International Rice Research Institute Research Articles

Validation of Genes Affecting Rice Grain Zinc Content Through Candidate Gene-Based Association Analysis.

Several key genes governing Zn homeostasis and grain zinc content (GZC) have been functionally characterized. However, the effects of these genes in diverse breeding populations have not been evaluated; thus, their availability in breeding is unclear. In this study, the effects of 65 genes related to rice zinc responses on GZC were evaluated using two panels of breeding lines, and the superior haplotypes were identified. One panel consisted of mega varieties from the International Rice Research Institute (IRRI), South Asia, and Southeast Asia (SEA), and the other panel is breeding lines/varieties from South China (SC). In addition, a multiparent advanced generation intercross (MAGIC) population, named as DC1, was also employed. Three analytical methods, single-locus mixed linear model (SL-MLM), multilocus random-SNP-effect mixed linear model (mrMLM), and haplotype-based association analysis (Hap-AA), were applied. OsIDEF1 (which explained 12.3% of the phenotypic variance) and OsZIFL7 (8.3–9.1%), OsZIP7 (18.9%), and OsIRT1 (17.9%) were identified by SL-MLM in SEA and SC, respectively, whereas no gene was significantly associated with GZC in DC1. In total, five (OsNRAMP6, OsYSL15, OsIRT1, OsIDEF1, and OsZIFL7, 7.70–15.39%), three (OsFRDL1, OsIRT1, and OsZIP7, 11.87–17.99%), and two (OsYSL7 and OsZIP7, 9.85–10.57%) genes were detected to be significantly associated with GZC in SEA, SC, and DC1 by mrMLM, respectively. Hap-AA indicated that Hap1-OsNRAMP5, Hap5-OsZIP4, Hap1-OsIRT1, Hap3-OsNRAMP6, Hap6-OsMTP1, and Hap6-OsYSL15 had the largest effects for GZC in SEA, whereas Hap3-OsOPT7, Hap4-OsIRT2, Hap4-OsZIP7, Hap5-OsIRT1, and Hap5-OsSAMS1 were the most significant in the SC population. Besides, superior alleles were also identified for the significant genes. The genes significantly associated with GZC and their superior haplotypes identified in different panels could be used in enhancing GZC through molecular breeding, which could further address the problem of Zn malnutrition among rice consumers.

Scenario of Plant Breeding in Nepal and Its Application in Rice

Rice, the number one staple food crop of Nepal, contributes nearly 20% to the agricultural gross domestic product, almost 7% to gross domestic product, and supplies with 40% of the food calorie consumption of Nepalese people. Despite of increasing production, the national demand of rice cannot be fulfilled, and billions of rupees are spent yearly for importing rice from India. This article reviews history, recent scenario, prospects, and importance of rice breeding research in Nepal for self-sufficiency. Though plant breeding inception point in Nepal was 1951, the systematic research in rice was started from 1972 after the establishment of the National Rice Research Program. Introduction and evaluation of high yielding exotic germplasm of rice was the initial rice breeding activities. After analysing several foreign materials, CH-45 variety of rice was first recommended in 1959. Nepal Agriculture Research Council (NARC), the leading organisation for rice varietal improvement to date, has been doing rice research activities such as germplasm conservation, exchange, varietal development, verification of technologies, and knowledge updates in collaboration with various organizations. International Rice Research Institute (IRRI), since 1966, has been playing an important role in Nepal’s rice research. Major plant breeding achievements are introduction of exotic materials and their evaluation, local landraces identification, collection and analysis, crossing of local landraces with exotic genetic materials, heterosis breeding, tissue culture technology, genetic marker technology, and National Genebank. RAPD and SSR, DNA-based markers, are mostly used for diversity appraisal and selecting desirable genotypes. Integration of advanced tools such as genetic engineering, bioinformatics, protoplast fusion, and SNP markers could not be still applied in rice research and development. Hence, emphasis should be given to improve the capacity and abilities of the rice scientists and should release more short duration, drought, and submergence-tolerant rice varieties by optimum utilisation of local landraces combining modern and conventional breeding.

Genomic Prediction of Yield Traits in Single-Cross Hybrid Rice (Oryza sativa L.).

