不同耕作措施下旱作麦田CO2排放速率与土壤水热关系分析

采用定位试验,系统研究翻耕(T)、翻耕+秸秆还田(TS)、旋耕(RT)、旋耕+秸秆还田(RTS)、免耕(NT)、免耕+秸秆覆盖(NTS)6种不同耕作措施下土壤CO2排放速率的季节变化规律,分析土壤CO2排放速率与土壤水热的相互关系。结果表明,CO2排放速率有明显的季节变化规律,均表现为冬季低夏季高;整个生长季平均排放速率为TS>T>RTS>RT>NTS>NT,并且T、RT、NT 3种耕作措施之间差异均达到极显著水平(P<0.01);TS、RTS、NTS 3种有秸秆耕作措施的CO2排放速率均高于相应的T、RT、NT 3种无秸秆耕作措施,且T与TS之间差异达到极显著水平;土壤温度和CO2排放速率表现为极显著正相关,T、RT和NT分别与15、5、10 cm土层温度相关性最大,相关系数分别为0.899、0.779、0.934;土壤含水量与CO2排放速率未表现出显著相关性。     

Occurrence of Cucumber mosaic virus Subgroup IA in tomato in Pakistan

Journal of Plant Diseases and Protection - Infection of tomato in Faisalabad, Pakistan with subgroup IA strain of Cucumber mosaic virus (CMV) is reported for the first time. The virus was detected...     

Comparative studies on some yield contributing traits of wheat sown in binary mixtures

Cultivar mixtures have been suggested as ways to increase crop productivity. This field study was conducted to investigate the competition among five cultivated varieties of wheat (Triticum aestivum L.) for the traits like plant height, flag leaf area, fertile tillers per plant, spike length, spikelets per spike, spike density, grain weight per spike, and seed index in relation to competition with yield per plant. It was observed that cultivar mixtures ought to be more productive than corresponding pure stands. Four binary combinations of Seher2006-Kohistan97, Farid2006-SH2002, SH2002-Shahkar95, and SH2002-Kohistan97 were superior in performance, showing land equivalent ratio (LER) values greater than one for plant height, fertile tillers per plant, spike density, grain weight per spike, and grain yield per plant. It was observed that the performance of binary mixtures was mainly due to the increased average performance in spike density, grain weight per spike, and grain yield per plant. The competitive ability of wheat varieties in mixtures was independent of each other for the respective traits, which lead to cumulative effects for the increased performance within the associates in mixtures.     

Influence of alginate oligosaccharides on growth, yield and alkaloid production of opium poppy (Papaver somniferum L.)

Opium poppy (Papaver somniferum L.), an important medicinal plant, produces several opiate alkaloids including morphine, thebaine, codeine, papaverine and noscapine. Polysaccharides, such as sodium alginate, have been used in depolymerized form as wonderful promoters of plant growth. The present study has revealed that application of alginate oligosaccharides (AO), obtained from sodium alginate irradiated by Co-60 gamma rays, significantly enhances certain physiological/biochemical parameters as well as the overall growth of opium poppy. The highest dose applied was the most effective in increasing the morphine and codeine contents as well as the overall yield of crude opium per plant.     

Optimizing nitrogen levels combined with gibberellic acid for enhanced yield, photosynthetic attributes, enzyme activities, and artemisinin content of Artemisia annua

Artemisia annua L. is an aromatic-antibacterial herb that destroys malarial parasites, lowers fever, and checks bleeding, and from which the secondary compound of interest is artemisinin. It has become increasingly popular as an effective and safe alternative therapy against malaria, and its derivatives are effective against multidrug resistant Plasmodium falciparum strains. Nitrogen is required by the plants in the largest quantity and is most limiting where biomass production is desired. On the other hand, gibberellic acid plays an important role in flowering, growth, and development and also in other physiological and biochemical processes. The feasibility of foliar GA₃ (75 mg·L⁻¹) alone or with varying levels of soil applied nitrogen (40, 80, and 120 mg·kg⁻¹ soil) was tested on A. annua in the present study. The application of GA₃ proved effective in alleviating the growth, photosynthesis, and enzyme activities of A. annua. However, N levels combined with GA₃ showed better responses, and further improvement in these parameters was observed. Furthermore, the most important task we were interested in was to increase the artemisinin content and its yield on a per plant basis. The N combination (80 mg·kg⁻¹ soil) together with GA₃ augmented the content (21.8% more) and yield (55.8% more); this is true for both the treated plants, which were more than the control.     

Molecular screening for identification of blast resistance genes in North East and Eastern Indian rice germplasm (Oryza sativa L.) with PCR based makers

