Construction of EMS-Induced Peanut Mutant Libraries and Identification of Pod-Related Traits Mutant Lines

Peanut(Arachis hypogaea L.)is an oil and economic crop of vital importance,and peanut pod is the key organ influencing the yield and processing quality.Hence,the Pod-related traits(PRTs)are considered as important agronomic traits in peanut breeding.To broaden the variability of PRTs in current peanut germplasms,three elite peanut cultivars were used to construct Ethyl methane sulfonate(EMS)-induced mutant libraries in this study.The optimal EMS treatment conditions for the three peanut varieties were determined.It was found that the median lethal dose(LD50)of EMS treatment varied greatly among different genotypes.Finally,the EMS-induced peanut mutant libraries were constructed and a total of 124 mutant lines for PRTs were identified and evaluated.Furthermore,“M-8070”,one of the mutant lines for pod constriction,was re-sequenced via high-throughput sequencing technology.The genome-wide variations between“M-8070”and its wild parent“Fuhua 8”(FH 8)were detected.2994 EMS-induced single nucleotide polymorphisms(SNPs)and 1188 insertion-deletions(InDels)between“M-8070”and its wild parent were identified.The predominant SNP mutation type was C/G to T/A transitions,while the predominant InDel mutation type was“1-bp”.We analyzed the distribution of identified mutations and annotated their functions.Most of the mutations(91.68%of the SNPs and 77.69%of the InDels)were located in the intergenic region.72 SNPs were identified in the exonic region,leading to 27 synonymous,43 nonsynonymous and 2 stop-gain variation for gene structure.13 Indels were identified in the exonic region,leading to 4 frame-shift,8 non-frame-shift and 1 stop-gain variations of genes.These mutations may lead to the phenotypic variation of“M-8070”.Our study provided valuable resources for peanut improvement and functional genomic research.

Determination of Heterotic Groups and Heterosis Analysis of Yield Performance in indica Rice

To compare the heterosis levels among various groups of parental lines used extensively in China, identify foundational heterotic groups in parental pools and understand the relationship between genetic distance and heterosis performance, 16 parental lines with extensive genetic variation were selected from various sub-groups, and 39 hybrid combinations were generated and evaluated in Fujian and Hainan Provinces of China. The main results were as follows： （1） The 16 parental lines can be grouped into 7 sub-groups consisting of 1 maintainer sub-group and 6 restorer sub-groups; （2） Mean grain yield of the restorer lines was higher than that of the maintainer lines, and mean yield of parental lines was higher than that of the hybrid combinations; （3） The two best heterotic patterns were II-32A × G5 and II-32A × G6, moreover, the order of restorer sub-groups according to grain yield, from the highest to lowest, was G7, G6, G5, G4, G3 and G2; High specific combining ability values were observed for combinations of II-32A × G5, II-32A × G6 and Tianfeng A × G7; （4） Hybrid combinations derived from II-32A crossed with 13 restorer lines had higher yield trait values （mid-parent heterosis, better-parent heterosis, standard heterosis over check and specific combining ability） than any other combinations; （5） Genetic distance was positively correlated with panicle number, grain length and length-to-width ratio （P 〈 0.05） and negatively correlated with grain width, grain yield, seed-setting rate, as well as mid-parent heterosis, standard heterosis over check, and specific combining ability for grain yield （P 〈 0.01）. These heterotic groups and patterns and their argonomic traits will provide useful information for future hybrid rice breeding programs.

SH3P2,an SH3 domain-containing protein that interacts with both Pib and AvrPib,suppresses effector-triggered,Pib-mediated immunity in rice

Plants usually keep resistance(R)proteins in a static state under normal conditions to avoid autoimmunity and save energy for growth,but R proteins can be rapidly activated upon perceiving pathogen invasion.Pib,the first cloned blast disease R gene in rice,encoding a nucleotide-binding leucine-rich repeat(NLR)protein,mediates resistance to the blast fungal(Magnaporthe oryzae)isolates carrying the avirulence gene AvrPib.However,the molecular mechanisms about how Pib recognizes AvrPib and how it is inactivated and activated remain largely unclear.In this study,through map-based cloning and CRISPR-Cas9 gene editing,we proved that Pib contributes to the blast disease resistance of rice cultivar Yunyin(YY).Furthermore,an SH3 domain-containing protein,SH3P2,was found to associate with Pib mainly at clathrin-coated vesicles in rice cells,via direct binding with the coiled-coil(CC)domain of Pib.Interestingly,overexpression of SH3P2 in YY compromised Pib-mediated resistance to M.oryzae isolates carrying AvrPib and Pib-AvrPib recognition-induced cell death.SH3P2 competitively inhibits the self-association of the Pib CC domain in vitro,suggesting that binding of SH3P2 with Pib undermines its homodimerization.Moreover,SH3P2 can also interact with AvrPib and displays higher affinity to AvrPib than to Pib,which leads to dissociation of SH3P2 from Pib in the presence of AvrPib.Taken together,our results suggest that SH3P2 functions as a“protector”to keep Pib in a static state by direct interaction during normal growth but could be triggered off by the invasion of AvrPib-carrying M.oryzae isolates.Our study reveals a new mechanism about how an NLR protein is inactivated under normal conditions but is activated upon pathogen infection.