Hybrid rice varieties can outyield the best inbred varieties by 15 – 30% with appropriate management. However, hybrid rice requires more inputs and management than inbred rice to realize a yield advantage in high-yielding environments. The development of stress-tolerant hybrid rice with lowered input requirements could increase hybrid rice yield relative to production costs. We used genomic prediction to evaluate the combining abilities of 564 stress-tolerant lines used to develop Green Super Rice with 13 male sterile lines of the International Rice Research Institute for yield-related traits. We also evaluated the performance of their F1 hybrids. We identified male sterile lines with good combining ability as well as F1 hybrids with potential further use in product development. For yield per plant, accuracies of genomic predictions of hybrid genetic values ranged from 0.490 to 0.822 in cross-validation if neither parent or up to both parents were included in the training set, and both general and specific combining abilities were modeled. The accuracy of phenotypic selection for hybrid yield per plant was 0.682. The accuracy of genomic predictions of male GCA for yield per plant was 0.241, while the accuracy of phenotypic selection was 0.562. At the observed accuracies, genomic prediction of hybrid genetic value could allow improved identification of high-performing single crosses. In a reciprocal recurrent genomic selection program with an accelerated breeding cycle, observed male GCA genomic prediction accuracies would lead to similar rates of genetic gain as phenotypic selection. It is likely that prediction accuracies of male GCA could be improved further by targeted expansion of the training set. Additionally, we tested the correlation of parental genetic distance with mid-parent heterosis in the phenotyped hybrids. We found the average mid-parent heterosis for yield per plant to be consistent with existing literature values at 32.0%. In the overall population of study, parental genetic distance was significantly negatively correlated with mid-parent heterosis for yield per plant (r = −0.131) and potential yield (r = −0.092), but within female families the correlations were non-significant and near zero. As such, positive parental genetic distance was not reliably associated with positive mid-parent heterosis.

Idealizing inflorescence architecture to enhance rice yield potential for feeding nine billion people in 2050

Rice serves as the staple food in meeting the energy needs of more than half of the global population. Several high-yielding, semi-dwarf rice varieties, including the milestone variety IR8 that was developed by the International Rice Research Institute (IRRI) through the introduction of the semi-dwarf1 (sd1) allele of GA20-ox-2 gene and the beneficial allele of HIGH TILLERING AND DWARF 1/DWARF17 (Wang et al., 2020), doubled the yield over traditional germplasm and contributed to the Green Revolution in Asia.

Preface

The 2nd International Conference of Bio-Based Economy for Application and Utilization (ICBEAU) 2020 has been successfully performed on December 16th, 2020. This event was run virtually via the Zoom Meeting platform with The Institution of Research and Community Services (LPPM) of Andalas University, Padang West Sumatera, Indonesia acted as the organizer.The important reason why the 2nd ICBEAU 2020 was held in the virtual meeting instead of the offline meeting is due to the COVID-19 pandemic situation where travel restriction, social distancing were strictly implemented across the globe. The event was scheduled for September 2020, a similar time to the 1st ICBEAU 2019. However, the pandemic issue has continued until the end of the year 2020, and even nowadays in 2021. Therefore, the organizer has discussed with the steering committee, keynote speakers, representative of Bio-Based Communities and finally agree to delay the conference until December 2020. One of the important considerations of delaying the schedule instead of postponing was due to the significant interest in the event as an information exchange forum especially in using bio-based material for immune system improvement to face some actual pathogen like the Coronavirus SAR2. Therefore, in this event two speakers: dr, Rauza Sukma Rita, Ph.D. from Medical Faculty of Andalas University and Assoc. Prof. Dr. Pasupuleti Visweswara Rao from The University Malaysia Sabah was invited.To assure the quality and success of speech delivery during the conference; a Business Zoom Meeting Platform that can facilitate up to 150 participants for the plenary session was specially ordered from the vendor. The plenary sessions involved 5 keynote speakers connected virtually from their own country namely: Indonesia, Malaysia, Philippines, Thailand, and India. All 5 keynote speakers were distributed into two sessions in which every keynote speaker presented their speech including discussion in 60 minutes so in total 240 minutes (5 hours) were allocated for all 5 speakers. Since the virtual meeting application platform is also facilitated with the “breakout rooms menu”, it was possible to run 8 virtual parallel sessions (each 15-20 speakers per parallel session) connecting at least 25 different countries simultaneously. Every speaker in the parallel session should use 7-10 minutes to deliver their speech and use the rest of their 5 minutes for the discussion (Question-Answer session).On behalf of the committee, let us express our great thanks to all parties involving and contributing to the implementation of the 2nd ICBEAU seminar. Special thanks to our respected keynote speakers; Prof. Dr. Inez H. Slamet Loedin. from The International Rice Research Institute, Philippines; dr, Rauza Sukma Rita, Ph.D. from Andalas University; Assoc. Prof. Dr. Pasupuleti Visweswara Rao from The Universiti Malaysia Sabah, Malaysia; Asst Prof Saowakon Wattanachant Ph.D., from The Prince of Songkla University Thailand and Dr. Rosewine Joy, from The Presidency University India-for their collaboration and their kindness to share their valuable experiences and their expertise in the seminar event. Many thanks also we have to address to the Rector of Andalas University which is represented by Dr. Uyung Gatot S Dinata, MT. as Head of the Institution of Research and Community Service of Andalas University, and also to all parties and valuable participants. Finally, we would like also to thanks the IOP Publisher, which kindly helps us to publish this proceeding.March, 16th 2021Chairman of the Committee, 2nd International Conference of Bio-Based Economy for Application and Utilization (ICBEAU 2020) list of titles are available in the pdf

