Weed Seeds Research Articles

Seed Germination and Seedling Recruitment Behavior of Winged Sea Lavender (Limonium lobatum) in Southern Australia

AbstractWinged sea lavender [Limonium lobatum(L.f. Chaz)] is emerging as a significant weed of field crops in southern Australia. Several environmental factors affecting germination and seedling recruitment were examined to provide a better understanding of the behavior of its seedbank. At maturity, weed seeds were dormant for a period of around 2 mo, but dormancy was easily broken with scarification or by pretreatment with 564 mM NaOCL for 30 min, which confirms the role of the seed coat in regulating seed germination. Exposure to light significantly increased germination. Seeds were able to germinate over a broad range of temperatures (5 to 30 C), with maximum germination (~92%) at temperatures between 10 and 30 C. At 20 to 25 C, 50% germination was reached within 1.3 to 2 d, and the predicted base temperature for germination of the two populations ranged from 1.4 to 3.9 C. The NaCl concentration required to inhibit germination by 50% was 230 mM, with some seeds capable of germination at salinity levels as high as 480 mM. These results indicated greater tolerance to salinity inL. lobatumthan many other Australian agricultural weed species previously investigated. Seedling emergence was the highest (51% to 57%) for seeds present on the soil surface and was significantly reduced by burial at 1 cm (≤11%) and 2 cm (≤2%), with no emergence at 5 cm. Under field conditions, seedling recruitment varied considerably among the three experimental sites. The level of seedling recruitment was negatively associated with rainfall received at the site, organic carbon (OC) level, and microbial biomass of the soil. Rapid decay of weed seeds in high-OC soils appears to be an important determinant of seedling recruitment in this species and could explain greater occurrence ofL. lobatumon soils with low OC and low microbial activity in low-rainfall areas of southern Australia. Furthermore, many such soils in southern Australia are affected by salinity, which would enableL. lobatumto be more competitive with crops and other weeds present at a site.

Intercropped Watermelon for Weed Suppression in a Low-input Organic System

The inclusion of a smother crop used as a cash crop in an intercropping system may be an effective cultural control strategy for the management of weeds in organic production systems. In addition, a multilayered canopy created when intercropping species with different growth forms may limit germination cues for weed seeds and can allow for a more efficient utilization of resources that reduce competition to target crops from weeds. Watermelon (Citrullus lanatus) was evaluated for its ability to reduce weeds in a low-input organic system in Texas when planted alone or in various intercropping combinations that also included peanut (Arachis hypogaea), okra (Abelmoschus esculentus), cowpea (Vigna unguiculata), and hot pepper (Capsicum annuum). Watermelon significantly reduced total weed biomass when planted in monoculture and in all intercropping combinations compared with peanut, okra, cowpea, and pepper monocultures in year 1 of the 2-year study. Total weed biomass was reduced by 81%, 83%, 88%, and 92% in treatments containing watermelon on average as compared with pepper, peanut, okra, and cowpea grown in monoculture, respectively. Less effective weed suppression was obtained with watermelon in year 2. Pepper grown in monoculture had significantly higher weed biomass than all other treatments in year 2. Broadleaf weeds were effectively suppressed across all intercropping treatments in year 1, but nutsedges (Cyperus sp.) were consistently reduced both years, particularly when compared with monocrops with small leaf area such as pepper. The three and four species intercropping combinations consistently had high leaf area index (LAI) values, whereas pepper monoculture had significantly lower LAI values than all other treatments except for cowpea monoculture. There was a significant negative relationship between LAI and total weed biomass 33 d after last planting (r = −0.51, P < 0.01). There was a significant negative relationship between total weed biomass and total fruit yield in year 1 (r = −0.64, P < 0.01) but no significant relationship in year 2. Although findings were inconsistent in year 2 because of changes in precipitation amounts and in relative planting dates, these findings suggest that incorporating a multifunctional intercropping system that includes a low-growing vining crop such as watermelon or at least an architecturally complex mixture can optimize canopy density to reduce weed pressure from resilient perennial weeds such as nutsedge. This may offer organic producers another management tool for the control of perennial weeds.

