Tbe distribution of important plant-parasitic and free-living nematodes in tbe cereal production areas of tbe Central Anatolian Plateau (CAP) of Turkey was investigated witb systematic surveys. Two important plant-parasitic nematode groups were found widely distributed; cereal-cyst nematodes (78.3%) and root-lesion nematodes (42.6%). Cereal cyst nematodes (CCN) were identified as Heterodera filipjevi in 18 provinces. Heterodera latipons was found in only one province. Pratylenchus thornei and P. neglectus were tbe most widely distributed species of root-lesion nematodes. Otber frequently recorded plant-parasitic nematodes belonged to tbe genera Geocenamus (52.4%), Pratylenchoides (35.6%), Helicotyienchus (29.7%) and Paratylenchus (19.2%). Konya on tbe soutbern CAP bad a significantly bigb incidence of P. neglectus as well as free-living nematodes. Tbe incidence of CCN was greatest in areas of sandy soils on tbe CAP, witb densities of up to 95 cysts (100 g soil)"'. Population densities of Geocenamus, Pratylenchus and Pratylenchoides were bigb in some locations. Soil pbysicocbemical properties were investigated for tbeir relationship to nematode distribution. Tbere was a sligbt positive correlation of P. thornei and clay content; conversely, there was a significant negative correlation of P. negiectus witb clay and a positive correlation witb sand. Electrical conductivity (EC) was positively correlated witb P. neglectus. Nematodes in tbe genera Heiicotylenchus, Paratylenchus, Trophurus and Tylenchorhynchus were only recorded at low population densities in tbe sampled area. By contrast, nematodes in tbe genera Aphelenchus, Apheienchoides, Dityienchus, Dorylaimus, Tylenchus and bacterivorous genera bad relatively bigb populations. Total free-living nematodes were positively correlated witb EC and zinc (Zn) concentration. Tbe Zn content of soil was generally at a level deficient for plant growtb.

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Expressed sequenced tags containing simple sequence repeats (EST-SSRs) were used to identify molecular markers associated with yellow rust resistance in wheat (Triticum aestivum L.). A cross between yellow rust resistant (PI178383) and susceptible (Harmankaya99) wheat genotypes was performed and respective DNA pools from the resistant and susceptible F 2 seedlings were constructed. 78 EST-SSR primers were used for bulked segregant analysis and one EST-SSR marker (Pk54), identified as 200 bp fragment, was present in the resistant parent and resistant F 2 hybrids but not in the susceptible ones. 108 wheat genotypes differing in yellow rust resistance were screened with Pk54 and 68 % of the wheat genotypes, known to be yellow rust resistant, had the Pk54 marker, further suggesting that the presence of this marker correlates with yellow rust resistance.

Bulk segregant analysis (BSA) was used to identify molecular markers associated with yellow rust disease resistance in wheat (Triticum aestivum L.). DNAs isolated from the selected yellow rust tolerant and susceptible F 2 individuals derived from a cross between yellow rust resistant and susceptible wheat genotypes were used to established a "tolerant" and a "susceptible" DNA pool. The BSA was then performed on these DNA pools using 230 markers that were previously mapped onto the individual wheat chromosomes. One of the SSR markers (Xgwm382) located on chromosome group 2 (A, B, D genomes) was present in the resistant parent and the resistant bulk but not in the susceptible parent and the susceptible bulk, suggesting that this marker is linked to a yellow rust resistance gene. The presence of Xgwm382 was also tested in 108 additional wheat genotypes differing in yellow rust resistance. This analysis showed that 81% of the wheat genotypes known to be yellow rust resistant had the Xgwm382 marker, further suggesting that the presence of this marker correlates with yellow rust resistance in diverse wheat germplasm. Therefore, Xgwm382 could be useful for marker assisted selection of yellow rust resistances genotypes in wheat breeding programs.

One of the most important diseases of wheat in Turkey is yellow rust. The severe epidemic in the 1997–1998 growing season, which caused significant yield reductions, and the absence of infection at the Hamidiye Substation of the Anatolian Agricultural Research Institute made it possible to calculate the yield losses due to stripe rust. This calculation was based on yield differences between genotypes at infected and disease-free locations using various methods.Using the method suggested by Campbell et al. (1975) the calculated yield loss due to stripe rust varied among genotypes and locations with an overall range of 12.7 to 87.0%.By the second method, entries were divided into five groups according to their Average Coefficients of Infection (ACI) and the yield losses in each group were calculated. Yield reductions when ACI was over 70 reached up to 57.5 % in Regional Yield Trials.In the third method, regression analysis was applied to estimate the effect of ACI on grain yields. A highly significant linear relationship was found between the ACI values of the entries and their grain yields, with an estimate of 21.4 kg/ha yield reduction per unit increase in ACI.

Soil-borne wheat mosaic virus (SBWMV) is an important disease of wheat production areas throughout the world, causing a great reduction in wheat and barley yields. The most effective way of controlling the disease is the use of resistant varieties in infested areas. In this study, the effects of SBWMV on yields and some yield components of eight susceptible, one moderately susceptible/resistant and nine resistant varieties were evaluated using data from 9 virus-infested and 6 non-infested sites in Eskisehir, Turkey over 6 years. The susceptible varieties yielded 5.35% more than resistant varieties in noninfested sites, while they gave 28.98% lower yield in infested sites. Significant yield loss differences were observed between the varieties in infested sites. Decreases were also observed in yield components at various levels. This study showed that SBWMV is an important disease, which survives in soil for long periods and causes significant yield decreases in wheat. Recently developed varieties have good resistance to the disease and are recommended to farmers in infested areas.

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