Husrev Mennan

Seasonal cycles in germination and seedling emergence of summer and winter populations of catchweed bedstraw (Galium aparine) and wild mustard (Brassica kaber)

Abstract Catchweed bedstraw and wild mustard each produce two populations per year: a winter population (WP) in June, and a summer population (SP) in September. Experiments were conducted to determine whether the WP and SP differ in seed mass and seasonal germination. Seeds of both weeds were buried at 0, 5, 10, and 20 cm in cultivated fields, and retrieved at monthly intervals for 24 mo for germination tests in the laboratory. Additionally, seedling emergence from seeds buried at 0, 5, and 10 cm in the field was evaluated for 1 yr. Seeds from the WP were heavier than those from the SP for both species. Germination of exhumed seeds was affected by burial depth and by seed population. It was highest for seeds that remained on the soil surface and declined with increasing depth of burial. The WP of catchweed bedstraw produced two germination peaks per year, whereas the SP and all populations of wild mustard had only one peak. The WP of both weeds germinated earlier than the SP. Seedling emergence for both species in the field was greater for the WP than for the SP. Increasing soil depth reduced seedling emergence of both the WP and SP of wild mustard and affected only the WP of catchweed bedstraw. We conclude that the WP and SP of catchweed bedstraw and wild mustard seeds used in this study differed in seed mass, seasonal germination, and seedling emergence. The ability of a WP to produce large seeds that germinate early and have two germination peaks per year could make these populations a serious problem in cropping systems. Nomenclature: Catchweed bedstraw, Galium aparine L., GALAP; wild mustard, Brassica kaber (DC.) L.C. Wheeler. SINAR.

Occurrence of viruses in field-grown pepper crops and some of their reservoir weed hosts in Samsun, Turkey.

Pepper production is affected by several viral diseases in Samsun, Turkey. To determine the identity of these viruses, a total of 313 samples from field-grown peppers were collected during surveys in 1998 and 1999, and tested by enzyme linked immunosorbent assay (ELISA). Six viruses,Alfalfa mosaic virus (AMV),Cucumber mosaic virus (CMV),Potato virus Y (PVY),Tomato mosaic virus (ToMV),Tobacco mosaic virus (TMV) andTomato spotted wilt virus (TSWV) were detected in the samples. Of 313 plants tested, 42 were doubly infected, and TMV+PVY (15.4%) was the most common double infection. This is also the first report of AMV in pepper fields in Turkey. The effect of some weed species that may act as reservoir of these viruses was also investigated in the region and of 24 weed species belonging to 15 families tested, 16 were found to be infected with at least one virus.Amaranthus retroflexus (Redroot pigweed) appeared to be a common host of CMV, PVY, ToMV, TMV and TSWV, whereasHibiscus trionum (Venice mallow) was recorded as a new weed host of PVY and TSWV. The majority of weed species found to be virus infected were very common in the pepper growing areas of the region. This indicates that pepper fields contaminated with these weeds are under risk of viral infections.

The Critical Period for Weed Control in Corn in Turkey

Field studies were conducted in 2001 and 2002 in the Black Sea Region of northern Turkey to determine the critical period for weed control (CPWC) in corn and the effects of weed interference on corn height. Treatments of increasing duration of weed interference and weed-free period were imposed at weekly intervals from 0 to 12 wk after crop emergence (WAE). The CPWC was determined with the use of 2.5, 5, and 10% acceptable yield loss levels by fitting logistic and Gompertz equations to relative yield data. With 5% yield loss level, the CPWC was 5 wk, starting at 0.2 WAE and ending at 5.2 WAE, which corresponded to the one- to five-leaf stage of corn. The CPWC increased to 8.9 wk, starting at 0 WAE and ending at 8.9 WAE, at the 2.5% yield loss level. At 10% yield loss level, the CPWC decreased to 1.7 wk, starting at 2.1 WAE and ending at 3.8 WAE. Nomenclature: Corn, Zea mays L. Additional index words: Maize, weed competition, weed interference. Abbreviations: AYL, acceptable yield loss level; CLS, corn leaf stage; CPWC, critical period for weed control; DAE, days after emergence; WAE, weeks after emergence.

