Genetic Variation of Plant Height and Stem Diameter Traits in Maize (Zea mays L.) under Drought Stress at Different Growth Stages

Plant height and stem diameter are essential traits in maize breeding. A study was carried out to estimate the extent of genetic variability in genotypes of Maize (Zea mays L.). Fifteen genotypes of maize were evaluated on season (2003/2004) across the two environments in Sudan, to obtain information on morphological and genetic diversity in plant height and stem diameter traits were estimated in a split-plot layout within randomized complete block design with three replications. Significant differences among genotypes were found in all traits, except stem diameter (45 days). High genotypic coefficient of variation, genetic advance and heritability were exhibited by plant height at 60 days and stem diameter at 60 days. Grain yield was significantly and positively associated, at the phenotypic level, with a plant height at 45 days and a stem diameter at 45 days. Based on the results the characters plant height and a stem diameter to be the important characters which would be used in selection for maize improvement under drought stress at vegetative and reproductive stages. Keywords: Maize (Zea mays L.), Genetic variability, plant height, stem diameter, drought

Genetic Variations of Leaf Trait in Maize (Zea mays L.) under Drought Stress in Different Growth Stages

Maize is the third most important food crop worldwide, and it is more sensitive to drought. Two field experiments were conducted under drought in different growth stages at two locations, the Demonstration Farm, Faculty of Agriculture, University of Khartoum, at Shambat, and the Gezira Research Station Farm, at Medani, in season (2003/2004). To estimate the pattern of inheritance, determine the relative magnitude of genetic variation effects for a number of leaves/plant and leaf area index in fifteen maize genotypes. A split-plot design, layout within randomized complete block design with three replications was used for the experiment. Significant differences among genotypes were detected in all traits, except, leaf area index (30 and 60 days) and number of leaves/plant (45 days). High genotypic coefficient of variation, genetic advance and heritability were exhibited by a number of leaves/plant for 60 days. Grain yield was significantly and positively associated at the phenotypic level with the leaf area index and a number of leaves/plant at 60 days. Thus the characters leaf area index and number of leaves/plant to be the important traits which would be an effectual in selection for maize improvement under drought stress at different growth stages. Based on their positive association with grain  yield, the traits  leaf area index and number of leaves/plant would be the exploited for improving grain yield and facilitate further efforts in the maize improvement program in the country. Keywords: correlation; heritability; morphological traits; vegetative and reproductive phases; water stres

Genetic Variation of Flowering Trait in Maize (Zea mays L.) under Drought Stress at Vegetative and Reproductive Stages

A study was conducted under water stress in vegetative and reproductive growth stages at two locations (Shambat and Medani) in Sudan during the season (2003/2004). Genotypic and phenotypic variability, genetic advance and heritability in a broad sense were estimated in a split-plot layout within randomized complete block design with three replications. Fifteen genotypes of maize were used for the study.  Phenotypic correlation coefficient between grain yield and 25%, 50% and 95% of flowering trait anthesis and silking were evaluated. All flowering stages were found significant differences among the genotypes, except days to 95% anthesis. Significant differences among water treatments were observed for days to 25% silking at Medani. High heritability, genotypic coefficient of variation and genetic advance were exhibited by days to 25% silking. Grain yield was significantly and negatively associated with days to (50% and 95%) silking. Based on the results drought stress at vegetative and reproductive stages of maize results in a drastic reduction in grain yield, and flowering character would be the important selection, creation for maize improvement under drought stress. Keywords: Maize (Zea mays L.), Genetic variability, heritability, correlation, flowering, drought

Phenotypic Variations of Drought Tolerance Parameters in Maize (Zea mays L.) under Water Stress at Vegetative and Reproductive Stages

Two field experiments were conducted at Shambat and Medani in Sudan under water stress in vegetative and reproductive growth stages during the season (2003/2004). The objective of the study was to assess phenotypic variability and phenotypic correlation between drought tolerance parameters in maize genotypes. A split-plot layout within randomized complete block design with three replications was used for the experiment. Fifteen genotypes of maize were examined through the study. The effect due to genotypes x location was highly significant for all drought tolerance parameters studied. Highly significant and favorable correlation for Yw with SSI2, SSI3, GMP2, GMP3, STI2 and STI3, while highly significant and negative with Yd2/Yw and Yd3/Yw. Based on the result's drought stress at vegetative and reproductive stages of maize results in a drastic reduction in grain yield, and the strong positive correlation of Yw with SSI, GMP and STI, indicates that selection for high values of these parameters improves yield under stress and non-stress environments. Drought tolerance parameters can be used for improving grain yield and facilitate further efforts in maize breeding programs. Keywords: Correlation, drought, genetic variability, heritability, Maize (Zea mays L.).

