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1.
Prospects of reducing Striga hermonthica (Del.) Benth. parasitism by means of cultural control measures were assessed. In a pot experiment, deep planting, the use of transplants and shallow soil-tillage, strongly delayed and reduced Striga infection of a sensitive and a tolerant sorghum cultivar. Application of all three measures combined resulted in a four-week delay in first emergence of the parasite, a reduced number of emerged Striga plants and a decimation of Striga dry weight. With the sensitive cultivar CK-60B a yield loss of 92% was reduced to 26%, whereas with the tolerant cultivar Tiemarifing application of the cultural control measures completely cancelled out a yield loss of 28%. Evaluation of these cultural measures under field conditions in Mali resulted in a strong reduction in Striga-infection level (85%). At the same time, the measures did not result in delayed first emergence of the parasite and had no beneficial effect on crop yield. It was argued that the presence of a natural Striga soil seed bank, with seeds throughout the tilth, might be an important reason for the reduced effectiveness of the proposed cultural control measures under field conditions.  相似文献   

2.
Field trials were conducted in 1997 and 1998 wet seasons to determine the effect of seed treatment of different sorghum varieties with brine (NaCl) on the control of Striga hermonthica in sorghum. The varieties of sorghum used were ICSV 1002, ICSV 1007 (improved resistant varieties from ICRISAT, Mali), BES (a local improved variety), and War-warabashi (a local susceptible variety). Different concentrations of brine at 0.5, 1.0, 1.5, and 2.0 M were used. The results show that the varieties, ICSV 1002 and ICSV 1007 had significantly higher establishment count than the BES and War-warabashi varieties, but had shorter plants. Similarly, the ICSV 1002 and ICSV 1007 and War-warabashi varieties had significantly larger LAI values than the BES variety, although the BES significantly out yielded them. The susceptible War-warabashi variety supported the highest number of Striga emergence than the improved varieties. The effect of brine treatments on plant establishment, growth and yield of sorghum under Striga infestation shows that there was a decrease in crop stands with increase in brine concentration, with the least value at 2.0 M brine treatment, which was damaging at this rate. Plant height and, leaf area index (LAI) of sorghum increased with increasing concentration of brine to a maximum at 1.5 M and declined at 2.0 M brine treatment. The 1.5 M brine treatment produced the highest grain yield. Striga shoot emergence significantly declined with increasing brine concentration reaching the lowest values at 1.5 and 2.0 M brine treatments. The interaction between sorghum varieties and brine concentrations shows that War-warabashi with 1.5 M brine treatment had the tallest plants and largest LAI, while BES and 1.5 M brine produced the highest grain yield. In general, the interaction between the varieties and all the brine concentrations significantly reduced Striga emergence. Irrespective of the sorghum varieties the use of brine at 1.5 M was found optimal for controlling Striga emergence resulting in increased crop growth and grain yield. This implies that which ever variety farmers are using either resistant, tolerant or susceptible, they could easily use brine at 1.5 M to effectively control Striga and increase in grain yield. The mechanism by which brine successfully controlled Striga, is, however, not clear and needs to be investigated.  相似文献   

3.
Seed survival of Striga hermonthica is influenced by amendments of organic matter; however, the role of organic matter quality (C:N ratio) and mechanisms for enhanced seed decay are inadequately understood. In a field experiment, plots received a single dose of 6 t organic matter per hectare but with large differences in quality in terms of C:N ratio. Soil moisture, soil temperature and soil ethylene concentrations were measured, while buried nylon seed bags were periodically withdrawn from the soil and assayed for seed viability and germination. Organic matter amendments incorporated in the soil significantly depressed S. hermonthica seed survival. The effect was strongest with organic matter of high quality. Organic matter of low-quality enhanced soil water content during the first five days after a rainfall event and resulted in a 0.5 °C lower soil temperature. The highest observed ethylene concentrations in the soil were between 2 and 3 ppm, high enough to stimulate S. hermonthica seed germination. Maximal seed germination in vitro was obtained after 48 h of exposure to 1 ppm ethylene. However, observed changes in seed germination and viability of retrieved seed batches (seed survival) did not correlate with soil ethylene concentrations. The latter in turn did not differ between qualities of the applied organic matter. Seed survival decreased with increasing time of burial, especially after 4–8 weeks. As S. hermonthica attachment mainly occurs during the first four weeks of the cropping season the observed effect of seed decay may hardly be beneficial for the on-going cropping season. Nutrient release through decomposition of organic matter, enhancing decay of S. hermonthica seeds, is proposed as the probable cause of seed depletion in the soil.  相似文献   

