Inoculation of grain legumes with rhizobia may improve biological N2 fixation and crop yield. However, drought, high temperature and soil salinity constrain legume root-nodule formation and function. Here, two rhizobial strains nodulating Tunisian chickpea, Mesorhizobium ciceri strain CMG 6 and Mesorhizobium mediterraneum strain CTM 226 originating from semi-arid regions, were selected for their symbiotic performance and their salt stress tolerance (3 % NaCl). Both strains were then examined as inoculants in different soils and field conditions. Field experiments were conducted in four sites using four chickpea cultivars. Rhizobia occupying nodules in non-inoculated plots were isolated and characterized using 16S rDNA typing; to examine nodule occupancy by the inoculant strains we used polymerase chain reaction (PCR)-restriction fragment length polymorphism of 16S rDNA gene and repetitive extragenic palindromic PCR. The inoculant strains gave a significant increase in nodule number, shoot dry weight and grain yield in all the experimented fields for the four cultivars used, even in the non-irrigated soils. The improvement in plant production was equal to or better than nitrogen fertilization. Moreover, the monitoring of the nodule occupancy showed that inoculant strains competed well in the native populations of rhizobia. These results suggest that nodulation and yield of chickpea can be improved by inoculation with competitive and salt-tolerant rhizobia and is economically promising to increase chickpea production in water-limited regions. 相似文献
Journal of Crop Science and Biotechnology - Agronomic performance of Robusta coffee (Coffea canephora) is affected by genotype by environment interaction, which demands multi-environment testing of... 相似文献
Size, caloric value and chemical composition were measured separately in the progeny of two northern pike (Esox lucius) females at 3-day intervals during the endogenous feeding period from hatching to final yolk resorption. Tissue, yolk and entire larvae were analysed separately in three groups of larvae that hatched at different times (between 88 and 106 degree-days post-fertilization). An integrated approach with the Gompertz model was used to compute the yolk conversion efficiency and time to maximum tissue size in early, mid and late hatched larvae. At hatching, unresorbed yolk of early hatched larvae contained more energy (39.20 J) and more protein (0.99 mg) compared to the yolk of larvae that hatched later (38.13 J and 0.92 mg protein for late hatched larvae, p < 0.05). In contrast, a significant reduction in tissue weight (?0.7 mg DW) and protein content (?0.5 mg) was found in early hatched larvae compared to those which hatched later (p < 0.05). Between days 9 and 12 post-hatching (108 and 144 degree-days post-hatching), close to the final yolk resorption, late hatched larvae stopped growing and their tissue began to be resorbed. This tissue resorption time was delayed in early hatched larvae which presented at the end of the experiment a greater tissue weight than late hatched ones. Yolk conversion efficiency in term of energy from hatching to complete yolk resorption stage was significantly higher for early and mid hatched larvae (51 %) compared to late hatched ones (44 %) (p = 0.004). Furthermore, the time to maximum tissue size was found to be negatively related to hatching time which implies that early hatched larvae take longer time to switch from one developmental stage to the next. The maximum tissue dry weight and energy content were found to be reached at approximately the same age post-fertilization for both early hatched and late hatched larvae, suggesting that the principal steps in a fish’s lifespan are better correlated with time of fertilization than hatching time. 相似文献
Promising results from an increasing number of field evaluations of the System of Rice Intensification (SRI) conducted in
Asia and Africa indicate that African farmers could increase their rice production while lowering costs of operation and reducing
the need for water by utilizing its principles and practices. This system relies not on external inputs to raise productivity
but on alternative methods for managing rice plants and the soil and water resources devoted to their cultivation. Farmers
in sub-Saharan Africa increasingly have to cope with the impacts of adverse climate effects because water shortages and long
dry spells during the cropping season are becoming common, even in lowland rice agroecosystems. SRI management practices create
both larger rice root systems that make their plants more resistant to biotic and abiotic stresses and more conducive environments
for beneficial soil microflora and fauna to flourish. Better plant growth and development result from promoting plant–soil
synergies. Controlled fertilizer management experiments conducted with SRI practices in The Gambia have showed that grain
production can be significantly increased without higher application of inorganic fertilizer and with less requirement for
water. SRI management practices with fertilizer application at the national recommended dose produced a grain yield of 7.6 t ha−1. Water productivity was greatly increased, with 0.76 g of grain produced per kg total water input, compared to 0.10 g of
grain per kg of water when the crop was continuously flooded. Recent hikes in fuel prices and consequent rises in input costs
are making domestic rice production less attractive and importation even more attractive. Computation of production costs
showed that SRI production, not needing heavy applications of fertilizer, is economically cost-effective. Achieving yield
increases through ever-higher fertilizer applications is not economically or environmentally viable. SRI management with recommended
fertilizer applications produced a net return of $853 ha−1 compared to $853 ha−1 compared to 37 when using farmers’ present low-productivity practices. 相似文献
