A 1.1 kb rice genomic DNA fragment, containing a chitinase gene under the control of the CaMV 35S promoter, was cloned into the rice transformation vector pGL2. After transformation of Indica rice protoplasts in the presence of polyethyleneglycol, plants were regenerated. The presence of the chimeric chitinase gene in T0 and T1 transgenic rice plants was detected by Southern blot analysis. Western blot analysis of transgenic plants and their progeny revealed the presence of two proteins with apparent molecular weights of 30 and 35 kDa that reacted with the chitinase antibody. Progeny from the chitinase-positive plants were tested for their resistance to the sheath blight pathogen, Rhizoctonia solani. The degree of resistance displayed by the transgenic plants to this pathogen correlated with the level of chitinase expression.

Genetic engineering of rice for resistance to sheath blight and other agronomic characters

Virus Diseases of Peanut

Empirical threshold values for quantitative trait mapping.

Rice sheath blight disease, caused by the basidiomycetous necrotroph Rhizoctonia solani,
became one of the major threats to the rice cultivation worldwide, especially after the adoption
of high-yielding varieties. The pathogen is challenging to manage because of its extensively
broad host range and high genetic variability and also due to the inability to find any satisfactory
level of natural resistance from the available rice germplasm. It is high time to find remedies to
combat the pathogen for reducing rice yield losses and subsequently to minimize the threat to
global food security. The development of genetic resistance is one of the alternative means to
avoid the use of hazardous chemical fungicides. This review mainly focuses on the effort of
better understanding the host–pathogen relationship, finding the gene loci/markers imparting
resistance response and modifying the host genome through transgenic development. The latest
development and trend in the R. solani–rice pathosystem research with gap analysis are
provided.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/pbi.13312

Understanding sheath blight resistance in rice: the road behind and the road ahead

Rhizoctonia solani (RS) is a necrotrophic fungi causing sheath blight in rice leading to substantial loss in yield. Excessive and persistent use of preventive chemicals raises human health and environment safety concerns. As an alternative, use of biocontrol agents is highly recommended. In the present study an abiotic stress tolerant, plant growth promoting rhizobacteria Bacillus amyloliquefaciens (SN13) is demonstrated to act as a biocontrol agent and enhance immune response against RS in rice by modulating various physiological, metabolic and molecular functions. A sustained tolerance by SN13 primed plant over a longer period of time, post RS infection may be attributed to several unconventional aspects of the plants’ physiological status. The prolonged stress tolerance observed in presence of SN13 is characterized by (a) involvement of bacterial mycolytic enzymes, (b) sustained maintenance of elicitors to keep the immune system induced involving non-metabolizable sugars such as turanose besides the known elicitors, (c) a delicate balance of ROS and ROS scavengers through production of proline, mannitol and arabitol and rare sugars like fructopyranose, β-d glucopyranose and myoinositol and expression of ferric reductases and hypoxia induced proteins, (d) production of metabolites like quinozoline and expression of terpene synthase and (e) hormonal cross talk. As the novel aspect of biological control this study highlights the role of rare sugars, maintenance of hypoxic conditions, and sucrose and starch metabolism in Bacillus amyloliquifaciens (SN13) mediated sustained biotic stress tolerance in rice.

/pdf/unraveling-aspects-of-bacillus-amyloliquefaciens-mediated-188nww49rd.pdf

Unraveling Aspects of Bacillus amyloliquefaciens Mediated Enhanced Production of Rice under Biotic Stress of Rhizoctonia solani.

Sheath blight, caused by the pathogenic fungus Rhizoctonia solani Kuhn, is one of the most devastating diseases in rice. Breeders have always faced challenges in acquiring reliable and absolute resistance to this disease in existing rice germplasm. In this context, 40 rice germplasm including eight wild, four landraces, twenty- six cultivated and two advanced breeding lines were screened utilizing the colonized bits of typha. Except Tetep and ARC10531 which expressed moderate level of resistance to the disease, none could be found to be authentically resistant. In order to map the quantitative trait loci (QTLs) governing the sheath blight resistance, two mapping populations (F2 and BC1F2) were developed from the cross BPT-5204/ARC10531. Utilizing composite interval mapping analysis, 9 QTLs mapped to five different chromosomes were identified with phenotypic variance ranging from 8.40 to 21.76%. Two SSR markers namely RM336 and RM205 were found to be closely associated with the major QTLs qshb7.3 and qshb9.2 respectively and were attested as well in BC1F2 population by bulk segregant analysis approach. A hypothetical β 1–3 glucanase with other 31 candidate genes were identified in silico utilizing rice database RAP-DB within the identified QTL region qshb9.2. A detailed insight into these candidate genes will facilitate at molecular level the intricate nature of sheath blight, a step forward towards functional genomics.

/pdf/identification-of-qtls-and-possible-candidate-genes-2t8ul4c2wa.pdf

Identification of QTLs and possible candidate genes conferring sheath blight resistance in rice (Oryza sativa L.)