4.
The effect of organic amendments on the interactions between Striga hermonthica and a sorghum host was studied in a field experiment during three cropping seasons, following a three-factorial design with (i) bare fallow versus continuous cropping, (ii) two Strigahermonthica infection levels and (iii) five organic matter levels, a single inorganic fertiliser treatment of 120 kg N ha−1 and a control. The effects of two different cotton by-products and their mixtures on sorghum yield were well described by their N-mineralisation pattern. The impact of organic amendments in the sorghum production system was directly related to N-mineralisation in the three cropping seasons. There was an increasing negative effect of organic matter on S. hermonthica as the quality of the applied material increased. The emerged numbers of S. hermonthica were well described by N-release after one month, while S. hermonthica biomass and sorghum biomass were well described by N-release after three months. As a stand-alone measure, addition of low-quality organic matter is disadvantageous in cropping systems with high S. hermonthica seed densities, as it does not improve sorghum performance compared to no addition of organic matter, while S. hermonthica numbers increase. Implications for integrated soil fertility and S. hermonthica management under different infection levels of S. hermonthica are discussed.  相似文献   

5.
《Field Crops Research》1987,16(3):255-272
Cereal/cereal intercrop systems are commonly used by farmers in the higher-rainfall areas of the South Sudanian and Guinean savanna zones of West Africa. Towards the North Sudanian zone these systems become less common, because of a shorter rainy season with a more abrupt start and end. However, previous work on the responses of maize (Zea mays), sorghum (Sorghum bicolor), and pearl millet (Pennisetum americanum) crops to the different toposequence land types indicated that crop mixtures of sorghum/millet for uplands and sorghum/maize for lowlands would be less prone to drought stress and waterlogging risks than would the respective sole crops.The present studies showed consistent intercropping advantages of at least 25% for sorghum/maize systems when both crops are sown at the same time. The relative advantages from this system were greatest for the uplands.Intercropping advantages were generally less for the sorghum/millet systems, and it proved essential to delay the millet sowing to prevent serious competition to the sorghum. Sorghum/millet intercropping provides a risk-reducing alternative to sole cropping, because sorghum plants lost during the common early droughts can be replaced by an early-maturing millet sown in July. However, because of the unpredictability of the early-season rainfall, sorghum/millet systems will be difficult to standardize; both the sowing date and the plant densities of the component crops may require adjustments each year in response to the starting date of the rains and the extent to which the sorghum has survived the early-season droughts.  相似文献   

6.
Accelerated aging at 50 °C significantly affected the physical and chemical properties of sorghum and maize. Aging caused associations between starch granules, protein matrix, and cell walls. During aging, floury areas of the endosperm became more corneous; as the endosperm hardened, strong associations between starch and protein developed, causing the endosperm to fracture through endosperm cells instead of along cell walls, which is common for non-aged maize. Aging significantly decreased the pasting viscosity of starch, molecular solubility at 85 °C and the molecular weight of solubilized starch. Solubility of albumins and globulins decreased while solubility of proteins extracted by a reducing agent and/or in alkaline pH increased during aging. Decreased solubility and functionality of starch and protein in aged grain appear to be due to protein oxidation.  相似文献   