Changes in the weed communities as affected by different primary soil tillage and deep loosening

ABSTRACTLong-term soil cultivation at the same depth affects soil characteristics and crop productivity. The aim of the study was to investigate the impact of a long-term different intensity soil tillage methods and deep loosening on weed number, weed agrobiological group and soil seed bank changes in till Bathygleyic Dystric Glossic Retisol soil under the climatic conditions of the Western Lithuania (geographical coordinates 55°43′38″N, 21°27′43″E). The study included different soil tillage methods (conventional ploughing, shallow ploughing and shallow ploughless tillage) and deep loosening. During investigational years, the greatest weed number in crops and the greatest weed seed number in the seed bank were determined in the soil reduced tillage (shallow ploughing and shallow ploughless tillage). The weed number in crops of conventional ploughing soil was 35.8% lover compared to reduced tillage soil. The weed seed number in the seed bank of conventional ploughing was 49.6% lover compared to reduced tillage Decreasing soil tillage intensity resulted in weed seeds concentration in the upper topsoil. A one-time deep loosening had a significant effect during the crop rotation: the weed number in crops and weed seed number in the seed bank were determined to have increased by 26.6% and 51.6% in conventional ploughing soil and by 11.9% and 23.2% shallow ploughless soil respectively. However, after deep loosening, the number of Poa annua in crops decreased 2.9 times in plots of conventional ploughing and 1.7 times – in plots of shallow ploughing soil.

Exploiting Waste Heat from Combine Harvesters to Damage Harvested Weed Seeds and Reduce Weed Infestation

Weeds are mainly controlled with herbicides in intensive crop production, but this has resulted in increasing problems with herbicide-resistant weeds and public concerns about the unwanted side-effects of herbicide use. Therefore, there is a need for new alternative methods to reduce weed problems. One way to reduce weed infestation could be to collect or kill weed seeds produced in the growing season. Crop and weeds are harvested simultaneously with the combine harvester, but most of the weed seeds are returned with the chaff to the field creating new problems in future growing seasons. During the harvesting process, the harvester produces heat. Under normal harvest conditions, the exhaust gas temperature measured directly behind the turbocharger of the engine of a combine harvester may reach between 400 °C and 480 °C depending of the size of the engine. These high temperatures indicate that there is a potential for developing a system which perhaps could be utilized to kill or damage the weeds seeds. We investigate how much heat is needed to damage weed seeds significantly and focuses on the germination patterns over time in response to these treatments. We investigated if heat treatment of weed seeds could kill the seeds or reduce seed vigour or kill the seeds before they are returned to the field. The aim is to avoid harvested viable weed seeds being added to the soil seed bank. During the threshing and cleaning process in the combine harvester, most weed seeds and chaff are separated from the crop grains. After this separation, we imagine that the weed seeds could be exposed to a high temperature before they are returned to the field. Seeds of nine common weed species were treated with temperatures of 50 °C, 100 °C, 150 °C, 200 °C, and 250 °C for 0, 2, 5, 10, and 20 s, respectively. Afterwards, the seeds were germinated for fourteen days. Seeds were differently affected by the heat treatments. We found that 50 °C and 100 °C was insufficient to harm the seeds of all species significantly at all durations. Heating with a temperature of 50 °C and 100 °C showed a slight tendency to break the dormancy of Alopecurus myosuroides Huds. and Papaver rhoeas L., but the results were not statistically significant. Seeds treated with 150 °C gave varying results depending on the duration and the weed species. The germination of A. myosuroides was significantly repressed when seeds were exposed to 250 °C for 5 s. Most species were significantly damaged when they were exposed to 250 °C for more than 10 s. Our results showed that there is a potential to explore how the waste heat energy produced by combine harvesters can be exploited to either kill or reduce the vigour of weed seeds before they are returned to the field with the chaff.

Arable weed seeds as indicators of regional cereal provenance: a case study from Iron Age and Roman central-southern Britain