CFD-Simulink Modeling of the Inflatable Solar Dryer for Drying Paddy Rice

Small-scale farmers in developing Asian countries have minimal agricultural mechanisms available to them. In the Philippines, postharvest losses in rice production can reach about 36% in the drying process alone. Thus, the inflatable solar dryer (ISD) was developed through the collaboration of the University of Hohenheim, the International Rice Research Institute, and GrainPro Philippines Inc. Although the ISD was successfully tested with different agricultural products, further characterization of the ISD design is required for predicting the drying performance. To this end, the airflow behavior in the ISD was simulated using computational fluid dynamics (CFD) via ANSYS Fluent. Moreover, a thermal model was developed in MATLAB/Simulink by taking into account heat transfer in the heating area and coupled heat and mass transfer within the drying area. Three batches of drying experiments were performed and airflow measurements were taken inside the dryer to validate the models. The MATLAB/Simulink model was further used to predict the drying performance under various weather conditions spanning 10 years. The simulated temperatures and moisture content in the ISD showed high accuracy (mean absolute percentage error (MAPE) < 10%) with the experimental data. The proposed dynamic model provides an efficient computational tool that can be applied to predict the drying performance and to optimize the ISD design.

Recanvassing of Select Wild Rice (Oryza spp.) in the Philippines

Wild rice relatives (WRRs) have been used by breeders to draw genes needed to develop varieties that are resistant to pests and diseases and can adapt to adverse environments, especially to climate change. This study was conducted to reassess the presence of WRRs in their natural habitats. A total of 14 WRR were collected: three samples of O. meyeriana, nine samples of O. minuta, and two samples of O. rufipogon from Luzon, Visayas, and Mindanao. In comparison with previous recollection and recanvassing mission and deposited WRR at the International Rice Research Institute (IRRI) Genetic Resources Center (GRC), we see the existence of O. meyeriana population in new sites in Salong and Magballo, Kabankalan in Negros Occidental, Visayas while O. minuta confirms previously identified natural habitat in Pangil, Laguna in Luzon; however, new sites were identified in Magballo, Kabankalan, Negros Occidental. O. rufipogon populations were still found in Lake Apo, as previously reported but limited publication on the populations found in Lake Napalit – both in Bukidnon, Mindanao. Further study is needed to characterize the existing WRRs and expand the recanvassing sites to develop a more holistic conservation program in support to pre-breeding programs

Growth and Productivity Assessment of Short-Duration Rice (Oryza sativa L. and Upland NERICA) Genotypes in Semiarid North-Central Namibia