The Effects of Depth and Duration of Seed Burial on Viability, Dormancy, Germination, and Emergence of Ivyleaf Speedwell (Veronica hederifolia)'

Experiments were conducted to investigate the effects of depth and duration of burial on seasonal germination, primary and secondary dormancy, viability, and seedling emergence of ivyleaf speedwell (Veronica hederifolia L.) seeds. The seeds were buried at 0, 5, 10, or 20 cm and retrieved from the field at monthly intervals. The exhumed seeds were germinated at 5 C. In the second experiment, seeds were stored in the laboratory after harvest and tested for germination at monthly intervals. In each experiment, nongerminated seeds were treated with triphenyltetrazolium chloride at monthly intervals to test their viability. The effects of stratification and burial depth on seedling emergence were observed for 1 yr. The seeds exhumed from the soil were dormant at the beginning of the experiment and exhibited dormancy/nondormancy/conditional dormancy cycling throughout the experiment. Depth of burial and time affected seed germination. Seeds retrieved from the soil surface germinated well initially, but germination decreased as depth of burial increased. In the dry storage experiment, seeds had a high level of primary dormancy, and viability decreased over time. Seedling emergence decreased when depth of burial increased. Seedlings emerged nonuniformly throughout the year and demonstrated typical winter annual characteristics. Nomenclature: Veronica hederifolia, Ivyleaf speedwell, #3 VERHE Additional index words: Primary/secondary dormancy, weed management, wheat, germination ecology. Abbreviations: TTC, triphenyltetrazolium chloride.

Weed Management in Organically Grown Kale Using Alternative Cover Cropping Systems

Abstract Organic vegetable producers have limited options for managing weeds. They cite weed management as their number one research priority. Studies were conducted in 2004 and 2005 at the Black Sea Agricultural Research Institute, Samsun, Turkey, to determine the weed suppressive effects of summer cover crops in organic kale production. Treatments consisted of grain sorghum, sudangrass, hairy vetch, grain amaranth, pea, and fallow. Weed density and total weed dry biomass were assessed before and at 14, 28, and 56 d after incorporation (DAI) of the cover crops. Kale was transplanted 14 DAI and hand weeded once after last weed evaluation (56 DAI). All cover crops produced at least 1 ton/ha (t/ha) biomass; grain sorghum produced more dry matter than all other cover crops in both years. After incorporation of the cover crops, hairy vetch and sorghum treatments showed fewer species, lower weed density, and total weed dry biomass compared with other treatments. Cover crops suppressed emergence of common purslane, common lambsquarters, redroot pigweed, European heliotrope, field pennycress, annual sowthistle, black nightshade, shepherds-purse, wild mustard, sun spurge, Persian speedwell, annual mercury, and jimsonweed up to 56 DAI. Total kale yield in hairy vetch treatments was more than double that of the no cover crop, and was significantly higher than yield from the other cover crop treatments. These results indicate that hairy vetch, grain sorghum, and sudangrass have ability to suppress early-season weeds in organic kale production. Nomenclature: Annual mercury, Mercurialis annua L.; annual sowthistle, Sonchus oleraceus L. SONOL; black nightshade, Solanum nigrum L. SOLNI; common lambsquarters, Chenopodium album L. CHEAL; common purslane, Portulaca oleracea L. POROL; European heliotrope, Heliotropium europaeum L. HEOEU; field pennycress, Thlaspi arvense L. THLAR; jimsonweed, Datura stramonium L. DATST; Persian speedwell, Veronica persica Poir. VERPE; redroot pigweed, Amaranthus retroflexus L. AMARE; shepherds-purse, Capsella bursa-pastoris L. Medik. CAPBP; sun spurge, Euphorbia helioscopia L. EPHHE; wild mustard, Sinapis arvensis L. SINAR; grain amaranth, Amaranthus cruentus L.; grain sorghum, Sorghum bicolor (L.) Moench spp. Bicolor SORVU; hairy vetch, Vicia villosa Roth.; kale, Brassica oleracea L. var. acephala DC; pea, Pisum sativum L.; sudangrass, Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan

Influence of wheat seeding rate and cultivars on competitive ability of bifra (Bifora radians)

Bifra is an annual noxious broadleaf weed of winter-sown crops in the Central Anatolia and Middle Black Sea regions of Turkey. This species has become more prevalent in wheat fields in the past three decades because of poor chemical control. Field experiments were conducted in Havza and Kavak, Samsun, Turkey, to evaluate the effect of cultivar and seeding rate on the competitive interaction between bifra and wheat at four bifra densities. Wheat grain yield increased with seeding rate, either in the presence or in the absence of bifra in both locations. Decreasing the seeding rate from 250 to 200 kg/ha or 150 kg/ha decreased wheat yield in the presence of bifra in all cultivars. The percentage yield decreases were different according to cultivars, although yields decreased in all cultivars. On the basis of the analysis of yield variables, data suggest that the relative competitiveness was ‘Bezostaja’ > ‘Momtchill’ > ‘Kate A-1’ = ‘Panda’. Bifra biomass and seed numbers were reduced not only by an increase in the wheat seeding rate but also by cultivars. Bifra seed production in Bezostaja, Kate A-1, Momtchill, and Panda were diminished 60, 53, 54, and 46%, respectively, at the seeding rate of 250 kg/ha compared with bifra alone at a density of 350 plants/ m2. Nomenclature: Bifra, Bifora radians Bieb.; Winter wheat, Triticum aestivum L. ‘Bezostaja’, ‘Kate A-1’, ‘Momtchill’, ‘Panda’. Additional index words: Competition, weed management, wheat cultivars.

Tolerance of two Bifora radians Bieb populations to ALS inhibitors in winter wheat

BACKGROUND Bifora radians, an annual weed in winter wheat, is distributed mainly in the Mediterranean area, Asia Minor and the Caucasus. It infests winter-sown crops of the Central Anatolia and Middle Black Sea regions of Turkey. Field experiments in heavily B. radians-infested fields were conducted over 3 years in Samsun, Turkey, to determine the response of B. radians to ALS-inhibiting herbicides, because growers had complained of a decrease in herbicide effect. RESULTS The efficacy of ALS inhibitors on a putatively tolerant population sprayed annually with ALS inhibitors and an adjacent allegedly sensitive population was estimated at the ED(50) and ED(90) response levels. The recommended rates of herbicides controlled 90% of the weed (ED(90)) in the sensitive population at the early stage of B. radians development, but not in the tolerant population. The relative potencies (ED(x(tolerant))/ED(x(sensitive))) of herbicides on the two populations were estimated by assuming years as being random effects. The relative potency was on average about 1.7, irrespective of the ED(x) levels. CONCLUSION Although the relative potencies were not large, they were large enough to be noted by growers. In field experiments it would be important to establish tools demonstrating when farmers recognise loss of herbicide efficacy. There has been no indication of evolution of resistant biotypes so far, but continuous spraying favours biotypes with increased levels of tolerance.

Molecular Techniques for Discrimination of Late Watergrass (Echinochloa oryzicola) and Early Watergrass (Echinochloa oryzoides) Species in Turkish Rice Production

