Effect of Leaf Phosphorus and Potassium Concentration on Chlorophyll Meter Reading in Rice

Chlorophyll meter (SPAD) is a convenient tool to estimate leaf nitrogen (N) concentration of rice plants. There is no information on the effects of leaf phosphorus (P) and potassium (K) concentration on SP AD readings and on the relationship between SPAD values and leaf N concentration in the literature. In 1996 dry season, cv IR72 was grown at the International Rice Research Institute (IRRI) and the Philippine Rice Research Institute (PhilRice) under various N, P and K fertilizer combinations. SPAD measurements were made on the topmost fully expanded leaves at mid-tillering and panicle initiation. The leaves were then detached, dried and analyzed for N, P and K. The SPAD values were highly correlated with leaf N concentration (r = 0.93 to 0.96). Fertilizer-K application did not affect SP AD values, leaf N concentration, or the relationship between the two. Phosphorus deficiency reduced leaf N concentration at mid-tillering, but increased leaf N concentration at panicle initiation when the same amount of N was applied. The SPAD values were 1 to 2 units greater for zero-P plants than P-treated plants at a given leaf N concentration at mid-tillering. At panicle initiation, the relationship between SPAD values and leaf N concentration was not significantly affected by leaf P status. These results suggest that a different regression equation between SP AD values and leaf N concentration should be used to estimate leaf N concentration of P-deficient and P-sufficient rice leaves at vegetative stage using a SPAD

Rice yields decline with higher night temperature from global warming

The impact of projected global warming on crop yields has been evaluated by indirect methods using simulation models. Direct studies on the effects of observed climate change on crop growth and yield could provide more accurate information for assessing the impact of climate change on crop production. We analyzed weather data at the International Rice Research Institute Farm from 1979 to 2003 to examine temperature trends and the relationship between rice yield and temperature by using data from irrigated field experiments conducted at the International Rice Research Institute Farm from 1992 to 2003. Here we report that annual mean maximum and minimum temperatures have increased by 0.35°C and 1.13°C, respectively, for the period 1979–2003 and a close linkage between rice grain yield and mean minimum temperature during the dry cropping season (January to April). Grain yield declined by 10% for each 1°C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant. This report provides a direct evidence of decreased rice yields from increased nighttime temperature associated with global warming

The Chamber for Studying Rice Response to Elevated Nighttime Temperature in Field

An in situ temperature-controlled field chamber was developed for studying a large population of rice plant under different nighttime temperature treatments while maintaining conditions similar to those in the field during daytime. The system consists of a pipe hoop shed-type chamber with manually removable covers manipulated to provide a natural environment at daytime and a relatively stable and accurate temperature at night. Average air temperatures of 22.4 ± 0.3°C at setting of 22°C, 27.6 ± 0.4°C at 27°C, and 23.8 ± 0.7°C ambient conditions were maintained with the system. No significant horizontal and vertical differences in temperature were found and only slight changes in water temperatures were observed between the chambers and ambient conditions at 36 days after transplanting. A slight variation in CO2 concentration was observed at the end of the treatment during the day, but the 10-μmol CO2 mol−1 difference was too small to alter plant response. The present utilitarian system, which only utilizes an air conditioner/heater, is suitable for studying the effect of nighttime temperature on plant physiological responses with minimal perturbation of other environmental factors. At the same time, it will enable in situ screening of many rice genotypes

Effect of Leaf Phosphorus and Potassium Concentration on Chlorophyll Meter Reading in Rice

Chlorophyll meter (SPAD) is a convenient tool to estimate leaf nitrogen (N) concentration of rice plants. There is no information on the effects of leaf phosphorus (P) and potassium (K) concentration on SP AD readings and on the relationship between SPAD values and leaf N concentration in the literature. In 1996 dry season, cv IR72 was grown at the International Rice Research Institute (IRRI) and the Philippine Rice Research Institute (PhilRice) under various N, P and K fertilizer combinations. SPAD measurements were made on the topmost fully expanded leaves at mid-tillering and panicle initiation. The leaves were then detached, dried and analyzed for N, P and K. The SPAD values were highly correlated with leaf N concentration (r = 0.93 to 0.96). Fertilizer-K application did not affect SP AD values, leaf N concentration, or the relationship between the two. Phosphorus deficiency reduced leaf N concentration at mid-tillering, but increased leaf N concentration at panicle initiation when the same amount of N was applied. The SPAD values were 1 to 2 units greater for zero-P plants than P-treated plants at a given leaf N concentration at mid-tillering. At panicle initiation, the relationship between SPAD values and leaf N concentration was not significantly affected by leaf P status. These results suggest that a different regression equation between SP AD values and leaf N concentration should be used to estimate leaf N concentration of P-deficient and P-sufficient rice leaves at vegetative stage using a SPAD

The blaster: A methodology to induce rice lodging at plot scale to study lodging resistance

