Assessment of the combining ability and authentication of F1 hybrids using SSR markers in wheat (Triticum aestivum L.)

Six wheat genotypes (three female and three male) were crossed for the study of some quantitative traits in wheat. Analysis of variance showed a highly significant difference for all the characters except flag leaf area, which was significant. Testers revealed that LU26S was the best general combiner only for plant height. Mehraj showed a good general combining ability effect on plant height, flag leaf area, peduncle length, and 1000-grain weight. Farid 2006 was the best male parent as general combiner for plant height, peduncle length, spike length, number of grains per spike, and grain yield per plant. The wheat parental lines revealed that 9381 was the best general combiner for plant height, flag leaf area, peduncle length, 1000-grain weight, and grain yield per plant. Whereas 9428 was the best general combiner for flag leaf area, spike length, and number of spikelets per spike. Among crosses, LU26S × 9272, LU26S × 9381, Mehraj × 9272, and Mehraj × 9381 showed a significant effect of specific combining ability (SCA) on grain yield per plant. Other crosses with significant and positive SCA effects were LU26S × 9272 on plant height and 1000-grain weight grain yield per plant, LU26S × 9428 on peduncle length, and Mehraj × 9381 on plant height and grain yield per plant. These crosses with significant effects of general combining ability (GCA) on grain yield per plant can be used in the development of new varieties. These crosses with nonadditive genes would give transgressive segregants. For yield improvement, vigilant selection of the potent transgressive segregants through family selection would be valuable for yield enhancement. A total of 15 SSR primers of Xgwm series and 5 of X series were used to find out the codominant loci in the hybrid and single dominant loci in parents. Out of 15 primers only, Xgwm-314 gave the polymorphic banding pattern. This primer showed the polymorphic dominant loci in the parents (LU26S, Mehraj, 9272 and 9381) and codominant loci midway between these parents. Therefore, this SSR primer was used to confirm the two best performing hybrids (LU26S × 9272 and Mehraj × 9381) on the bases of positively significant effects of GCA and SCA on plant height, 1000-grain weight and grain yield per plant, and other economically important traits. The two hybrids namely LU26S × 9272 and Mehraj × 9381 can be used in the further breeding program for the development of high yielding varieties.     

Mechanisms of metal-phosphates formation in the rhizosphere soils of pea and tomato: environmental and sanitary consequences

Purpose

At the global scale, soil contamination with persistent metals such as lead (Pb), zinc (Zn), and copper (Cu) induces a serious threat of entering the human food chain. In the recent past, different natural and synthetic compounds have been used to immobilize metals in soil environments. However, the mechanisms involved in amendment-induced immobilization of metals in soil remained unclear. The objective of the present work was therefore to determine the mechanisms involved in metal-phosphates formation in the rhizospheric soils of pea and tomato currently cultivated in kitchen gardens.

Materials and methods

Pea and tomato were cultivated on a soil polluted by past industrial activities with Pb and Zn under two kinds of phosphate (P) amendments: (1) solid hydroxyapatite and (2) KH₂PO₄. The nature and quantities of metal-P formed in the rhizospheric soils were studied by using the selective chemical extractions and employing the combination of X-ray fluorescence micro-spectroscopy, scanning electron microscopy, and electron microprobe methods. Moreover, the influence of soil pH and organic acids excreted by plant roots on metal-P complexes formation was studied.

Results and discussion

Our results demonstrated that P amendments have no effect on metal-P complex formation in the absence of plants. But, in the presence of plants, P amendments cause Pb and Zn immobilization by forming metal-P complexes. Higher amounts of metal-P were formed in the pea rhizosphere compared to the tomato rhizosphere and in the case of soluble P compared to the solid amendment. The increase in soil-metal contact time enhanced metal-P formation.

Conclusions

The different forms of metal-P formed for the different plants under two kinds of P amendments indicate that several mechanisms are involved in metal immobilization. Metal-P complex formation in the contaminated soil depends on the type of P amendment added, duration of soil-plant contact, type of plant species, and excretion of organic acids by the plant roots in the rhizosphere.     

Interaction of Rhizobium and Pseudomonas with Wheat (Triticum Aestivum L.) in Potted Soil with or Without P2O5

The effect of inoculation of Rhizobium or Pseudomonas, or both, in the presence and absence of phosphorus pentoxide (P₂O₅) fertilizer on wheat yield was tested. The experiment was conducted outdoors in potted soil during two consecutive years under natural conditions. Rhizobial strain (Thal 8-chickpea nodulating bacteria) and Pseudomonas strain (54RB), both indigenous P solubilizers were applied in broth culture at seedling stage. Fertilizer in the form of P₂O₅ was an additional treatment applied at sowing time. Results revealed that inoculation of Pseudomonas strain in presence of phosphorus (P) fertilizer increased yield up to 41.8% when it was compared with only P fertilizer applied. Co-inoculation of Rhizobium and Pseudomonas strains with the P₂O₅ treatment however resulted in increased grains yield by 10% over the P₂O₅ treatment alone. It is inferred that inoculation with Rhizobium and Pseudomonas combined with P₂O₅ is not only environmentally beneficial but also economically sound and productive, with wheat yield increases of 10% to 42%.     

Weed flora composition of different barley‐based cropping systems under conventional and conservation tillage practices

Phytoparasitica - Tillage is among the most important soil management practices, which exert strong impacts on weed flora composition in different cropping systems. The large-scale adoption of...     

