Root-Knot Nematode Management in Double-Cropped Plasticulture Vegetables

Combination treatments of chisel-injected fumigants (methyl bromide, 1,3-D, metam sodium, and chloropicrin) on a first crop, followed by drip-applied fumigants (metam sodium and 1,3-D ± chloropicrin) on a second crop, with and without oxamyl drip applications were evaluated for control of Meloidogyne incognita in three different tests (2002 to 2004) in Tifton, GA. First crops were eggplant or tomato, and second crops were cantaloupe, squash, or jalapeno pepper. Double-cropped vegetables suffered much greater root-knot nematode (RKN) pressure than first crops, and almost-total yield loss occurred when second crops received no nematicide treatment. On a first crop of eggplant, all fumigants provided good nematode control and average yield increases of 10% to 15 %. On second crops, higher application rates and fumigant combinations (metam sodium and 1,3-D ± chloropicrin) improved RKN control and increased yields on average by 20% to 35 % compared to the nonfumigated control. Oxamyl increased yields of the first crop in 2003 on average by 10% to 15% but had no effect in 2004 when RKN failed to establish itself. On double-cropped squash in 2003, oxamyl following fumigation provided significant additional reduction in nematode infection and increased squash yields on average by 30% to 75%.     

Arthropods and biofuel production systems in North America

Abstract Biomass harvest may eventually be conducted on over 100 000 000 ha of US crop and forest lands to meet federally-mandated targets for renewable biofuels. Such large-scale land use changes could profoundly impact working landscapes and the arthropod communities that inhabit them. We review the literature on dedicated biofuel crops and biomass harvest from forests to look for commonalities in arthropod community responses. With expanded biofuel production, existing arthropod pests of biofuel crops will likely become more important and new pests will emerge. Beneficial arthropods will also be influenced by biofuel crop habitats, potentially altering the distribution of pollination and pest control services to the surrounding landscape. Production of biofuel crops including initial crop selection, genetic improvement, agronomic practices, and harvest regimes will also influence arthropod communities. In turn, arthropods will impact the productivity and species composition of biomass production systems. Some of these processes have the potential to cause landscape-level changes in arthropod community dynamics and insect-vectored plant diseases. Finally, changes in arthropod populations and their spatiotemporal distribution in the landscape will have impacts on consumers of insects at higher trophic levels, potentially influencing their population and community dynamics and producing feedbacks to arthropod communities. Given that dedicated biofuel crops and intensified biomass harvest from forests are still relatively uncommon in North America, as they increase, we anticipate ‘predictably unpredictable’ shifts in arthropod communities and the ecosystem services and functions they support. We suggest that research on arthropod dynamics within biofuel crops, their spillover into adjacent habitats, and implications for the sustainability of working landscapes are critical topics for both basic and applied investigations.     

Les levures des Drosophiles de savane d'Afrique intertropicale (Savanes De Lamto,Côte d'ivoire)

Yeasts from crops of Drosophilidae (154 flies belonging to 22 species) of Lamto savannas (Ivory Coast) were studied. 50 yeast strains (belonging to 19 species) were isolated and studied. The most frequently isolated yeasts wereHanseniaspora andPichia membranaefaciens s.l.; these yeasts ferment and assimilate few of the carbon compounds. Some crops contained until 100 000 yeast cells. In 25% of the flies, these yeasts belonged to several different species.     

美国North Dakota州土地利用研究及对我国草地利用的启示

草地退化不仅仅是今天中国才发生的事情。历史上曾经发生"黑尘暴"的美国Nort hDakota州,现仍有62.7%土地被用作耕作,林地所占面积仅为1%。私有制以及种植业较高的利润率,是该州种植业比重高于畜牧业的重要原因。草原保护项目(CRP)得到了美国政府财政的大力支持,在North Dakota州采用了以草地恢复为主的措施。美国发达的教育体系带来的高流动率,使得North Dakota州自30年代后居住人口稳定在60～70万成为可能,从而避免了中国出现的草原地区不断增加的人口压力。由此可见:草地作为重要的自然资源,不可能完全保护起来;没有其它配套措施,私有制可能会带来新一轮垦殖;草地畜牧业仍然是畜牧业的重要组成部分,畜牧业发展需要结合种植业尤其需要与饲料生产相结合。     

Synchronising diagnosis and correction of nitrogen deficiency in barley grown in semi-arid environments

In field experiments conducted from 1986 to 1989, nitrogen (N) deficiency in barley crops was corrected with the same efficiency by applying N fertilizer at sowing or by broadcasting it at early tillering. Four plant tests for diagnosing and predicting N deficiency in barley were evaluated. Of these the basal stem nitrate-N test was best with a calibrated critical range of 12 000 to 15 000 mg kg^-1 when sampling was during early tillering.     

