Days After Seeding Research Articles

Produção e qualidade fisiológica de semente de feijão após aplicação do herbicida Diquat

The objective of this research was to evaluate the influence of Diquat herbicide application, at different periods, on production and physiological quality of bean seeds, cultivar: Perola. The experimental design used was a randomized block (RBD). The treatments were constituted of application of such herbicide with dosage of 400 g ai / ha in eight stages of application (83, 85, 87, 89, 91, 93 and 95 days after seeding (DAS) and without application with 97 days – witness .) The analyzed variables were moisture content (%), germination (%), first count of germination (%)velocity index of germination, seedling emergence (%), initial stand (%)velocity index of emergency, thousand seed weight (g) and production (kg ha-1). The moisture content of the bean seeds at the times of herbicide application declined, anticipating up to 14 days to harvest beans. For the first counting and germination no difference was observed between treatments. But for the IVG observed superior results at 83 DAS. For emergence percentage and EVI the values were lower at 87 and 89 DAS. On the other hand, the data obtained for the initial stand did not differ. For the thousand seed weight and production results were superior to 89 DAS and at 89 and 95 DAS, respectively. The application of Diquat desiccant in bean crop from 83 days after sowing did not affect the germination of the seeds, however, affect significantly the production of seeds.

English

Luxuriant weed growth destroying rice crops is a major problem in tropical Africa. The objective of this study was to determine the critical period of weed infestation in upland rice varieties in order to enable the development of more precise weed management recommendations for farmers. The effects of 10 differing periods of weed management on upland rice yield were studied in experiments with five rice varieties (three interspecific NERICA: NERICA1, NERICA2, and NERICA4) and the parents (Oryza sativa WAB 56-104 andOryza glaberrima CG 14) during the 2004 and 2005 rainy seasons at Farako (Mali). INTERCOM model was used to explore the relationship between duration and timing of weed competition and rice crop yield loss, and the applicability of the model in rice cropping based weed management. The critical period of weed infestation determined from the field experiment was similar for the three New Rice for Africa (NERICA) varieties and theO. sativa parent (WAB 56-104), and was between 14 and 42 days after seeding (DAS). For the O. glaberrimaparent (CG 14), the critical period was between 28 and 42 DAS. Weed competition either before or after these critical periods had negligible effects on crop yield. During the 2 years, yields of NERICA varieties and WAB 56-104 averaged 2700 and 400 kg ha-1 under weed-free plots and no weed control plots, respectively, indicating a yield loss of 85%. For GG 14, yields averaged 900 and 300 kg ha-1 under weed-free plots and no weed control plots, respectively, resulting in a 66% yield loss. The occurrence and composition of weeds during the two years were similar with a mean of 40% broadleaves, 35% grasses and 25% sedges. The most important weeds were Imperata cylindrica, Cyperus sphacelatus and Digitaria longiflora. During both calibration and testing efforts, the INTERCOM model satisfactorily simulated rice NERICA1 LAI, shoot dry weight and yields (r2 ranging from 0.71 to 0.87). There appears to be room for improvement in the model with regard to the assumption that nutrients are not limiting to crop growth, but the use of the model for simulating the interactions between rice crop yield losses, weed density, and duration of weed competition appears promising. Results of this study can serve as a guide for optimum timing of weed control to maximize upland rice yield in West Africa.   Key words: Critical period, northern Guinea savanna, upland rice, New Rice for Africa (NERICA), INTERCOM.

자연실온 및 변온 조건에서 세엽형 훼스큐속 잔디의 발아특성 및 일일 발아패턴 비교

The study was conducted to investigate early establishment characteristics and germination pattern of fine-textured fescues (FF) under natural room temperature and to analyze differences between alternative and natural conditions for a practical application. Six cultivars from chewings fescue (CF), creeping red fescue (CRF), hard fescue (HF) and sheep fescue (SF) were evaluated in the study. Daily and cumulative germination pattern were measured and analyzed. Significant differences were greatly observed in germination pattern, days to the first germination, days to 60% germination, and germination percentage with environments, species and cultivars. Final germination rate was 29.7 to 80.0% under natural conditions. The first germination was initiated between 8 and 10 DAS (days after seeding) under natural conditions, being 3 to 4 days later as compared with ISTA conditions. Days to the 60% germination were 12.1 to 19.0 DAS, being 3.0 to 4.2 days slower than that under ISTA conditions. CF ‘Jamestown II’ wasthe fastest cultivar, while the slowest CRF ‘Audubon’. Turf establishment speed was faster in CRF < SF < HF and < CF in order. Information on differences in germination characteristics and pattern between alternative and natural conditions would be practically useful for a golf course construction etc., when established with FF.