The ability to provenance crop remains from archaeological sites remains an outstanding research question in archaeology. Archaeobotanists have previously identified the movement of cereals on the basis of regional variations in the presence of cereal grain, chaff and weed seeds (the consumer–producer debate), and weed seeds indicative of certain soil types, principally at Danebury hillfort. Whilst the former approach has been heavily criticised over the last decade, the qualitative methods of the latter have not been evaluated. The first interregional trade in cereals in Britain is currently dated to the Iron Age hillfort societies of the mid 1st millennium bc. Several centuries later, the development of urban settlements in the Late Iron Age and Roman period resulted in populations reliant on food which was produced elsewhere. Using the case study of central-southern Britain, centred on the oppidum (large fortified settlement) and civitas capital of Silchester, this paper presents the first regional quantitative analysis of arable weed seeds in order to identify the origin of the cereals consumed there. Analysis of the weed seeds which were present with the fine sieve by-products of the glume wheat Triticum spelta (spelt) shows that the weed floras of samples from diverse geological areas can be separated on the basis of the soil requirements of individual taxa. A preliminary finding is that, rather than being supplied with cereals from the wider landscape of the chalk region of the Hampshire Downs, the crops were grown close to Late Iron Age Silchester. The method presented here requires further high quality samples to evaluate this conclusion and other instances of cereal movement in the past.

Increase of rotation angle of soil layers during plow operation

One of the advantages of plowing is the ability of the plow to hide the weed seeds deep into the soil. The depth of the embankment exceeds 10-12 cm, from there the weeds can not rise to the surface of the soil. They perish halfway. But for this, it is necessary to wrap the soil layers at an angle close to 180 °. Modern ploughs can not turn the layers of soil at an angle of more than 135 °, therefore the plow is required to be equipped with additional working elements. The aim of the study is to create an adaptation to the plow to expand the furrow before laying the next soil layer. In a wide furrow, the formation will completely tip, the previous layer will not interfere with it. The device is a set of vertical shields. Each shield is fixed behind the working body of the plow. It is installed with an angle of attack of 20-25 ° to move the previous layer to expand the furrow by 10-12 cm. The model and industrial samples of the plow have shown improved agrotechnical indicators. The average angle of the formation rotation was 177 °, the burial of plant residues in the soil increased from 61 to 99%. The field surface with blocks more than 5 cm decreased from 36.3 to 13.4%, the height of the ridges decreased from 7 to 4 cm. The force of soil pressure on the shield was measured by a strain gage. It is 130-330 N depending on the depth of processing and the speed of movement. The increase in power costs for the four-hull plow was 190-750 W. The coulters on the plow are unnecessary, and this saves energy more than its increase for shields.

Research issues, challenges, and opportunities for weed management in Japan

This review states the outline of field crop production of Japan and weed problems to be solved. Field crop production of Japan is characterized by rice cultivation and small size farming. Most major field crops other than rice are imported, and various kinds and a very large amount of living weed seeds contaminate the imported grains. These alien weeds sometimes invade agricultural fields and cause serious losses of crop yields and reductions in the quality of agricultural products. Emergence of herbicide resistant biotypes of weeds, especially paddy weeds, is also issues to be solved. Weedy rice is recently emerging again due to the change of rice production system and the origin of recently emerging weedy rice is not clarified yet.

Effects of Incorporated Rye and Hairy Vetch Cover Crop Residue on the Persistence of Weed Seeds in the Soil

AbstractIncorporation of cover crop residue into the soil has been suggested as a means for reducing weed seedbanks. To explore this hypothesis, we buried mesh bags of seeds mixed with sand at 15-cm depth in late fall in plots that had been planted with rye (Secale cerealeL.) or hairy vetch (Vicia villosaRoth.) or left unplanted. Separate bags contained either velvetleaf (Abutilon theophrastiMedik.), giant foxtail (Setaria faberiHerrm.), Powell amaranth (Amaranthus powelliiS. Watson), or common lambsquarters (Chenopodium albumL.). The experiment used a randomized complete block design with five replications, and enough bags were buried to allow a final recovery in each of the following three springs. Each spring, bags were exhumed, and seeds were either counted and tested for viability or mixed with chopped cover crop material or simply stirred for control bags, and the material was reburied. The experiment was completed twice with initial burials in fall of 2011 and 2013. Rye had no consistent effect on persistence of seeds of any of the species. For two observation intervals, rye increased persistence of a species; for another two intervals, it decreased persistence relative to the control; but mostly rye did not affect persistence. Hairy vetch decreased persistence ofC. albumandA. powelliiin both runs of the experiment but had no effect on persistence ofA. theophrastiandS. faberi. Germination of the first two species is promoted by nitrate, whereasA. theophrastigermination is not sensitive to nitrate, andS. faberiis only rarely nitrate sensitive. We suggest that nitrate released during decomposition of hairy vetch may have promoted fatal germination ofC. albumandA. powellii. Incorporation of legume cover crops like hairy vetch may provide a means for decreasing the seedbanks of the many weed species whose germination is promoted by nitrate. The lack of any reduction ofA. theophrastiandS. faberiseed persistence in response to hairy vetch and the inconsistent and mostly negligible effect of rye indicate that a general increase in readily decomposable organic matter through incorporation of cover crops may be ineffective at reducing weed seedbanks.

