Mechanical Harvesting Effects on Seed Yield Loss,Quality Traits and Profitability of Winter Oilseed Rape (Brassica napus L.)

China is one of the most important rapeseed producing countries in the world. Effective mechanical harvesting time for decreasing harvesting loss of winter oilseed rape has been becoming a critical factor. An elite cultivar Zhongshuang 11 （Brassica napus L.） was employed in two rounds of field experiments from 2009 to 2011. Seeds were sown with machine, three combine harvesting times namely combine harvesting A, B, and C （CHA, CHB, and CHC） were designed and manual harvesting （MH） as control was performed at maturity. The harvesting treatments were determined according to color of pod and seed in the field. Seed yield loss and quality in different treatments were evaluated. Results showed that both seed yields and harvesting losses in 2009-2010 were higher than that in 2010-2011, whereas seed oil contents in 2010-2011 were higher than that in 2009-2010. The highest yield appeared in CHB, which was significantly higher than that in MH. Furthermore, harvesting loss in CHB were 50% that in MH. Seed oil content and chlorophyll exhibited no obvious difference between CHB and MH. Economic profit analysis demonstrated that mechanical sowing/combine harvesting （MS/CH） showed an input/output ratio of 1：1.6, and it was 1：1.2 in mechanical sowing/manual harvesting （MS/MH）. Labor-cost accounted for more than 70% of the total cost in MS/MH, which led to low profitability to a great extent. Our results suggested that CHB was the optimum harvesting time for winter oilseed rape along the Yangtze River.

Regulatory Network of Transcription Factors in Response to Drought in Arabidopsis and Crops

Drought is one of the most important environmental constraints limiting plant growth, development and crop yield. Many drought-inducible genes have been identified by molecular and genomic analyses in Arabidopsis, rice and other crops. To better understand reaction mechanism of plant to drought tolerance, we mainly focused on introducing the research of transcription factors （TFs） in signal transduction and regulatory network of gene expression conferring drought. A TF could bind multiple target genes to increase one or more kinds of stress tolerance. Sometimes, several TFs might act together with a target gene. So drought-tolerance genes or TFs might respond to high-salinity, cold or other stresses. The crosstalk of multiple stresses signal pathways is a crucial aspect of understanding stress signaling.

DOF transcription factors in developing peanut (<i>Arachis hypogaea</i>) seeds

DNA binding with one finger (DOF) transcription factors play important roles in storage material accumulation and morphogenesis of developing seeds. Oil and protein contents varied in different cultivars in important oil crop peanut. DOF proteins have not been studied in this crop. In this paper, we analyzed all the DOF genes expressed in developing seeds from a cDNA library with 20,000 transcripts, cloned and compared similar genes of GW391729 from eight peanut cultivars, and analyzed similar genes expressed in root and leave with control and inoculated with Ralstonia solanacearum. The results indicate that total eight types of DOF genes were expressed in developing seeds of cultivar 063103. Most of DOF transcription factors expressed involved in developmental process in a complicated way. Among them, GW391729 is possible related to the seed number in fruit, and also is possible related to leafspot resistance. Detailed function of these DOF proteins need to be further studied.

Estimation of chlorophyll content in Brassica napus based on unmanned aerial vehicle images

The chlorophyll content has a direct effect on photosynthesis of crops.In order to explore a quick and convenient method for estimating the chlorophyll content of Brassica napus and facilitate efficient crop monitoring,we measured the actual value of chlorophyll with a SPAD-502 chlorophyll detector,and collected aerial images of B.napus with an unmanned aerial vehicle(UAV)carrying a RGB camera in this study.The total number of 270samples collected images were divided into regions according to the planting conditions of different B.napus varieties in the field.Then,according to the empirical formula,there were 36 colors’characteristic parameters calculated and combined.To estimate the chlorophyll content of rape,189 samples were included in the modeling set,while the other 81 samples were enrolled in the validation set for testing the accuracy of this model.After the combination of R(red),G(green)and B(blue)color channels,the results showed that the color characteristics B/(R+G),b,B/G,(G-B)/(G+B),g-b were highly connected with the measured value of chlorophyll SPAD,and the correlation coefficient between the combination based on B/(R+G)and SPAD value was 0.747.With R2=0.805,RMSE=3.343,and RE=6.84%,the regression model created using random forest had superior outcomes,according to the model comparison.This study offers a new method for quickly estimating the amount of chlorophyll in rapeseed and a workable reference for crop monitoring using the UAV platform.

