Effect of Corn, Sugarbeets, and Fallow on Zinc Availability to Subsequent Crops
Field observations indicated that Zn deficiency of beans (Phaseolus 
vulgaris L.) was sometimes more severe than expected when 
grown on fallowed soil that was low to marginal in available Zn. 
The objectives of this study were to determine the effects of fallow, 
sugarbeets (Beta vulgaris L.), and corn (Zea mays L.) on Zn availability 
to subsequent crops grown on a Portneuf silt loam (Durixerollic 
Calciorthids, coarse silty, mixed, mesic). The sugarbeet and 
corn plant tops and sugarbeet roots were removed, and 11.2 kg Zn 
ha-1 was applied on one-half of each plot before fall plowing 25-cm 
deep. Beans, sweet corn, or potatoes (Solanum tuberosum L.) were 
planted the following spring. Whole plant samples of beans and 
sweet corn and potato stems, leaflets, and petioles were sampled for 
chemical analyses during the growing season. All bean plants were 
Zn deficient when grown after fallow or sugarbeets but not after 
corn or where Zn fertilized. Potatoes and sweet corn did not show 
any Zn deficiency symptoms or any growth responses to Zn fertilization. 
The average zinc concentration in beans (vegetative development 
stage, V3) following Corn was 20.5 mg kg-1 compared with 
12.5 mg kg-1 following fallow or sugarbeets without Zn fertilization. 
The average Zn uptake by beans (V3) following corn was 1.3 g ha-1 
compared with 0.6 g ha-1 after fallow or suprbeets without Zn 
fertilization. The Zn uptake after corn was even greater than where 
11.2 kg Zn ha-1 was applied to fallow or sugarbeets (1.3 vs. 0.9 g 
Zn ha-1). Enhanced Zn availability following corn persisted 
throughout the growing season and into a second bean crop, although 
at a decreased level. Similar trends occurred with potatoes 
and sweet corn. Soil DTPA-extractable Zn was not significantly 
different after fallow, sugarbeets, or corn. These results indicate that 
Zn deficiency in sensitive crops may be alleviated or prevented depending 
upon the preceding crop grown, and that factors not measured 
by DTPA can significantly influence Zn availability.
Prediction of zinc deficiency in navy beans (Phaseolus vulgaris) by soil and plant analyses
Navy beans (Phaseolus vulgaris cv. Gallaroy) were grown with 7 rates of zinc (Zn) in a Zn-deficient gravelly sandy loam in a glasshouse experiment. The plant shoots were harvested 31 days after sowing and the Zn concentration in each of 4 plant parts (YL, young leaf; YOL, young open leaf; YFEL, youngest fully expanded leaf; and whole shoots) was related to the fresh weight of the shoots. The critical Zn concentrations (mgtkg) in the plant parts determined by the 2 intersecting straight lines model were 21.1 for YL (r2 = 0.66), 17.1 for YOL (r2 = 0.83), 10.6 for YFEL (r2 = 0.91) and 12.5 for the whole tops (r2 = 0.88). The YFEL was selected as an appropriate diagnostic tissue because it is readily identifiable in the field and had the highest 1.2 with fresh weight. In a second glasshouse experiment, the critical Zn concentration in the YFEL and 5 soil tests were evaluated for their ability to predict the Zn status of navy beans. There were 13 soils from sands to clays with a wide range of chemical properties. The soil tests were 0.1 mol/L HCl, DTPA, EDTA, dilute CaCl2 and soil solution Zn. The concentration of Zn in the YFEL correctly predicted Zn deficiency or adequacy in about 77% of samples. The results from both experiments showed that a critical Zn concentration of 10-11 mg/kg in the YFEL can be used to diagnose the Zn status of Gallaroy navy beans. It was not possible to recommend a single soil test for prediction of the relative yield of navy beans. A combination of quantity (HCl, EDTA, DTPA) and intensity (soil solution, 0.002 mol/L CaCl2, 0.01 mol/L CaCl2) parameters were able to explain most of the variation in the Zn concentration of the YFEL, a more sensitive measure of nutrient availability than relative yield. EDTA-Zn in combination with 0.01 mol/L CaCl2-Zn explained 90% of the variation in the Zn concentration in the YFEL, while HCl- or DTPA-Zn and 0.01 mol/L CaCl2 explained about 80% of the variation. As soil solution Zn was significantly correlated with 0.002 and 0.01 mol/L CaCl2-Zn (r = 0.75, P<0.01; r = 0.62, P<0.05, respectively), CaCl2-Zn may be used as a more convenient measure of Zn intensity than soil solution Zn.
Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes
Background After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits. Review Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation. Conclusions Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.