Evidence that the Biofungicide Serenade (Bacillus subtilis) Suppresses Clubroot on Canola via Antibiosis and Induced Host Resistance

This study investigated how the timing of application of the biofungicide Serenade (Bacillus subtilis QST713) or it components (product filtrate and bacterial cell suspension) influenced infection of canola by Plasmodiophora brassicae under controlled conditions. The biofungicide and its components were applied as a soil drench at 5% concentration (vol/vol or equivalent CFU) to a planting mix infested with P. brassicae at seeding or at transplanting 7 or 14 days after seeding (DAS) to target primary and secondary zoospores of P. brassicae. Quantitative polymerase chain reaction (qPCR) was used to assess root colonization by B. subtilis as well as P. brassicae. The biofungicide was consistently more effective than the individual components in reducing infection by P. brassicae. Two applications were more effective than one, with the biofungicide suppressing infection completely and the individual components reducing clubroot severity by 62 to 83%. The biofungicide also reduced genomic DNA of P. brassicae in canola roots by 26 to 99% at 7 and 14 DAS, and the qPCR results were strongly correlated with root hair infection (%) assessed at the same time (r = 0.84 to 0.95). qPCR was also used to quantify the transcript activity of nine host-defense-related genes in inoculated plants treated with Serenade at 14 DAS for potential induced resistance. Genes encoding the jasmonic acid (BnOPR2), ethylene (BnACO), and phenylpropanoid (BnOPCL and BnCCR) pathways were upregulated by 2.2- to 23-fold in plants treated with the biofungicide relative to control plants. This induced defense response was translocated to the foliage (determined based on the inhibition of infection by Leptosphaeria maculans). It is possible that antibiosis and induced resistance are involved in clubroot suppression by Serenade. Activity against the infection from both primary and secondary zoospores of P. brassicae may be required for maximum efficacy against clubroot.

The effect of temperature, water input and length of growing season on sugar beet yield in five locations in Greece

SUMMARYFrom 1999 to 2006, 36 field experiments were conducted in five sugar beet growing areas in Greece (Larissa, Plati, Serres, Xanthi and Orestiada) to monitor yield. Locations differed significantly regarding thermal variables during the growing season with Xanthi having the most favourable thermal conditions (Tmax, average daily maximum temperature;Tmean, average daily mean temperature; GDD, growing degree days) for sugar beet growth. From early June to the end of the harvesting campaign, successive harvests were conducted. Over the years, fresh root weight and sugar yield at the last harvest of the season (FRWLH, SYLH) did not differ significantly among locations. Also, there were no significant differences among locations regarding GDD for maximum FRW and SY (GDDMFRW, GDDMSY), with the means over location estimated at 2639·9 and 2792·5 °C, respectively. Days after seeding (DAS) necessary for maximum yield (DASMFRW, DASMSY, respectively) differed among locations, with the longest period (DASMFRW206·4 days, DASMSY: 204·5 days) occurring in the northernmost location (Orestiada). Means for DASMFRWand DASMSYat the five locations were estimated at 190·4 and 188·9·days, respectively. Excluding Xanthi and combining the remaining locations, FRWLHand SYLHwere negatively correlated with the average temperatures (Tmean,TmaxandTmin, daily minimum temperature) over the growing season. The opposite was evident for Xanthi where sugar beet was grown under sub-optimal temperatures. The optimum meanTmaxof the five locations was estimated at 25·5 and 25·1 °C for FRWLHand SYLH, respectively. Elongation of the growing season, by means of early sowing, would increase yield by decreasing average temperatures (Tmean,Tmax) over the growing season in locations with the highest recorded temperatures (Larissa, Plati, Serres and Orestiada). In Xanthi, the projected temperature increase, as a result of climate change, is expected to have a positive effect on yields.

