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28 January 2018, Volume 25 Issue 1 Previous Issue    Next Issue
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Application of Statistical Tools for Data Analysis and Interpretation in Rice Plant Pathology Nayak Parsuram, Kumar Mukherjee Arup, Pandit Elssa, Kumar Pradhan Sharat 2018, 25(1): 1-18.  DOI: 10.1016/j.rsci.2017.07.001 Abstract ( )   HTML ( )   PDF (648KB) ( )   There has been a significant advancement in the application of statistical tools in plant pathology during the past four decades. These tools include multivariate analysis of disease dynamics involving principal component analysis, cluster analysis, factor analysis, pattern analysis, discriminant analysis, multivariate analysis of variance, correspondence analysis, canonical correlation analysis, redundancy analysis, genetic diversity analysis, and stability analysis, which involve in joint regression, additive main effects and multiplicative interactions, and genotype-by-environment interaction biplot analysis. The advanced statistical tools, such as non-parametric analysis of disease association, meta-analysis, Bayesian analysis, and decision theory, take an important place in analysis of disease dynamics. Disease forecasting methods by simulation models for plant diseases have a great potentiality in practical disease control strategies. Common mathematical tools such as monomolecular, exponential, logistic, Gompertz and linked differential equations take an important place in growth curve analysis of disease epidemics. The highly informative means of displaying a range of numerical data through construction of box and whisker plots has been suggested. The probable applications of recent advanced tools of linear and non-linear mixed models like the linear mixed model, generalized linear model, and generalized linear mixed models have been presented. The most recent technologies such as micro-array analysis, though cost effective, provide estimates of gene expressions for thousands of genes simultaneously and need attention by the molecular biologists. Some of these advanced tools can be well applied in different branches of rice research, including crop improvement, crop production, crop protection, social sciences as well as agricultural engineering. The rice research scientists should take advantage of these new opportunities adequately in adoption of the new highly potential advanced technologies while planning experimental designs, data collection, analysis and interpretation of their research data sets.

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Yield Traits and Associated Marker Segregation in Elite Introgression Lines Derived from O. sativa × O. nivara Haritha G., P. M. Swamy B., L. Naik M., Jyothi B., Divya B., Malathi S., Sarla N. 2018, 25(1): 19-31.  DOI: 10.1016/j.rsci.2017.11.001 Abstract ( )   HTML ( )   PDF (1198KB) ( )   Introgression lines (ILs) derived from interspecific crosses are a source of new genetic variability. A total of 55 ILs derived from two crosses Swarna × O. nivara IRGC81848 (population A) and Swarna × O. nivara IRGC81832 (population B) were characterized for yield and yield-related traits/QTLs. Segregation of 103 simple sequence repeat (SSR) markers associated with yield-related QTLs was studied. Population A showed an average of 12.6% homozygous O. nivara alleles and population B showed 10.6%. Interestingly, three SSR markers, RM223, RM128 and RM517, showed conspicuous pattern of segregation. The distribution of parental alleles at three loci RM223, RM128 and RM517 linked to yield-related traits was unique. These markers flanked to several yield-related QTLs. RM223, flanking to qyld8.3, was heterozygous in almost all the 55 ILs except in IL10-3S and IL131S. RM128 on chromosome 1 and RM517 on chromosome 3 were mutually exclusive in 46 out of 55 ILs. These 46 ILs showed either of the marker allele RM128 or RM517 from O. nivara but not both. IL166S had both RM128 and RM517 from O. nivara and the other ILs showed homozygous Swarna allele at RM517 except IL65S. Population structure assigned the 55 ILs to three sub-populations based on their genomic diversity. IL65S, IL166S, IL248S, IL7K and IL250K showed high yields in multi-location trials, and IL248S was released for cultivation as DRRDhan 40.

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Relationship Between Allelopathic Effects and Functional Traits of Different Allelopathic Potential Rice Accessions at Different Growth Stages Gaofeng Xu, Shicai Shen, Fudou Zhang, Yun Zhang, Hisashi Kato-Noguchi, Clements David Roy 2018, 25(1): 32-41.  DOI: 10.1016/j.rsci.2017.09.001 Abstract ( )   HTML ( )   PDF (625KB) ( )   In this study, effects of temperature, light and their interactions on allelopathic effects and the functional traits specific leaf area (SLA) and stem mass fraction (SMF) of different allelopathic potential rice accessions at different growth stages were analyzed. The main results were as follows: Allelopathic responses to temperature and light varied with different allelopathic potential rice accessions at different growth stages. With the rise of temperature and the extension of photoperiod, allelopathic effect increased firstly and then decreased at 2-3 leaf stage, but increased constantly at the 4-5 and 7-8 leaf stages in strong allelopathic rice accessions [O. longistaminata, F1 (O. longistaminata × RD23), F2 (RL159 and RL169)]. Temperature had significant impact on allelopathic effect without considering light factors, but light showed little effect on rice allelopathy at the same temperature conditions. The greatest allelopathic effect was attained with moderate temperature and long photoperiod at 2-3 leaf stage in strong allelopathic rice accessions, but all the rice accessions showed weak allelopathic effects at the low temperature condition (15 ºC/10 ºC), and the influence of different factors on allelopathy followed a general trend as temperature > leaf stage > light, indicating that among the multiple factors impacting rice allelopathy, temperature was the main factor. Allelopathic characteristics of F1 and F2 to various temperature and light were similar to O. longistaminata, showing that allelopathic genes from wild rice can be expressed in its descendants. Temperature and light also had significant effects on SLA and SMF, and rice allelopathy was closely correlative to SLA in strong allelopathic rice accessions at the 4-5 and 7-8 leaf stages, but there was no correlation between rice allelopathy and SMF at different growth stages. These results suggested that rice adjust the relationship between allelopathy and SLA and adapt to the varied environments, and that high temperature and long photoperiod can enhance rice allelopathic activity.