In semiarid regions, drought is the major threat to crop production, but climate change and variability often bring floods to the regions, forming seasonal wetlands causing damage to local, drought-adapted staple grains and, hence, low yields and food deficit. Introduction of the semiaquatic crop rice (Oryza spp.) to these semiarid wetlands could complement the dryland crop low yields and overcome the food shortage problem. A field experiment was carried out at the University of Namibia-Ogongo Campus during the 2016/2017 and 2017/2018 cropping seasons to assess the growth and yield of rice genotypes. Twelve short-duration rice genotypes, nine from the International Rice Research Institute (IRRI) and three locally grown upland NERICA genotypes, were used. Parametric analysis of variance was performed to test their effects on crop growth and yield characters. The results showed significant genotype by year interaction for days to heading, plant height, the number of tillers per m2, shoot biomass, the number of panicles per m2, 1000-grain weight, harvest index, and grain yield. The IRRI genotypes produced a higher number of tillers, shoot biomass, and grain yield than the NERICA ones, which were early maturing, were taller, and had higher 1000-grain weight across the years. Generally, most of the genotypes had lower grain yield and higher shoot biomass in the first year, due to the prevailing cool, rainy, and seemingly cloudy weather conditions associated with lower temperature and lower solar radiation. Grain yield was positively correlated with most characters but negatively correlated with the 1000-grain weight. These results demonstrate the yield superiority of IRRI genotypes over their early-maturing NERICA counterparts. However, further studies on morphological characters and drought tolerance of the IRRI genotypes are warranted to ascertain production sustainability under semiarid environments.

Assessment of Socioeconomic and Climate Change-related Factors to Meeting Recommended Energy Intake (REI) of Filipino Households

This study aimed to determine the sociodemographic, socioeconomic, and climate change-related factors associated with meeting recommended energy intake (REI) among Filipino households. This paper utilized data from selected components of the 2013 National Nutrition Survey (NNS) and 2015 Updating Survey of the Department of Science and Technology – Food and Nutrition Research Institute (DOST-FNRI), typhoon/flood occurrence from online reports of the National Disaster Risk Reduction and Management Council (NDRRMC) and drought data for the first quarter (Q1) of 2015 from the Philippine Rice Information System (PRiSM) of the International Rice Research Institute (IRRI). Multiple logistic regression using the backward elimination method was done and post-estimation tests were applied to the final model. Filipino households with more than three members were food insecure and were poor were less likely to meet the REI. On the other hand, households engaged in agricultural work, having a member working abroad, residing in rural areas, and shorter time lag exposure to typhoons/floods were more likely to meet REI. Filipino households in Mindanao, meanwhile, were less likely to meet REI if they had more than three members and were food insecure and more likely to meet REI if they were engaged in agricultural work. The study provides a snapshot of a seemingly minute but significant facet of the health and nutrition situation in the Philippines, which is meeting the REI at the household level in relation to exposure to extreme weather events such as typhoons, floods, and drought brought about by climate change. The results of the study may provide vital inputs to climate change adaptation programs of the government for vulnerable population groups, particularly among farming- and fishing-dependent households who will likely absorb the long-term impact of the extreme weather events to their livelihoods.

In Quest of Nitrogen Use-Efficient Rice Genotypes for Drought-Prone Rainfed Ecosystems

Nitrogen (N) use efficiency in rainfed agriculture is generally low because of poor management and unavailability of suitable rice genotypes. There is a need to select rice genotypes with high N use efficiency for these specific environments, which was investigated at the Bangladesh Rice Research Institute, Regional Station, Rajshahi, in two successive years. The performance of six rice genotypes, IR7437170-1-1, BR7873-5*(NIL)-51-HR6, IR83377-B-B-93-3, International Rice Research Institute (IRRI) 123, IR83381-B-B-6-1, and Binadhan-7, were tested under four N rates (0, 55, 83, and 110 kg N ha−1) in a strip-plot design. Grain yields generally increased up to 83 kg N ha−1 and declined thereafter. Depending on N rates, mean grain yields increased by 35–45% compared to the control (N0). However, the grain yields of IR83377-B-B-93-3, IRRI 123, and Binadhan-7 increased up to 110 kg N ha−1. N uptake and its use efficiencies were the highest in IR83377-B-B-93-3, which was at par with those in IRRI 123. Bangladesh Rice Research Institute (BRRI) dhan56 and Binadhan-7 showed intermediate performance, while BRRI dhan57 and IR83381-B-B-6-1 showed lower N uptake and N efficiencies. Between 16.5 and 19.2 kg N uptake was required to produce 1 ton of paddy. The genotypes IR83381-B-B-93-3 and IRRI 123 were the most N use efficient irrespective of N rates, but BRRI dhan57 and IR87781-B-B-6-1 were observed to be inefficient genotypes, while BRRI dhan56 and Binadhan-7 were intermediate. Thus, this study indicates the need to test existing and new germplasm for optimal N rates and their NUE, especially in rainfed environments where optimized resource use is essential for higher yields and increased farmers' income.