Transplanting by Uprooting Tillers from Dibbled Field: An Idea for Crop Intensification and Sustainable Rice Cultivation

An experiment was conducted in the field laboratory of Bangladesh Rice Research Institute to determine the suitable time for uprooting of the tillers from dibbled plots for transplanting as well as nitrogen management system in the transplanted field. It was revealed that uprooting of half of the tillers from dibbled plots did not reduce crop yield in the dibbled plots (after uprooting of half of the tillers) compared with dibbled plots without tiller uprooting. In both irrigated and rainfed management systems, transplanting with uprooted tillers from dibbled plot at 30 to 40 days after seeding (DAS) produced optimum yield. Significant yield reduction was observed when the uprooted tillers were transplanted after 40 DAS. In nitrogen fertilizer management system, two split of urea application was proved to be effective. Considering both tiller splitting time and urea fertilizer applications, uprooting of half of the tillers from dibbled plot at 30 DAS and transplanting to new areas with two split of urea application were found to be effective. This method of rice farming might be suitable for salinity affected coastal areas to escape detrimental effect of salinity during germination and early seedling establishment, as well as suitable to increase cropping intensity.

Transplanting by Uprooting Tillers from Dibbled Field: An Idea for Crop Intensification and Sustainable Rice Cultivation

An experiment was conducted in the field laboratory of Bangladesh Rice Research Institute to determine the suitable time for uprooting of the tillers from dibbled plots for transplanting as well as nitrogen management system in the transplanted field. It was revealed that uprooting of half of the tillers from dibbled plots did not reduce crop yield in the dibbled plots (after uprooting of half of the tillers) compared with dibbled plots without tiller uprooting. In both irrigated and rainfed management systems, transplanting with uprooted tillers from dibbled plot at 30 to 40 days after seeding (DAS) produced optimum yield. Significant yield reduction was observed when the uprooted tillers were transplanted after 40 DAS. In nitrogen fertilizer management system, two split of urea application was proved to be effective. Considering both tiller splitting time and urea fertilizer applications, uprooting of half of the tillers from dibbled plot at 30 DAS and transplanting to new areas with two split of urea application were found to be effective. This method of rice farming might be suitable for salinity affected coastal areas to escape detrimental effect of salinity during germination and early seedling establishment, as well as suitable to increase cropping intensity.

Integration of agronomic practices with herbicides for sustainable weed management in aerobic rice.

Till now, herbicide seems to be a cost effective tool from an agronomic view point to control weeds. But long term efficacy and sustainability issues are the driving forces behind the reconsideration of herbicide dependent weed management strategy in rice. This demands reappearance of physical and cultural management options combined with judicious herbicide application in a more comprehensive and integrated way. Keeping those in mind, some agronomic tools along with different manual weeding and herbicides combinations were evaluated for their weed control efficacy in rice under aerobic soil conditions. Combination of competitive variety, higher seeding rate, and seed priming resulted in more competitive cropping system in favor of rice, which was reflected in lower weed pressure, higher weed control efficiency, and better yield. Most of the herbicides exhibited excellent weed control efficiency. Treatments comprising only herbicides required less cost involvement but produced higher net benefit. On the contrary, treatments comprising both herbicide and manual weeding required high cost involvement and thus produced lower net benefit. Therefore, adoption of competitive rice variety, higher seed rate, and seed priming along with spraying different early-postemergence herbicides in rotation at 10 days after seeding (DAS) followed by a manual weeding at 30 DAS may be recommended from sustainability view point.

Establishment and Performance of Bluegrass Species and Tall Fescue under Reduced-input Maintenance in a Temperate Mediterranean Environment

Turfgrass water conservation has become important in many parts of the world, including the transition zones of Mediterranean Europe. Species selection is considered one of the most important factors influencing turfgrass water use, and drought-tolerant cool-season species are encouraged to be used in areas where long dormancy periods of warm-season grasses is unacceptable. A field study was conducted from Mar. 2007 to Sept. 2009 at Padova University, Italy, to evaluate establishment and performance of nine turfgrass cultivars under reduced-input maintenance. The study included hybrid bluegrass (Poa pratensis × P. arachnifera) cultivars Solar Green, Thermal Blue, and Thermal Blue Blaze; kentucky bluegrass (Poa pratensis) cultivars Cocktail, Cynthia, and Geronimo; and tall fescue (Festuca arundinacea) cultivars Apache, Murray, and Regiment. Establishment rate was assessed after two seeding dates (20 Mar. and 20 Sept.), and grasses were subsequently fertilized with 15 g·m−2 nitrogen per year and irrigated once every 2 weeks at 40% of reference evapotranspiration from June to August. Turfgrass and weed cover were estimated 60 days after seeding (DAS), and turf quality was evaluated weekly on a scale of 1 (worst) to 9 (best). Normalized difference vegetation index (NDVI) was measured weekly during 2009. Tall fescue cultivars exhibited greater quality than hybrid bluegrass or kentucky bluegrass, under both spring and autumn seeding. Hybrid bluegrass had similar quality to kentucky bluegrass cultivars, although they performed well only when sown in autumn. Our results suggest that among the tested grasses, tall fescue performed better under the reduced irrigation in a Mediterranean transition zone climate than kentucky bluegrass or hybrid bluegrass.