Preparation of glucosamine from exoskeleton of shrimp and predicting production yield by response surface methodology

Chitin was prepared from Persian Gulf shrimp (Metapenaeus monoceros), and then, the obtained chitin was hydrolyzed by hydrochloric acid solutions. The production yield of glucosamine hydrochloride from chitin was optimized, and the effect of three factors (acid concentration, acid to chitin ratio, and reaction time) was investigated. A Box-Behnken design by Minitab software created 12 reactions with different conditions. Each reaction was performed in two replicates. Response surface methodology was used for predicting the glucosamine preparation. The optimum conditions for glucosamine hydrochloride preparation were 30 and 37% hydrochloric acid, 9:1 (v/w) acid solution to solid ratio, and 4 h of reaction time. Time ratio and time acid concentrations were the effective factors on the yield.     

Assessment of genetic diversity among wheat (Triticum aestivum L.) cultivars from a range of localities across Pakistan using random amplified polymorphic DNA (RAPD) analysis

Genetic diversity among 20 wheat genotypes/cultivars from diverse locations of Pakistan was studied using random amplified polymorphic DNA (RAPD) analysis. A total of 445 DNA fragments were amplified with50 random decamer primers 64.38% of which were polymorphic. Genetic similarity matrix based on Nei & Li's (1979) index detected coefficients ranging from 75.60% to 92.74%. These coefficients were used to construct a dendrogram using unweighted pair group of arithmetic means (UPGMA). The wheat genotypes were clustered into one major group (A) and two small groups (B and C). The most distant genotype in the dendrogram was PARC-1 that was 75.60% to 84.94% genetically similar with the other genotypes and clustered with PARC-3 which formed a group distantly related with the other clusters. Moreover, most of the wheat genotypes developed from the same breeding centre clustered in one group. It has been clearly shown that most of the cultivars except PARC-1possessed narrow genetic background. The information would be helpful for future genome mapping programs as well as for the application of intellectual breeder rights in the country. The study will also work as indicator for wheat breeders to evolve varieties with diverse genetic background to achieve sustainability in wheat production in the country. This revised version was published online in August 2006 with corrections to the Cover Date.     

Proposal for equitable water allocation for rotational irrigation in Pakistan

A rotational water supply system is designed to deliver a constant flow of water among irrigators along a tertiary canal. Under the existing rotational system in Pakistan transmission losses along the canal are not considered. A constant time per unit irrigated area is allocated to all the farmers regardless of their location along the canal. This results in decreasing volumes of water delivered to downstream farmers. A variable time model is developed which allocates more time to the downstream farmers to deliver a constant volume of water per unit area to all the farmers in the command area of a tertiary unit.     

FOLIAR APPLICATION OF BORON INFLUENCES THE LEAF MINERAL STATUS,VEGETATIVE AND REPRODUCTIVE GROWTH,YIELD AND FRUIT QUALITY OF ‘KINNOW’ MANDARIN (CITRUS RETICULATA BLANCO.)

The effects of foliar application of boron (B) in the form of boric acid on vegetative and reproductive growth, yield and fruit quality of ‘Kinnow’ mandarin (Citrus reticulate Blanco.) were investigated. Kinnow mandarin was sprayed with different concentrations of boric acid viz. (0.1%, 0.2%, 0.3% and 0.4%) at fruit set stage. Leaf nitrogen (N), phosphorus (P), potassium (K), B, and zinc (Zn) along with flush length, tree height, tree spread and tree trunk diameter increased, while leaf length and leaf age showed non-significant results after foliar B application. Yield of the ‘Kinnow’ mandarin was significantly affected by foliar application of B and a significant increase in fruit weight at harvest was also observed. Soluble solid concentration (SSC): titratable acidity (TA) ratio, ascorbic acid, total sugars, total phenolic content (TPC) and total antioxidants significantly affected, while pH of juice, SSC, TA, reducing sugars and non-reducing sugars showed non- significant results.     

Irrigation with brackish water modifies the boron requirement of mungbean (Vigna radiata L.) on typic calciargid

The boron (B) sufficiency range for plant growth is narrow and its management is problematic under brackish irrigation water. This study was conducted to evaluate the B requirement of mungbean at different sodium adsorption ratios of irrigation waters (SAR_iw) [control, 8 and 16 (mmol_c L^?1)^1/2]. The boron adsorption characteristics of a loamy soil were first determined in the laboratory by equilibrating 2.5 g soil with 0.01 M CaCl₂ solution containing different B levels. Boron rates for a pot study were computed against different soil solution levels by fitting sorption data in a modified Freundlich model [x/m = K _f (EBC)^1/n ]. The maximum increase in shoot dry matter was 11.9% when B was applied at 1.29 mg kg^?1 soil at control SAR_iw. Visual leaf B toxicity symptoms appeared at higher B rates and became severe at higher SAR_iw. By contrast to Ca, shoot concentrations of B and Na increased significantly with B application and SAR_iw. For optimum shoot growth, internal and external B requirements were 25 mg B kg^?1 shoot dry matter and 0.39 mg B L^?1 soil solution, respectively, at control SAR_iw. At higher SAR_iw, a lower concentration of B in plant shoots and soil solution had an inhibitory effect on plant growth.