Efficacy of Different Level of Systemic Fungicides on Management of Rice Blast at Baitadi, Nepal

Rice blast (Pyriculariaoryzae Cavara) is one of the most devastating diseases affecting the rice crop in across the world. Systemic fungicides are used for the suppression of blast diseases caused by fungal pathogens. Propiconazole and Carbendazim are commercial chemical control products available in markets for the control of the fungal pathogen. An experiment was conducted to examine the effectiveness of systemic fungicide on suppression of rice blast incidence in farmers' field during wet seasons in 2016. The treatments consisted of the use of different levels of propiconazole and Carbendazim on ‘Rato Basmati’ a landrace rice variety. The experiments were arranged in a randomized complete block design with three replications. The disease was scored according to the standard scale developed by the International Rice Research Institute (IRRI). Disease severity and Area under Disease Progressive curve (AUDPC) was computed based on that scale score. Propiconazole and Carbendazim at different levels reduce disease development than no treatment (control). But its efficacy was not consistent. The magnitude of disease suppression by Propiconazole was high as compared to Carbendazim. The application of propiconazole at the rate of 1.5 ml effectively reduced disease severity and AUDPC at different dates. So propiconazole at the rate of 1.5 ml thrice at weekly intervals is effective to reduce the disease development

Design and Development of a Comprehensive, Robust and KM-Scalable Database (Backend) for a PILI (Canarium ovatum Engl.) Information System

This paper presents the results of efforts to design and develop a comprehensive repository of knowledge for Pili (Canarium ovatum Engl.), an endemic crop in the Bicol Region known for its various uses. This study, in general, responds to the challenges entailed in the national government’s having identified “PILI” as the flagship commodity of the Bicol region. In particular, it seeks to address the dearth of accessible knowledge on the Pili industry. Enabling users around the world to become acquainted with this endemic crop. The database’s initial goal is to provide key facts on population dynamics of Pili crop (Canarium ovatum Engl.) varieties and is designed and structured towards knowledge management (KM) buildup. Many similar information systems applied in agriculture were consulted and visited by the researchers in the literature such as the International Rice Research Institute (IRRI’s) comprehensive crop information system [1], and the more recent Mango Resource Information System [2] which was developed for the management of the phenotypic, genetic, molecular to chemical and other information on mango cultivars. The breadth and depth of information in the database are designed to cater to the different needs of diverse groups of stakeholders (farmers, vendors, processors, scientists, researchers, policy-makers, teachers, and students). Its various applications range from basic Pili bio-ecological data management to e-commerce and analytics. This Pili database covers the more than 14 NSIC (National Seed Industry Council) accredited pili varieties, 200 accessions compiled from more than 150 references in partnership with more than 10 collaborators, and more than 500 pictures taken from different cultivars in the Bicol region. At present, the database has 180 tables, enriched by the collection of various Pili related information ranging from its nomenclature, accession, NSIC registration, distribution, morphological characteristics, genetic resources, geo-mapping and characterization, propagation techniques, emerging diseases, growth and yield response, postharvest processing, to products, e-commerce, data analytics and other related data present in different cultivars. The database is normalized to handle complex queries needed to generate knowledge not only for Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD) and its member-agencies but for Pili farmers/producers, vendors, enthusiasts, retail outlets, and the market as a whole. It is designed with flexibility in mind to interface and interconnect/link with other PCAARRD systems for a dynamic web of knowledge. It is believed that making information and data on Pili publicly available will enliven and invigorate the stakeholders in this industry and help boost yield/production, encourage more research and development efforts, promote innovation, step up marketability of various pili-related products, and consequently improve the living conditions of marginalized farmers and vendors.