Stale seedbed technique for weed control negatively impacts the indigenous AM fungal population

Among weed control tools available to organic farmers are a variety of stale seedbed techniques. Stale seedbed methods create a surface layer of soil depleted in viable weed seeds through repetitive cycles of seed germination followed by cultivation to uproot and kill those seedlings. Two experiments were conducted to examine the impact of two stale seedbed techniques, roto-tilling and spading (each at two frequencies), upon the native AM fungal communities in organically farmed high P soils. Weed biomass, propagule densities of the indigenous AM fungal communities, development of mycorrhizas in roots of transplanted leek (Allium porrum L.) seedlings, and impact of AM fungus inoculation upon growth and yield were measured for repetitively cultivated vs. control planting beds. Stale seedbed treatments had significant negative impact upon total weed biomass the first month after planting the leek seedlings. Control beds, cultivated only just before planting, had significantly greater AM fungus propagule density than soils roto-tilled (Pr > F = 0.0004) or spaded (Pr > F = 0.0008) at 2–4 week intervals. Early season development of mycorrhizas in transplanted seedlings was greater in the control beds than in repetitively cultivated beds, e.g. 6% vs. 1% of root length colonized (Pr > F = 0.0001) two weeks after transplanting in Exp II. Even though the stale seedbed techniques had negative impacts upon the indigenous AM fungal populations, there was no measurable impact on crop yield in the high P soils used here. Nevertheless, farmers may want to consider use of AM fungus inoculation of vegetable seedlings transplanted into stale seedbed-treated fields low in plant available P.

Seed production capability of monocotyledonous and dicotyledonous weeds in segetal and ruderal habitats

The main cause of wide presence of weeds in segetal and ruderal habitats is their high seed production capacity. It defined in expressly establishing field experiments, in industrial sowings, in segetal and ruderal habitats of steppe zones of Ukraine. It is determined that average fruitfulness of weeds in ruderal habitats was larger, than in segetal habitats by 3.8 times, and indexes of the maximum fruitfulness – by 4.0 times and reached accordingly 7028 and 9345 pieces, and 20112 and 98337 pieces. In segetal habitats monocotyledonous species of weeds on seed production on conceded dicotyledonous species by 2.9–3.7 times, and on ruderal habitats – by 9.8–10.5 times. Average seed production of monocotyledonous plants made up accordingly 3594 and 5660, and dicotyledonous – 12417 and 55629 pieces of seeds from one plant. Most species of monocotyledonous weeds (56,1 %) formed on one plant from 1 to 10 thousand pieces of seeds, and dicotyledonous weeds (37,9 %) – more than 10 thousand pieces of seeds. In segetal habitats the maximum seed production had families Asteraceae, Brassicaceae, Chenopodiaceae, Lamiaceae, and on ruderal habitats – Asteraceae, Chenopodiaceae, Caryophyllaceae, Apiaceae, Brassicaceae. The highest seed production the most widespread and abundant in sowings and on ruderal habitats had weeds: Convolvulus arvensis L., Ambrosia artemisiifolia L., Cynodon dactylon (L.) Pers., Echinochloa crus-galli (L.) P.Beauv., Eragrostis minor Host, Descurainia sophia (L.) Webb ex Prantl, Cirsium arvense (L.) Scop., Chenopodium album L., Amaranthus retroflexus L., etc. The greatest reserve weed seeds in soil in segetal habitats descended at the expense of species from genera Amaranthus, Galium, Cirsium, Setaria, and on ruderal habitats – Amaranthus, Chenopodium, Plantago, etc. In segetal habitats proof presence of weeds of genera with low seed production was sustained at the expense of their larger number of species, and genera with low number of species – at the expense of high seed production. In ruderal habitats – as at the expense of larger number of species, and their high seed production. The absolute maximum of seed production in segetal habitats have been reached at weeds of genera Amaranthus, Cirsium, Galium – from 3288 to 242266 pieces, and in ruderal habitats – Amaranthus, Chenopodium, Plantago – from 108903 to 1911683 pieces from one plant.