Winners and losers of land use change: A systematic review of interactions between the world’s crane species (Gruidae) and the agricultural sector

While agricultural intensification and expansion are major factors driving loss and degradation of natural habitat and species decline, some wildlife species also benefit from agriculturally managed habitats. This may lead to high population densities with impacts on both human livelihoods and wildlife conservation. Cranes are a group of 15 species worldwide, affected both negatively and positively by agricultural practices. While eleven species face critical population declines, numbers of common cranes (Grus grus) and sandhill cranes (Grus canadensis) have increased drastically in the last 40 years. Their increase is associated with higher incidences of crane foraging on agricultural crops, causing financial losses to farmers. Our aim was to synthesize scientific knowledge on the bilateral effects of land use change and crane populations. We conducted a systematic literature review of peer‐reviewed publications on agriculture‐crane interactions (n = 135) and on the importance of agricultural crops in the diet of cranes (n = 81). Agricultural crops constitute a considerable part of the diet of all crane species (average of 37%, most frequently maize (Zea mays L.) and wheat (Triticum aestivum L.)). Crop damage was identified in only 10% of all agriculture‐crane interactions, although one‐third of interactions included cranes foraging on cropland. Using a conceptual framework analysis, we identified two major pathways in agriculture‐crane interactions: (1) habitat loss with negative effects on crane species dependent on specific habitats, and (2) expanding agricultural habitats with superabundant food availability beneficial for opportunistic crane species. The degree to which crane species can adapt to agricultural land use changes may be an important factor explaining their population response. We conclude that multi‐objective management needs to combine land sparing and land sharing strategies at landscape scale. To support viable crane populations while guaranteeing sustainable agricultural production, it is necessary to include the perspectives of diverse stakeholders and streamline conservation initiatives and agricultural policy accordingly.     

Use of Green Manure Crops in Control of Hirschmanniella mucronata and H. oryzae in Irrigated Rice

Four field experiments were conducted to study the effect of Sesbania rostrata and Aeschynomene afraspera as rotational and green manure crops on the population dynamics of Hirschmanniella mucronata and H. oryzae, and subsequent rice yields. The sequential cropping of the legumes with rice controlled both nematode species. In two experiments, yield of rice was related to the nematode population denisites at planting and harvesting of the second rice crop (R² = 0.391, P < 0.001, and R² = 0.57, P < 0.001), regardless of the treatments. Rice yield increases were attributed to nutritional effect of the green manure and the reduction of the nematode populations or the modification of a factor(s) linked to the nematode populations induced by their cropping. As the two leguminous crops do not generate direct return, using them to control the rice-root nematodes was not economical, despite the significant yield increase obtained.     

Reproduction of Heterodera schachtii Schmidt on Resistant Mustard,Radish, and Sugar Beet Cultivars

The reproduction of a Wyoming population of Heterodera schachtii was determined for resistant trap crop radish (Raphanus sativus) and mustard (Sinapis alba) cultivars, and resistant and susceptible sugar beet (Beta vulgaris) cultivars in a greenhouse (21 °C/16 °C) and a growth chamber study (25 °C). Oil radish cultivars also were field tested in 2000 and 2001. In the greenhouse study, reproduction was suppressed similarly by the resistant sugar beet cultivar Nematop and all trap crop cultivars (P ≤ 0.05). In the growth chamber study, the radish cultivars were superior to most of the mustard cultivars in reducing nematode populations. All trap crops showed less reproduction than Nematop (P ≤ 0.05). In both studies, Nematop and all trap crops had lower Pf than susceptible sugar beet cultivars HH50 and HM9155 (P ≤ 0.05). In field studies, Rf values of radish cultivars decreased with increasing Pi of H. schachtii (r² = 0.59 in 2000 and r² = 0.26 in 2001). In 2000, trap crop radish cv. Colonel (Rf = 0.89) reduced nematode populations more than cv. Adagio (Rf = 4.67) and cv. Rimbo (Rf = 13.23) (P ≤ 0.05) when Pi was lower than 2.5 H. schachtii eggs and J2/cm³ soil. There were no differences in reproductive factors for radish cultivars in 2001 (P ≤ 0.05); Rf ranged from 0.23 for Adagio to 1.31 for Commodore for all Pi.     

