Genetic Advancement of Newly Developed Wheat Populations Under Drought-Stressed and Non-Stressed Conditions

Journal of Crop Science and Biotechnology - Genetic variation and heritability estimates in early generations are important in identifying superior families that can be targeted for genetic...     

Increasing incomes of Malian cotton farmers: Is elimination of US subsidies the only solution?

In a WTO battle and the press the argument is often made that eliminating US cotton subsidies would have a large effect on the incomes and competitive position of farmers in developing countries. In Francophone West Africa cotton productivity has stagnated after rapid gains in the first two decades following independence (1960-1980). A farm model was constructed based on farmers’ definition of their decision-making framework which they use to respond to income and weather risks. With this model the effects on farmers of eliminating US subsidies are compared with various productivity increasing measures for cotton and sorghum in Dioila, Mali. Dioila is located in a representative cotton region producing 16% of the cotton in Mali. We include sorghum due to its importance for consumption and the observation of Malian farmers substituting cereals (sorghum and maize) for cotton as the returns to cotton have fallen in the 21st Century. In the farm model, the elasticity of transmission of a change in the world cotton price to the farm gate price is taken into account. The gains from eliminating US subsides are small. In contrast, the various technological alternatives including Bt cotton introduction, the use of higher fertilization levels for cotton, and the introduction of improved sorghum cultivars and moderate fertilization along with a marketing package all have substantially higher returns Even with substantial improvement in the mechanisms enabling farmers to benefit from the higher prices resulting from elimination of US subsidies, there are still much higher returns resulting from the various types of productivity increases.     

Relationships between genetic distance measured by RAPD-PCR and heterosis in inbred lines of white clover (Trifolium repens L.)

The RAPD-PCR technique has been used to generate DNA amplification profiles from a set of advanced generation inbred lines of white clover ( Trifolium repens L.). The genetic distances between lines have been estimated and have been compared with the extent of positive heterosis for dry matter yield in hybrid crosses. The analysis clearly separated the four major groups (H, J, R and S), with little within group variation. Heterosis, previously shown to be positively correlated with the extent of phenotypic variation between parental lines, was greatest between lines from groups showing the least genetic distance. The lack of correlation between heterosis and genetic divergence is discussed in the context of results from other systems. Additionally, the data allow a comparison of the extent of phenotypic variation for a trait under selective pressure with the degree of variation at the DNA level detected with the RAPD technique. This revised version was published online in July 2006 with corrections to the Cover Date.     

Soil drought duration and severity affect cotton boll biomass by altering recovery times and carbon dynamics of subtending leaf

Drought appears at flowering and boll formation for cotton frequently. However, reports on the impact of carbon dynamics in the subtending leaf on boll biomass under periodic droughts are limited. To investigate this, experiments were carried out with two cultivars (drought-tolerant: Dexiamian 1; drought-sensitive: Yuzaomian 9110), three water levels [soil relative water content (SRWC): control (75 ± 5)%, moderate drought (60 ± 5)%, severe drought (45 ± 5)%] and five drought durations (10, 17, 24, 31 and 38 days). A 38-day drought declined the net photosynthetic rate of subtending leaf, which could be collectively attributed to the reduction in carboxylation with reduced ribulose-1,5-bisphosphate carboxylase activity, and stomal limitation with decreased stomatal conductance, along with the damage of photosynthetic apparatus with depressed maximum and actual photochemical quantum yield, leading to lower starch content. A 38-day drought also increased the activities of sucrose phosphate synthase (SPS), sucrose synthase (Susy) and expressions of genes (GhSPS1, GhSPS2, GhSusA and GhSusB) associated with these enzymes, causing the accumulation of sucrose content, finally resulting in lower boll biomass. Some of the above parameters fully recovered under more than 17-day moderate drought or over 10-day severe drought, but boll biomass still decreased after re-watering. Under 10-day moderate drought, all aforementioned indices and boll biomass were completely recovered within 7 days of re-watering, and the recovery capacity of Yuzaomian 9110 was lower than that of Dexiamian 1. Therefore, rapid recovery of photosynthesis and decline in the subtending leaf sucrose content to pre-stress levels are important factors in lessening the impacts of drought on boll biomass and are indicative of cultivar tolerance to short-term moderate water deficit.     

