Identification of a pleiotropic QTL cluster for Fusarium head blight resistance,spikelet compactness,grain number per spike and thousand-grain weight in common wheat

Simultaneously improving Fusarium head blight(FHB)resistance and grain yield is challenging in wheat breeding.The correlations between spikelet compactness(SC),grain number per spike(GNS),thousandgrain weight(TGW)and FHB resistance remains unclear in common wheat.Identification of major quantitative trait loci(QTL)conferring FHB resistance and yield components,and development of breeder-friendly markers for the QTL are prerequisites for marker-assisted selection(MAS).Here,a recombinant inbred line(RIL)population derived from a cross between a resistant cultivar Yangmai 12(YM12)and a susceptible cultivar Yanzhan 1(YZ1)was used to map QTL for FHB resistance and yield components.A total of 22 QTL were identified;among these,six are likely to be new for corresponding traits.A QTL cluster(Qclu.yas-2D)for FHB type II resistance,SC,GNS,and TGW was detected on chromosome 2D.Breeder-friendly kompetitive allele-specific PCR(KASP)markers flanking the interval of Qclu.yas-2D were developed and validated in a diverse panel of 166 wheat cultivars and advanced lines.The YM12 alleles of Qclu.yas-2D significantly increased FHB resistance,SC,and GNS but decreased TGW in the validation population.The KASP markers developed for Qclu.yas-2D have great potential for breeding high-yielding wheat cultivars with enhanced FHB resistance.

Influence of water potential and soil type on conventional japonica super rice yield and soil enzyme activities

We carried out a pool culture experiment to determine the optimal water treatment depth in loam and clay soils during the late growth stage of super rice. Three controlled water depth treatments of 0-5, 0-10 and 0-15 cm below the soil surface were established using alternate wetting and drying irrigation, and the soil water potential （0 to -25 kPa） was measured at 5, 10 and 15 cm. A 2-cm water layer was used as the control. We measured soil enzyme activities, root antioxidant enzyme activities, chlorophyll fluorescence parameters, and rice yield. The results showed that the 0-5-cm water depth treatment significantly increased root antioxidant enzyme activities in loam soil compared with the control, whereas soil enzyme activities, chlorophyll fluorescence parameters and yield did not differ from those of the control. The 0-10- and 0-15-cm water depth treatments also increased root antioxidant enzyme activities, whereas soil enzyme activities, chlorophyll fluorescence parameters and yield decreased. In clay soil, the soil enzyme activities, root antioxidant enzyme activities, chlorophyll fluorescence parameters, and yield did not change with the 0-5-cm water treatment, whereas the 0-10- and 0-15-cm water treatments improved these parameters. Therefore,the appropriate depths for soil water during the late growth period of rice with a 0 to -25 kPa water potential were 5 cm in loam and 15 cm in clay soil.

Characterization and map-based cloning of miniature2-m1, a gene controlling kernel size in maize

Kernel development plays an important role in determining kernel size in maize.Here we present the cloning and characterization of a maize gene,nitrate transporter1.5(NRT1.5),which controls small kernel phenotype by playing an important role in kernel development.A novel recessive small kernel mutant miniature2-m1(mn2-m1)was isolated from self-pollinated progenies of breeding materials.The mutant spontaneously showed small kernel character arresting both embryo and endosperm development at an early stage after pollination.Utilizing 21 polymorphic SSR markers,the mn2-m1 locus was limited to a 209.9-kb interval using 9176 recessive individuals of a BC1 segregating population from mn2-m1/B73.Only one annotated gene was located in this 209.9 kb region,Zm00001 d019294,which was predicted to encode nitrate transporter1.5(NRT1.5).Allelism tests confirmed that mn2-m1 was allelic to miniature2-m2(mn2-m2)and miniature2-710 B(mn2-710 B).The mn2-m1 and mn2-m2 alleles both had nucleotide deletions in the coding region resulting in premature termination,and the mn2-710 B allele had some missence mutations.Subcellular localization showed that Miniature 2(MN2)is localized in the plasma membrane.Quantitative real-time PCR(qRT-PCR)analysis revealed that the expression of MN2 and some genes involved in the basal endosperm transfer layer(BETL)and embryo surrounding region(ESR)development were affected in mn2-m1 seeds.These results suggested that MN2 plays an important role in maize seed development.

