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排序方式: 共有233条查询结果,搜索用时 31 毫秒
61.
Agricultural food production in arid and semi-arid regions faces the challenge to ensure high yields with limited supply of water. This raises the question to which extent irrigation supply can be reduced without detriment to yield. Our study focuses on the yield-water uptake relationship for maize in the moderate water stress range in order to determine the onset of stress-induced dry-matter and yield losses. Compensatory plant responses under moderate stress levels are discussed in relation to seasonal climatic conditions.Summer-sown and spring-sown maize were irrigated with a decreasing amount of water in a field experiment in Pakistan. Water supply ranged from 100% water required to maintain soil at field capacity (FC) to 40% of FC. The average dry-matter and yield levels were slightly higher for summer-sown (15.0 Mg ha−1) compared to spring-sown maize (13.1 Mg ha−1). The onset of significant dry-matter and yield reduction started at the least irrigation treatment in both seasons. The amount of water required to avoid production losses was 272 mm in the summer-sown maize during the autumn growing season, and 407 mm for the spring-sown maize in the summer season, when the evaporative demand of the atmosphere was +27% higher. Water use efficiency (WUEET), normalized by vapour pressure deficit, of the summer-sown maize which was 10.0 kg kPa m−3, was +15% higher compared to the spring-sown crop; while the irrigation water productivity (2.9 kg m−3) was +11% more. WUEET increased over the whole range of applied water deficits for summer-sown maize, while the spring-sown crop showed a decreasing WUEET in the less irrigated treatment. Due to the higher efficiency in summer-sown maize, the potential in irrigation reduction without production losses (129 mm) was higher compared to the spring-sown maize (57 mm). Our results showed that in Pakistan water saving irrigation practices can be applied without yield loss mainly during the cooler growing season when the crop can efficiently compensate a lower total water uptake by increased use efficiency. For spring-sown maize the increasing evaporative demand of the atmosphere towards summer implies a higher risk of yield losses and narrows the range to exploit higher irrigation water productivity under moderate water deficit conditions. 相似文献
62.
Chickpea (Cicer arietinum L.), is an important grain legume crop throughout the world especially in developing countries. However the average yield worldwide is considered to be lower than its potential yield (Singh et al., 1994). The average yield of chickpea is much lower in Pakistan, which is about 5500-650 kg/hm^2 due to various abiotic and biotic stresses (Shah et al., 2005). 相似文献
63.
Muhammad Iqbal Robert H. J. Verkerk Michael J. Furlong Pek Choo Ong Syed Abdul Rahman Denis J. Wright 《Pest management science》1996,48(1):89-97
The efficacy of Bacillus thuringiensis (Bt) subsp. kurstaki HD-1 (‘Dipel’™; Btk; CryIA & CryII) and Bt. subsp. aizawai (‘Florbac’™; Bta; CryIA & CryIC) was assessed against larvae from various field populations of Plutella xylostella (F2 generation) collected in the Cameron Highlands, Malaysia in April 1994 and a lowland population (SERD 2; F10 generation) collected in December 1993. Evidence of resistance to Btk and to a lesser extent Bta is reported in these populations (LC50 Toxicity Ratios [TR]=3–14 and 2–8 respectively), most notably in SERD 2. The first recorded evidence of resistance to abamectin (TR=17–195-fold) in field populations of P. xylostella is also reported. In an unselected sub-population of SERD 2, the TR values for Btk, Bta and abamectin declined 2- to 3-fold (P<0·01) over six generations in the laboratory (F10–F16) while in sub-populations of SERD 2 selected with these products (F11–F15) there was a significant (P<0·01) increase in the TR (15-, 3- and 2·5-fold respectively) when compared with the F10 generation. This suggests the presence of marked resistance to Btk and some resistance to Bta and abamectin. There is also evidence of slight cross-resistance to Btk in the Bta-selected sub-population but no evidence for the reverse selection of resistance or for cross-resistance between Btk and abamectin. Concurrent selection studies (F11–F15) with another sub-population of SERD 2 demonstrated resistance to the acylurea insect growth regulator, teflubenzuron (‘Nomolt’™) (29-fold increase in TR). Based on the selection experiments with SERD 2, estimates of realised heritability (h2) of resistance gave very high values for teflubenzuron and Btk (c.0·7) and moderate values for abamectin and Bta (c.0·3). The results are discussed in relation to integrated pest management (IPM) and insecticide resistance management (IRM) strategies for P. xylostella. 相似文献
64.
A. Yang S. S. Akhtar M. Amjad S. Iqbal S.‐E. Jacobsen 《Journal of Agronomy and Crop Science》2016,202(6):445-453
Quinoa (Chenopodium quinoa Willd.), traditionally called the mother of grains, has the potential to grow under high temperatures and drought, tolerating levels regarded as stresses in other crop species. A pot experiment was conducted in a climate chamber to investigate the potential of quinoa tolerance to increasing drought and temperature. Quinoa plants were subjected to three irrigation and two temperature regimes. At low temperature, the day/night climate chamber temperature was maintained at 18/8 °C and 25/20 °C for high temperature throughout the treatment period. The irrigation treatments were full irrigation (FI), deficit irrigation (DI) and alternate root‐zone drying (ARD). FI plants were irrigated daily to the level of the pot's water‐holding capacity. In DI and ARD, 70 % water of FI was applied either to the whole pot or to one side of the pot alternating, respectively. The results indicated that plant height and shoot dry weight significantly decreased by ARD and DI compared to FI treatment both at low and at high temperatures. However, plants in ARD treatment showed significantly higher plant height and shoot dry weight compared to DI especially at higher temperature, which is linked to increased xylem ion content. Higher quinoa plant growth in ARD was associated with increase in water‐use efficiency (WUEi) due to higher abscisic acid concentration and higher nutrient contents compared to DI. From results, it can be concluded that quinoa plant growth is favoured by high temperature (25/20 °C) and ARD is an effective irrigation strategy to increase WUE in drought prone areas. 相似文献
65.
