Identification of Zinc Efficiency-Associated Loci (<i>ZEAL</i>s) and Candidate Genes for Zn Deficiency Tolerance of Two Recombination Inbred Line Populations in Maize

Zinc (Zn) deficiency is one of the most common micronutrient disorders in cereal plants, greatly impairing crop productivity and nutritional quality. Identifying the genes associated with Zn deficiency tolerance is the basis for understanding the genetic mechanism conferring tolerance. In this study, the K22×BY815 and DAN340×K22 recombination inbred line (RIL) populations, which were derived from Zn-inefficient and Zn-efficient inbred lines, were utilized to detect the quantitative trait loci (QTLs) associated with Zn deficiency tolerance and to further identify candidate genes within these loci. The BLUP (Best Linear Unbiased Prediction) values under Zn-deficient condition (-Zn) and the ratios of the BLUP values under Zn deficient condition to the BLUP values under Zn-sufficient condition (-Zn/CK) were used to perform linkage mapping. In QTL analysis, 21 QTLs and 33 QTLs controlling the Zn score, plant height, shoot and root dry weight, and root-to-shoot ratio were detected in the K22×BY815 population and the DAN340×K22 population, explaining 5.5–16.6% and 4.2–23.3% of phenotypic variation, respectively. In addition, seventeen candidate genes associated with the mechanisms underlying Zn deficiency tolerance were identified in QTL colocalizations or the single loci, including the genes involved in the uptake, transport, and redistribution of Zn (ZmIRT1, ZmHMAs, ZmNRAMP6, ZmVIT, ZmNAS3, ZmDMAS1, ZmTOM3), and the genes participating in the auxin and ethylene signal pathways (ZmAFBs, ZmIAA17, ZmETR, ZmEIN2, ZmEIN3, ZmCTR3, ZmEBF1). Our findings will broaden the understanding of the genetic structure of the tolerance to Zn deficiency in maize

Effects of Soil Aeration and Fertilization Practices on Alleviating Iron Deficiency Chlorosis in “Huangguan” Pears Grafted onto Quince A in Calcareous Soils

In North China, the high-quality pear cultivar “Huangguan” (Pyrus bretschneideri Rehd. cv), which is grafted onto dwarf quince A (Cydonia oblonga Mill. cv) rootstock and grown in calcareous soil, experiences severe iron (Fe) deficiency; this deficiency greatly constrains tree growth as well as fruit yield and quality. Therefore, we evaluated the effects of six practices for alleviating chlorosis caused by Fe deficiency in “Huangguan” grafted onto quince A (HG-QA). The practices included ridging with landscape fabric mulching as a control, flattening with landscape fabric mulching (FM), ridging without landscape fabric mulching (R), flattening without landscape fabric mulching (F), Fe fertilizer application in soil (SFe), foliar Fe application (FFe), and manure application (M). The results showed that the leaf Fe concentration increased by 356% under FFe, compared to that under the control, but the practice failed to alleviate Fe deficiency chlorosis. In contrast, an increase in leaf Fe concentration and chlorosis alleviation were observed under F. F alleviated chlorosis mainly by increasing the root ferric-chelate reductase activity. These results indicate that Fe uptake and utilization in leaves are independent biochemical processes and soil aeration improvement have positive effect on increasing Fe uptake. M improved both the soil active Fe concentration and leaf Fe utilization. Thus, manure application should be the first choice for alleviating Fe deficiency chlorosis in HG-QA grown in calcareous soils. Combining manure application with other practices that increase Fe uptake would likely be an effective way to address the problem of Fe deficiency chlorosis