Diversity in phosphorus mobilisation and uptake in ectomycorrhizal fungi

• Introduction   

Phosphorus (P) is often the first or second element limiting aboveground net primary productivity of forests. Besides low available inorganic orthophosphate (Pi) concentrations, soil may contain high total P contents, as insoluble mineral P or as organic P. Most plants form mycorrhizal associations that improve their P nutrition. Three main hypotheses have been proposed to explain this positive effect through an increase of (1) P mobilisation from mineral P, (2) P mobilisation from organic P and (3) soil exploration and P uptake. However, the positive effect of mycorrhizal symbiosis may be variable with the fungal species forming the association. This could be due to the different abilities of mycorrhizal fungi to mobilise P and/or to take up Pi from the soil.     

Yield potential and salt tolerance of quinoa on salt‐degraded soils of Pakistan

Quinoa is recently introduced to Pakistan as a salt‐tolerant crop of high nutritional value. Open field trials were conducted to evaluate its performance on normal and salinity/sodicity‐degraded lands at two locations of different salinity/sodicity levels, S₁ (UAF Farm, Normal Soil), S₂ (Paroka Farm UAF, saline sodic), S₃ (SSRI Farm, normal) and S₄ (SSRI Farm, saline sodic) during 2013–2014. Two genotypes (Q‐2 and Q‐7) were grown in lines and were allowed to grow till maturity under RCBD split‐plot arrangement. Maximum seed yield (3,062 kg/ha) was achieved by Q‐7 at normal field (S₁) soil which was statistically similar with yield of same genotype obtained from salt‐affected field S₂ (2,870 kg/ha). Furthermore, low yield was seen from both genotypes from both S₃ and S₄ as compared to S₁ and S₂. Q‐7 was best under all four conditions. Minimum yield was recorded from Q‐2 (1,587 kg/ha) at S₄. Q‐7 had higher SOD, proline, phenolic and K⁺ contents, and lower Na⁺ content in leaves as compared to Q‐2. High levels of antioxidants and K⁺/Na⁺ of Q‐7 helped to withstand salt stress and might be the cause of higher yields under both normal and salt‐affected soils. Seed quality (mineral and protein) did not decrease considerably under salt‐affected soils even improved seed K⁺, Mg²⁺ and Mn²⁺.     

Trait phenotyping and molecular marker characterization of barley (Hordeum vulgare L.) germplasm from Western Himalayas

Genetic Resources and Crop Evolution - Barley (Hordeum vulgare L.) is one of the principal cereal crops grown in Western-Himalayas of India. A set of 105 barley genotypes including 38...     

Assessment of gut microbiota in different developmental stages of Malaysian Mahseer (Tor tambroides)

Malaysian Mahseer (Tor tambroides) has a good prospect for aquaculture because of its high market demand. However, there is a scarce information on gut microbiota associated with Malaysian Mahseer unlike other fish species. Therefore, we constructed and compared gut microbiota in different developmental stages (larval, juvenile, fingerling, yearling, and adult) using culture dependent and PCR‐DGGE fingerprinting technique for better understanding of gut microbiota composition associated with T. tambroides. Culturable gut microbiota composition in all developmental stages were composed of β‐ and γ‐Proteobacteria, and Bacilli. Biodiversity analysis of culturable gut microbiota showed that larval, juvenile, and adult stages have higher diversity than fingerling and yearling stages. Ward's linkage cluster analysis showed that culturable gut microbiota composition in larval and juvenile stages were close to adult stages, whereas fingerling and yearling stage composed same cluster. PCR‐DGGE fingerprinting technique showed that unculturable gut microbiota were constituted by α‐and γ‐Proteobacteria, and Actinobacteria. Ward's linkage cluster analysis showed that unculturable gut microbiota composition in both larval and juvenile stages were distinct from other developmental stages. Our results revealed that gut microbiota composition were varied in different developmental stages of Malaysian Mahseer and continuous shifts of gut microbiota from larval to adult stages.     

Application of Biofloc Technology for the culture of Heteropneustes fossilis (Bloch) in Bangladesh: stocking density,floc volume,growth performance,and profitability

Though Biofloc Technology is a new concept in Bangladesh, it provides advantages for improving aquaculture production in many countries, leading to achieve sustainable development goals. The objectives of this study were to determine the effects of stocking densities on the growth performance of stinging catfish (Heteropneustes fossilis) under Biofloc Technology and assess the economic prospects and business feasibilities. Fingerlings were stocked in unique 5000-L tanks with three stocking densities, i.e., 3500 fish/tank (Treatment-I), 4000 fish/tank (Treatment-II), 4500 fish/tank (Treatment-III). The treatments showed significant differences (P?<?0.05) considering the species-specific growth rate, feed conversion ratio, and protein efficiency ratio. Treatment-I had significantly ((P?<?0.05) higher final biomass (29.51 ± 0.04 kg/m³) than the other treatments. The present findings revealed that using a lower stocking density, the Biofloc Technology reduced ammonia (NH₃), nitrite (NO₂), nitrate (NO₃), TDS, and floc volume but significantly increased the dissolved oxygen. As a result, Treatment-I had generated significantly higher net income (BANGLADESHI TAKA—BDT 86,278.90) over the other treatments. Moreover, the NPV, net BCR, and RoR with 4% and 9% opportunity cost were also significantly higher in Treatment-I than other treatments. The internal rate of return (IRR) and SWOT analysis index indicates that investing in Biofloc Technology is far superior, and a stocking density of 3500 fish/tank (Treatment-I) resulted in a faster investment return.