The Biology and Thermal Requirements of the Fennel Aphid Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae)

The relationship between the insect development rate and temperature was established very early and represents an important ecological variable for modeling the population dynamics of insects. The accurate determination of thermal constant values and the lower and upper developmental thresholds of Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) on fennel (Foeniculum vulgare Miller (Apiales: Apiaceae)) crops would obviously benefit the effective application of control measures. This paper is a study of the biology and thermal requirements of H. foeniculi. Winged insects were collected from fennel crops at the Embrapa Algodão in Campina Grande, Paraíba. Nymphs (age ≤24 h) produced by winged insects were subjected to constant temperatures of 15, 20, 25, 28, 30 or 33°C, a photophase of 12 h and a relative humidity of 70±10%. The results of the study showed that at temperatures between 15 and 30°C, H. foeniculi nymphs were able to develop normally. The four instars were found at all temperatures tested. However, temperatures of 3 and 33°C were lethal to the nymphs. The nymph stage development time varied from 5 (30°C) to 19 (15°C) days. The influence of temperature on the development time is dependent on the instar. The base temperature (Tb) and the thermal constant (K) for the nymph stage were estimated at 11.2°C and 107.5 degree-days, respectively. The shortest nymph development stage was observed at 30°C, and the highest nymph viability (85.0%) was observed at 28°C. This information can be used for developing phenological models based on the temperature and development rate relationships so that outbreaks of H. foeniculi in the fennel crop can be predicted, therefore improving the application of control programs targeting this fennel pest.     

农田景观格局对南疆枣园传粉昆虫群落多样性的影响

[目的]明确新疆南疆地区农田景观格局对枣园传粉昆虫群落多样性的影响.[方法]2019和2020年在新疆阿克苏地区共选取29个试验站点,通过陷阱诱集法获取中心枣园内传粉昆虫多样性数据,调查中心枣园周围半径2 000 m范围内土地使用信息,建立枣园传粉昆虫群落指数与景观变量之间的线性混合模型,使用基于赤池信息准则的多模型推...     

Preparation of liver microsomes with high recovery of endoplasmic reticulum and a low grade of contamination

A modified procedure for preparing the microsomal fraction from rat liver was developed with the aim of increasing the recovery without increasing the degree of contamination. 87% of the membranes of the microsomal fraction isolated from the first mitochondrial (10 000 X g) supernatant originates from the endoplasmic reticulum, representing a 35% yield. By gentle resuspension of the 10 000 X g pellet followed by differential centrifugation a second crop of microsomes can be prepared which, together with the first crop, gives a 55% total recovery of microsomal markers. 87% of the protein in this second crop also originates from the endoplasmic reticulum and this fraction has properties similar to those of the first crop. Contaminating membranes include Golgi membranes (0.6% of the total protein), mitochondria (2.5%), lysosomes (5%) and plasma membranes (5%). Collecting further crops increases the contamination. Subfractionation studies revealed almost identical distributions of ribosome-rich, ribosome-poor and smooth membranes in the two crops of microsomal fractions. The results obtained after treatment of the animals with phenobarbital or methylcholantrene were similar to those obtained with control animals; but in the case of methylcholantrene treatment the second crop represents a larger portion of the total membranes of the endoplasmic reticulum.     