An Approach to High-Resolution Rice Paddy Mapping Using Time-Series Sentinel-1 SAR Data in the Mun River Basin, Thailand

Timely and accurate regional rice paddy monitoring plays a significant role in maintaining the sustainable rice production, food security, and agricultural development. This study proposes an operational automatic approach to mapping rice paddies using time-series SAR data. The proposed method integrates time-series Sentinel-1 data, auxiliary data of global surface water, and rice phenological characteristics with Google Earth Engine cloud computing platform. A total of 402 Sentinel-1 scenes from 2017 were used for mapping rice paddies extent in the Mun River basin. First, the calculated minimum and maximum values of the backscattering coefficient of permanent water (a classification type within global surface water data) in a year was used as the threshold range for extracting the potential extent. Then, three rice phenological characteristics were extracted based on the time-series curve of each pixel, namely the date of the beginning of the season (DBS), date of maximum backscatter during the peak growing season (DMP), and length of the vegetative stage (LVS). After setting a threshold for each phenological parameter, the final rice paddy extent was identified. Rice paddy map produced in this study was highly accurate and agreed well with field plot data and rice map products from the International Rice Research Institute (IRRI). The results had a total accuracy of 89.52% and an F1 score of 0.91, showing that the spatiotemporal pattern of extracted rice cover was consistent with ground truth samples in the Mun River basin. This approach could be expanded to other rice-growing regions at the national scale, or even the entire Indochina Peninsula and Southeast Asia.

Phenotypic response of farmer‐selected CWR‐derived rice lines to salt stress in the Mekong Delta

AbstractBreeding for salt tolerance or abiotic stress, in general, requires rapid but reliable screening protocols that reflect the actual field situation as much as possible. A collection of 200 crop wild relative (CWR)‐derived BC3F3‐4 rice (Oryza sativa L.) lines developed at the International Rice Research Institute (IRRI) were evaluated by farmers in the Mekong Delta over two seasons for agronomic performance. Fifty stable BC3F5 lines were selected and subsequently screened in hydroponics using three NaCl concentrations to assess their phenotypic response to salt stress. The lines and check varieties were grown in a salinized Yoshida nutrient solution at three concentrations: 68, 102, and 13 mM NaCl. Several lines were identified to be tolerant to salinity stress and ANOVA showed significant differences among genotypes and NaCl concentrations. Root and shoot growth parameters showed an inverse relationship with increasing NaCl concentration. Population genetic analysis suggested four groups of genotypes, where the median salt injury score across the three NaCl concentrations was identified as the main clustering factor. Lines from Cluster 3 were identified as the most promising donors of salt tolerance.

Genetic gain for rice yield in rainfed environments in India.

The complexity of genotype × environment interactions under drought reduces heritability, which determines the effectiveness of selection for drought tolerance and development of drought tolerant varieties. Genetic progress measured through changes in yield performance over time is important in determining the efficiency of breeding programmes in which test cultivars are replaced each year on the assumption that the new cultivars will surpass the older cultivars. The goal of our study was to determine the annual rate of genetic gain for rice grain yield in a drought-prone rainfed system in a series of multi-environment trials conducted from 2005 to 2014 under the Drought Breeding Network of Indian sites in collaboration with the International Rice Research Institute (IRRI). Our results show a positive trend in grain yield with an annual genetic yield increase of about 0.68 % under irrigated control, 0.87 % under moderate reproductive stage drought stress and 1.9 % under severe reproductive stage drought stress due to breeding efforts. The study also demonstrates the effectiveness of direct selection for grain yield under both irrigated control as well as managed drought stress screening to improve yield in typical rainfed systems. IRRI's drought breeding programme has exhibited a significant positive trend in genetic gain for grain yield over the years under both drought stress as well as favorable irrigated control conditions. Several drought tolerant varieties released from the programme have outperformed the currently grown varieties under varied conditions in the rainfed environments on farmers' fields.