     

Dietary protein requirement of juvenile marbled spinefoot rabbitfish Siganus rivulatus

Rabbitfish are an Indo‐Pacific herbivorous marine fish that have good market demand and are suitable for aquaculture. The present work was performed to determine dietary protein inclusion necessary for optimal growth of juvenile rabbitfish Siganus rivulatus. Six diets with increasing levels of protein (10, 20, 30, 40, 50 and 60 g crude protein 100 g^?1 feed) and similar levels of gross energy (20 MJ kg^?1) were prepared and offered to S. rivulatus juveniles maintained in triplicate cages placed in two large water tanks for 49 days. Growth progressively improved with dietary protein for fish offered diets from 10% to 40% protein inclusion. Diets with greater protein levels did not improve fish growth beyond that observed in the 40% group. Daily feed intake, apparent protein utilization and feed conversion ratio decreased as dietary protein increased. Protein efficiency (PE) was greatest (1.47) in fish offered the 10% protein diet and least in fish offered the 60% protein diet (0.80). No differences in PE were observed among all other treatments (20–50%). Results of the present work suggest that minimum dietary requirement for suitable growth of S. rivulatus juveniles is 40% protein when digestible energy of the diet is 16–18 MJ kg^?1.     

氮肥配施下不同C/N作物残渣还田对红壤温室气体排放的影响

氮肥配施能够促进还田秸秆的分解,为了解其对不同C/N秸秆还田下温室气体排放的影响,采用培养实验方法,研究了油菜饼(C/N为4)、玉米秸秆(C/N为28)、水稻秸秆(C/N为41)和小麦秸秆(C/N为71)等4种不同C/N植物残渣在不同量氮肥(无氮、低氮和高氮)配施下对红壤温室气体(CO2、CH4和N2O)排放的影响。结果显示,氮肥配施增加了不同植物残渣的CO2-C累积排放量,且仅在高C/N的小麦秸秆处理中发现存在显著性差异,在低氮和高氮下CO2-C累积排放量分别达到1 271.44、1 212.83 mg·kg-1,显著高于无氮肥配施的883.40 mg·kg-1。土壤N2O累积排放量最大的为油菜饼处理组,低氮量的配施进一步增强了N2O的产生,其累积排放量达到5 550.42μg·kg-1,显著高于无氮肥配施的4 430.44μg·kg-1,然而当氮肥施用量进一步增加时却抑制了N2O的排放(3752.84μg·kg-1)。氮肥配施并未显著影响玉米秸秆和小麦秸秆处理组的N2O累积排放量。在培养期内,每一个处理均表现为CH4的吸收现象,氮肥施用能够增加土壤对CH4的累积吸收量,但差异显著性仅在对照和油菜饼处理中发现。     

Role of nitrogen supplementation in alleviating drought‐associated growth and metabolic impairments in Phoebe zhennan seedlings

Drought is one of the major environmental stresses altering forest productivity. However, nutrient availability can modulate drought resistance. Phoebe zhennan (gold Phoebe) is a high‐quality timber‐producing but threatened tree species in China, facing serious anthropogenic disturbances and abiotic constraints that restrict its growth and development. However, little attention has been given to designing adaptive strategies for its management by evaluating the possible role of major nutrients, particularly nitrogen (N), on its morphological and physio‐biochemical responses under water stress. To evaluate these responses, a complete randomized design was followed to investigate the effects of two irrigation levels (well‐watered and drought‐stressed conditions) and N fertilization treatments (with and without N). Drought stress significantly affected the growth of seedlings, as indicated by impaired photosynthesis, pigment degradation, disrupted N metabolism, over‐production of reactive oxygen species and enhanced lipid peroxidation. Nitrogen supplementation under drought stress had remarkable positive effects on the growth through physio‐biochemical adjustments as shown by higher level of nitrogenous compounds and up‐regulation of N‐associated metabolic enzymes activities which might be due to N‐mediated improved leaf relative water contents and photosynthetic efficiency. In addition, N application reduced oxidative stress and membrane damage, and maintained a high accumulation of osmolytes. However, in well‐watered seedlings N fertilization significantly improved root biomass and net CO₂ assimilation rate suggesting high N‐use efficiency of the seedlings. These findings reveal that drought significantly affects the growth of P. zhennan, while N fertilization plays a crucial role in alleviating water stress damage by improving its drought tolerance potential at low metabolic costs. Therefore, N fertilization could be considered as an effective strategy for the conservation and management of P. zhennan in the face of future climate change.     

Soil available potassium affected by rice straw incorporation and potassium fertilizer application under a rice–oilseed rape rotation system

Data from 147 field trials were collected to study the influence of straw incorporation on soil potassium (K) under an intensive rice–oilseed rape rotation system, while pot experiments were conducted to evaluate the effects of rice straw incorporation on soil K availability. A significant correlation was observed between the soil available K and the relative yield (RRY) and the relative K uptake (RKU) of oilseed rape, with R² values ranging from 0.07 to 0.08 and from 0.10 to 0.11, respectively, when data were fitted to a logarithmic equation model. In approximately 30% of trials, RRY reached 90%, while soil test available K values were below the critical limit, indicating that soil K values at the time of sampling (within 1 week of rice harvest) underestimated the actual soil K supply capacity. The pot experiment results showed that soil available K was affected by straw incorporation and soil type in the fallow period. The NH₄OAc‐K and NaBPh₄‐K concentrations of soils increased at first, and then, plateaued after 28 days. Straw incorporation significantly influenced the critical soil K concentration, which is important for making accurate K fertilizer recommendation. These results suggested that straw K should be seriously considered in making K fertilizer recommendations. Extending the sampling time from 1 to 3 weeks after the harvesting of rice to stabilize the effects of straw incorporation may help achieve a more accurate evaluation of soil available K.