[Show abstract][Hide abstract] ABSTRACT: Leaf rust is a major disease of wheat crop in the world as a whole. This study was undertaken to find the genetic effects of adult plant leaf resistance in wheat (Triticum aestivum L.). Three wheat crosses were developed from three resistant and one susceptible parent. Six populations (P 1 , P 2 , F 1 , F 2 , BC 1 and BC 2) of each cross were grown under field conditions and were artificially inoculated with isolates of mixture of leaf rust prevalent races. Leaf rust intensity and reaction type were observed and the coefficient of infection was computed. Generation means and variance analyses were performed for the estimation of additive, dominance and epistatic genetic effects. Additive and dominance, as well as epistatic genetic effects, are involved in the inheritance of leaf rust resistance. However, the narrow sense heritability estimates were low, which also exhibited the presence of epistatic genetic effects. Thus, selection of resistant adult plant in later segregating generations would be useful for the development of high yielding wheat genotypes.
AFRICAN JOURNAL OF BIOTECHNOLOGY 04/2011; 10(16). · 0.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A procedure based on QuEChERS extraction and a simultaneous liquid-liquid partition clean-up was developed. The procedure involved extraction of hydrated soil samples using acetonitrile and clean-up by liquid-liquid partition into n-hexane. The hexane extracts produced were clean and suitable for determination using gas chromatography-tandem mass spectrometry (GC-MS/MS). The method was validated by analysis of soil samples, spiked at five levels between 1 and 200 microg kg(-1). The recovery values were generally between 70 and 100% and the relative standard deviation values (%RSDs) were at or below 20%. The procedure was validated for determination of 19 organochlorine (OC) pesticides. These were hexachlorobenzene (HCB), alpha-HCH, beta-HCH, gamma-HCH, heptachlor, heptachlor epoxide (trans), aldrin, dieldrin, chlordane (trans), chlordane (cis), oxychlordane, alpha-endosulfan, beta-endosulfan, endosulfan sulfate, endrin, p,p'-DDT, o,p'-DDT, p,p'-DDD and p,p'-DDE. The method achieved low limits of detection (LOD; typically 0.3 microg kg(-1)) and low limits of quantification (LOQ; typically 1.0 microg kg(-1)). The method performance was also assessed using five fortified soil samples with different physico-chemical properties and the method performance was consistent for the different types of soil samples. The proposed method was compared with an established procedure based on Soxtec extraction. This comparison was carried out using six soil samples collected from regions of Pakistan with a history of intensive pesticide use. The results of this comparison showed that the two procedures produced results with good agreement. The proposed method produced cleaner extracts and therefore led to lower limits of quantification. The proposed method was less time consuming and safer to use. The six samples tested during this comparison showed that soils from cotton growing regions contained a number of persistent OC residues at relatively low levels (<10 microg kg(-1)). These residues were alpha-HCH, gamma-HCH, heptachlor, chlordane (trans), p,p'-DDT, o,p'-DDT, p,p'-DDD, p,p'-DDE, beta-endosulfan and endosulfan sulfate.
Journal of Chromatography A 03/2010; 1217(17):2933-9. DOI:10.1016/j.chroma.2010.02.060 · 4.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wild relatives of wheat as new sources of genetic diversity are a potent resource for addressing biotic and abiotic stress constraints that limit wheat productivity. These are distributed in the three gene pools of the Triticeae and over the last two decades are being extensively utilized in breeding programmes globally. In this study, 200 accessions of Triticum turgidum (2n=4x=28; AABB), 40 accessions of Aegilops tauschii (2n=2x=14;DD), and 6 accessions of Ae. triuncialis (2n=4x=28;CCUU) were screened against stripe rust of wheat (Puccinia striiformis tritici) at seedling stage. Bulk inoculum collected from environmentally diverse wheat growing areas of Pakistan was used for the seedling screening. The innoculum had virulence for genes Yr1, Yr3, Yr4, Yr5, Yr6, Yr7, Yr8, Yr9, Yr18, YrSp, YrSD, and YrCV. Infection types (ITs) ranging from low to high were recorded within each germplasm category where 35 durum lines (T. turgidum,) and 13 of Ae.tauschii had good seedling resistance (0-2). Another 20 durum and 12 Ae. tauschii lines were found moderately resistant. Frequency distributions of the ITs was higher for Ae. tauschii lines (34%) as compared to the durum wheats (20%). Advanced germplasm testing involving synthetic hexaploid wheats have made available several lines that are resistant to stripe rust. The source of resistance in this germplasm is attributed to alleles on the A and B genomes of durum parents, or on the Ae. tauschii's D genome, or is a combination of genes that are pyramided as a consequence of A, B and D genome hybridizations. Ample diversity has been identified that warrants exploitation in wheat breeding.
Pakistan Journal of Botany 04/2007; 39(2). · 0.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Amongst alien germplasms that provide much needed genetic diversity for resistance to leaf-blotch (caused by Cochliobolus sativus) and karnal bunt (caused by Tilletia indica) is the tertiary gene pool tetraploid Aegilops variabilis (2n=4x=28; UUSS) resource. In order to exploit this species potential, it is crucial that intergeneric hybrids are first produced from which stable genetic stocks are developed for subsequent agricultural utilization. The hybridization of several durum and bread wheat cultivars with Ae. variabilis is reported herein which have yielded cytologically characterized normal F 1 hybrids (2n=4x=28, ABUS or 2n=5x=35, ABDUS). These upon colchicine treatment have generated fertile octoploid and decaploid amphiploids. The amphiploids in all cases possessed aneuploidy that was more pronounced with bread wheat cultivars (2n=10x=70, AABBDDUUSS). Durum amphiploid combinations had more normal 56 chromosome plant types with perfect bivalent meiosis (2n=8x=56, AABBUUSS and 28 bivalents across variable ring and rod associations). Reported here is the cytogenetics of these intergeneric hybrid cross combinations that have enabled the production of a novel genetic resource in the form of fertile amphiploids that hold the potential to address future work on improving wheat cultivars for resistance to C. sativus and T. indica.
Pakistan Journal of Botany 01/2007; · 0.82 Impact Factor