Effects of drought on weed emergence and growth vary with the seed burial depth and presence of a cover crop

In conservation agriculture, weed seed germination could decrease with the presence of a cover crop, surface weed seed location and temporal drought in summer just after seed shedding. This study simultaneously examined the effects of a cover crop, burial depth (seed location) and hydric stress on weed emergence and early growth. It was hypothesized that drought would reduce weed emergence and the initial growth of weed seeds and that this effect would be greater when the seeds were on the soil surface and in the presence of a cover crop. Four annual weed species were chosen that are frequently found (Anisantha sterilis, Vulpia myuros, Sonchus asper, Veronica persica) and not frequently found (Alopecurus myosuroides, Poa annua, Cyanus segetum, Capsella bursa‐pastoris) in fields that implement conservation agriculture. The unburied seeds had 26% lower emergence, on average, than the buried seeds (significant for six of the eight species), hydric stress reduced emergence by 20% (for seven of the eight species) and the presence of a cover crop reduced the level of emergence by 17% (for all species). The unburied seeds with hydric stress were emerging under the “most stressful” set of factors, with a 45% decrease in emergence, compared with the seeds emerging under the “least stressful” set of factors (buried seeds without hydric stress). All the weed growth measurements (height, dry matter content and number of leaves) decreased with the presence of a cover crop. The species that are found frequently in the fields that implement conservation agriculture, compared with the species that are not frequently found in conservation agriculture fields, had higher rates of germination and a higher tolerance of hydric stress when their seeds were unburied.

Opportunities and challenges for harvest weed seed control in global cropping systems.

The opportunity to target weed seeds during grain harvest was established many decades ago following the introduction of mechanical harvesting and the recognition of high weed-seed retention levels at crop maturity; however, this opportunity remained largely neglected until more recently. The introduction and adoption of harvest weed seed control (HWSC) systems in Australia has been in response to widespread occurrence of herbicide-resistant weed populations. With diminishing herbicide resources and the need to maintain highly productive reduced tillage and stubble-retention practices, growers began to develop systems that targeted weed seeds during crop harvest. Research and development efforts over the past two decades have established the efficacy of HWSC systems in Australian cropping systems, where widespread adoption is now occurring. With similarly dramatic herbicide resistance issues now present across many of the world's cropping regions, it is timely for HWSC systems to be considered for inclusion in weed-management programs in these areas. This review describes HWSC systems and establishing the potential for this approach to weed control in several cropping regions. As observed in Australia, the inclusion of HWSC systems can reduce weed populations substantially reducing the potential for weed adaptation and resistance evolution. © 2017 Society of Chemical Industry.

تأثیر دما و تنش خشکی بر جوانهزنی بذر تاج خروس خزنده (Amaranthus viridis L.) و خوابیده (Amaranthus blitoides S. Watson)

جوانه‌زنی بذر در مدیریت علف‌های هرز فرآیندی کلیدی است بطوری‌که می‌تواند بر تعداد علف‌های هرز سبز شده و زمان سبز شدن آنها تعیین کننده باشد. تاج خروس خزنده و خوابیده از جمله علف‌های هرز مهم سبزیجات و گیاهان زراعی تابستانه در ایران هستند. به منظور ارزیابی اثر دما بر جوانه‌زنی این دو علف هرز، آزمایشی در قالب طرح کاملا تصادفی و با 4 تکرار در دانشگاه آزاد اسلامی- واحد علوم و تحقیقات در سال 1394 انجام شد. بذور با دماهای 5، 10، 15، 20، 25، 30، 35، 40 و 45 درجه سانتی‌گراد تیمار شدند. با توجه به مدل خطوط متقاطع دماهای پایه، بهینه و بیشینه به ترتیب در تاج خروس خزنده 37/14، 21/34 و 50/44 و در تاج خروس خوابیده 24/14، 65/31 و 20/44 درجه سانتی‌گراد به دست آمدند. در آزمایشی دیگر 7 سطح پتانسیل اسمزی (0، 2/0-، 4/0-، 6/0-، 8/0- و 1- مگاپاسکال) مورد بررسی قرار گرفتند. به منظور ارزیابی پتانسیل سطوح مختلف تنش خشکی در کاهش درصد جوانه‌زنی بذر از مدل سیگموئید سه پارامتری استفاده شد. به طور کلی مقادیر x50 (پتاسیل لازم برای کاهش 50 درصدی جوانه‌زنی) به دست آمده برای تاج خروس خوابیده نسبت به تاج خروس خزنده کمتر بود. تاج خروس خزنده در پتانسیل 1- مگاپاسکال توانست 25/9 درصد جوانه زند ولی در این پتانسیل تاج خروس خوابیده جوانه نزد که نشان دهنده تحمل بالاتر تنش خشکی توسط این گونه بود. با توجه به داده‌های به دست آمده هر دو گونه می‌توانند در اقلیم‌های نیمه گرم و گرم جوانه زنند. تحمل هر دو گونه نسبت به تنش خشکی بالا بود اما تاج خروس خزنده تحمل بالاتری داشته و بنابراین پتانسیل تهاجم بیشتری به مناطق خشک دارد.

