International Journal of Plant Production
Volume:2 Issue: 4, Oct 2008

Phosphorus (P) deficiency is a major constraint to crop production on highly weathered, lowactivity clay soils in the humid zone of West Africa. Past research suggested a linear relationship between grain yield and P uptake over a range of fertilizer P applied to upland rice cultivars. However, there is lack of information on how these relationships are affected by the long-term fertilizer P effects, although such information is needed for developing P management strategies because phosphate fertilization effects last for several seasons. Results from a long-term field experiment (1993-1998) conducted to determine the response of four improved upland rice cultivars to fertilizer P (0, 45, 90, 135 and 180 kg P ha-1) applied only once in 1993 and to its residues in 1994, 1995, 1996 and 1998, were used to determine grain yield and P uptake relationships. The soil at the experimental site, in the humid forest zone of Côte d’Ivoire (West Africa), was an Ultisol with acidic pH and low in available P. Significant linear relationships (R varying between 0.796 and 0.956) were observed between grain yield and total P uptake for each of the crops grown during 1993-1998. The results indicate that P uptake based models can be used to determine P requirements of rice cultivars under direct and residual P.

Incorporation of plant residues in soil affects N and C content and dynamics. This study determined the effects of short-term alternative rice (Oryza sativa L.) residue management on N mineralization and uptake by rice. Pot and laboratory incubation experiments were established by incorporating 15N-labeled rice straw and rice straw compost in paddy soil. The 15N recovered by rice averaged 16.6%; most of this recovered 15N-fertilizer was cycled through soil pools and only small amounts originated from labeled rice residues. At harvest, denitrification rate of rice straw and rice straw compost was 27.2% and 38.5%, respectively in the pot experiment, while residual N in soil ranged from 56.2% and 55.1%, respectively. The incubation study showed that about 22-26% of N from 15N-labeled rice straw was mineralized over a period of 105 days. Recovery of residual 15Nfertilizer appears to contribute little to total inorganic N. The results showed that rice residues exerted a small and short-term positive effect on N mineralization and N uptake

An important step in plant breeding programs is identification of parents that are genetically distant from each other, to find crossing combinations with better prospects of hybrid vigor. The potential of identifying genetically distant parents depends on genetic diversity of population. 58 lines of rice from diverse origins have been employed to study genetic variation in order to identify the most effective components of grain yield. Using cluster analysis, the lines were classified into three distinct classes; some of classes containing lines from different origins. Factor analysis has been conducted to identify important components of variation and contributions of traits in each factor. Based on factor analysis, 6 components were identified, explaining ~82% of observed variation. Evaluation of heterosis of crosses, whose parents were selected based on genetic distances (GD), showed that maximum heterosis was obtained for crosses containing the furthest lines. All together, our results support the idea that the level of correlation between hybrid performance and genetic divergence is depends on the germplasm used

Trehalose is the non-reducing alpha-alpha-1, 1-linked glucose disaccharide. The biosynthesis precursor of trehalose, trehalose-6-phosphate (T6P), is essential for plant development, growth, carbon utilization and alters photosynthetic capacity but its mode of action is not understood. In the current research, 6 days old seedlings of Arabidopsis thaliana (Columbia ecotype) were grown in liquid culture containing 100 mM trehalose, sorbitol or sucrose for 24 hours. Changes in the genes expression patterns were studied by cDNA microarray analysis. In sucrose treatment expression of 1745 genes was significantly changed. But trehalose changed significantly the expression of only 162 genes compared to sorbitol after 24h treatment. Gene expressions profiles revealed that 100 mM trehalose altered 5% of the genes which are changed by 100 mM sucrose. Statistical analysis showed that only 4 genes which are induced by trehalose repressed by sucrose. Exogenous trehalose treatment did not down-regulate the expression of carbon catabolite genes, but up-regulates a specific combination of genes known from biotic stress responses. Trehalose induced gene expression responses related to ROS and secondary metabolism activation. The expression profile shows particularly up-regulation (8-fold) of a glutathione transferase (GST22) under trehalose but not sucrose. Also, trehalose treatment induced expression of the JA and ethylene signaling pathways factors. These findings revealed that trehalose or its precursor, T6P, are important in gene expression regulation of plants.