Inherently low genetic yield potential and susceptibility to biotic and abiotic stresses contribute to low productivity in sesame. Development of stress resistant varieties coupled with high yield is the viable option to raise the genetic yield ceiling. 35 sesame germplasm accessions obtained from diverse agro-climatic regions of India were screened both under natural field and greenhouse conditions to identify disease reaction to the pathogen Fusarium oxysporum spp. sesami. Pathogen was isolated from infected plants and identified fungus inoculum was used to confirm disease reaction. All the accessions displayed some percent infection rate and none could be described as immune. Accessions NSKMS 260, NSKMS-267, NSKMS-261 and TMV-3 were found to be resistant with infection rates of 13.1, 14.6, 15.1 and 15.7% respectively. Accessions RT-54, TMV-4, and NSKMS-115 were found to be moderately resistant. Rest others were found to be moderately susceptible or susceptible or highly susceptible with infection percent ranging from 44.7% to 94.11%. Of all the susceptible ones, TKG-22 and VRISV-1 showed severe infection percent of about 94.1 and 92.3 respectively. Though all the accessions studied were categorized into various classes based on percent disease infection, statistically there is no significant difference in majority of the accessions except NSKMS accessions 260, 261 and 267 and TMV-3. The accessions identified in the present study may be considered in crop improvement programmes involved in developing wilt resistant varieties, however further efforts need to be concentrated on identifying highly resistant genotypes with the inclusion of vast germplasm in screening procedures.

Assessment of resistance to Fusarium wilt disease in sesame (Sesamum indicum L.) germplasm

The population consisting of 210 F2:3 individuals from the cross between BPT-5204 (highly susceptible to sheath blight) and ARC-10531 a land race from Assam (moderately resistant to sheath blight) was analyzed to identify the markers associated with sheath blight resistance and to study any association of any morphological trait to disease incidence. The frequency distribution curve of F2:3 progenies for disease trait were continuous, indicating the polygenic control over the trait. The range of relative lesion height was 21-75% with a mean of 38.59%.No significant association between sheath blight disease and other morphological traits were detected in F2:3 populations. Parental polymorphisms were surveyed with 500 primer pairs of simple sequence repeats (SSR), revealed 70 polymorphic markers between the parents. In order to detect the major effect, QTL associated with sheath blight resistance, a strategy of combining the DNA pooling from selected segregants and genotyping was adopted. The association of putative markers identified based on DNA pooling from selected segregant was established by Single Marker Analysis (SMA).The results of SMA revealed that SSR markers, RM336 (chromosome#7) and RM205 (chromosome#9) showed significant association with sheath blight and accounted for 21.8% and 17.3% of total variation respectively. The results obtained from the DNA pooling of phenotypic extremes could be a useful strategy to detect the genetic loci with major effects of the complex trait such as disease resistance in rice.

Bulked Segregant Analysis to Detect Main Effect of QTL Associated withSheath Blight Resistance in BPT-5204/ARC10531 Rice (Oryza sativa L)

Introduction Analogue studies are one of the most possible approach and are important sites on the earth to understand the behavior of extraterrestrial planets. Volcanoes, the natural phenomenon that occurs in all terrestrial planets have believed to be playing a very important role in creating the landforms and life cycle on planet Earth. Initially, the mechanism and features of volcanoes in the world are very much complicated to characterize their structures and behavior. But recent developments in geosciences made it easy in understanding the formations and characterizing the volcanoes. The various geomorphological features of volcanoes will determined the types of volcanoes i.e. active volcanoes; dormant volcanoes; extinct volcanoes; mud volcanoes. These volcanoes are directly or indirectly reveals the nature of tectonics associated with them. In recent decades, planetology communities in the world are taking up the challenges to understand the formation and life in other terrestrial planets through various techniques especially in case of planet Mars. The most common landforms on the Mars surface are pitted cones, mounds and lobate flows which are mostly deciphered as having formed through a variety of overlapping processes like periglacial, glacial, volcanic, and/or impact processes [1, 2] . A crucial component in Martian analogy for the mud volcanoes is what a potential Martian mud volcano’s morphometry/morphology reveals about it’s the formation conditions [3]. On Earth, the studies divulge that mud volcanoes most are geomorphologically variable and are finely exaggerated by several overlapping process and conditions. Most of the terrestrial mud volcanoes form proximal to paleo-depo-centers within structurally-controlled sedimentary basins that are experiencing active deformation. As a consequence, mud volcanoes are mostly situated along the major geological structures (faults and fold axes) that related to deformation of the sedimentary sequence. In case of extraterrestrial studies, we are strictly limited to depend on the remote based observations to interpret geologic processes and history.

Ravuru Sudhakar

Papers

Identification of QTLs and possible candidate genes conferring sheath blight resistance in rice (Oryza sativa L.)

Assessment of resistance to Fusarium wilt disease in sesame (Sesamum indicum L.) germplasm

Bulked Segregant Analysis to Detect Main Effect of QTL Associated withSheath Blight Resistance in BPT-5204/ARC10531 Rice (Oryza sativa L)

Baratang island mud volcanoes, india: a potential candidate for martian