International audienceLodging is a major yield-reducing factor in rice systems, particularly under intensified cultivation using high-yielding cultivars. It is usually triggered by rainstorms during grain filling. The study of natural lodging is difficult due to unpredictable weather. Proxy traits for lodging resistance such as stem morphology and breaking moment have limited validity because lodging is complex. We present a new mobile, low-cost field methodology called Blaster. It uses a wind turbine creating a 1 m wide and 6 m deep wind path in the field with wind speed adjustable to 30, 45 and 60km h(-1). Water injected into the air stream provides for wetting of the crop. A measurement cycle takes ca. 10 min per plot. The lodging response of 20, mostly high-yielding but diverse rice genotypes was studied in 2013, 2014 and 2015 under irrigated transplanted conditions in the Philippines. Genotypic responses were reproducible between seasons and were predictive of natural lodging observed in the wet season for a subset of 8 genotypes. Cultivars PARAO and CT 5805 from Latin America consistently stood out for superior lodging resistance. Across genotypes, morphological traits such as plant height, biomass or stem diameter were not or poorly predictive of lodging induced by Blaster. The best single proxy trait, stem-base bending moment at breakage (BM), explained about 40% of Blaster-induced lodging, and the Lodging Resistance Index composed of plant height, wet biomass and BM explained about 70%. We propose that Blaster is a reliable tool to evaluate crop lodging resistance as affected by genotype, cultural practices or season

Water Use Efficiency and Physiological Response of Rice Cultivars under Alternate Wetting and Drying Conditions

One of the technology options that can help farmers cope with water scarcity at the field level is alternate wetting and drying (AWD). Limited information is available on the varietal responses to nitrogen, AWD, and their interactions. Field experiments were conducted at the International Rice Research Institute (IRRI) farm in 2009 dry season (DS), 2009 wet season (WS), and 2010 DS to determine genotypic responses and water use efficiency of rice under two N rates and two water management treatments. Grain yield was not significantly different between AWD and continuous flooding (CF) across the three seasons. Interactive effects among variety, water management, and N rate were not significant. The high yield was attributed to the significantly higher grain weight, which in turn was due to slower grain filling and high leaf N at the later stage of grain filling of CF. AWD treatments accelerated the grain filling rate, shortened grain filling period, and enhanced whole plant senescence. Under normal dry-season conditions, such as 2010 DS, AWD reduced water input by 24.5% than CF; however, it decreased grain yield by 6.9% due to accelerated leaf senescence. The study indicates that proper water management greatly contributes to grain yield in the late stage of grain filling, and it is critical for safe AWD technology

Improving yield potential of tropical rice: achieved levels and perspectives through improved ideotypes

Improving the genetic yield potential (YP) of tropical, irrigated rice varieties is a priority objective of rice breeding programs worldwide in the interest of achieving food security and maintaining political stability. But YP has stagnated at about 10 Mg ha−1 since the Green Revolution. We present a survey of researchers' current top yields across different environments and countries, experimentally investigate YP-related traits and radiation use efficiency (RUE) of 12 elite materials, and use a simple model to explore traits that would raise the yield ceiling. The survey indicated that maximal grain yield is between 5 and 12 Mg ha−1 depending on radiation during flowering and grain filling. The experiments conducted in several environments in the Philippines indicated that (1) different morphologies in terms of panicle number and size and leaf size lead to similar YP due to trait–trait compensation, and (2) differences in RUE are partly attributable to variation in terminal senescence which is strongly environment dependent. Simulations thus focused on post-floral physiological processes, namely dynamics of light interception, carbon assimilation and maintenance burden. Scenarios of different degree of stay-green indicated that terminal senescence is essential to limit N requirements and maintenance burden, but partial stay-green would strongly benefit RUE and YP, particularly if accompanied with increased leaf photosynthetic capacity. The need to increase pre-floral C and N reserves for grain filling is discussed, resulting in a concept to refine current ideotypes such as IRRI's New Plant Type and China's Super Hybrid Rice. In conclusion, current best tropical breeding products do not have higher YP than some varieties dating 30–40 years, and new concepts are needed in rice breeding. Breeding for such plants should be done under high N inputs. (Résumé d'auteur

Delineating the 15q13.3 microdeletion phenotype: a case series and comprehensive review of the literature

PURPOSE: Recurrent 15q13.3 deletions are enriched in multiple neurodevelopmental conditions including intellectual disability, autism, epilepsy, and schizophrenia. However, the 15q13.3 microdeletion syndrome remains ill-defined. METHODS: We systematically compiled all cases of 15q13.3 deletion published before 2014. We also examined three locally available cohorts to identify new adults with 15q13.3 deletions. RESULTS: We identified a total of 246 cases (133 children, 113 adults) with deletions overlapping or within the 15q13.3 (breakpoint (BP)4–BP5) region, including seven novel adult cases from local cohorts. No BP4–BP5 deletions were identified in 23,838 adult controls. Where known, 15q13.3 deletions were typically inherited (85.4%) and disproportionately of maternal origin (P < 0.0001). Overall, 198 cases (121 children, 77 adults; 80.5%) had at least one neuropsychiatric diagnosis. Accounting for ascertainment, developmental disability/intellectual disability was present in 57.7%, epilepsy/seizures in 28.0%, speech problems in 15.9%, autism spectrum disorder in 10.9%, schizophrenia in 10.2%, mood disorder in 10.2%, and attention deficit hyperactivity disorder in 6.5%. By contrast, major congenital malformations, including congenital heart disease (2.4%), were uncommon. Placenta previa occurred in the pregnancies of four cases. CONCLUSION: The 15q13.3 microdeletion syndrome is predominantly characterized by neuropsychiatric expression. There are implications for pre- and postnatal detection, genetic counseling, and anticipatory care