The effects of water management, timing and the rate of several herbicides on the growth of Murdannia keisak (Hassk.) Handel-Mazz

Murdannia keisak is a competitive rice weed found throughout the world. The aims of this study were to investigate the influence of different water managements on the growth of M. keisak under greenhouse conditions, and to assess the efficacy of common rice herbicides against it under field conditions.Three water management techniques were tested under greenhouse conditions: saturation, intermittent irrigation, and continuous flooding. The efficacy against M. keisak was evaluated in paddy fields during 2003–2005. In 2003, bispyribac-sodium was applied alone or in combination with triclopyr or metosulam at 20, 27, and 32 days after seeding (DAS). In 2004 and 2005, bispyribac-sodium was applied once (30 DAS), but at two application rates.Results for the three water treatments showed continuous flooding reduced M. keisak biomass most as confirmed by aboveground fresh weights. In the paddy field experiments, bispyribac-sodium also proved highly effective against M. keisak and was selective to rice with more than 90% efficacy. The addition of tryclopyr or metosulam to bispyribac-sodium failed to improve its herbicidal efficacy. Finally, the best M. keisak control at field condition was obtained with continuous flooding combined with bispyribac-sodium.

Managing phosphorus fertilizer to reduce algae, maintain water quality, and sustain yields in water-seeded rice

In water-seeded rice systems, cyanobacteria (Nostoc spongiaeforme) hinder early-season crop growth by dislodging and reducing light to seedlings. Since algae are often phosphorus (P) limited, we investigated whether changing the timing of P fertilizer application could reduce algal growth without reducing crop yields or increasing mid-season water P concentrations to levels of concern for water quality. Water P and algae were monitored in 10 and 12 (respectively) side-by-side fields (16–60ha in size) where P fertilizer was applied pre-plant or where P application was delayed until after rice plants had emerged above the surface of the floodwater (2–5 weeks after seeding). Early-season water P concentration and algal occurrence were higher (P<0.001 and P=0.018, respectively) when P fertilizer was applied pre-plant as opposed to delayed. In fields receiving a delayed P application, water P increased to as high as 1.68mgL−1 immediately following application and subsequently declined by 0.054mgL−1day−1 (P=0.029). A separate study evaluated the effect of P fertilizer timing on crop productivity and P uptake. Triple-super-phosphate was either not applied or was applied to the soil surface in the fall prior to the cropping season, immediately prior to planting, 35 days after seeding (DAS) and 49 DAS at a rate of 25kgha−1P. P uptake and agronomic P use efficiency (APUE) were similar when P was applied at seeding or 35 DAS. However, relative to P application at seeding, yields were reduced by 6% and there was lower APUE when P was applied after harvesting the previous crop or at 49 DAS (P<0.05). These results indicate that correctly timed, delayed fertilizer P applications can maximize rice yield while reducing early-season interference from algae. However, because delayed applications of P fertilizer also increased water P concentrations, drainage water must be managed carefully following application.