Pathogenicity and population structure analysis of Pyricularia oryzae in different districts of Jiangsu province, China

AbstractRice blast caused by Pyricularia oryzae is one of the most destructive rice diseases worldwide. In this study, 224 isolates were isolated from neck blast samples from nine districts in Jiangsu. We analysed the resistance frequency of 24 resistance (R) genes using 32 monogenic rice lines from the International Rice Research Institute (IRRI), including Pii, Pik‐h, Pi5, Piz‐5, and Piz, which exhibit high resistance frequencies. PAC (pathogenicity association coefficients) and VAC (virulence association coefficients) analyses identified three combinations of R genes, Piz/Pii, Piz/Piz‐5, and Piz/Pi5, as being suitable for use in Jiangsu. Mating‐type analysis of P. oryzae isolates indicated that sexual reproduction occurred less frequently in northern Jiangsu than in other areas, which may affect genetic diversity and dissemination. Pot2‐TIR analysis indicated that the genetic diversity of P. oryzae in Xuzhou was mainly due to the insertion of transposable elements, while that of Nanjing was due to both the insertion of transposable elements and sexual recombination. Therefore, some R genes or gene combinations were suitable for resistance breeding in Jiangsu, and repetitive‐PCR (rep‐PCR) is a cost‐effective tool for genetically differentiating distinct cultivar‐specific populations or lineages with well‐defined virulence patterns, because of the close correspondence between rep‐PCR based clusters and pathotypes of inbred lines.

Influence of Tillage, Herbicide and Planting Delay on Nutrient Status and Yield of Cluster Bean as Replacement Crop Following Pearl Millet Stand Failure

Background: Cluster bean [Cyamopsis tetragonoloba (L.) Taub.], with vernacular name of Guar, is annual, economically important and drought-hardy legume (Mondal and Gera, 2020) salinity tolerant grown under semiarid and subtropical regions. It is cultivated under both irrigated and rainfed condition in India (Rathod et al. 2020). India is its major producer, accounting for 80% of world’s total production (Meena et al., 2018). Cluster bean is grown in India on 5.60 Mha and produces of 2.82 million tonnes with a low national average yield of merely 504 kg/ha (Anonymous, 2019). Methods: The experiments were conducted at the Agronomy Farm, College of Agriculture, SK Rajasthan Agricultural University (SKRAU), Bikaner during kharif seasons of 2018 and 2019. The Farm is situated on Bikaner - Sriganganagar road situated at 28°4’21" NL latitude and 73°20’17" EL longitude with an altitude of 234.7 meters above the mean sea level. The experiment was laid out in strip plot design in three factors with 32 treatments comprising four tillage, two herbicide and four planting delay treatments. Statistical analysis by using STAR (R-Packages 1.5 STAR 2.0.) (Statistical Tool for Agricultural Research), software developed by Department of Plant Breeding Genetics and Biotechnology, IRRI (International Rice Research Institute), Manila, Phillipines. Result: The disc plough (T2), control (H0) and early planting P1 (July 10) significantly increased N, P, K, total nutrient uptake and partial nutrient balance (PBN) than other treatments. All the interactions were found significant in nutrient of cluster bean. The seed and straw yield of cluster bean was found significantly higher in disc plough (T2), control (H0) and early planting P1 (July 10) compared to other treatments of pooled basis. The interactions were found significant between tillage × herbicide × planting delay in yield of cluster bean.

An Assessment on the Technical and Economic Feasibility of Mechanized Rice Straw Collection in the Philippines