Mahalanobis’ D-square (D2) statistics was applied to assess diversity in the 9 genotypes collected of semi-arid region of India (7 genotypes from Gujarat and Rajasthan for normal toxic and two from Orissa csmcri’s plantation of non toxic nature. These genotypes were grouped into five. Cluster I and III had two genotypes, cluster II had three genotypes and cluster VI and V contributed as solitary germplasms. The genotypes in cluster II had the maximum divergence which was closely followed by cluster III. The maximum and minimum divergence was revealed between clusters I with cluster V and cluster I and cluster V with cluster IV, respectively. In general, cluster III and IV exhibited high and low mean values, respectively for most of the characters. It has been suggested that for varietal improvement, hybridization among the genotypes of divergent clusters should be done in order to obtain better results in terms of variability and diversity

During 2000 and 2001, the prevalence of fungal diseases of alfalfa was surveyed under environmental conditions in Zanjan province, Iran. In total, 15 genera of fungal pathogens were isolated from plants sampled from the fields. All of these disease interactions had not been previously recorded in Zanjan and Colletotrichum truncatum, Leptotrochila medicaginis, Phoma medicaginis, Rhizoctonia crocorum on alfalfa were new disease reports for Iran. In 2000, the mean disease incidence of fungal pathogens of alfalfa varied by sampling time and field location. Decreases in the incidence of diseases occurred after cuttings. The incidence of diseases detected in 2000 was correlated negatively with mean monthly temperature and positively with monthly total rainfall, indicating that reductions in diseases were associated with higher temperature and less humidity, irrespective of fungal species. In 2001, Ph. medicaginis was the predominant fungus infected 42.8% of plants in the alfalfa fields followed by Pseudopeziza medicaginis (39.1%), Uromyces striatus (33.3%), Peronospora trifoliorum (29.8%), Sporonema phacidioides (17.7%), and Leveillula taurica (10.1%), irrespective of sampling time and field location. There was no significant correlation between weather variables and disease incidence for Ph. medicaginis or L. taurica. However, the incidence of common leaf spot and downy mildew were significantly correlated with both monthly mean temperature and total rainfall. The incidence of rust was positively correlated with mean monthly temperature, whereas the incidence of yellow leaf blotch was negatively correlated with monthly total rainfall. This improved knowledge of diseases of alfalfa in Zanjan will assist in the future selection of management strategies and breeding of suitable cultivars for use in regions with similar climatic conditions

This study investigated the effects of soil amendment with olive mill by-products (Jift) on growth of chickpea and their symbiosis with Vesicular arbascular (VA) fungi. A split plot design with three replications was used, in which soil treatments (methyl bromide fumigated, fungicide, and untreated control) were assigned to main plots and soil-Jift mixtures(Jift: Soil; 0:10, 1:9, 2:8, 3:7, and 4:6) to sub plots . Results indicated that the highest seed yield (2295 kg ha-1) was attained under untreated control followed by those which treated with fungicide (2260 kg ha-1) and methyl bromide (2031 kg ha-1). When Jift was considered as main factor, seed yield was found to be increased as Jift level was increased in soil mixtures. However, the greatest Jift level at the rate of 3:7 produced insignificant increase of seed and over the yields produced at the rate of 2:8. Phosphorus content per plant was senior under untreated control plots than under methyl bromide and fungicide treatments. There was a propensity of improved phosphorus content along with increasing Jift level in soil mixtures. On the other hand, the highest Jift level (3:7) caused phosphorus content to be somewhat decreased compared to Jift at the rate of 2:8, under untreated control and methyl bromide treatment

The possible involvement of activated oxygen species in the mechanism of damage by NaCl stress was studied in leaves of two varieties of pea (Pisum sativum L.) cv. EC 33866 and Puget. The level of lipid peroxidation, enzyme activity of superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), dihydroascorbate reductase (DHAR, 1.8.5.1) were studied. High chlorophyll stability was observed in EC 33866 varieties than Puget. Significant accumulation in the levels of Na and Cl- was observed in Puget as the concentration of salt increased. Decrease in levels of K, Ca2 and Mg2 was recorded in both varieties but Puget showed more decrease as compared to EC 33866. Salt stress increased the rate of lipid peroxidation in both the varieties of pea but more decrease was observed in Puget. Salt stress induced significant increase in the activities of the antioxidant enzymes. The SOD and APX increased in both varieties at all concentrations but the increase was more in EC 33866 variety than Puget. GR and DHAR were increased in both the varieties at 150 mM NaCl, however at 200 mM NaCl decline was observed. Decline of DHAR and GR was more pronounced in Puget as compared to the EC 33866 variety.