Field evaluation of selected NERICA rice cultivars in Western Kenya

Food shortage is a major problem in sub-Saharan Africa as population increases. NERICA (New Rice for Africa), the high yielding rice cultivars with short growth cycle were developed to solve the food crisis. The progeny has shown high potential to revolutionize rice farming, producing high yield with minimum inputs in stress-afflicted ecologies. However, information on their performance in Kenya has not been documented. A study was conducted in a field located at Alupe farm of Lake Basin Development Authority (LBDA), in Western Kenya for a period of three years (2005 - 2007). Four NERICA rice cultivars (NERICA 1, NERICA 4, NERICA 10, and NERICA 11) and a local landrace “Dourado precoce” were planted in a completely randomized block design. Result showed that NERICA 10 attained physiological maturity most quickly [97 days after seeding (DAS)] followed by NERICA 1 (102 DAS). Dourado precoce took a much longer time to mature (116 DAS) than the other cultivars. On grain yield, NERICA 1 (4.1 ton ha-1) produced the highest while Dourado precoce (2.5 ton ha-1) gave the least in 2006. NERICA 10 (2.7 ton ha-1) however, produced the lowest grain yield in the same period among the NERICAs. NERICA 1, the most outstanding cultivar gave the highest yield (4.3 ton ha-1) in 2005 and yielded more than 4.0 ton ha-1 in the other seasons. Key words: NERICA, upland rice, yield, moisture stress, Kenya.

Using penoxsulam ALS inhibitor as a broad-spectrum herbicide in Chilean rice

M. Kogan, P. Gomez, A. Fischer, and C. Alister. 2011. Using penoxsulam ALS inhibitor as a broad-spectrum herbicide in Chilean rice. Cien. Inv. Agr. 38(1): 83-93. The continuouslyflooded rice production system in Chile has selected highly competitive aquatic weeds selection capable of reducing paddy yields by 25 to 50%. Penoxsulam is a broad-spectrum triazolopyrimidine (ALS inhibitor) commercially introduced in Chile in 2006, where Alisma plantago aquatica hads already evolved resistance to sulfonylurea herbicides (SU). Several field trials with water seeded rice were conducted during 2003 and 2004 in Chile to determine efficacy, timing of application, spectrum of control, and control of SU-resistant A. plantago aquatica with the herbicide penoxsulam, either in single applications or in sequence with other herbicides. Penoxsulam was applied a) 12 days after seeding (DAS) into the water (IW), b) in postemergence after draining the water from field (ADW) at 35 DAS or c) IW followed by ADW applications of MCPA, cyhalofop, bentazon, or triclopyr. Penoxsulam was tested at 20, 30, and 40 g a.i. ha -1 . Comparisons were made with recommended rates of other IW treatments (metsulfuron, bensulfuron and cyclosulfomuron) and sequential applications of molinate (IW) followed by ADW applications of MCPA, cyhalofop, bentazon, or triclopyr. One IW penoxsulam application was sufficient to achieve broad-spectrum control: Echinochloa spp. (100% control), A.plantago-aquatica (80 to 100%), Schoenoplectus mucronatus (50 to 80%), and Cyperus difformis (80 to 100%). Rice yields in penoxsulam-treated plots were 30 to 56% higher than in the untreated controls. Yields with penoxsulam IW (all rates) were similar (P>0.05) to those obtained using molinate (IW) followed by ADW applications of bentazon or MCPA. Although penoxsulam is an ALS inhibitor, it controlled A. plantago-aquatica resistant to metsulfuron and bensulfuron.

Avaliação de herbicidas para dois cultivares de mandioca

É importante avaliar a tolerância de variedade de mandioca a novas alternativas de controle químico, com o intuito de ampliar as opções disponíveis. Este trabalho teve como objetivo avaliar a seletividade de herbicidas aplicados em pré-emergência, para duas importantes variedades de mandioca cultivadas no Estado do Paraná. Os herbicidas e respectivas doses (g i.a. ha-1) avaliadas foram: diuron (400 e 800), metribuzin (360 e 720), isoxaflutole (60), atrazine (720), S-metolachlor (1.920) e as misturas ametryn + clomazone (1.350+1.900), ametryn+trifluralin (1.500+1.350), isoxaflutole+metribuzin (60+320), isoxaflutole+diuron (60+400), combinados com uso de uma testemunha dupla adjacente a cada tratamento. Os cultivares utilizados neste trabalho foram Fécula Branca e Fibra. Apenas o herbicida S-metolachlor, para ambos os cultivares, e metribuzin (360 g i.a. ha-1), para o cultivar Fibra, não provocaram injúrias. Atrazine provocou redução de estande para o cultivar Fécula Branca aos 60 DAP, mas não foi detectada redução na altura de plantas. Tanto atrazine (para os dois cultivares) quanto diuron na dose de 800 g i.a. ha-1 (para o cultivar Fécula Branca) afetaram a produtividade de raízes. Dessa forma, atrazine foi considerado não seletivo para ambos os cultivares, e a maior dose de diuron foi também considerada não seletiva para o cultivar Fécula Branca. Há diferenças de tolerância entre os cultivares, sendo o Fibra, de modo geral, mais tolerante aos herbicidas avaliados.