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Starch Digestibility and Functional Properties of Rice Starch Subjected to Gamma Radiation Fernando Polesi Luís, Bruder Silveira Sarmento Silene, Guidolin Canniatti-Brazaca Solange 2018, 25(1): 42-51.  DOI: 10.1016/j.rsci.2017.08.003 Abstract ( )   HTML ( )   PDF (581KB) ( )   This study investigated the effect of gamma radiation on the digestibility and functional properties of rice starch. Rice cultivars IRGA417 and IAC202 were used for isolation of starch by the alkaline method. Starch samples were irradiated with 1, 2 and 5 kGy doses of 60Co at a rate of 0.4 kGy/h. A control sample, which was not irradiated, was used for comparison. Irradiated and control starches were characterized by in vitro starch digestibility, total dietary fiber, color, water absorption index, water solubility index, syneresis, swelling factor, amylose leaching, pasting properties and gel firmness. Irradiations changed starch digestibility differently in either cultivar. Increasing radiation doses promoted increase in the color parameter b* (yellow), elevation in the capacity to absorb water, and solubility in water as well as the amylose leached from granules for both cultivars. Pasting properties showed a decrease that was proportional to the dose applied, caused by the depolymerization of starch molecules. Gel firmness of the starch from IAC202 was inversely proportional to the radiation dose applied, whereas for IRGA417, there was a reduction at 5 kGy dose. Rice starches can be modified by irradiation to exhibit different functional characteristics and they can be used by the food industries in products such as soups, desserts, flans, puddings and others.

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Marker-Assisted Selection of Xa21 Conferring Resistance to Bacterial Leaf Blight in indica Rice Cultivar LT2 Thi Nguyen Hue, Hong Vu Quang, Van Mai Tan, Thi Nguyen Thu, Duc Vu Lam, Thanh Nguyen Tung, Viet Nguyen Long, Thu Thi Vu Hien, Thi Nong Hue, Nguyen Dinh Trung, Toshitsugu Nakano, Van Vu Liet 2018, 25(1): 52-56.  DOI: 10.1016/j.rsci.2017.08.004 Abstract ( )   HTML ( )   PDF (460KB) ( )   Bacterial leaf blight of rice (BLB), caused by Xanthomonas oryzae pv. oryzae, is one of the most destructive diseases in Asian rice fields. A high-quality rice variety, LT2, was used as the recipient parent. IRBB21, which carries the Xa21 gene, was used as the donor parent. The resistance gene Xa21 was introduced into LT2 by marker-assisted backcrossing. Three Xoo races were used to inoculate the improved lines following the clipping method. Eleven BC3F3 lines carrying Xa21 were obtained based on molecular markers and agronomic performance. The 11 lines were then inoculated with the three Xoo races. All the 11 improved lines showed better resistance to BLB than the recipient parent LT2. Based on the level of resistance to BLB and their agronomic performance, five lines (BC3F3 5.1.5.1, BC3F3 5.1.5.12, BC3F3 8.5.6.44, BC3F3 9.5.4.1 and BC3F3 9.5.4.23) were selected as the most promising for commercial release. These improved lines could contribute to rice production in terms of food security.

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Diversity of dsRNA Viruses Infecting Rice Sheath Blight Fungus Rhizoctonia solani AG-1 IA Li Zheng, Chen Liu, Meiling Zhang, Mei Yang, Erxun Zhou 2018, 25(1): 57-60.  DOI: 10.1016/j.rsci.2017.09.002 Abstract ( )   HTML ( )   PDF (485KB) ( )   Rice sheath blight, caused by Rhizoctonia solani (Kühn), is a notorious soil-borne disease prevalent in many rice-growing regions. Although several sporadic studies of mycoviruses in R. solani AG-1 IA have been reported for single strain of R. solani AG-1 IA, there have been no reports describing the distribution and diversity of mycoviruses in natural populations. In this study, 43 R. solani AG-1 IA strains collected from different locations in China were examined for the presence of dsRNA elements to confirm the presence of viral infections. Electrophoretypes showed that 16 of the 43 fungal strains (37.2%) contained dsRNAs that can be characterized as viruses. Furthermore, the species-specific reverse transcription PCR (RT-PCR) showed dsRNA bands with similar sizes do not always contain the same virus but exist as mixed mycoviral infections. Thus, our findings indicate mycoviruses infecting R. solani AG-1 IA in China are diverse, widespread and universal.