Diversity in Weed Phenological Pattern and Seed Rain in Dryland and Irrigated Agroecosystems of Indian Dry Tropics

This study was carried out to compare the diversity in weed phenological events, seed production and seed rain in a dryland and an irrigated agroecosystems of Indian dry tropics. Diverse weed phenological patterns were noted in dryland and irrigated agroecosystems. During winter season, in dryland agroecosystem, dominant weeds like Anagallis arvensis, Chenopodium album and Phalaris minor showed approximately one month early germination and vegetative stage compared to irrigated agroecosystem for same species. The annual flower, fruit and seed production were higher in the dryland agroecosystem (344-351, 219-238 and 365-397 x 103 m-2, respectively) compared to irrigated agroecosystem (211-237, 132-142 and 252-261 x 103 m-2, respectively). The estimated annual seed rain by all species in the dryland agroecosystem (102-112 × 103 m−2) significantly exceeded (P less than 0.05) the seed rain in the irrigated agroecosystem (73−80 × 103 m−2) during both annual cycles. The difference was more marked during the winter season, when more than 3 fold the number of seeds were collected in seed rain during the dryland agroecosystem. There was strong positive correlation between seed production and seed rain, showing the dependency of seed rain (mostly dominated by annual species) on seed production in agroecosystems. Two different agricultural practices that continued for more 50 years on same type of land have cause changes in weed phenological pattern. Greater seed production, seed rain, and longer seed formation period indicate an adaptive mechanism of weed seeds in the dryland agroecosystem.

Defense Enzyme Responses in Dormant Wild Oat and Wheat Caryopses Challenged with a Seed Decay Pathogen.

Seeds have well-established passive physical and chemical defense mechanisms that protect their food reserves from decay-inducing organisms and herbivores. However, there are few studies evaluating potential biochemical defenses of dormant seeds against pathogens. Caryopsis decay by the pathogenic Fusarium avenaceum strain F.a.1 was relatively rapid in wild oat (Avena fatua L.) isoline “M73,” with >50% decay after 8 days with almost no decay in wheat (Triticum aestivum L.) var. RL4137. Thus, this fungal strain has potential for selective decay of wild oat relative to wheat. To study defense enzyme activities, wild oat and wheat caryopses were incubated with F.a.1 for 2–3 days. Whole caryopses were incubated in assay reagents to measure extrinsic defense enzyme activities. Polyphenol oxidase, exochitinase, and peroxidase were induced in whole caryopses, but oxalate oxidase was reduced, in response to F.a.1 in both species. To evaluate whether defense enzyme activities were released from the caryopsis surface, caryopses were washed with buffer and enzyme activity was measured in the leachate. Significant activities of polyphenol oxidase, exochitinase, and peroxidase, but not oxalate oxidase, were leached from caryopses. Defense enzyme responses were qualitatively similar in the wild oat and wheat genotypes evaluated. Although the absolute enzyme activities were generally greater in whole caryopses than in leachates, the relative degree of induction of polyphenol oxidase, exochitinase, and peroxidase by F.a.1 was greater in caryopsis leachates, indicating that a disproportionate quantity of the induced activity was released into the environment from the caryopsis surface, consistent with their assumed role in defense. It is unlikely that the specific defense enzymes studied here play a key role in the differential susceptibility to decay by F.a.1 in these two genotypes since defense enzyme activities were greater in the more susceptible wild oat, compared to wheat. Results are consistent with the hypotheses that (1) dormant seeds are capable of mounting complex responses to pathogens, (2) a diversity of defense enzymes are involved in responses in multiple plant species, and (3) it is possible to identify fungi capable of selective decay of weed seeds without damaging crop seeds, a concept that may be applicable to weed management in the field. While earlier work on seed defenses demonstrated the presence of passive defenses, this work shows that dormant seeds are also quite responsive and capable of activating and releasing defense enzymes in response to a pathogen.