7.
Sorghum, pearl millet, and finger millet flours (60% of each) were blended with toasted mung bean flour (30%) and nonfat dry milk (10%) and extruded (Brabender single screw) to make precooked, ready-to-eat, weaning foods. The extruded foods had high cold paste viscosity, but their cooked paste viscosity was lower than that of the respective blends. Chemical scores of the extruded foods were 78 for sorghum, 80 for pearl millet, and 96 for finger millet. Protein digstibility corrected amino acid scores (PD-CAS) were similar for pearl millet (68%) and finger millet (69%); PD-CAS for sorghum was 57%. Total dietary fiber content of the foods ranged from 7.6 to 10.1%, with the soluble dietary fiber content of the foods being about 10% higher than that of the corresponding blends. Extrusion enhanced the in vitro protein digestibility of foods, but no marked difference occurred in the in vitro carbohydrate digestibility among the unprocessed blends and the extruded foods. The net protein ratio, protein efficiency ratio, and biological values were higher for the finger millet food than for the pearl millet food, probably because of the higher lysine content of the finger millet protein.Contribution No. 95-253-J of the Kansas Agricultural Experiment Station.  相似文献   

8.
Host-plant resistance is an effective and economical means of controlling downy mildew (DM) diseases in maize (Zea mays L.). Crosses involving 10 inbred maize lines in all possible combinations (diallel cross) showed that susceptibility to sorghum DM (Peronosclerospora sorghi (Weston and Uppal) C. G. Shaw) is generally inherited as a dominant characteristic. However, progenies of crosses between one of the lines (CM105) resistant to DM, and susceptible lines, showed intermediate levels of resistance, indicating that several genes are involved and that their effects are additive. Progenies of crosses between resistant lines were more resistant than their parents, probably because of interactions between different resistance genes (epistasis). Both additive and non-additive gene action was detected by partitioning gene effects by generation mean in each 16 DM-resistant × DM-susceptible combinations, which indicates that the reactions of maize to DM are governed by several genes (i.e. polygenically) and that the inheritance of resistance is complex. An inbred line from Mexico, Tuxpeno Gpo. 48-Var. 168-1, is a particularly promising general source of resistance to DM.  相似文献   

9.
Storage retrogradation behavior and properties of sorghum, maize, and rice starches were compared to better understand the relationship of amylopectin fine structure to quality issues. Long-term changes in texture of starch gels were attributed to amylopectin retrogradation. In starch pastes aged 7 days at 4 °C, change in the storage modulus (ΔG) during heating (representing intermolecular associations) was highly and positively correlated (r = 0.93, p < 0.01) with the proportion of fraction I (FrI) long chains from debranched amylopectin. One sorghum cultivar, Mota Maradi, showed a dramatic increase in the storage modulus (G′) over the 7 day storage period that was related to its high proportion of FrI. Pastes/gels made from starches with normal (20–30%) amylose content and higher proportions of FrI long chains from debranched amylopectin tended to become firmer with more syneresis during extended storage. Both degree of polymerization measurements and previous models for amylopectin structure indicate that FrI represents long B chains of amylopectin. Cereal cultivars having amylopectin structures with lower proportion of long B chains were speculated to give improved quality products with lower rates of retrogradation and staling. This is particularly an issue in sorghum foods where products generally lack storage stability and tend to stale relatively quickly.  相似文献   

10.
测定了布氏潜蝇茧蜂[Fopius vandenboschi(Fullaway)]和长尾潜蝇茧蜂[Diachasmimorpha longicaudata(Ashmead)]这2种寄生蜂对寄主植物挥发物中主要的9种化合物的触角电位反应。结果表明:布氏潜蝇茧蜂雌雄成虫均对朱栾倍半萜反应最大,并且均对石竹烯反应最小。长尾潜蝇茧蜂雌虫对α-法呢烯反应最大,对柠檬烯反应最小;雄虫对反-2-癸烯醛反应最大,对β-紫罗兰酮和石竹烯反应最小。  相似文献   