Comparative Efficiency of Soil and Foliar Applied Zinc in Improving Yield and Yield Components of Wheat (Triticum aestivum L.) Variety Kiran-95

A field study was undertaken to evaluate the comparative efficacy of zinc application through soil and foliar spray on growth and yield of wheat variety Kiran-95 at Soil Chemistry Section, Agriculture Research Institute, Tandojam during Rabi 2013-14. The experiment was laid out in three replicated randomized complete block design. The treatments comprised Control (No Zinc), Soil applied Zinc 5.0 kg ha-1 at tillering stage, Soil applied Zinc 10.0 kg ha-1 at tillering stage, Soil applied Zinc 5.0 kg ha-1 at tillering + 5.0 kg ha-1 at booting stage, Foliar applied Zinc 0.2% at tillering stage, Foliar applied Zinc 0.4% at tillering and Foliar applied Zinc 0.2% at tillering stage + 0.2% at booting stage. The statistical analysis of data suggested that soil and foliar applied zinc affected significantly (P<0.05) growth and yield traits of wheat variety Kiran-95. The results illustrated that Soil applied Zinc 5.0 kg ha-1 at tillering + 5.0 kg ha-1 at booting stage produced maximum plant height (99.0 cm), tillers (410.7 m-2), spike length (13.1 cm), spikelets per spike (23.0), grains per  spike (45.1), seed index (43.4 g), biological yield (9354.4 kg ha-1) and grain yield (5123.4 kg ha-1), closely followed by Foliar applied Zinc 0.2% at tillering stage + 0.2% at booting stage with 97.6 cm plant height, 408.8 tillers m-2, 13.0 cm spike length, 22.8 spikelets per spike, 45.0 grains per spike, 43.2 g seed index, 9273.4 kg ha-1 biological yield and 5080.7 kg ha-1 grain yield. The performance of wheat variety Kiran-95 ranked 3rd, 4th, 5th and 6th almost in all the growth and yield parameters particularly grain yield (kg ha-1) when fertilized with Soil applied Zinc 10.0 kg ha-1 at tillering stage, Foliar applied Zinc 0.4% at tillering, Soil applied Zinc 5.0 kg ha-1 at tillering stage and Foliar applied Zinc 0.2% at tillering stage.  However, minimum growth and yield traits were registered in Control (No Zinc). Furthermore, the results concluded that although numerically maximum growth and yield values were recorded in Soil applied Zinc 5.0 kg ha-1 at tillering + 5.0 kg ha-1 at booting stage but statistically the differences between Soil applied Zinc 5.0 kg ha-1 at tillering + 5.0 kg ha-1 at booting stage and Foliar applied Zinc 0.2% at tillering stage + 0.2% at booting stage were non-significant. Hence, Foliar applied Zinc 0.2% at tillering stage + 0.2% at booting stage were found the most economical treatment for obtaining optimum yield of wheat variety Kiran-95. Keywords: Wheat, Comparative Efficiency, Soil, Foliar, Zinc, Improving Yield and Yield Component

Association of Agronomic Traits with SNP Markers in Durum Wheat (Triticum turgidum L. durum (Desf.))

