Recovery of cover-crop-N in the soil-plant system in the Guinea savannah zone of Ghana

In order to understand the efficiency of residue-N use and to estimate the minimum input required to obtain a reasonable level of crop response, it is important to quantify the fate of the applied organic-N. The recovery of N from ¹⁵N-labelled Crotalaria juncea was followed in the soil and the succeeding maize crop. Apparent N recovery (ANR) by maize from unlabelled Crotalaria juncea, Crotalaria retusa, Calopogonium mucunoides, Mucuna pruriens and mineral fertilizer at three locations were also evaluated. The maize crop recovered 4.7% and 7.3% of the ¹⁵N-labelled C. juncea-N at 42 days after sowing (DAS) and at final harvest, respectively. The corresponding ¹⁵N recovery from the soil was 92.4% and 58.5%. The highest mean ANR of 57.4% was with mineral fertilizer, whereas the mean ANR of 14.3% from C. retusa was the lowest. A large pool substitution and added-N interaction effect was observed when comparing N recovery from the labelled and unlabelled C. juncea. The amount of residue-N accounted for by the isotope dilution method at 42 DAS was 97.1% and at final harvest 65.8%. The large residue-N recovery in the soil organic-N pool explains the residual effect usually observed with organic residue application.     

Biomolecular relationships among isolates of<Emphasis Type="Italic">Tomato Yellow Leaf Curl Tanzania Virus</Emphasis>

An investigation of the biological properties of the virus causing tomato yellow leaf curl disease in Tanzania was initiated to compare it with other known tomato yellow leaf curl viruses. Properties relating to acquisition and inoculation feeding time, persistence, mechanical inoculation, seed transmission and host range were studied. Results obtained indicate that the virus was transmitted persistently byBemisia tabaci Genn., but it was not mechanically, sap- or seed-transmissible. Minimum acquisition and inoculation feeding time was 30 min.Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum andLycopersicon esculentum were found to be hosts of the virus among the plant species tested, whereasPhaseolus vulgaris was not. It is concluded that the properties of the agent causing yellow leaf curl symptoms in tomato plants from different regions in Tanzania are similar to those ofTomato yellow leaf curl Sardinia virus species studied elsewhere. http://www.phytoparasitica.org posting Feb. 20, 2003.     

Ameliorating Nickel Stress by Jasmonic Acid Treatment in <Emphasis Type="Italic">Zea mays</Emphasis> L.

Plants need various micro and macronutrients for their growth and metabolism. Of these nickel (Ni) plays a role of micronutrient but causes adverse effects when present above optimum level. To combat such situations plants possess different growth regulators. Jasmonates are a class of plant growth regulators modulating various growth and physiological responses in plants. Aiming to evaluate the effect of nickel and jasmonic acid on growth and antioxidant enzymes Superoxide distmutase (SOD), Catalse (CAT), Ascorbate peroxidase (APX), Guaiacol peroxidase (GPX) and glutathione reductase (GR), seeds of Zea mays L. were sown in field after giving presowing treatment of NiSO₄ · 6H₂O (8 mM), jasmonic acid JA (10^–6, 10^–8 and 10^–10 M) alone and JA (10^–6, 10^–8 and 10^–10 M) in 1: 1 combination with NiSO₄ · 6H₂O (8 mM) in plant conservatory, Punjabi University, Patiala, Punjab, India. Plants of each treatment group were then subjected to spraying treatment with the respective treatment solutions at regular intervals of 22 days up to 66 days after sowing (DAS). The present findings signified reduced growth with Ni treatment but co-application of JA alleviated the effect of nickel through activity of antioxidant enzymes.     

Effect of Developmental Stages Length on Yield and some Quality Traits of Turkish Durum Wheat (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. Convar. <Emphasis Type="Italic">durum</Emphasis> (Desf.) Mackey) Landraces: Influence of Developmental Stages Length on Yield and Quality of Durum Wheat

The study aimed at exploring durum wheat landraces to be utilized in breeding programs. 566 single durum wheat plants selected from 117 populations collected from 12 provinces were studied. The selected material was planted for characterizing their some qualitative and quantitative traits such as percent vitreousness, pearling index, grain protein content, seed yield and thousand kernel weight; as well as determining time frame for germination-tillering, germination-shooting, germination-heading, germination-maturity, tillering-shooting (T-S), tillering-heading (T-H), tillering-maturity, shooting-heading, shooting-maturity, and heading-maturity. Mean, coefficient of variation, and confidence intervals (0.95) were computed for each of 12 provinces, for altitudinal origins with 200 m of ranges and, for each of two geographical regions separately. The highest variation existed for number of days between T-H and the lowest for number of days between T-S. The highest variation within developmental stages was observed in samples from Diyarbakir with a CV of 32.96%, from 600 to 799 altitude range with a CV of 18.86%, and from Southeast Anatolia with a CV of 20.12%.     

<Emphasis Type="Italic">p</Emphasis>-Coumaric can alter the composition of cucumber rhizosphere microbial communities and induce negative plant-microbial interactions

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions.     