Genome-wide association study of grain iron and zinc concentration in common bean (Phaseolus vulgaris)

Common bean is one of the widely consumed food security crop in Africa, Asia and South America. It is a rich source of protein, minerals and micronutrients. High genotype by environment interaction is one of the main challenge in breeding for high grain micronutrient concentration. The objective of this study was to estimate SNP markers associated with grain Fe and Zn concentration using 289 common bean genotypes and 11,480 SNP markers. The study revealed that 43 quantitative trait loci (QTLs) were associated with grain Fe and Zn concentration. Five quantitative trait nucleotides (QTNs), that is, QTN Fe_1.1, QTN Fe_6.3, QTN Fe_6.5, QTN Fe_10.3 and QTN Fe_11.6 were detected both at Haramaya and Melkassa locations. Two of the markers, that is, QTN Fe_6.3 and QTN Fe_6.5, were located on chromosome 06 while QTN Fe_1.1, QTN Fe_10.3 and QTN Fe_ 11.6 were residing on chromosomes 01, 10 and 11, respectively. Among these, QTN Fe_11.6 had a large and positive consistent effect across locations. The five stable QTNs along with the potential candidate genes could be used for Fe biofortification through marker assisted selection.     

Application of the relevance vector machine to canal flow prediction in the Sevier River Basin

This work addresses management of water for irrigation in arid regions where significant delays between the time of order and the time of delivery present major difficulties. Motivated by improvements to water management that will be facilitated by an ability to predict water demand, it employs a data-driven approach to developing canal flow prediction models using the relevance vector machine (RVM), a probabilistic kernel-based learning machine. A search is performed across model attributes including input set, kernel scale parameter and model update scheme for models providing superior prediction capability using the RVM. Models are developed for two canals in the Sevier River Basin of southern Utah for prediction horizons of up to 5 days.     

Fossilized nuclei and germination structures identify Ediacaran "animal embryos" as encysting protists

Globular fossils showing palintomic cell cleavage in the Ediacaran Doushantuo Formation, China, are widely regarded as embryos of early metazoans, although metazoan synapomorphies, tissue differentiation, and associated juveniles or adults are lacking. We demonstrate using synchrotron-based x-ray tomographic microscopy that the fossils have features incompatible with multicellular metazoan embryos. The developmental pattern is comparable with nonmetazoan holozoans, including germination stages that preclude postcleavage embryology characteristic of metazoans. We conclude that these fossils are neither animals nor embryos. They belong outside crown-group Metazoa, within total-group Holozoa (the sister clade to Fungi that includes Metazoa, Choanoflagellata, and Mesomycetozoea) or perhaps on even more distant branches in the eukaryote tree. They represent an evolutionary grade in which palintomic cleavage served the function of producing propagules for dispersion.     

Activation of integrin alphaIIbbeta3 by modulation of transmembrane helix associations

Transmembrane helices of integrin alpha and beta subunits have been implicated in the regulation of integrin activity. Two mutations, glycine-708 to asparagine-708 (G708N)and methionine-701 to asparagine-701, in the transmembrane helix of the beta3 subunit enabled integrin alphaIIbbeta3 to constitutively bind soluble fibrinogen. Further characterization of the G708N mutant revealed that it induced alphaIIbbeta3 clustering and constitutive phosphorylation of focal adhesion kinase. This mutation also enhanced the tendency of the transmembrane helix to form homotrimers. These results suggest that homomeric associations involving transmembrane domains provide a driving force for integrin activation. They also suggest a structural basis for the coincidence of integrin activation and clustering.     

Europium chelate and fluorescent brightener staining of soil propagules and their photomicrographic counting—I. Methods

A method tor direct visual or photomicrographic enumeration of soil propagules in soil-agar films and soil smears, stained with a mixture ofeuropium(III) ttienoyltrifluoroacetonate and the disodium salt of 4,4¹-bis(4-anilino-6-bis(2-hydroxyethyl)amino-S-triazin-2-ylamino)2,2¹-stilbene disulphonic acid, abbreviated to Eu(TTA)₃ and fluorescent brightener (FB), respectively, is described.Soil-agar suspensions at 55–60°C were introduced into haemocytometer sample chambers of 100 μm and 20 μm depth which gave soil-agar film thicknesses of 25 μm and 12 μm, respectively, after air-drying. Soil smears air-dried on 1.25 cm² and 1.0 cm² areas of glass slide were 5.2–6.0 μm and 6.0–8.0 μm thick, respectively.The Eu(TTA)₃ is best formulated in 50% (v/v) ethanol. The best concentrations of Eu(TTA)3 and FB for staining soil propagules were 2 mM and 25 μM. respectively. A staining period of 18 h for soil-agar films and 90–120 min for soil smears was found to be optimal. The optimum volumes of 50% ethanol for rinsing soil-agar films and soil smears were found to be 12.5 and 5.0 ml. respectively.Lack of in-depth focusing on agar films 25 μm thick resulted in 15–17 per cent error in enumerations. The 12 μm agar films and soil smears required little in-depth focusing and were acceptable for photomicrographic recording of numbers of soil propagules. It is concluded that incident u.v. photomicrographic recording of soil propagule numbers in thin agar films or soil smears is a practical solution to operator fatigue likely to occur during direct microscopy.