat cultivars.

   Cultivar  Nitrogen, kg/ha
 0  60  120  180  240
 1996  1997  1996  1997  1996  1997  1996  1997  1996  1997
 LC 318 22.4  16.7 11.6 7.2 6.8 4.0 2.8 4.0 3.6 5.6
 Zlatostrui  19.2 16.4 9.2 8.0 7.2 4.4 1.6 5.2 2.4 9.6
 Perla  14.4 9.6 4.8 4.4 2.8 3.6 0.8 1.2 0.8 0.0
 Sadovo 1  14.0 9.6 10.8 4.4 5.6 4.0 2.4 3.2 1.2 2.8
 No 301 6.8  6.0 7.2 2.4 2.4 4.0 2.4 2.8 0.8 6.4
 Sadovo 552  6.8 8.4 3.6 7.6 0.8 3.6 0.4 4.8 1.2 4.8
 Pobeda  4.8 5.6 2.8 9.6 1.2 2.0 0.8 3.2 0.4 3.2
 Slavyanka 196  3.2 4.4  2.8 5.6 2.0 0.8 0.0 3.2 0.0 2.8
 Momchil  2.4 6.0 3.6 2.4 1.2 4.4 0.0 5.6 0.0 2.8
 Katya  2.4 6.4 1.2 1.6 0.0 2.0 1.2 2.8 0.0 2.0

 

Black point of grain in winter bread wheat: 2. Biotic and abiotic causal agents.

V.I. Vassilev, S. Stoyanova, Z. Dachev, and Ch. Fylipov.

Germination tests (according ISTA) of seed samples were planted in four replicates at 20 C in vertical paper rolls. Evaluation of the grain surface, culms, and roots were made 4 days later using a 16­50 X stereo-microscope. The wheat cultivar Sadovo 1 was used as the standard. The main fungi present in black-pointed wheat grains were Alternaria, Fusarium, and Drechslera (Helminthosporium ) species (Table 2).

Table 2. Fungal species observed in black-pointed grain of unfertilized winter wheat cultivars 4 days after germination. Observations were made at 16-50 X using a stereo-microscope.

 Species  Number  Percent
 Alternaria  2 x 50  88-100
 Helminthosporium  2 x 50  34-82
 Fusarium  2 x 50  0-8

 

Diseased kernels were discolored and black pointed. The seed coat also was discolored and invaded by hyphae in many cases. The isolated bacterial and fungal species, except for Fusarium, were not pathogenic when artificially inoculated onto 3­5 leaves of adult wheat plants. Several roots were rarely invaded by these fungi. In comparison with the first year of investigation, a higher percent of nonpathogenic Helminthosporium spp. is now observed. Many of the black-pointed grains were clean of pathogenic fungi. Some abiotic factors induced discoloration in and around the embryos. This phenomenon is expected when seedborne cereal diseases are evaluated in different environmental conditions, especially in low-level nitrogen fertilization conditions.

 

Black point of grains in bread winter wheat: 3. Effect on seed viability.

S. Stoyanova, Z. Dachev, Ch. Fylipov, and V.I. Vassilev.

Ten bread wheat cultivars were evaluated in order to describe the variation in black point on the grain and the effect on seed germination and survival under unfavorable conditions. The seed germination tests were according to ISTA standards (1985). Germinated seeds were evaluated 4 and 7 days after planting. Seed viability was observed using an accelerated-aging test at 60°C and a seed moisture content between 14.7 and 15.2 %. The seed viability constants Ki and p50 were derived by the seed viability equations and probit analysis as described by Roberts and Ellis (1982). Our results indicate that the incidence of black point is not absolutely associated with poor seed germination (Table 3).

Table 3. Comparison of seed germination between wheat seed lots affected by black point of grain harvested in 1997.

 Cultivar  Black-pointed grain(%)  Germinated seed
 % in main lot  % in black-pointed seed lot
 4 days  7 days  4 days  7 days
 Sadovo 1 9.6  96 96 94 95
 Momchil 6.0  97 98 96 96
 LC 318 16.7  94 94 100 100
 Slavianka 196 4.4  92 93 93 94
 Pobeda 5.6 90  94 93 94
 Perla 9.6   94 95 96 97
 Zlatostrui 16.4 98 98 96 96
 No 301 6.0   90 90 92 92
 Sadovo 552 8.4   92 95 91 94
 Katya  6.4  94 94 92 92

 

Table 4. Seed viability constants observed by accelerated aging test of 10 wheat cultivars with different values of black-pointed germ.

 Cultivar

 Seed equation-K

V v = Ki­p/·

 Correlation coefficient Ki (probits)  P50 (days)  Seed viability (%)
 Sadovo 1  v = 2.38­0.61.p  - 0.97 2.38  3.90 99.13
 Momchil  v = 2.24­0.45.p  - 0.98 2.24  4.98 98.74
 LC 318  v = 1.64­0.24.p  - 0.97 1.64  6.83 94.95
 Slavianka 196  v = 1.98­0.33.p  - 0.96 1.98 5.99 97.61
 Pobeda  v = 1.92­0.54.p  - 0.96 1.92  3.25 97.25
 Perla  v = 2.44­0.39.p  - 0.98 2.44 6.25 99.26
 Zlatostrui  v = 2.12­0.44.p  - 0.96 2.12  4.82 98.30
 No 301  v = 1.31­0.37.p  - 0.93 1.31  3.87 79.10
 Sadovo 552  v = 2.21­0.57.p  - 0.95 2.21  3.30 98.64
 Katya  v = 1.55­0.47.p  - 0.95 1.55  3.30 93.94

 

In five of the wheat cultivars, affected seeds had higher or similar germinability than Sadovo 1. Although our previous investigations with Sadovo 1 indicated a slightly lower initial germination rate in seeds with black point (AWN 1997); this might not be due only to the presence of black-point fungi. The seed viability constant defines the viability of the initial seed lot (Ki), and the period of time for seed viability to be reduced to 50 % (p50). These values confirm that seed viability and seed storability vary between cultivars, but this variation may not be caused only by the presence of black points (Table 4).

References.

Al-Sallami F, Karov S, and Vassilev V. 1996. Pseudomonas syringae pv. atrofaciens associated with fungal diseases of wheat (Triticum aestivum) grain. In: 5th Inter Wheat Conf 10-14 June, 1996, Ankara, Turkey. Pp. 111-112.

Al-Sallami F, Karov S, Vassileva P, Popova R, and Vassilev V. 1997. Pseudomonas syringae pv. atrofaciens associated with fungal black point of wheat (Triticum aestivum) grain. In: Development in Plant Pathology vol. 9. Pseudomonas syringae pathovars and related pathogens. Kluwer Academic Publishers, Dordrecht/Boston/London. Pp. 505-508.

ISTA. 1985. International Rules for Seed testing. Seed Science and Technology. 13:2.

ISTA. 1987. In: 19 th International Seminar on Seed Pathology Wageningen 10­18 May, 1987. Zurich, Switzerland.

Roberts EH and Ellis RH. 1982. Physiological, ultrastructural and methabolic aspects of seed viability. In: The Physiology and Biochemistry of Seed Development, Dormancy and Germination (Khan AA ed). Elsevier Biomedical Press. Pp. 465-485.