Foliar K application delays leaf senescence of winter rapeseed(Brassica napus L.) under waterlogging

To better understand waterlogging effect on leaf senescence in winter rapseed (Brassica napus L.) during flowering stage, experiments were designed to explore foliar K application influences on adverse effects of waterlogging stress. Winter rapeseed was sprayed with K after waterlogging at initial flowering stage. Results indicated that waterlogging significantly decreased leaf net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr). It also declined maximum quantum yield of PS II (Fv/Fm), quantum yield of electron transport (ΦPS II) and photochemical quenching (qP), but increased leaf non-photochemical quenching (NPQ) and minimal fluorescence (Fo). Interestingly, exogenous application of K significantly alleviated waterlogging-induced photosynthesis inhibition. Foliar K application increased RuBisCO activation, chlorophyll and soluble protein contents, while significantly decreased MDA content under waterlogging stress. Moreover, K supplementation improved accumulation of K+, Ca2+, Mg2+, N, Zn2+, Mn2+, Fe2+ in leaves. In general, foliar K application is effective inalleviating deleterious effects of waterlogging stress and delays leaf senescence of winter rapeseed.

Development and validation of simple sequence repeat markers from Arachis hypogaea transcript sequences

Simple sequence repeats(SSRs) are important molecular markers for assessing genetic diversity in Arachis hypogaea L. and many other crops and constructing genetic linkage maps for important agricultural traits. In this study, 29,357 potential SSRs were identified in 22,806 unigenes assembled from A. hypogaea transcript sequences. Of these unigenes, 1883 and 4103 were annotated and assigned in Kyoto Encyclopedia of Genes and Genomes Orthology and Eukaryotic Orthologous Groups databases, respectively. Among the SSR motifs, mono-(19,065; 64.94%) and trinucleotide(5033; 17.14%) repeats were the most common, and the three most dominant motifs were A/T(18,358; 62.54%), AG/CT(2804;9.55%), and AAG/CTT(1396; 4.76%). Polymerase chain reaction(PCR) primer pairs were designed for 4340 novel SSR markers and 210 new SSRs were validated using 24 A. hypogaea varieties. Of the 210, 191(91%) yielded PCR products, with 37(18%) identifying polymorphisms. The 37 polymorphic SSR markers detected 146 alleles(2–10 alleles per locus), and the average polymorphic information content was 0.403(with a range of 0.077 to0.819). The new SSRs enrich the current marker resources for A. hypogaea and may also be useful for genetic diversity analysis, functional genomics research, and molecular breeding.

Characterization of the petiole length in soybean compact architecture mutant M657 and the breeding of new lines

Phenotypic screening of soybean germplasm suitable for high planting density is currently the most viable strategy to increase yield. Previous studies have shown that soybean varieties with dwarf features and a short petiole often exhibit a compact plant architecture which could improve yield through increased planting density, although previously reported short petiole accessions were ultimately not usable for breeding in practice. Here, we established a method to assess petiole length and identified an elite mutant line, M657, that exhibits high photosynthetic efficiency. The agronomic traits of M657 were evaluated under field conditions, and appeared to be stable for short petiole across seven locations in northern, Huang–Huai, and southern China from 2017 to 2018. Compared with the Jihuang 13 wild type, the mutant M657 was shorter in both petiole length and plant height, exhibited lower total area of leaf, seed weight per plant and 100-seed weight, but had an increased number of effective branches and the growth period was prolonged by 2–7 days. Using M657 as a parental line for crosses with four other elite lines, we obtained four lines with desirable plant architecture and yield traits, thus demonstrating the feasibility of adopting M657 in breeding programs for soybean cultivars of high density and high yield.

Herbivore defense responses and associated herbivore defense mechanism as revealed by comparing a resistant wild soybean with a susceptible cultivar

Plants have evolved sophisticated defense mechanisms against herbivores to help them adapt to the environment. Understanding the defense mechanisms in plants can help us control insects in a more effective manner. In this study, we found that compared with Tianlong 2(a cultivated soybean with insect susceptibility), ED059(a wild soybean line with insect resistance)contains sharper pubescence tips, as well as lower transcript levels of wound-induced protein kinase(WIPK) and salicylic acid-induced protein kinase(SIPK), which are important mitogen-activated protein kinases involved in early defense response to herbivores. The observed lower transcript levels of WIPK and SIPK induced higher levels of jasmonic acid(JA), JA biosynthesis enzymes(AOC3) and some secondary metabolites in ED059. Functional analysis of the KTI1 gene via Agrobacterium-mediated transformation in Arabidopsis thaliana indicated that it plays an important role in herbivore defense in ED059. We further investigated the molecular response of third-instar Helicoverpa armigera(Hübner) larvae to Tianlong 2 and ED059. We found apoptotic cells only in the midguts of larvae that fed on ED059. Compared with larvae reared on the susceptible cultivar Tianlong 2, transcript levels of catalase(CAT) and glutathione S-transferase(GST) were up-regulated, whereas those of CAR, CHSB, and TRY were down-regulated in larvae that fed on the highly resistant variety ED059. We propose that these differences underlie the different herbivore defense responses of ED059 and Tianlong 2.