11.
拟小食螨瓢虫对小薯上朱砂叶螨种群数量具有一定的控制作用.为研究利用拟小食螨瓢虫控制朱砂叶螨,在观察拟小食螨瓢虫成虫对朱砂叶螨成、若螨和卵的逐日捕食量基础上,测定拟小食螨瓢虫对不同密度朱砂叶螨+螨害木薯叶VS健康木薯叶的选择性,调查拟小食螨瓢虫和朱砂叶螨在木薯上的空间分布相关性.结果表明:①拟小食螨瓢虫羽化后第3天对朱砂叶螨成、若螨和卵的捕食量达最大值,并趋于稳定.②当朱砂叶螨若螨和成螨密度为30头/叶及40头/叶时,拟小食螨瓢虫显著地趋向朱砂叶螨+螨害木薯叶复合体;(③当朱砂叶螨若螨和成螨在木薯上的分布数量分别为41.90头和32.60头时,拟小食螨瓢虫在木薯上的分布数壁达最大;(④天敌拟小食螨瓢虫对木薯朱砂叶螨的行为选择与二者在木薯上的空间分布之间存在正相关关系.本研究结果可为探讨拟小食螨瓢虫对木薯朱砂叶螨的选择机制,以便更好地利用其控制木薯朱砂叶螨为害提供科学依据.  相似文献   

12.
狗牙根对铝胁迫响应及临界浓度的研究   总被引:1,自引:0,他引:1  
以狗牙根为研究对象,利用水培法进行耐铝鉴定,初步研究不同铝浓度胁迫对狗牙根叶色、耐铝指数、坪用质量、枯黄率、相对地上部干重、相对根系干重的影响。结果表明,在250、500、750、1 000、1 250μmol/L铝浓度处理下,狗牙根受胁迫影响较小,不同浓度处理之间差异不明显。在1 500、1 750、2 000、2 250μmol/L铝浓度处理下,狗牙根随着胁迫时间的增长,叶色、均一性逐渐降低。在2 500、2 750、3 000、3 250、3 500μmol/L铝浓度处理下,狗牙根受胁迫影响较大,叶色、均一性明显降低,与对照相比表现出显著差异或极显著差异。通过建立回归方程,以狗牙根耐铝指数下降到60%作为狗牙根存活临界铝离子浓度,求得狗牙根致死临界铝浓度为2 520μmol/L。  相似文献   

13.
Analysis of responses received from 40 cooperators in 20 countries to a questionnaire on nematode problems of groundnut, pigeonpea, chickpea, sorghum and pearl millet suggested that Meloidogyne spp. are internationally important nematode pests of groundnut, chickpea and pigeonpea. Pratylenchus spp. are important on all the five crops. In India, Heterodera cajani and Rotylenchulus reniformis are important pathogens of pigeonpea. Over the last 10–15 years, extensive nematode disease surveys have been undertaken for these crops in Australia, Egypt, India, Jamaica, Senegal, Sudan, Thailand and Zimbabwe; however, < 10% of the total crop areas were covered by these surveys. Except for Brazil, Egypt, USA and Zimbabwe, growers do not use nematicides to control the nematodes. Cultural practices, especially crop rotations, are the most commonly used control measures. Species of Meloidogyne, Pratylenchus and Rotylenchulus on the legumes, and species of Hoplolaimus, Pratylenchus, Quinisulcius and Xiphinema on the cereals, are strongly suspected of increasing the severity of fungal diseases. Work aimed at finding host resistance is being done in Brazil, Fiji, India and the USA, and some sources of resistance have been identified against Meloidogyne arenaria, M. incognita, M. javanica and R. reniformis. Facilities for resistance screening work now exist in many countries. Information on damage thresholds of important pest species are available only from Brazil, Fiji, India and the USA.  相似文献   

