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231.
Khurram Bashir Nasir Mahmood Khan Sultana Rasheed Muhammad Salim 《Paddy and Water Environment》2007,5(2):73-81
Pakistan is well known for its basmati rice with long grain and aroma, as well as for non-basmati indica varieties; however
average yield is lower as compared with other countries. Besides, cultural practices, the main reason for low productivity
in Pakistan is that, local varieties are susceptible to different biotic and abiotic factors like insect pests, diseases,
drought, and salinity. Different approaches have been undertaken in Pakistan to tackle these problems through traditional
breeding of selection and crossing, mutation breeding, somaclonal variation as well as plant transformation studies in recent
past. For variety development, the most successful examples arose from traditional breeding that produced famous basmati varieties
like Basmati 370, Basmati 385 and Super basmati, and non-basmati varieties such as IRRI-6, DR-82, DR-83, DR-92, Swat-I and
Swat-II, which earn a significant share of foreign exchange every year. Six varieties have also been developed through mutation
breeding, and one through exploitation of somaclonal variation but their contribution to the national economy is not significant.
On the other hand, no variety has been registered as commercial by plant transformation groups. This review discusses the
problems and prospects of rice breeding with special emphasis on basmati rice in Pakistan particularly in Pakistani Punjab
(a major producing area), as well as focuses on future research programs. 相似文献
232.
Luís?M.?CarvalhoEmail author Patrícia?M.?Correia Isabel?Ca?ador M.?Amélia?Martins-Lou??o 《Biology and Fertility of Soils》2003,38(3):137-143
Salt marshes are characterized by the occurrence of combined salinity and flooding stresses. The individual and combined effects of salinity and flooding on the establishment and activity of arbuscular mycorrhizal (AM) colonization in the salt marsh halophyte Aster tripolium L. by indigenous salt marsh AM fungi were evaluated. A. tripolium plants were cultivated in a mixture of sand and salt marsh soil under different salinity concentrations (5%, 50% or 100% artificial seawater) and water regimes (non-flooding, tidal flooding and continuous flooding). Plants were harvested after 3 and 8 weeks and their growth was negatively influenced by increased salinity and water level. Increased salinity level affected the establishment of AM colonization, AM fungal growth and activity (measured as succinate dehydrogenase activity) within roots, and extraradical mycelium growth. The influence of flooding on the establishment of colonization and on intra- and extraradical AM fungal growth was dependent on the water regime. Continuous flooding reduced colonization and AM fungal growth, whereas tidal flooding did not affect these parameters unless combined with intermediate salinity level (50% seawater) at the end of the experiment. The water regime did not influence AM active colonization. The ratio of root to soil AM fungal growth increased as the water level increased. The results of this study demonstrate that the establishment and activity of AM colonization in A. tripolium is more influenced by salinity than by flooding, and suggests that the functionality of salt marsh AM fungi is not affected by flooding. 相似文献
233.
Comparison of two versions of the acetylene inhibition/soil core method for measuring denitrification loss from an irrigated wheat field 总被引:5,自引:0,他引:5
Two versions of the acetylene inhibition (AI)/soil core method were compared for the measurement of denitrification loss
from an irrigated wheat field receiving urea-N at a rate of 100 kg ha–1. With AI/soil core method A, the denitrification rate was measured by analysing the headspace N2O, followed by estimation of N2O dissolved in the solution phase using Bunsen absorption coefficients. With AI/soil core method B, N2O entrapped in the soil was measured in addition to that released from soil cores into the headspace of incubation vessels.
In addition, the two methods were also compared for measurement of the soil respiration rate. Of the total N2O produced, 6–77% (average 40%) remained entrapped in the soil, whereas for CO2, the corresponding figures ranged from 12–65% (average 44%). The amount of the entrapped N2O was significantly correlated with the water-filled pore space (WFPS) and with the N2O concentration in the headspace, whereas CO2 entrapment was dependent on the headspace CO2 concentration but not on the WFPS. Due to the entrapment of N2O and CO2 in soil, the denitrification rate on several (18 of the 41) sampling dates, and soil respiration rate on almost all (27 of
the 30) sampling dates were significantly higher with method B compared to method A. Averaged across sampling dates, the denitrification
rate measured with method B (0.30 kg N ha–1 day–1) was twice the rate measured with method A, whereas the soil respiration rate measured with method B (34.9 kg C ha–1 day–1) was 1.6 times the rate measured with method A. Results of this study suggest that the N2O and CO2 entrapped in soil should also be measured to ensure the recovery of the gaseous products of denitrification by the soil core
method.
Received: 12 May 1998 相似文献
234.
Mohammad Javad Mehdipour Moghaddam Adeleh Alsadat Mirbagheri Zivar Salehi Seyyed Mahmood Habibzade 《Iranian Biomedical Journal》2015,19(4):233-239