AbstractAssociation mapping is a powerful approach to detect associations between traits of interestand genetic markers based on linkage disequilibrium (LD) in molecular plant breeding. Inthis study, 150 accessions of worldwide originated durum wheat germplasm (Triticum turgidumspp. durum) were genotyped using 1,366 SNP markers. The extent of LD on eachchromosome was evaluated. Association of single nucleotide polymorphisms (SNP) markerswith ten agronomic traits measured in four consecutive years was analyzed under a mixlinear model (MLM). Two hundred and one significant association pairs were detected inthe four years. Several markers were associated with one trait, and also some markerswere associated with multiple traits. Some of the associated markers were in agreementwith previous quantitative trait loci (QTL) analyses. The function and homology analyses ofthe corresponding ESTs of some SNP markers could explain many of the associations forplant height, length of main spike, number of spikelets on main spike, grain number perplant, and 1000-grain weight, etc. The SNP associations for the observed traits are generallyclustered in specific chromosome regions of the wheat genome, mainly in 2A, 5A, 6A,7A, 1B, and 6B chromosomes. This study demonstrates that association mapping can complementand enhance previous QTL analyses and provide additional information formarker-assisted selection

Association of Agronomic Traits with SNP Markers in Durum Wheat (<i>Triticum turgidum</i> L. <i>durum</i> (Desf.))

<div><p>Association mapping is a powerful approach to detect associations between traits of interest and genetic markers based on linkage disequilibrium (LD) in molecular plant breeding. In this study, 150 accessions of worldwide originated durum wheat germplasm (<i>Triticum turgidum</i> spp. <i>durum</i>) were genotyped using 1,366 SNP markers. The extent of LD on each chromosome was evaluated. Association of single nucleotide polymorphisms (SNP) markers with ten agronomic traits measured in four consecutive years was analyzed under a mix linear model (MLM). Two hundred and one significant association pairs were detected in the four years. Several markers were associated with one trait, and also some markers were associated with multiple traits. Some of the associated markers were in agreement with previous quantitative trait loci (QTL) analyses. The function and homology analyses of the corresponding ESTs of some SNP markers could explain many of the associations for plant height, length of main spike, number of spikelets on main spike, grain number per plant, and 1000-grain weight, etc. The SNP associations for the observed traits are generally clustered in specific chromosome regions of the wheat genome, mainly in 2A, 5A, 6A, 7A, 1B, and 6B chromosomes. This study demonstrates that association mapping can complement and enhance previous QTL analyses and provide additional information for marker-assisted selection.</p></div

SNP locus pairs in different linkage stage with significant (P<0.01) and highly significant (p<0.001) linkage disequilibrium (LD) and R² values on genome level in durum wheat.

<p>^a Locus on the same linkage group.</p><p>^b Locus from different linkage groups.</p><p>^c Locus pairs and percentage of all possible locus pairs showing significant LD at P<0.01.</p><p>^d Locus pairs and percentage of all possible locus pairs showing significant LD at P<0.001.</p><p>^e Locus pairs and percentage of all possible locus pairs showing significant LD at R²>0.1; P<0.01 adjusted for locus pairs description.</p><p>^f Locus pairs and percentage of all possible locus pairs showing significant LD at R²>0.1; P<0.001 adjusted for locus pairs description.</p><p>SNP locus pairs in different linkage stage with significant (P<0.01) and highly significant (p<0.001) linkage disequilibrium (LD) and R² values on genome level in durum wheat.</p

Frequency distribution of the 10 examined agronomic traits of durum wheat in four consecutive years.

<p>P value of Kolmogorov-Smirnov test for each year was shown, the hypothesis of normal distribution could be accepted when P>0.05 (significant at P = 0.05), and the trend lines of the accepted normal distribution were shown. PH, plant height (cm); ES, number of effective spikes, LMS, length of main spike (cm); RLMS, rachis internode length of main spike (cm); LFPMS, panicle neck length of main spike (cm); SMS, number of spikelets on main spike; NSPP, number of spikelets per plant; GNP, grain number per plant; GWP, grain weight per plant (g); KGW, 1000-grain weight (g).</p

Chromosome bin map of plausible QTLs anchored by SNP markers in durum wheat.

<p>The relative interval length is indicated on the left of each chromosome and QTLs represented by SNP-based associations and relative R value (%) are shown on the right. The number in front of the symbol means the repeats of the associations anchored in the interval in the corresponding years and without a number in front of the symbol means one repeat of the association anchored in the interval in one corresponding year. Details of the associations are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130854#pone.0130854.s002" target="_blank">S2 Table</a>. The exact bins of some associated EST markers are unknown, and thus are shown below the chromosome.</p