14.
Striga hermonthica (Delile) Benth., stemborers, and declining soil fertility are serious threats to sustainable food production in the Lake Victoria zone of Kenya. To address these constraints, promising integrated crop management technologies were evaluated, using a multi-locational design in four sub-locations in Siaya and Vihiga district (western Kenya) for six cropping seasons. Technologies evaluated consisted of the traditional maize (Zea mays L.) – bean (Phaseolus vulgaris L.) intercrop, maize – Desmodium (Desmodium uncinatum (Jacq.) DC.) push–pull intercrop, Crotalaria (Crotalaria ochroleuca G. Don) – maize rotation, and soybean (Glycine max (L.) Merr) – maize rotation. Within each of these systems, imazapyr-coated herbicide-resistant maize (IR-maize) and fertilizer were super-imposed as sub-plot factors. The push–pull system was observed to significantly reduce Striga emergence and stemborer damage from the second season onwards. IR-maize reduced and delayed Striga emergence from the first cropping season. Differences in Striga emergence and stemborer damage between the other systems were not significantly different. After five cropping seasons, the Striga seedbank was significantly higher in the maize-bean intercrop system than in the push–pull system under both maize varieties while the rotational systems had intermediate values not different from the day zero values. Under IR-maize, the Striga seedbank was significantly lower than under local maize for all cropping systems. Maize yields varied between seasons, districts, and cropping systems. Yields in the push–pull system were higher than in the maize-bean intercrop after two seasons and in the absence of mid-season drought stress. Both maize and soybean responded significantly to fertilizer application for both districts and for most seasons. The various interventions did not substantially affect various soil fertility-related parameters after five seasons. In the short term, IR-maize integrated in a push–pull system is the most promising option to reduce Striga while the rotational systems may need a longer timeframe to reduce the Striga seedbank. Finally, farmer-led evaluation of the various technologies will determine which of those is really most acceptable under the prevailing farming conditions.  相似文献   

15.
Reduced lignin concentration in brown mid-rib mutants in both maize and sorghum have resulted in improved dry matter digestibility, increased milk yield and higher energy in lactating cows. However, the mutations were not widely deployed due to concern that reduced lignin concentration might increase vulnerability to lodging and stalk rot incidence. The objective of this study was to determine the effects of the mutations on stalk strength and stalk rot resistance in both sorghum and maize. Six brown midrib (bmr) sorghum, four brown midrib (bm) maize, and their normal isolines were evaluated for stalk strength and stalk rot disease reaction at two locations in four replications. Three randomly selected plants in each plot were inoculated with Macrophomina phaseolina at 14 d after flowering by using the toothpick inoculation technique. On 28 d after inoculation, the plants were rated for disease severity by measuring the length of necrotic lesions in the stalks. Stalk strength was determined from another three random plants in each plot by using a rind penetrometer. The mutations had no effect on stalk rot disease severity in either sorghum or maize though stalks strength was markedly affected by the mutations in both species. While maize bm entries broke easily in response to mild mechanical stress, bmr sorghums did not exhibit sign of stalk collapse in all backgrounds. The result suggests that the bmr genes in both maize and sorghum can be deployed without incurring losses to stalk rot disease.  相似文献   

16.
张成和  刘爱国 《玉米科学》1995,3(Z1):021-024
河北省为玉米大、小斑病混合发生区,近年来玉米矮花叶病发病逐年加重。通过对河北省玉米生产上的11份主栽玉米杂交种和11份骨干玉米自交系对大、小斑病和矮花叶病的单独接种和复合接合鉴定结果看出,被玉米矮花叶病侵染的玉米对大、小斑病的抗性严重丧失,病级一般加重2~3级,病指增高40%以上,由抗病品种变成了感病品种,所以选育种植抗大、小斑病的玉米品种时,必须同时兼抗玉米矮花叶病。  相似文献   

17.
为探究异源染色体对小麦抗旱能力的影响,选取3个普通小麦-欧山羊草异附加系和3个普通小麦为试验材料,以聚乙二醇(PEG6000)模拟干旱胁迫,在苗期测定干旱胁迫下叶片丙二醛(MDA)积累量、可溶性蛋白含量和酶促防御系统(SOD、POD和CAT)活性变化。结果表明,随着干旱胁迫程度的加重和时间的延长,供试基因型所测定的五个生理指标的变化趋势较为一致。MDA含量都不断升高,三个普通小麦-欧山羊草异附加系(Ae9013、Ae9041和Ae9061)的MDA积累幅度较抗旱性最好的小麦对照晋麦47小,积累量也较少。三个异附加系的可溶性蛋白含量受干旱胁迫影响较小,虽有小幅度的下降,但保持着较高的含量。干旱胁迫下,各基因型的SOD、POD和CAT活力增加,在一定时间内,随着干旱胁迫的持续,晋麦47表现出先上升后下降的趋势,而Ae9013、Ae9041和Ae9061的SOD和POD活力随着胁迫程度的加重和时间的延长呈现不断上升趋势;Ae9013、Ae9041的CAT活力在15%PEG6000胁迫下不断增加,在25%PEG6000胁迫下先增加后下降,而Ae9061的CAT活力在高浓度PEG6000胁迫下仍持续增加。由此可见,普通小麦-欧山羊草异附加系具备更有效的酶促防御系统和渗透调节能力,说明U组染色体附加提高了小麦的抗旱能力。  相似文献   

