Development of Super Hybrid Rice for Food Security in China

The current population in China is over 1.3 billion and will reach 1.4 billion soon.Meanwhile,China's arable land is decreasing year by year.Facing such a severe situation of population-growth pressure plus cropland reduction,it is obvious that the only way to solve the food shortage problem is to greatly enhance the yield level of food crops per unit

OsGRF4 controls grain shape, panicle length and seed shattering in rice

Traits such as grain shape, panicle length and seed shattering, play important roles in grain yield and harvest. In this study, the cloning and functional analysis of PANICLE TRAITS 2 （PT2）, a novel gene from the Indica rice Chuandali （CDL）, is reported. PT2 is synonymous with Growth-Regulating Factor 4 （OsGRF4）, which encodes a growth-regulating factor that positively regulates grain shape and panicle length and negatively regulates seed shattering. Higher expression of OsGRF4 is correlated with larger grain, longer panicle and lower seed shattering. A unique OsGRF4 mutation, which occurs at the OsmiRNA396 target site of OsGRF4, seems to be associated with high levels of OsGRF4 expression, and results in phenotypic difference. Further research showed that OsGRF4 regulated two cytokinin dehydrogenase precursor genes （CKX5 and CKX1） resulting in increased cytokinin levels, which might affect the panicle traits. High storage capacity and moderate seed shattering of OsGRF4 may be useful in high-yield breeding and mechanized harvesting of rice. Our findings provide additional insight into the molecular basis of panicle growth.

Balancing selection and wild gene pool contribute to resistance in global rice germplasm against planthopper

Interactions and co-evolution between plants and herbivorous insects are critically important in agriculture.Brown planthopper(BPH)is the most severe insect of rice,and the biotypes adapt to feed on different rice genotypes.Here,we present genomics analyses on 1,520 global rice germplasms for resistance to three BPH biotypes.Genome-wide association studies identified 3,502 single nucleotide polymorphisms(SNPs)and 59 loci associated with BPH resistance in rice.We cloned a previously unidentified gene Bph37 that confers resistance to BPH.The associated loci showed high nucleotide diversity.Genome-wide scans for trans-species polymorphisms revealed ancient balancing selection at the loci.The secondarily evolved insect biotypes II and III exhibited significantly higher virulence and overcame more rice varieties than the primary biotype I.In response,more SNPs and loci evolved in rice for resistance to biotypes II and III.Notably,three exceptional large regions with high SNP density and resistance-associated loci on chromosomes 4 and 6 appear distinct between the resistant and susceptible rice varieties.Surprisingly,these regions in resistant rice might have been retained from wild species Oryza nivara.Our findings expand the understanding of long-term interactions between rice and BPH and provide resistance genes and germplasm resources for breeding durable BPH-resistant rice varieties.

Lipidomic analyses reveal enhanced lipolysis in planthoppers feeding on resistant host plants

The brown planthopper(BPH)(Nilaparvata lugens St?l)is a highly destructive pest that seriously damages rice(Oryza sativa L.)and causes severe yield losses.To better understand the physiological and metabolic mechanisms through which BPHs respond to resistant rice,we combined mass-spectrometry-based lipidomics with transcriptomic analysis and gene knockdown techniques to compare the lipidomes of BPHs feeding on either of the two resistant(NIL-Bph6 and NIL-Bph9)plants or a wild-type,BPH susceptible(9311)plant.Insects that were fed on resistant rice transformed triglyceride(TG)to phosphatidylcholine(PC)and digalactosyldiacylglycerol(DGDG),with these lipid classes showing significant alterations in fatty acid composition.Moreover,the insects that were fed on resistant rice were characterized by prominent expression changes in genes involved in lipid metabolism processes.Knockdown of the NlBmm gene,which encodes a lipase that regulates the mobilization of lipid reserves,significantly increased TG content and feeding performance of BPHs on resistant plants relative to dsGFP-injected BPHs.Our study provides the first detailed description of lipid changes in BPHs fed on resistant and susceptible rice genotypes.Results from BPHs fed on resistant rice plants reveal that these insects can accelerate TG mobilization to provide energy for cell proliferation,body maintenance,growth and oviposition.