Protoporphyrinogen Oxidase (Protox) 유전자 과다발현 제초제 저항성 형질전환 벼의 생육저해 기작

본 연구의 목적은 다양한 생물종의 Protox 유전자 과다발현 제초제 저항성 형질전환 벼의 저항성 수준과 생육저해 원인이 생육시기별 tetrapyrrole 중간물질 축적과 대사 경로 물질, 활성산소 발생, 지질과산화 작용 및 항산화 효소 능력과 관련성이 있는지를 조사하는데 있다. Myxococcus xanthus(MX, MX1, PX), Arabidopsis thaliana(AP31, AP36, AP37) 및 인간(H45, H48, H49) Protox 과다발현 형질전환벼는 비형질전환벼에 비해 oxyfluorfen에 각각 43~65, 41~72 및 17~70배 저항성을 보였다. 다양한 생물종의 Protox 유전자 과다발현 제초제 저항성 형질전환 벼 중에 일부 라인은 다른 광조건하에서 정상적인 생육을 보인 반면에 일부 라인은 초장 및 생체중 감소가 야기되었다. 그러나 일관성 있게 파종 후 7일과 14일에 초장의 감소가 야기 되었던 형질전환 라인은 AP37뿐이었다. 또한 이들 형질전환 벼 라인들은 저광 및 암조건보다 고광조건하에서 초장 및 생체중 감소가 뚜렷하였다. 파종 후 7일째 Proto IX 축적은 AP31, AP37 및 H48에서 비형질전환벼에 비해 유의적으로 많았고, 파종 후 14일째에는 PX, AP37 및 H48에서 유의적으로 많았다. 파종 후 7일째 Mg-Proto IX은 일부 라인(H41과 H48)을 제외하고 그리고 Mg-Proto IX monomethyl ester는 MX, MX1, PX를 제외한 형질전환 라인 간에 차이가 없었다. 비록 terapyrrole 중간물질이 축적 되었더라도 이들 축적량은 Protox 과다발현 형질전환벼의 생육을 저해 하는데 충분하지 않았을 것으로 생각된다. 또한 활성산소종 (<TEX>$H_2O_2$</TEX>와 <TEX>${O_2}^{{\cdot}_-}$</TEX>), MDA, ALA 합성 및 엽록소 함량에서도 형질전환 라인간에 유의적인 차이가 인정되지 않아 tetrapyrrole 축적량이 형질전환 벼의 생육저해에 충분하지 못했음을 확인할 수 있었다. 따라서 일부 형질전환벼에서 초기 생육저해는 어떤 단일 요인에 기인되는 것보다 복합적인 요인에 의해 기인되는 것으로 생각된다. We investigated the levels of resistance and accumulation of terapyrroles, reactive oxygen species, lipid peroxidation, and antioxidative enzymes for reasons of growth reduction in herbicide-transgenic rice overexpressing Myxococcus xanthus, Arabidopsis thaliana, and human protoporphyrinogen oxidase (Protox) genes. The transgenic rice overexpressing M. xanthus (MX, MX1, PX), A. thaliana (AP31, AP36, AP37), and human (H45, H48, H49) Protox genes showed 43~65, 41~72 and 17~70-fold more resistance to oxyfluorfen, respectively, than the wild type. Among transgenic rice lines overexpressing Protox genes, several lines showed normal growth compared with the wild type, but several lines showed in reduction of plant height and shoot fresh weight under different light conditions. However, reduction of plant height of AP37 was much higher than other lines for the experimental period. On the other hand, the reduction of plant height and shoot fresh weight in the transgenic rice was higher in high light condition than in low light condition. Enhanced levels of Proto IX were observed in transgenic lines AP31, AP37, and H48 at 7 days after seeding (DAS) and transgenic lines PX, AP37, and H48 at 14 DAS relative to wild type. There were no differences in Mg-Proto IX of transgenic lines except for H41 and H48 and Mg-Proto IX monomethyl ester of transgenic lines except for MX, MX1, and PX. Although accumulation of tetrapyrrole intermediates was observed in transgenic lines, their tetrapyrrole accumulation levels were not enough to inhibit growth of transgenic rice. There were no differences in reactive oxygen species, MDA, ALA synthesizing capacity, and chlorophyll between transgenic lines and wild type indicating that accumulated tetrapyrrole intermediate were apparently not high enough to inhibit growth of transgenic rice. Therefore, the growth reduction in certain transgenic lines may not be caused by a single factor such as Proto IX, but by interaction of many other factors.