18.
The ‘push–pull’ technology (PPT), developed in Africa, offers effective control of cereal stemborers and Striga weed in maize-based cropping systems. It involves intercropping maize with desmodium, Desmodium uncinatum, with Napier grass, Pennisetum purpureum, planted as border around this intercrop. Desmodium repels the stemborer moths (push) that are subsequently attracted to the Napier grass (pull). Desmodium also suppresses and eliminates Striga. We assessed economic performance of this technology compared to the conventional maize mono- and maize–bean intercropping systems in six districts in western Kenya over 4–7 years. Ten farmers were randomly recruited in each district and each planted three plots representing the three cropping systems. The cost–benefit analyses were carried out, together with the systems’ net returns to land and labour and their discounted net present values (NPV). Maize grain yields and associated gross margins from the PPT system were significantly higher than those in the other two systems. Although the production costs were significantly higher in the PPT than in the two cropping systems in the first cropping year, these reduced to either the same level or significantly lower than in the maize–bean intercrop from the second year onwards in most of the districts. Similarly, the net returns to land and labour with the PPT were significantly higher than with the other two systems. The PPT consistently produced positive NPV when the incremental flows of its benefits compared to those of the two conventional systems were discounted at 10–30%, indicating that PPT is more profitable than the other two systems under realistic production assumptions. PPT is thus a viable option for enhancing productivity and diversification for smallholder farmers who largely depend on limited land resource. Hence, enhancing farmers’ access to less costly planting materials and promoting quality education and training in the use of this knowledge-intensive technology could stimulate its successful adoption.  相似文献   

19.
The phytochemical composition of three aromatic plants (Cistus ladanifer L., Cupressus lusitanica Mill. and Eucalyptus gunnii Hook. f) was evaluated, in order to valorize them as sources of nutraceuticals. Samples were analysed for ascorbic acid by spectrophotometric assay, tocopherols by high performance liquid chromatography (HPLC) coupled to a fluorescence detector, sugars by HPLC coupled to a refraction index detector (RID), and fatty acids by gas-chromatography (GC) coupled to a flame ionization detector (FID). The analysed plants contain very useful compounds such as vitamins (ascorbic acid and tocopherols), reducing sugars (glucose and fructose) and polyunsaturated fatty acids (linoleic, α-linoleic and eicosadienoic acids). Their vitamins and sugars could be useful in diseases related to oxidative stress, in dermatological applications or in cosmetics. The polyunsaturated fatty acids, including omega-3 and omega-6 families, detected in the plants constitute another important class of phytochemicals due to their generalized beneficial health effects.  相似文献   

20.
A study was conducted to determine consumer acceptable proportions of flours in sorghum (var. serena) and maize or sorghum, maize and cassava composite flours. Breeder's serena flour extracted at 75 percent was mixed at various proportions with maize or with maize and cassava to constitute composite flours. The various composite flours were made into stiff porridge and presented to a group of panellists for sensory evaluation. The evaluation was conducted by scoring on a hedonic scale of 0–5 for poor to excellent, respectively, for the parameters colour, texture, flavour, taste and overall acceptability. The responses were analysed statistically. Alternatively the panellists were allowed to eat ad-lib any of the presented samples which appealed to them. The results demonstrated that slight incorporation (<10%) of sorghum (var. serena) to maize flour leads to reduction in consumer acceptability. However, increased incorporation of sorghum in excess of 10 percent leads to no significant decrease in consumer acceptability until a level of 30 percent incorporation is exceeded. In sorghum, maize, cassava composite flours the formulation of 30:40:30, respectively, was found to be most acceptable. It is suggested that at this combination of flours desirable textural characteristics of the porridge overrides other factors in contributing to its acceptability.  相似文献   

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