A. Sakina I. Ahmed A. Shahzad M. Iqbal M. Asif 《Journal of Agronomy and Crop Science》2016,202(1):25-36
Soil salinity is one of the major production constraints. Development and planting of salt‐tolerant varieties can reduce yield losses due to salinity. We screened 185 rice genotypes at germination stage in petri dishes under control, 50, 100 and 150 mm salt stress, and at seedling stage in Yoshida's hydroponic nutrient solution under control, 50 and 100 mm salt stress. At germination stage, 15 genotypes including Nona Bokra, Sonahri Kangni, 7421, 7423 and 7467, whereas at seedling stage, 28 genotypes including Nona Bokra, Jajai‐77, KSK‐133, KSK‐282, Fakhr‐e‐Malakand, Pakhal, IR‐6, Khushboo‐95, Shahkar and Shua‐92 were found salt tolerant. Basmati‐370, Mushkan, Homo‐46 and accessions 7436, 7437 and 7720 were sensitive to salinity at both germination and seedling stage. We further screened a subset of 33 salt‐tolerant and salt‐sensitive genotypes with SSR markers. Four SSR markers (RM19, RM171, RM172 and RM189) showed significant association with two or more of the studied traits under 50, 100 and 150 mm salt stress. These markers may be further tested for their potential in marker‐assisted selection. The salt‐tolerant genotypes identified in this study may prove useful in the development of salt‐tolerant rice varieties in adapted genetic background. 相似文献
66.
67.
The seed of the Momordica cochinchinensis (Lour.) Spreng as a traditional Chinese medicine has been utilized in China for more than 1 200 years. It is traditionally
used for the treatment of inflammatory swelling, scrofula, tinea, diarrhea as well as suppurative skin infections such as
sore, carbuncles, furuncles and boils in both humans and animals. In this study, an extract from Cochinchina momordica seeds (ECMS) is evaluated for its adjuvant effect and safety. The results suggest that when co-administered with ECMS in
Balb/c mice, ovalbumin (OVA, 10 μg) may induce significantly higher specific antibody production than OVA used alone (P < 0.05). Analysis of antibody isotypes indicates that the ECMS can promote the production of both IgG1 and IgG2a, but favor the IgG2a. Splenocyte proliferative responses to concanavalin A, lipopolysaccharides or OVA are significantly higher in mice immunized
with OVA mixed with ECMS than immunized with OVA alone or mixed with aluminum hydroxide (P < 0.05). No local reactions and negative effects on the body weight gain occurred after the injection of OVA mixed with various
amounts of ECMS in mice. Therefore, the ECMS is safe for injection and can be used as a potential vaccine adjuvant biasing
the production of IgG2a in mice. 相似文献
68.
Sandip Kumar Khurana Anju Sehrawat Ruchi Tiwari Minakshi Prasad Baldev Gulati Muhammad Zubair Shabbir Rajesh Chhabra Kumaragurubaran Karthik Shailesh Kumar Patel Mamta Pathak Mohd. Iqbal Yatoo Vivek Kumar Gupta Kuldeep Dhama Ranjit Sah Wanpen Chaicumpa 《The Veterinary quarterly》2021,41(1):61
Brucellosis is a zoonotic disease of great animal welfare and economic implications worldwide known since ancient times. The emergence of brucellosis in new areas as well as transmission of brucellosis from wild and domestic animals is of great significance in terms of new epidemiological dimensions. Brucellosis poses a major public health threat by the consumption of non-pasteurized milk and milk products produced by unhygienic dairy farms in endemic areas. Regular and meticulous surveillance is essentially required to determine the true picture of brucellosis especially in areas with continuous high prevalence. Additionally, international migration of humans, animals and trade of animal products has created a challenge for disease spread and diagnosis in non-endemic areas. Isolation and identification remain the gold standard test, which requires expertise. The advancement in diagnostic strategies coupled with screening of newly introduced animals is warranted to control the disease. Of note, the diagnostic value of miRNAs for appropriate detection of B. abortus infection has been shown. The most widely used vaccine strains to protect against Brucella infection and related abortions in cattle are strain 19 and RB51. Moreover, it is very important to note that no vaccine, which is highly protective, safe and effective is available either for bovines or human beings. Research results encourage the use of bacteriophage lysates in treatment of bovine brucellosis. One Health approach can aid in control of this disease, both in animals and man. 相似文献
69.
Akhtar Waseem Ali Iqbal Zaidi S. S. H. Jilani Seema 《Water, air, and soil pollution》1997,94(1-2):99-107
A study was carried out recently to determine the pollution level of waters in the Karachi harbour and adjoining backwaters. Nine locations were selected, four in the backwaters, two on the seaside, and three in the main navigable channel. Four of these locations were deliberately selected to coincide with those of a previous study conducted in 1982 by Pakistan Council of Scientific and Industrial Research (PCSIR) so that the values for the concentration of different pollutants could be compared. Analysis was conducted for pH, bicarbonates, Total Solids, Volatile matter in Total Solids, Chlorides, Sulphates, Calcium, Magnesium, Sodium and Potassium. The results indicate that the composition of sea water as far as the concentration of above constituents is concerned has not changed much since the time of the PCSIR study, viz 1982, except that the organic matter concentration has increased. The reasons for this increase in organic loading and its possible impact are discussed in this paper. 相似文献
70.