Unraveling waterlogging tolerance-related traits with QTL analysis in reciprocal intervarietal introgression lines using genotyping by sequencing in rapeseed(Brassica napus L.)

Soil waterlogging is a major environmental stress that suppresses the growth and productivity of rapeseed(Brassica napus L.).Natural genetic variations in waterlogging tolerance(WT)were observed but no QTL mapping has been done for WT related traits in rapeseed.In this study,QTL associated with three WT related traits including relative root length(RRL),relative hypocotyl length(RHL)and relative fresh weight(RFW)were dissected using a set of reciprocal introgression lines(ILs)derived from the cross GH01×ZS9,which showed significant difference in WT.Genotyping-by-sequencing(GBS)of the populations were performed,totally 1468 and 1450 binned SNPs were identified for GIL(GH01 as the recurrent parent)and ZIL(ZS9 as the recurrent parent)population,respectively.A total of 66 distinct QTLs for WT at the seedling establishment stage including 31 for RRL,17 for RHL and 18 for RFW were detected.Among the 66 QTLs,20(29.4%)QTLs were detected in both genetic backgrounds and then they were integrated into six QTL clusters,which can be targeted in rapeseed breeding for improvement of WT through marker-assisted selection(MAS).Based on the physical positions of SNPs and the functional annotation of the Arabidopsis thaliana genome,56 genes within the six QTL cluster regions were selected as preliminary candidate genes,then the resequencing and transcriptome information about parents were applied to narrow the extent of candidate genes.Twelve genes were determined as candidates for the six QTL clusters,some of them involved in RNA/protein degradation,most of them involved in oxidation-reduction process.These findings provided genetic resources,candidate genes to address the urgent demand of improving WT in rapeseed breeding.

A Domestication-Associated Gene GmPRR3b Regulates the Circadian Clock and Flowering Time in Soybean

Improved soybean cultivars have been adapted to grow at a wide range of latitudes,enabling expansion of cultivation worldwide.However,the genetic basis of this broad adaptation is still not clear.Here,we report the identification of GmPRR3b as a major flowering time regulatory gene that has been selected during domestication and genetic improvement for geographic expansion.Through a genome-wide association study of a diverse soybean landrace panel consisting of 279 accessions,we identified 16 candidate quantitative loci associated with flowering time and maturity time.The strongest signal resides in the known flowering gene E2,verifying the effectiveness of our approach.We detected strong signals associated with both flowering and maturity time in a genomic region containing GmPRR3b.Haplotype analysis revealed that GmPRR3bH6 is the major form of GmPRR3b that has been utilized during recent breeding of modern cultivars.mRNA profiling analysis showed that GmPRR3bH6 displays rhythmic and photoperiod-dependent expression and is preferentially induced under long-day conditions.Overexpression of GmPRR3bH6 increased main stem node number and yield,while knockout of GmPRR3bH6 using CRISPR/Cas9 technology delayed growth and the floral transition.GmPRR3bH6 appears to act as a transcriptional repressor of multiple predicted circadian clock genes,including GmCCAIa,which directly upregulates J/GmELF3a to modulate flowering time.The causal SNP(Chr12:5520945)likely endows GmPRR3bH6 a moderate but appropriate level of activity,leading to early flowering and vigorous growth traits preferentially selected during broad adaptation of landraces and improvement of cultivars.

Rationalizing the isolation distance needed for field trials involving genetically modified rapeseed (Brassica napus L.) in China

The isolation distance required for field trials of genetically modified (GM) rapeseed varies widely worldwide, with a 50-400 m distance in most nations contrasting with a minimum 1000-m isolation distance in China. The goal of this study was to evaluate the relevance of current regulations in China regarding the isolation distance needed for GM rapeseed trials. A pollen flow experiment was conducted based on the design of concentric circles, with the GM plants in a 20-m diameter circle at the centre, surrounded by non-GM plants to a distance 60 m from the perimeter of the circle containing GM plants. The rate of pollen flow was the highest at the isolation distance of 0.5 m, where it ranged from 2.3091% to 2.6711%. The general pattern of the pollen flow rate (y) with distance (x) was well described by the equation y = 1.3936x-0.9136 (R 2 = 0.9950). The long-distance pollen flow tested at the isolation distance of 800 m was 0.0018%, which agrees with the theoretical prediction. The results suggested that 300 m, rather than 1000 m, is a reasonable distance to ensure a tolerable threshold of pollen flow (less than 0.01%) under conditions of winter rapeseed production in China.