Agronomic characterization and genetic analysis of the supernume-r ary spikelet in tetraploid wheat(Triticum turgidum L.)

The supernumerary spikelets（SS）characters of tetraploid wheat（Triticum turgidum L.）resulting in more spikelets and kernels per spike,thus enhancing sink capacity may contribute to potential wheat yield improvement.In order to investigate the effect of different SS types on agronomic characters and understand the genetic base of SS phenotype in tetraploid wheat,near isogenic lines（NILs）,bh-50 with normal spikelets（NS）,bh-51 with four-rowed spikelets（FRS）,bh-52 with short-ramified spikelets（SRS）,and bh-53 with long-ramified spikelets（LRS）in a Triticum durum cv.ZY1286 genetic background were developed by continuous backcrossing.Agronomic characters showed that the SS phenotype lines,bh-51,bh-52and bh-53 have significant increase in the number of spikelets and grains per spike compared with the NS phenotype line bh-50（P〈0.05）,and bh-53 line showed much more increase than those of bh-51 and bh-52.However,bh-53 had the lowest grain weight and the longest spike development stage than those of other spike phenotypes.These results indicated that the different SS types have different effects on the agronomic and spike characters.Genetic analysis through bh-50/bh-51and bh-51/bh-53 F2 populations showed that a recessive major gene controlled the spike architecture to transform from NS to FRS,and a dominant major gene determined the change of spike phenotype from FRS to RS.DNA sequences of Tt BH/WFZP ortholog on chromosome 2AS revealed that a single nucleotide polymorphism（SNP）substitution happened in the open reading frame（ORF）region of all the SS tetraploid wheat accessions,which may lead to the generation of lateral meristems between glume and lemma during the immature spike development.While the fates of the lateral meristems,developing into lateral spikelets or branched spikelets,may be determined by another major gene.Our results presented here may advance our understanding and knowledge of the genes and genetic pathways determining the spike architecture development in wheat.

QTL consistency for agronomic traits across three generations and potential applications in popcorn

Favorable agronomic traits are important to improve productivity of popcorn. In this study, a recombinant inbred line（RIL） population consisting of 258 lines was evaluated to identify quantitative trait loci（QTLs） for nine agronomic traits（plant height, ear height, top height（plant height subtracted ear height）, top height/plant height, number of leaves above the top ear, leaf area, stalk diameter, number of tassel branches and the length of tassel） under three environments. Meta-analysis was conducted then to integrate QTLs identified across three generations（RIL, F2：3 and BC2F2） developed from the same crosses. In total, 179 QTLs and 36 meta-QTLs（m QTL） were identified. The percentage of phenotypic variation（R2） explained by any single QTL varied from 3.86 to 28.4%, and 24 QTLs with contributions over 15%. Nine common QTLs located in the same or similar chromosome regions were detected across three generations. Five meta-QTLs were identified including QTLs in three independent studies. Seven important m QTLs were composed of 11–26 QTLs for 4–7 traits, respectively. Only 11 m QTLs were commonly identified in the same or similar chromosome regions across agronomic traits, popping characteristics（popping fold, popping volume and popping rate） and grain yield components（ear weight per plant, grain weight per plant, 100-grain weight, ear length, kernel number per row, ear diameter, row number per ear and kernel ratio） by meta-QTL analysis. In conclusion, we identified a list of QTLs, some of which with much higher contributions to agronomic traits should be valuable for further study in improving both popping characteristics and grain yield components in popcorn.