Suppressing weeds in direct-seeded lowland rainfed rice: Effect of cutting dates and timing of fertilizer application

Weeds cause substantive yield losses in rainfed rice, particularly direct-seeded rice (DSR). Two field experiments were conducted in 2005 in north-east Thailand to examine the effects of cutting date and timing of fertilizer application on suppressed weed, growth and yield of DSR. Treatments consisted of two fertilizer applications to the main plots (top-dressing at the date of cutting and 15 days after cutting; DAC) and four cutting dates of the sub-plots. Rice and weed cutting was performed at 30, 45, 60 and 75 days after seeding (DAS), compared with an untreated control. Cutting resulted in a higher growth rate and improved grain yield of rice compared to the untreated control. Weed cutting at 60 DAS resulted in the greatest leaf area index, which contributed to the maximum number of tiller as well as maximum plant dry mass when observed at 30 DAC. Lower densities and dry weights of weeds at 30 DAC were observed when cutting was done 60 DAS, resulting in a higher grain yield than the other cutting dates. Timing of fertilizer application had no significant effect on the density and dry weight of grasses and broad-leaved weeds, but did have a significant affected on, resulting in the lowest density of sedges at 45 DAC was observed with fertilizer applied at cutting date. Rice grain yield was higher with top-dressing of fertilizer at 15 DAC than with fertilizer applied at cutting date. The cutting treatments resulted in higher net incomes than the untreated control. These results indicate that rice and weed cutting at an appropriate growth stage is an alternative method to chemical weed control for DSR in rainfed riceland.

Seed Coating and Seeding Rate Effects on Turfgrass Germination and Establishment

A field experiment was conducted at New Mexico State University to investigate the effect of seeding rates and ZEBA polymer [starch-g-poly (2-propenamide-co-propenoic acid) potassium salt] seed coating on the germination and establishment of warm- and cool-season grasses, and cool-season blends and mixtures. Grasses were established at recommended and reduced (50% of recommended) seeding rates with coated and uncoated seeds under two irrigation regimes (98% and 56% reference evapotranspiration). With the exception of ‘Bengal’ creeping bentgrass (Agrostis stolonifera), the polymer coating did not improve germination of the turfgrasses tested 22 days after seeding (DAS). However, at the end of the establishment period (92 DAS), plots established with ‘Bengal’, Dunes Mix [mixture of ‘Hardtop’ hard fescue (Festuca longifolia), ‘Baron’ kentucky bluegrass (Poa pratensis), ‘Barok’ sheep fescue (Festuca ovina)], ‘Panama’ bermudagrass (Cynodon dactylon), and Turf Sense™ [mixture of ‘Baronie’ kentucky bluegrass, ‘Barlennium’ perennial ryegrass (Lolium perenne), and ‘Barcampsia’ tufted hairgrass (Deschampsia cespitosa)] achieved greater coverage (based on visual estimations) when coated seed was used compared with uncoated seed. Establishment was greater for ‘Bengal’, Dunes Mix, ‘Panama’, Turf Sense™, and Turf Saver™ [blend of ‘Barlexas II’, ‘Barrington’, and ‘Labarinth’ tall fescue (Festuca arundinacea)] when normal seeding rates were applied compared with reduced seeding rates. ‘Barleria’ crested hairgrass (Koeleria macrantha) plots did not establish, regardless of the treatments applied. Results showed that seed coating has the potential to improve establishment at recommended and reduced seeding rates and can compensate for less favorable conditions such as reduced irrigation, reduced seeding rate, or for a combination of both. At the end of the establishment period, not all grasses achieved coverage greater than 50%. Further research over a longer establishment period is needed to determine if coated seed can be beneficial in achieving full coverage.