Synergistic Antifungal, Allelopatic and Anti-Proliferative Potential of Salvia officinalis L., and Thymus vulgaris L. Essential Oils.

The current study aimed to investigate the chemical composition and the synergistic potential of two essential oils (EOs), as obtained from Salvia officinalis L. (SEO), and Thymus vulgaris L. (TEO). The antifungal potential was tested in vitro against Fusarium graminearum (Fg 06_17), the herbicidal effect was studied using weed seeds of Amaranthus retroflexus (ARET), Chenopodium album (CALB), Echinochloa crus-galli (EGAL), but also wheat seeds (WS) of the Lovrin variety and tomato seeds Saint-Pierre of the variety. The GC-MS profile highlights that the mains compounds identified in SEO were: caryophyllene (25.364%), camphene (14.139%), eucalyptol (13.902%), and β-pinene (11.230%), while in TEO, the predominant phytochemicals were: γ-terpinene (68.415%) and p-thymol (24.721%). The results indicated that the tested EOs alone as well as in combination have allelopathic effect against investigated seeds, while the synergistic effect of TEO and SEO in terms of fungal growth was demonstrated at a level of 0.06%. Thyme and sage EOs exhibited in vitro anti-proliferative activity on two melanoma cell lines, namely A375 human melanoma and B164A5 mouse melanoma alone, as well as in combination. SEO was most effective in terms of decreasing the cell viability of murine and human melanoma cell lines when compared to TEO.

Weed dynamics in conservation agricultural systems as influenced by conservation tillage and nutrient management practices under rainfed finger millet

Weeds are major threats for loss of yield in any cropping system. Especially in conservation tillage systems, it is a basic necessary requirement to keep the weed population below their threshold levels to realize optimum grain yields. Managing weeds in conservation tillage systems are very essential to optimize crop production. Hence, to study the effect of conservation tillage practices on weed dynamics, soil weed seed bank and their distribution, a field experiment was conducted under rainfed finger millet (Eleusine coracana (L.) Gaertn.) on Alfisols for two consecutive seasons during 2014 and 2015 at All India Coordinated Research Project on Dryland Agriculture, University of Agricultural Sciences, GKVK, Bengaluru, India under split-plot design with three main plots (different tillages) and five sub-plots (different nutrient management). Conventional tillage has recorded significantly higher grain and straw yield of finger millet (3.04 and 4.69 t/ha, respectively) due to effective control of weeds as evidenced by lower total weed density and dry weight observed (13.7 no./m2, 8.0 g/m2 at 30 DAS and 23.9 no./m2, 9.0 g/m2 at 60 DAS) along with higher weed control efficiency (92.5–93.2% in 2014 and 93.3–93.8% in 2015) and lower weed index (7.6–10.3%) due to lower number of weed seeds observed during 2014 (12.3, 19.5 and 4.6/kg soil at 15, 30 and 60 days, respectively) and 2015 (11.3, 17.6 and 4.1/kg soil at 15, 30 and 60 days, respectively as compared to minimum tillage (2.60 and 4.03 t/ha, respectively). Whereas, zero tillage has recorded significantly lower grain and straw yield (2.09 and 3.24 t/ha, respectively) due to poor weed control as observed by higher soil weed seed bank. Among different nutrient management practices application of 100% recommended NPK + 7.5 t FYM/ha yielded significantly higher grain and straw yields (3.03 and 4.68 t/ha, respectively) over other nutrient management practices. Wherein, the soil weed seed bank was not significantly influenced by nutrient management practices and their interactions with the tillage.