Hessian fly (Mayetiola destructor (Say)) is a major pest in wheat producing areas of United States, Canada, Europe, and North Africa but has not been found in Australia. Host plant resistance is thought to involve a similar strategy used against plant pathogen, and in this study, we sought to investigate whether disease-resistance gene markers can also be useful in selecting against Hessian fly attack. The genome-wide association study involved 251 wheat genotypes of diverse origin and 72 SNPs, selected on the basis of significant similarity of their associated contig sequences to putative disease resistance genes. A novel statistical approach for genome-wide scan was applied, which utilised genotype data scored as Null alleles in the mixed model, instead of deleting or treating them as missing alleles. The analyses identified four markers with significant associations at the 5% level, after applying the false discovery rate. These were located on chromosomes 4A, 4B, 5A and 7D, with the 5A locus mapping to the cluster of major genes that confer resistance to multiple Hessian fly biotypes. Amongst the diverse wheat accessions analysed, most of the susceptible phenotypes carried the A–G–C–C haplotype at the BS00064369, BS00007416, BS00077047 and HfrDrd_nt_143 loci, respectively. When heterozygotes were excluded, all the Australian wheat accessions carried this allelic combination. The combination of alleles conferring resistance depended on the origin of the wheat accessions, with ICARDA accessions carrying a preponderance of the C–C–CG–T. Of the 11 USA accessions used for this study, only Lola carried a favourable combination of alleles for resistance at these loci. 相似文献
Phenolic compounds have been suggested as one of the defence mechanisms to cocoa swollen shoot virus disease (CSSVD), but not well studied. Correlation and genetic variation of total phenolic content (TPC) and CSSVD resistance among 53 cocoa families were investigated. Three‐month‐old seedlings of 15 families obtained from an incomplete 6 × 3 NCII mating design, of 24 families from a 3 × 8 NCII mating design and of 14 other families were evaluated for CSSVD and TPC. Plants were inoculated with viruliferous mealybugs carrying the New Juaben CSSV strain (1A) in a gauze house facility. A single seedling randomization within blocks procedure was followed, using the gauze house units as blocks. There were six blocks with five seedlings of each family randomized within each block. Disease severity scores on leaf flushes at the first, second, third and seventh flushes after inoculation were recorded. The TPC before and 3 months after inoculation was also determined. Family effects were highly significant (P ≤ 0.01) for CSSVD severity scores and TPC. Narrow‐ and broad‐sense heritability estimates were low for CSSVD severity but moderate to high for TPC evaluations. Correlations between severity scores and TPC were weak (r =?0.22 to 0.40) suggesting that the TPC may be of little value in selecting CSSVD resistance varieties in cocoa. Additive effect in terms of significant GCA was important for CSSVD severity scores whereas both additive and non‐additive effects were important for TPC values when the 3 × 8 and 6 × 3 NCII mating designs were analysed. Only clones GU 239/H, GU 290/H and GU 225/V had favourable GCA effects for CSSVD symptom expression indicating their potential for developing progeny with high levels of resistance to CSSVD infection. 相似文献
Worldwide population is in permanent growth, leading to an over-presser on the food resources. This demand leads to an over-exploitation of land and water resources. Recently, the quinoa plant has attracted attention as alternative crop with high nutritive value and high tolerance to the marginal conditions. In this study, a field experiment was conducted during two successive seasons to investigate the effect of deficit irrigation on the agronomic performance. Four treatments of deficit irrigation (100%, 50%, 33% ETc and rainfed) were applied to one variety in the first season and to four genotypes (two varieties and two lines). The results were evaluated by measuring biomass and seed quinoa yield, water-use efficiency, harvest index, seed size and 1000 seeds weight. Results show that the implementation of deficit irrigation is an appropriate strategy to reduce the use of agricultural water and maintain relatively high yields. On the other hand, the results of the economic quality reflected by the size and weight of seed yield, indicates that quinoa can be considered a well-adapted to the conditions of water scarcity culture. According to agronomic parameters, L143 line followed by the line L11 showed a high potential of adaptation under the different treatments of stress, while the “Puno” variety presented the best performance under the favorable conditions of irrigation (100% ETc).
Coxiella burnetii infection in pregnant sheep typically causes abortion or the birth of weak lambs. Two C. burnetii-related abortions in a group of 34 pregnant ewes were reported at their first lambing in our research institute. The seroprevalence of C. burnetii infection and bacteria shedding were investigated using an ELISA and PCR, respectively, during the course of two subsequent pregnancies. None of the ewes examined seroconverted from negative to positive at the time of the second and the third parturition and most of the ewes that were seropositive at the abortion episode remained positive throughout the investigation. The two successive pregnancies resulted in the birth of healthy lambs without PCR evidence of Coxiella infection from placenta and vaginal swabs taken postpartum. PCR assay performed on vaginal swabs taken from all animals 1, 5 or 12 days after the second lambing were also negative for Coxiella. However, one ewe that had previously experienced C. burnetii shedding at the first lambing excreted the bacteria in the genital tract after the third parturition. The bacteria could not be detected by PCR in milk and faecal samples taken up to 12 days after both parturitions. 相似文献