Molecular screening and genetic diversity of major rice blast resistance (R) genes were determined in 32 accessions of rice germplasm from North East and Eastern India with ten gene based single nucleotide polymorphisms and sequence tagged sites (STS) markers, namely z56592, zt56591, k39512, k3957, candidate gene marker, Pita3, YL155/YL87, YL183/YL87, Pb28, 195R-1 which showed close-set linkage to nine major rice blast resistance (R) genes, Piz, Piz-t, Pik, Pik-p, Pik-h, Pita/Pita-2, Pib and Pi9 and one susceptible pita gene. Among the 32 accessions, 13 were positive for Piz gene and six for Piz-t gene. Six accessions were positive for Pik gene, seven for Pik-p and 16 for Pik-h gene. One accession, Atte thima, was positive for three of Pik multiple genes. Out of 32, only two germplasm, Dudhraj and Nepali dhan, were detected with both Pita3 and YL155/YL87 marker for Pita/Pita-2 gene. The Pib gene appeared to be omnipresent and was detected in 31 of 32 germplasm with marker Pb28. The gene specific STS marker, 195R-1, for Pi9 gene produced positive bands in only two germplasm, Kalchatti and Bachi thima. The Uniform Blast Nursery (UBN) analysis showed that out of 32, six germplasm was resistant, ten moderately resistant and 16 germplasm were susceptible. Presence of Piz-t, Pita/Pita-2 and Pi9 gene ensured a resistant reaction in outdoor blast nursery whereas germplasm carrying Pib was susceptible when present alone. Presence of multiple genes, however, contributed to slow blasting resistance in the field. These results are useful in identification and incorporation of resistant genes from the germplasm into elite cultivars through marker assisted selection in rice breeding programs.     

Farmers' knowledge and perceptions of the stunting disease of Napier grass in Western Kenya

Production of Napier grass, Pennisetum purpureum, the most important livestock fodder in Western Kenya, is severely constrained by Napier stunt (Ns) disease. Understanding farmers' knowledge, perceptions and practices is a prerequisite to establishing an effective disease management approach. Using a random sample of 150 farmers drawn from Bungoma, Busia and Teso districts of Western Kenya, this study sought to: (i) assess farmers' perceptions and knowledge of Ns disease, including its effects on the smallholder dairy industry; (ii) record farmers' current practices in managing Ns disease; and (iii) identify Ns disease management challenges and intervention opportunities in order to develop an efficient integrated disease management approach. The majority (86·7%) of the farmers were aware of Ns disease and observed that it was spreading rapidly in the region, which was perfectly predicted by farmers' access to agricultural information (marginal effect = 0·164), indicating a need for extension platforms for knowledge sharing among the industry stakeholders. The disease had affected Napier grass yields so most farmers could not feed their livestock on the amounts they produced, and they were buying Napier grass. Those who relied on income from selling Napier grass received less due to loss in productivity. Milk production had reduced by over 35%. The cause of the disease was unknown to the farmers, with no effective disease management strategy available to them. An integrated disease management approach needs to be developed to fit within the mixed farming systems, supported by simple decision aids.     

Population dynamics of citrus leaf miner on different varieties of citrus in correlation with abiotic environmental factors in Sargodha District,Punjab, Pakistan

From January 2010 to December 2011, samples of leaves from citrus varieties Kinnow, Musambi and Feutral were taken from the five tehsils (administrative subdivisions) of Sargodha District in Pakistan including Sargodha, Bahalwal, Silanwalli, Sahiwal and Kotmomin, to study the population trends in citrus leaf miner (CLM), Phyllocnistis citrella (Stainton) (Lepidoptera: Gracillariidae), and its correlation with various environmental factors: (temperature, humidity and rainfall); plant morphological factors: moisture contents of leaves, leaf thickness, surface area (cm ² ), and biochemical percentage of calcium, potassium and magnesium in leaves. The maximum population of CLM was observed on Kinnow and Feutral, followed by Musambi. The effect of these factors on the larval population was 8.39- 2.30(Mg)+2.73(K)-0.398(Ca)-0.100(Temp)0.038(Humidity)+0.567(Rain)+0.07(Moist) 1.01 (Thickness)-0.022(Surface area). This equation revealed that magnesium, calcium, temperature, humidity, leaf thickness and leaf surface area are negatively correlated with larvae population, whereas potassium, rainfall and moisture are positively correlated with larvae population.     

Consequences of narrow crop row spacing and delayed Echinochloa colona and Trianthema portulacastrum emergence for weed growth and crop yield loss in maize

Echinochloa colona and Trianthema portulacastrum are weeds of maize that cause significant yield losses in the Indo‐Gangetic Plains. Field experiments were conducted in 2009 and 2010 to determine the influence of row spacing (15, 25 and 35 cm) and emergence time of E. colona and T. portulacastrum (0, 15, 25, 35, 45 and 55 days after maize emergence; DAME) on weed growth and productivity of maize. A season‐long weed‐free treatment and a weedy control were also used to estimate maize yield and weed seed production. Crop row spacing as well as weed emergence time had a significant influence on plant height, shoot biomass and seed production of both weed species and grain yield of maize in both years. Delay in emergence of weeds resulted in less plant height, shoot biomass and seed production. However, increase in productivity of maize was observed by delay in weed emergence. Likewise, growth of both weed species was less in narrow row spacing (15 cm) of maize, as compared with wider rows (25 and 35 cm). Maximum seed production of both weeds was observed in weedy control plots, where there was no competition with maize crop and weeds were in rows 35 cm apart. Nevertheless, maximum plant height, shoot biomass and seed production of both weed species were observed in 35 cm rows, when weeds emerged simultaneously with maize. Both weed species produced only 3–5 seeds per plant, when they were emerged at 55 DAME in crop rows spaced at 15 cm. Infestation of both weeds at every stage of crop led to significant crop yield loss in maize. Our results suggested that narrow row spacing and delay in weed emergence led to reduced weed growth and seed production and enhanced maize grain yield and therefore could be significant constituents of integrated weed management strategies in maize.