Growth and Yield of Rice (Oryza sativa L.) as affected by Cultivars, Seeding Depth and Water Deficits at Vegetative Stage

This study investigates the effects of different seeding depths and water stress on growth and yield of direct-seeded rice. The experiment was a 3x2x2 factorial in a randomized complete block design with four replications. The main factors (03) were seeding depths (0, 1 and 5 cm), water level (well watered and water stress at 30 days after seeding (DAS) and rice cultivars (Pathum Thani 1 and Suphan Buri 1). Above-ground biomass and root length density were significantly affected by rice cultivars, seeding depths and water stress. The Suphan Buri 1 had a higher above ground biomass and root length density than the Pathum Thani 1. At the first 7 days of water stress, maximum above-ground biomass was obtained at 1 cm seeding depth. But at a later stage, the highest above ground biomass was observed with a seeding depth of 5 cm at both 60 and 90 days after seeding. The greatest root length density was obtained at a seeding depth of 5 cm. Grain yield was significantly affected by seeding depths and water stress. The highest grain yield was obtained in 5 cm seeding depths compared with other low depth under water stress at vegetative stage (30 DAS). It was concluded that yield loss under water stress at vegetative stage may be compensated for by increasing seeding depth above shallow depth levels. (Resume d'auteur)

Rates and timing of phosphorus fertilizer on growth and yield of direct-seeded rice in rain-fed conditions

Phosphorus deficiency in soil and erratic rainfall limit rice production in Northeast Thailand. The objective of this study was to investigate rice's response to different rates and times of phosphorus fertilizer. A field trial was conducted in a farmer's field with a split plot design. Main plots were established using three rates: 15, 30, and 60 kg P ha−1. Five types of sub-plot were established as follows: (1) P fertilizer was applied by banding below the seeds' depth before seeding (BBS), (2) broadcasting and incorporation into the soil before seeding, and (3) topdressing at three different DAS (days after seeding). Fertilizer was spread onto the soil surface at 10, 20, and 30 DAS. Significant grain-yield increases were affected by time or rate of fertilizer application. Grain yields were maximized by a rate of 60 kg P ha−1. Fertilizer application by BBS produced higher grain yield than did other treatments, giving higher root-length density and shoot growth, phosphorus uptake, and greater phosphorus-use efficiency than did fertilizer applied by broadcasting or delayed topdressing. BBS resulted in the highest phosphorus enrichment in soil volume with a rate of 60 kg P ha−1. The high solubility of fertilizer in a localized placement may satisfy the seedlings' high initial demand of phosphorus and provide sufficient phosphorus availability to allow high productivity. Based on these data, in regions with low soil phosphorus availability where rainfall is also erratic, the management of sub-seed banding placement at the start of a crop at the rate of 60 kg P ha−1 is recommended as the optimum phosphorus fertilizer practice.

Induced systemic resistance (ISR) in bean (Phaseolus vulgaris L.) mediated by rhizobacteria against bean rust caused by Uromyces appendiculatus under greenhouse and field conditions

Bean rust caused by Uromyces appendiculatus Pers., is one of the major foliar diseases in bean (Phaseolus vulgaris L.) worldwide, which leads to considerable crop loss. Selected fluorescent rhizobacteria were screened for their ability to trigger induced systemic resistance (ISR) against rust in beans under greenhouse and field conditions. Rhizobacteria, applied as seed treatments, were compared to untreated seeds (control) for the suppression of rust. Because of rhizobacteria and the pathogen were spatially separated the phenomenon has to be attributed to ISR. Only three isolates out of four root colonizers namely Pseudomonas fluorescens WM35, Pseudomonas aureofaciens WM09 and Pseudomonas putida WM06 significantly protected bean leaves in detached leaf assays, indicating that apart from the root colonization some other criteria may play a role in triggering ISR by rhizobacteria. Moreover, Pseudomonas aeruginosa 7NSK2 and SA44, soil application of salicylic acid, previously reported ISR inducers in bean, also significantly reduced disease development in greenhouse pot experiments. Under field conditions, WM35, WM09 and WM06 significantly induced ISR against bean rust up to 30 days after seeding (DAS). However, only P. fluorescens WM35 and P. putida WM06 were able to protect bean plants from rust infection throughout the experiment. Therefore, this study clearly demonstrated the ability of rhizobacteria to suppress bean rust under field conditions.