Assessment of Genetic Diversity in Upland Cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) Breeding Lines by using Amplified Fragment Length Polymorphism (AFLP) Markers and Morphological Characteristics

Genetic diversity in 24 advanced breeding lines of cotton was studied by using six amplified fragment length polymorphism (AFLP) primer-pairs and 14 morphological characters. The six selected AFLP primer-pairs generated a total of 535 amplification products, of which 460 were found to be polymorphic resulting in 85.9% polymorphism. The observed genetic distances using AFLP markers ranged from 30% to 87% with an average of 34%. A wide range of variability was observed for all the morphological traits studied. The range in taxonomic distance was from 0.60 to 2.77. Most of the lines could be clustered in two major clusters in both the analyses. But the correlation coefficient between the pair-wise distances estimated from AFLPs and the average taxonomic distances estimated from morphological characters was found to be 0.04. UPGMA cluster analysis revealed inconsistencies in the clustering patterns, as the co-phenetic correlation coefficient between the dendrograms for morphological and AFLP data indicated a poor fit for the two data types. From combined information, genotypes ‘RST-12’, ‘H 1226’, ‘P 348’, ‘KDCAKD’, ‘CISV 24’ and ‘H1222’ were found to be distinct from rest of the material.     

Long-term changes in land use impact the accumulation of microbial residues in the particle-size fractions of a Mollisol

To test the impact of a range of long-term land use types on the partitioning of microbial residues among soil particles, samples from a Mollisol with plots under 100 years of continuous arable cropping, 30 years of simulated overgrazing to severely degraded bare soil, or 30 years of grassland restoration were investigated. The microbial residues, which were assessed among three particle-size fractions (<2, 2–20, and 20–250 μm) by amino sugar extraction, exhibited change with particle size and land use. Converting arable cropping to bare soil induced substantial depletion of amino sugars associated with the clay-size fraction, as a proportion of total carbon (C) and total soil mass, but not the silt- and sand-size fractions. Alternatively, switching arable soil to grassland increased amino sugar stocks in both the clay- and sand-size fractions. Analysis of the relative input of fungal and bacterial derived amino sugars indicated that fungal sources are the most dynamic with respect to land use change. These results highlight the selective vulnerability of microbial C pools in finer fractions under low plant C input and the selective recovery in specific fractions upon restoration, emphasizing the importance of the conversion of plant organic matter into mineral-associated microbial residues to promote stable soil organic C.     

Growth and yield of soybean varieties inoculated with <Emphasis Type="Italic">Bradyrhizobium</Emphasis> spp in N-deficient calcareous soils

This research reports the effect of Bradyrhizobium spp strains on dry matter yield, nodulation and seed yield of soybean varieties grown in N-deficient soil in Uzbekistan in pot and field experiments, in 2001 and 2002. The results of experiments revealed that significant positive effects on growth, nodule number and yield of soybean were obtained after inoculation with Bradyrhizobium spp strains; and, generally, strains S62 and S63 were more effective than strain S61. The protein content of seeds also increased after inoculation. Both Orzu and Uzb2 soybean varieties gave a higher response than the Uzb6 variety.     

Isolation,Characterization and Quantification of Tricin and Flavonolignans in the Medicinal Rice Njavara (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.), as Compared to Staple Varieties

Njavara is an important medicinal rice variety of Kerala, India, widely used in Ayurveda as a ‘health food’ and in the treatment of rheumatoid arthritis, paralysis, neurodegenerative diseases and in rejuvenation therapy. Phytochemical investigations and spectroscopic studies of the diethyl ether fraction of methanolic extract of Njavara Black (NB) rice bran gave three important compounds namely, tricin and two rare flavonolignans- tricin 4′-O-(erythro-β-guaiacylglyceryl) ether and tricin 4′-O-(threo-β-guaiacylglyceryl) ether. The EC₅₀ values of these compounds in DPPH system were 90.39, 352.04 and 208.1 μg/ml, respectively. Quantification of the compounds by HPLC in NB and staple, non-medicinal rice varieties Sujatha (SJ) and Palakkadan Matta (PM) showed that tricin is present 39.64 and 16.12 fold higher in NB, compared to SJ and PM, respectively. This is the first report on the occurrence of tricin at significantly higher levels in Njavara and occurrence of the two flavonolignans in Oryza sativa species. Of the three compounds, tricin and the threo- form of flavonolignan showed anti-inflammatory effect of >65% after 5 h, at 2 mg/kg, in carrageenan-induced, paw edema experiments in rats. The results of the study corroborate with the preferential use of Njavara in indigenous medicine, over staple varieties.     

Improvement of paddy field drainage for mechanization

In Japan, land consolidation and drainage improvement for farm mechanization in paddy fields began during the 1960 s. It was not easy to use big machines in the muddy conditions caused by the clayey soil and heavy rainfall during the harvesting period. A number of investigations were carried out by many researchers, and factors relating to drainage were clarified. Not only surface drainage but also underdrainage was planned. However, drainage was not always sufficient, because the clayey surface soil was impermeable to ponding water. It became clear that underdrainage for a clayey paddy field for the harvest is quite different from underdrainage for an ordinary field. Field and soil characteristics, as well as water conditions, should be examined carefully before planning drainage improvement for farm mechanization.Dr. Toshio Tabuchi is an honorable member of the Japanese Society of Irrigation, Drainage and Reclamation Engineering (JSIDRE), a former Professor of the University of Tokyo, and a former President of JSIDRE