Diversification practices reduce organic to conventional yield gap

Agriculture today places great strains on biodiversity, soils, water and the atmosphere, and these strains will be exacerbated if current trends in population growth, meat and energy consumption, and food waste continue. Thus, farming systems that are both highly productive and minimize environmental harms are critically needed. How organic agriculture may contribute to world food production has been subject to vigorous debate over the past decade. Here, we revisit this topic comparing organic and conventional yields with a new meta-dataset three times larger than previously used (115 studies containing more than 1000 observations) and a new hierarchical analytical framework that can better account for the heterogeneity and structure in the data. We find organic yields are only 19.2% (±3.7%) lower than conventional yields, a smaller yield gap than previous estimates. More importantly, we find entirely different effects of crop types and management practices on the yield gap compared with previous studies. For example, we found no significant differences in yields for leguminous versus non-leguminous crops, perennials versus annuals or developed versus developing countries. Instead, we found the novel result that two agricultural diversification practices, multi-cropping and crop rotations, substantially reduce the yield gap (to 9 ± 4% and 8 ± 5%, respectively) when the methods were applied in only organic systems. These promising results, based on robust analysis of a larger meta-dataset, suggest that appropriate investment in agroecological research to improve organic management systems could greatly reduce or eliminate the yield gap for some crops or regions.     

Field Performance of Resistant Potato Genotypes Transformed with the EFR Receptor from Arabidopsis thaliana in the Absence of Bacterial Wilt (Ralstonia solanacearum)

Bacterial wilt caused by the pathogen Ralstonia solanacearum is a devastating disease of potato crops. Harmonizing immunity to pathogens and crop yield is a balance between productive, economic, and environmental interests. In this work, the agronomic performance of two events of potato cultivar INIA Iporá expressing the Arabidopsis thaliana EFR gene (Iporá EFR 3 and Iporá EFR 12) previously selected for their high resistance to bacterial wilt was evaluated under pathogen-free conditions. During two cultivation cycles, the evaluated phenotypic characteristics were emergence, beginning of flowering, vigor, growth, leaf morphology, yield, number and size of tubers, analyzed under biosecurity standards. The phenotypic characteristics evaluated did not show differences, except in the morphology of the leaf with a more globose appearance and a shortening of the rachis in the transformation events with respect to untransformed Iporá. The Iporá EFR 3 genotype showed a ~40% yield decrease in reference to untransformed Iporá in the two trials, while Iporá EFR 12 did not differ statistically from untransformed Iporá. Iporá EFR 12 shows performance stability in the absence of the pathogen, compared to the untransformed control, positioning it as an interesting candidate for regions where the presence of the pathogen is endemic and bacterial wilt has a high economic impact.     

Identification of RAPD and ISSR markers for drought tolerance in wheat (Triticum aestivum L.)

Drought tolerance is the essential trait that needs to be incorporated in cereal crops, particularly those grown under the rainfed cultivation. Drought tolerance being contributed by several regions of the genome requires identification of these regions, using suitable molecular markers. Therefore, present investigation was aimed at analyzing the genetic diversity present among the cultivars of rainfed and the irrigated areas with respect to the drought tolerant trait. In all, 14 RAPD and 90 ISSR markers were used to identify these genomic regions. Out of 14 RAPD markers, one RAPD primer exhibited polymorphic banding pattern with 18.6 % polymorphism, clearly separating drought tolerant and drought susceptible genotypes. Out of 90 ISSR primers, only 3 ISSR primers revealed polymorphism in relation to the drought tolerance trait exhibiting 21.38 % polymorphism.     

Plant development controls leaf area expansion in alfalfa plants competing for light

Background and Aims

The growth of crops in a mixture is more variable and difficult to predict than that in pure stands. Light partitioning and crop leaf area expansion play prominent roles in explaining this variability. However, in many crops commonly grown in mixtures, including the forage species alfalfa, the sensitivity and relative importance of the physiological responses involved in the light modulation of leaf area expansion are still to be established. This study was designed to assess the relative sensitivity of primary shoot development, branching and individual leaf expansion in alfalfa in response to light availability.

Methods

Two experiments were carried out. The first studied isolated plants to assess the potential development of different shoot types and growth periods. The second consisted of manipulating the intensity of competition for light using a range of canopies in pure and mixed stands at two densities so as to evaluate the relative effects on shoot development, leaf growth, and plant and shoot demography.

