Rice direct seeding has the significant potential to save labor and water, conserve environmental resources, and reduce greenhouse gas emissions tremendously.  Therefore, rice direct seeding is becoming the major cultivation technology applied to rice production in many countries.  Identifying and utilizing genes controlling mesocotyl elongation is an effective approach to accelerate breeding procedures and meet the requirements for direct-seeded rice (DSR) production.  This study used a permanent mapping population with 144 recombinant inbred lines (RILs) and 2 828 bin-markers to detect quantitative trait loci (QTLs) associated with mesocotyl length in 2019 and 2020.  The mesocotyl lengths of the rice RILs and their parents, Lijiangxintuanheigu (LTH) and Shennong 265 (SN265), were measured in a growth chamber at 30°C in a dark environment.  A total of 16 QTLs for mesocotyl length were identified on chromosomes 1(2), 2(4), 3(2), 4, 5, 6, 7, 9, 11(2), and 12.  Seven of these QTLs, including qML1a, qML1b, qML2d, qML3a, qML3b, qML5, and qML11b, were reproducibly detected in both years via the interval mapping method.  The major QTL, qML3a, was reidentified in two years via the composite interval mapping method.  A total of 10 to 413 annotated genes for each QTL were identified in their smallest genetic intervals of 37.69 kb to 2.78 Mb, respectively.  Thirteen predicted genes within a relatively small genetic interval (88.18 kb) of the major mesocotyl elongation QTL, qML3a, were more thoroughly analyzed.  Finally, the coding DNA sequence variations among SN265, LTH, and Nipponbare indicated that the LOC_Os03g50550 gene was the strongest candidate gene for the qML3a QTL controlling the mesocotyl elongation.  This LOC_Os03g50550 gene encodes a mitogen-activated protein kinase.  Relative gene expression analysis using qRT-RCR further revealed that the expression levels of the LOC_Os03g50550 gene in the mesocotyl of LTH were significantly lower than in the mesocotyl of SN265.  In conclusion, these results further strengthen our knowledge about rice’s genetic mechanisms of mesocotyl elongation.  This investigation’s discoveries will help to accelerate breeding programs for new DSR variety development.

One of the most important objectives for breeders is to develop high-yield cultivars.  The increase in crop yield has met with bottlenecks after the first green revolution, and more recent efforts have been focusing on achieving high photosynthetic efficiency traits in order to enhance the yield.  Leaf shape is a significant agronomic trait of upland cotton that affects plant and canopy architecture, yield, and other production attributes.  The major leaf shape types, including normal, sub-okra, okra, and super-okra, with varying levels of lobe severity, are controlled by a multiple allelic series of the D-genome locus L-D₁.  To analyze the effects of L-D₁ alleles on leaf morphology, photosynthetic related traits and yield of cotton, two sets of near isogenic lines (NILs) with different alleles were constructed in Lumianyan 22 (LMY22) and Lumianyan 28 (LMY28) backgrounds.  The analysis of morphological parameters and the results of virus-induced gene silencing (VIGS) showed that the regulation of leaf shape by L-D₁ alleles was similar to a gene-dosage effect.  Compared with the normal leaf, deeper lobes of the sub-okra leaf improved plant canopy structure by decreasing the leaf area index (LAI) and increasing the light transmittance rate (LTR), and the mid-range LAI of sub-okra leaf also guaranteed the accumulation of cotton biomass.  Although the chlorophyll content (SPAD) of sub-okra leaf was lower than those of the other two leaf shapes, the net photosynthetic rate (P_n) of sub-okra leaf was higher than those of okra leaf and normal leaf at most stages.  Thus, the improvements in canopy structure, as well as photosynthetic and physiological characteristics, contributed to optimizing the light environment, thereby increasing the total biomass and yield in the lines with a sub-okra leaf shape.  Our results suggest that the sub-okra leaf may have practical application in cultivating varieties, and could enhance sustainable and profitable cotton production.

    Coated controlled-release fertilizers (CRFs) have been widely applied in agriculture due to their increased efficiency. However, the widespread and a lot of coated CRFs application may leave undesired coating residues in the soil due to their slow degradation. Limited information is available on the effects of substantial residual coatings on the soil bacterial community. By adding 0, 5, 10, 20, and 50 times quantities of residual coating from conventional application amount of resin and water-soluble coated CRFs, we studied the responses of soil properties and bacterial community composition to these two residual coatings in black soil. The results showed that the resin and water-soluble coatings did not essentially alter the properties of black soil or cause dramatic changes to bacterial diversity within the test concentration range. The residual resin and water-soluble coatings also did not distinctly alter the relative abundance of the top ten bacteria at phylum level. Heatmap results suggested that the treatments were basically clustered into two groups by concentration rather than types of coating material. Pearson correlation analysis showed that the Simpson’s diversity index of the bacterial community was significantly correlated with microbial biomass carbon (MBC, r=0.394, P<0.05), and the richness index abundance-based coverage estimator (ACE) of the bacterial community was significantly correlated with microbial biomass nitrogen (MBN, r=0.407, P<0.05). Overall, results of this study suggested that substantial residual resin and water-soluble coatings with 0–50 times quantities of residual coating from conventional application amount of coated CRFs did not generate obviously negative impacts on the bacterial community in black soil.