Biofumigation: Opportunities and Challenges for Control of Soilborne Diseases in Nursery Production

Soilborne diseases reduce crop performance, increase costs to the nursery producers, and can cause potential ecological damage to the natural environment. In particular, soilborne diseases caused by Phytophthora nicotianae and Rhizoctonia solani are the most economically important problems of southeastern U.S. nursery producers. Methyl bromide was widely used as a standard treatment in many parts of the world until the implementation of the Montreal Protocol. Since then, many chemical and nonchemical soilborne disease management methods have been tested but are not yet providing effective and consistent results like methyl bromide. Cover crops that belong to the Brassicaceae family can be incorporated into the soil to control soilborne diseases, and this process is widely known as biofumigation. Glucosinolates that are available inside Brassicaceae plant cells can be hydrolyzed into isothiocyanates, and these compounds are proven to be highly biocidal to many microorganisms (including fungi, oomycetes, nematodes, and bacteria), insects, and germinating weed seeds. The use of biofumigant cover crops is a newer area of research in woody ornamental nursery production that has been previously explored most extensively in row crop, vegetable, fruit, and flower production. This review article compiles previous research observations in biofumigation while emphasizing the potential of biofumigation to control diseases in nursery production caused by soilborne pathogens.

Control of soil weediness and sugar beets by after crop green manure and different tillages

The research program envisaged the studying of the variation of weediness of sugar beet crops under the influence of after crop sideration and the application of soil protection cultivation. The application of oil radish green manure provided a significant decrease in the amount of seed weeds in the entire 0-30cm layer of soil in comparison with the non-seeded background on 2.8-3.4 mln. seeds ha-1 and a significant decrease in the weed density of all biological groups weeds on 0.5-6.5 weeds m-2 and their weight on 5.6-77.4g m-2 for the period of growing sugar beets. Comparing to plowing the methods of mouldboard-free cultivation provided a significant increase in the quantity of weed seeds in the layer of soil 0-10cm to 18.3-22.9×106 seeds ha-1 and their significant decrease deeper than 10cm on 19.0-23.3 mln. seeds ha-1. Among the variants of mouldboard-free cultivation the lowest amount of weed seeds in the soil layer of 0-5cm was discounted at the deepest cultivation – 24.5 and 23.5×106 seeds ha-1. The decrease of the depth of the mouldboard-free cultivation led to a significant increase in the weed density (by 4.8-68.2 weeds m-2) and their weight (82.5-1193.5g m-2) in sugar beet crops and a substantial shortfall in yields of root crops – 2.9-5.8t ha-1. It follows from the research results that the application of after crop siderate of radish oil and basic mouldboard-free cultivation reduce the potential amount of weed seeds of root layer 0-30 сm; the deep soil cultivation on 28-30cm at the siderate background provides the greatest decrease in real weediness of sugar beet crops and allows to receive high yields of crops – 34.3 t ha-1.

Sugarcane Field Residue and Root Allelopathic Impact on Weed Seed Germination

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, which can include compounds released from a crop that adversely impact weed species. The objective of this research was to determine the allelopathic impact of sugarcane (Saccharum officinarum) field residue and root water extracts on seed germination of three weed species. Red morningglory (Ipomoea coccinea L.), redroot pigweed (Amaranthus retroflexus L.), and spiny amaranth (Amaranthus spinosus L.)] seeds were treated with five extract concentrations (0, 12.5, 25, 50, and 100 g/L) from either sugarcane field residue or sugarcane root extracts. The field residue and roots were from sugarcane variety ‘HoCP 96-540’ plant cane. Germination generally decreased with increasing sugarcane field residue extract concentrations in the three weed species tested. At the highest residue concentration (100 g/L), red morningglory, redroot pigweed, and spiny amaranth germination decreased by 29%, 17.5% and 80.5%, respectively. Germination generally decreased with increasing sugarcane root extract concentrations in red morningglory and redroot pigweed, but not with spiny amaranth. The highest root concentration (100 g/L) decreased red morningglory and redroot pigweed germination by 19.5% and 18.5%, respectively. This research provides the first bioassay demonstrating that sugarcane root extracts have allelopathic activity, and specifically in respect to red morningglory and redroot pigweed germination. Future research should investigate the allelopathic compounds present in the sugarcane field residue and roots, determine if the same allelopathic compounds are present and in similar concentrations among other sugarcane varieties, and further examine which weed species may be susceptible to the allelopathic compounds present in sugarcane roots.