The increasing utilization of rice combine harvesters in the Philippines has made collection of scattered rice straw difficult and laborious. While there are high demands for using rice straw, e.g., for feed or mushroom production, rice straw is predominantly burned in the field due to labor shortages and the high manual cost of collection, particularly for scattered rice straw harvested by combine harvesters. This study conducted an assessment and evaluated the feasibility of mechanized collection of rice straw by comparing the performance of two types of baler (i.e., roller and piston type) for two seasons—2019 wet and dry seasons at the International Rice Research Institute (IRRI) and in Nueva Ecija, the Philippines. The study collected data on fuel consumption, manpower requirements, and field capacity by operating the balers to collect scattered rice straw in the field and piled rice straw that was left in the field after threshing. The round baler operated at 35% lower effective field capacity (EFC) on piled rice straw than on scattered rice straw, while the square baler operated at 2.33 times and 5.79 times higher EFC compared with the round baler on piled and scattered rice straw, respectively. The square baler used for collecting scattered rice straw is more appropriate under Philippine conditions, with a significantly lower baling cost by about 68% and an average EFC that is 4.43 times higher compared to the round baler. With the increasing demand for rice straw as feedstock for ruminants and for other alternative uses, using mechanical balers to gather scattered rice straw in the field is a sustainable option for farmers to utilize the straw for value-adding purposes. This is a foremost study conducted in the Philippines to guide policy makers, development workers, and end-users on the suitability of either square balers or round balers to gather scattered rice straw in the field after rice harvesting with combines.

Utilization of SNP-based Highly Saturated Molecular Map of a RIL Population for the Detection of QTLs and Mining of Candidate Genes for Salinity Tolerance in Rice

Purpose : Previously, QTL hotspots were identified for salt tolerance from a RIL population of At354 x Bg352, under a temperature-controlled environment at the International Rice Research Institute, Philippine. However, as the rice-growing environment in Sri Lanka experiences salinity stress exaggerated with high temperature, the importance of revealing QTLs under such environment of a tropical region was realized. Therefore, the present study was focused to examine QTLs under such environment, deploying SNP-based molecular map, and retrieving potential candidate genes underlying the QTLs. Research Method : RIL population was assessed at 12 dSm-1 electrical conductivity coupled with average temperature ranged from 38 to 32 °C, day and night, respectively. QTLs were mapped using SNP markers. Potential candidate genes were identified using NGS-based high-throughput QTL-seq strategy employing whole-genome re-sequencing data of At354 and Bg352 and Gene Ontology approach. Findings : The results revealed a broad spectrum of phenotypic variation and a significant coefficient of correlation among the morpho-physiological traits in the RIL population. Four QTLs were revealed on chromosome 7, 9, and 11 for shoot Na+ concentration (qSNC7), shoot K+ concentration (qSKC9), shoot Na+/K+ ratio (qSNK9) and root length (qRL11). Five genes, Os07g0635900, Os07g0637300, Os09g0330000, Os11g0514500, and Os11g0523800 within novel QTLs with polymorphic variants between At354 and Bg352, were recognized as potential candidate genes regulating salinity stress. Originality / Value : The putative candidate genes have been reported to be involved in cellular transmembrane and growth modulating functions under stress, indicating their usefulness to be further researched.

Identification and characterization of high-yielding, short-duration rice genotypes for tropical Asia.

Previous efforts to increase the yield of tropical rice (Oryza sativa L.) have focused on medium‐duration varieties. However, there is increasing demand for high‐yielding short‐duration varieties that can adapt to intensified cropping systems and climate change. Our goal was to identify physiological traits associated with high yield in elite short‐duration genotypes suitable for tropical Asia. We conducted field experiments in five consecutive growing seasons at the International Rice Research Institute, the Philippines. We selected genotypes in the first two seasons, then performed a detailed characterization of the most promising genotypes in the following three seasons. Of the 50 advanced‐generation genotypes, three had consistently high yield and early maturity, with yields 11 to 38% higher than that of ‘IRRI104’ (‘IR50404‐57‐2‐2‐3’), a short‐duration variety that is widely grown in Southeast Asia. These genotypes were 20 to 32 cm taller than IRRI104. We found that for grain growth, low source capacity, defined as stem nonstructural carbohydrates at heading plus biomass accumulation after heading, was the major factor for the low yield of IRRI104. Although sink capacity (spikelets m−2 × grain weight) in the promising genotypes was comparable to that of IRRI104, they had a 25 to 53% higher source–sink ratio (source capacity/sink capacity) than IRRI104, which was attributed to larger leaf area and greater biomass accumulation during the grain‐filling stage. This result suggests that slight changes in plant development to promote height combined with increased leaf area around heading would improve the yield of short‐duration rice varieties in tropical Asia.