Potted experiments of rice (Oryza sativa L.) plants were conducted to produce various scales of brown planthopper [Nilaparvata lugens (Stål), Homoptera:Delphacidae] and leaffolder [Cnaphalocrosis medinalis Guenee (Lep., Pyralidae)] infestations, respectively, for canopy hyperspectral reflectance measurements, and then to identify spectral characteristics (SCs) associated with insect infestations leading to the establishment of spectral models for severity assessment. By linear correlation intensity analysis, correlation coefficients (r) along the spectral domain of 350 to 2400 nm were determined and narrow bands related to infestation severity were selected as SCs. The reflectance at green light (490–560 nm) maximum (RGREEN), red light (640–740 nm) minimum (RRED), and near‐infrared (740–1300 nm) peak (RNIR) were also considered. For canopies infested with brown planthopper, r value at 426 nm was the highest (r = 0.878**). Among the calculated spectral indices using two SCs, the determination coefficient of RNIR/RRED ratio was the highest (R2 = 0.922, P < 0.001). For leaffolder infested canopies, the most negative r value located at 757 nm (r = −0.613*) in active tillering stage but shifted to 445 nm (r = −0.928**) in heading stage. The index RNIR − RRED in the active tillering increased R2 value to 0.422 (P < 0.001), while no increase in R2 was found in the examined SIs in heading stage. Models with more than two SCs yielded from multiple linear regression analysis exhibited a further improvement for discriminating infestation severity.

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Secondary branch number per panicle plays a crucial role in regulating grain number and yield in rice. Here, we report the positional cloning and functional characterization for SECONDARY BRANCH NUMBER7 (qSBN7), a quantitative trait locus affecting secondary branch per panicle and grain number. Our research revealed that the causative variants of qSBN7 are located in the distal promoter region of FRIZZLE PANICLE (FZP), a gene previously associated with the repression of axillary meristem development in rice spikelets. qSBN7 is a novel allele of FZP that causes an ∼56% decrease in its transcriptional level, leading to increased secondary branch and grain number, and reduced grain length. Field evaluations showed that qSBN7 increased grain yield by 10.9% in a temperate japonica variety, TN13, likely due to its positive effect on sink capacity. Our findings suggest that incorporation of qSBN7 can increase yield potential and improve the breeding of elite rice varieties.

Secondary branch number (SBN) is an important component affecting spikelet number per panicle (SPP) and yield in rice. During recurrent backcross breeding, four BC2F4 populations derived from the high-yield donor parent IR65598-112-2 and the recurrent parent Tainan 13 (a local japonica cultivar) showed discontinuous variations of SPP and SBN within populations. Genetic analysis of 92 BC2F4 individuals suggested that both SPP and SBN are controlled by a single recessive allele. Two parents and 37 BC2F4 individuals showing high- and low-SBN type phenotypes were analyzed by restriction-site associated DNA sequencing (RAD-seq). Based on 2,522 reliable SNPs, the qSBN7 was mapped to a distal region of the long arm of chromosome 7. Trait-marker association analysis with an additional 166 high-SBN type BC2F4 individuals and 8 newly developed cleaved amplified polymorphic sequence markers further delimited the qSBN7 locus to a 601.4-kb region between the markers SNP2788 and SNP2849. Phenotype evaluation of two BC2F5 backcross inbred lines revealed that qSBN7 increased SPP by 83.2% and SBN by 61.0%. The qSBN7 of IR65598-112-2 could be used for improving reproductive sink capacity in rice.

Rice blast caused by Magnaporthe oryzae is a dangerous threat to rice production and food security worldwide. Breeding and proper deployment of resistant varieties are effective and environment-friendly strategies to manage this notorious disease. However, highly dynamic and quickly evolved rice blast pathogen population in the field has made disease control with resistance germplasms more challenging. Therefore, continued monitor of pathogen dynamics and application of effective resistance varieties are critical tasks to prolong or sustain field resistance. Here, we report a team project involved evaluation of rice blast resistance genes and surveillance of M. oryzae field population in Taiwan. A set of IRBLs (International Rice Research Institute-bred blast-resistant lines) carrying single blast resistance genes were utilized to monitor the field effectiveness of rice blast resistance. Resistance genes such as Ptr (formerly Pita2) and Pi9 exhibited best and durable resistance against rice blast fungus population in Taiwan. Interestingly, IRBLb-B line harboring Pib gene with good field protection has recently shown susceptible lesions in some locations. To dissect the genotypic features of virulent isolates against Pib resistance gene, M. oryzae isolates were collected and analyzed. Screening of AvrPib locus revealed that majority of field isolates still maintained the wild type AvrPib status, but eight virulent genotypes were found. Pot3 insertion appeared to be a major way to disrupt the AvrPib avirulence function. Interestingly, a novel AvrPib double allele genotype among virulent isolates was first identified. Pot2 rep-PCR fingerprinting analysis indicated mutation events may occur independently among different lineages in different geographic locations of Taiwan. This study provides our surveillance experience of rice blast disease and serves as the foundation to sustain rice production.