Key Results

Shoot development in the absence of light competition was deterministic (constant phyllochrons of 32·5 °Cd and 48·2 °Cd for primary axes and branches, branching probability of 1, constant delay of 1·75 phyllochron before axillary bud burst) and identical irrespective of shoot type and growth/regrowth periods. During light competition experiments, changes in plant development explained most of the plant leaf area variations, with average leaf size contributing to a lesser extent. Branch development and the number of shoots per plant were the leaf area components most affected by light availability. Primary axis development and plant demography were only affected in situations of severe light competition.

Conclusions

Plant leaf area components differed with regard to their sensitivity to light competition. The potential shoot development model presented in this study could serve as a framework to integrate light responses in alfalfa crop models.     

Species of Root-knot Nematodes and Fungal Egg Parasites Recovered from Vegetables in Almería and Barcelona,Spain

Intensive vegetable production areas were surveyed in the provinces of Almería (35 sites) and Barcelona (22 sites), Spain, to determine the incidence and identity of Meloidogyne spp. and of fungal parasites of nematode eggs. Two species of Meloidogyne were found in Almería—M. javanica (63% of the samples) and M. incognita (31%). Three species were found in Barcelona, including M. incognita (50%), M. javanica (36%), and M. arenaria (14%). Solanaceous crops supported larger (P < 0.05) nematode numbers than cucurbit crops in Almería but not in Barcelona. Fungal parasites were found in 37% and 45% of the sites in Almería and Barcelona, respectively, but percent parasitism was never greater than 5%. Nine fungal species were isolated from single eggs of the nematode. The fungi included Verticillium chlamydosporium, V. catenulatum, Fusarium oxysporum, F. solani, Fusarium spp., Acremonium strictum, Gliocladium roseum, Cylindrocarpon spp., Engiodontium album, and Dactylella oviparasitica. Two sterile fungi and five unidentified fungi also were isolated from Meloidogyne spp. eggs.     

Effects of Crop Canopies on Rain Splash Detachment

Crops are one of the main factors affecting soil erosion in sloping fields. To determine the characteristics of splash erosion under crop canopies, corn, soybean, millet, and winter wheat were collected, and the relationship among splash erosion, rainfall intensity, and throughfall intensity under different crop canopies was analyzed through artificial rainfall experiments. The results showed that, the mean splash detachment rate on the ground surface was 390.12 g/m²·h, which was lower by 67.81% than that on bare land. The inhibiting effects of crops on splash erosion increased as the crops grew, and the ability of the four crops to inhibit splash erosion was in the order of winter wheat>corn>soybeans>millet. An increase in rainfall intensity could significantly enhance the occurrence of splash erosion, but the ability of crops to inhibit splash erosion was 13% greater in cases of higher rainfall intensity. The throughfall intensity under crop canopies was positively related to the splash detachment rate, and this relationship was more significant when the rainfall intensity was 40 mm/h. Splash erosion tended to occur intensively in the central row of croplands as the crop grew, and the non-uniformity of splash erosion was substantial, with splash erosion occurring mainly between the rows and in the region directly under the leaf margin. This study has provided a theoretical basis for describing the erosion mechanisms of cropland and for assisting soil erosion prediction as well as irrigation and fertilizer management in cultivated fields.     

Description and SEM Observations of a New Species of Cyst Nematode Heterodera goldeni (Nematoda: Heteroderidae) Attacking Panicum coloratum in Egypt

A cyst nematode, Heterodera goldeni n. sp., is photographed and described from Qasabagrass roots (Panicum coloratum L.) in Alexandria, Egypt. It is characterized in having second-stage juveniles with body length of 546 µm (450-612), stylet length of 22.6 µm (22-23.5) with anchor-shaped knobs, lateral field with 3 lines, tail 60-75 µm, hyaline tail terminus 38.4 µm (33-43); cysts are lemon-shaped, dark to light brown with an extensive sub-crystalline layer covering the entire cyst, cuticular midbody pattern zig-zag, cysts ambifenestrate, well-developed underbridge with finger-like projections, bullae present, vulva slit measuring 44-48 µm long. Males are absent, and females have heavy punctations on the cuticle. Its relationship to H. graminophila described from Florida and Louisiana and H. leuceilyma described from Florida are discussed. The present known distribution is restricted to Alexandria, Egypt. Its economic importance in rangeland grasses and cultivated crops such as rice is not known.