Abstract Molecular techniques are useful tools for solving taxonomic confusion among species. Polymerase chain reaction (PCR) and polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) methods were applied for the identification of barnyardgrass, early watergrass, and late watergrass. Total DNA was extracted from 266 accessions, which were collected from different rice growing areas of Turkey. The two primer sets (trn-a and trn-b1, and trn-c and trn-d) specific to a target region of the intergenic spacer between trnT (UGU) and trnL (UAA) and the entire intron region of trnL (UAA), respectively, were used in PCR amplifications. Of the 266 accessions of Echinochloa spp., only eight accessions gave a similar fragment size, which was slightly shorter than 495 bp. The PCR product obtained with the primers trn-a and trn-b1 gave two fragments when EcoRI restriction enzyme was used in barnyardgrass and early watergrass. However, not all accessions of late watergrass were digested with this enzyme. In contrast to EcoRI, the PCR product obtained using the trn-c and trn-d primer set was digested into two fragments by using AluI restriction enzyme in all accessions of late watergrass; whereas, it was not digested in barnyardgrass and early watergrass. This molecular differentiation among barnyardgrass, early watergrass, and late watergrass supports the hypothesis that late watergrass is not a synonym of early watergrass in Turkish accessions. Nomenclature: Barnyardgrass, Echinochloa crus-galli (L.) Beauv., early watergrass, Echinochloa oryzoides (Ard.) Fritsch., late watergrass, Echinochloa oryzicola (Vasing.) Vasing., rice, Oryza sativa L.

Determination of Morphological and Biological Diversity of Acetolactate Synthase Inhibitor Herbicides Resistant and Susceptible Wild Bishop (Bifora radians M. Bieb.) Populations

Bifora radians M. Bieb. Dunya genelinde cok genis yayilim alani bulan Asya’ya ozgu tek yillik bir yabanci ottur. Genis bir ekolojik toleransinin ve yuksek rekabet yeteneginin olmasi, B. radians’i bugday yetistiriciligi yapilan alanlarda sorun haline getirmistir. Herbisitlere dayanikliligin, populasyon dinamiginin bilinme gerekliligi ve demografik verilere duyulan ihtiyactan dolayi bitkilerdeki varyasyon calismalari onem arz etmektedir. Asetolaktat sentez inhibitoru herbisitlere dayanikli 29 ve duyarli 22 olmak uzere 51 lokasyondan toplanan B. radians populasyonlari morfolojik ve biyolojik farkliliklarina gore karsilastirilmistir. Sonuclara gore parametre verileri dayanikli ve hassas populasyonlar arasinda belirgin farkliligi gostermis ve bu cesitlilik benzer lokasyonlar icin de gecerli olmustur. B. radians genotipleri arasindaki morfolojik ve biyolojik cesitlilik; cografi lokasyonlar, farkli aktif maddeli ve farkli etki tarzlarina sahip herbisit uygulamalari, yetistirilen urunler ve uygulanan farkli tarimsal uygulamalar nedeniyle meydana gelebilmektedir. Yabanci ot populasyonlari arasindaki farklilik biyolojik ve kimyasal mucadele calismalarini etkileyebilmektedir.

Response of two catchweed bedstraw (Galium aparine) populations to post-emergence herbicides in winter wheat

Catchweed bedstraw causes severe problems in winter wheat and other winter sown crops. Field experiments were conducted from 2005 to 2008 in wheat fields in Samsun, Turkey, to determine: (1) the response of catchweed bedstraw to chlorsulfuron, tribenuron-methyl plus thifensulfuronmethyl, dicamba plus triasulfuron and mesosulfuron-methyl plus iodosulfuron-methyl-sodium; and (2) possible resistance or tolerance to these herbicides. The herbicides were applied at the 2–4, 4–6, and 6–8 true leaf stages of biomass, there were large differences among the upper limits of the dose-response curves, and consequently, the actual response curve, an asymmetric sigmoid curve, was fitted to data to obtain 50% and 90% effective dose, ED50 and ED90, values. None of the herbicides reduced catchweed bedstraw biomass or populations satisfactorily when applied at the recommended field rate. Twice the recommended field rate was required to achieve acceptable reduction in biomass. Overall, inadequate control of this weed cannot be solely attributed to either acetolactate synthase (ALS) resistance or improper application methods. It is likely due to a slow and progressive development of ALS-tolerant populations after many years of consecutive use.