Emerging Minor Diseases of Rice in India: Losses and Management Strategies

Rice (Oryza sativa L) being one of the imperative food crops of the word contributes immensely to the food and nutritional security of India. The cultivation of rice is changed over the decades from a simple cultivation practices to the advanced cultivation to increase yield. Increased in rice yields especially after 1960s is mainly due to the introduction of high yielding semi-dwarf varieties which requires more inputs like chemical fertilizers, water and other resources. As a result, India achieved self sufficiency in rice and currently producing more than 115 MT of rice to meet country’s demand. Now India is exporting rice to other nations and earning foreign returns. With the change in rice cultivation practices, problems also aroused side by side. A number of biotic and abiotic stresses emerged as major constraints for rice cultivation in diverse agro-climatic conditions and growing ecologies. Diseases are the major biotic constraints to rice which can reduce the yields by 20–100% based on severity. Major diseases like blast, brown spot, bacterial blight, sheath blight and tungro still causing more damage and new minor diseases like bakanae, false smut, grain discoloration, early seedling blight, narrow brown spot, sheath rot have emerged as major problems. The losses due to these diseases may 1–100% based on the growing conditions, varietal susceptibility etc.., At present no significant source of resistance available for any of the above emerging diseases. But looking into the severity of these diseases, it is very important to address them by following integrated management practices like cultural, mechanical, biological and finally chemical control. But more emphasis has to be given to screen gerrmplasm against these diseases and identify stable source of resistance. Finally utilizing these sources in resistance breeding program by employing molecular breeding tools like marker assisted selection (MAS), marker assisted back cross breeding (MABB), gene pyramiding and transgenic tools. The present chapter discusses the importance of these emerging minor diseases of rice, the losses and possible management measures including resistance breeding

Comparison of various energy values and docking features for each of the best of modelled complex of Pi54 orthologues and AVR-Pi54 using ZDOCKER in DS3.5.

<p>Binding energy = energy of complex − [energy (receptor) + energy (ligand)].</p

<i>In vitro</i> expression and characterization of Pi54of protein.

<p>a: SDS-PAGE analysis of IPTG induced BL21 clones. Lane 2–7: <i>Pi54of</i> clones; Lane 8–13: <i>Pi54</i> clones. b: Western blot of <i>Pi54of</i> (1–3) and <i>Pi54</i> (4–6) protein using polyclonal Ab developed for Pi54 protein. c: Purified Pi54of protein. d: MS mass spectra MALDI-TOF analyzed Pi54of protein; ID 1233.555 showed match with Pi54 protein.</p

Phenotypic and expression analysis of <i>Pi54of</i> gene.

<p>Reaction of HR-12 (a) and <i>O. officinalis</i> (b) to with <i>M. oryzae</i>; c: Relative expression; pre-and-post inoculation of <i>O. officinalis</i> with <i>M. oryzae</i> using qRT-PCR at different intervals; d: Schematic representation of full length <i>Pi54of</i> gene; e: Structural analysis of <i>Pi54</i> orthologues in f: Nipponbare; g: Tetep (Sharma et al. 2005); h: <i>O. rhizomatis</i> (Das et al. 2012) and i: <i>O. officinalis</i>.</p

Genetic complementation of transgenic plants.

<p>Transgenic IET16310 plants challenged with <i>M. oryzae</i> stain RML21 (a) and 6-Sikkim (b). Detached leaves of transgenic TP309 plants challenged with <i>M. oryzae</i> (6-Sikkim) (c). NT (non transgenic) plants were used as control in all the experiments.</p

Possible molecular mechanism of <i>Pi54of</i> gene.

<p>Avr-Pi54 binds to Pi54of protein (blue) at the non-LRR region upstream to the LRR domain. Pi54of may perceive pathogen signals through STI1 which acts as an anchor for the so called defensome complex involving Os Rac1 (Rac/Rop GTPase), RACK1A (Receptor of Activated C Kinase), RAR (Required for Mla12 Resistance), SGT1 (Suppressor of the G2 allele of skp1), MAPK6 (a rice Mitogen-Activated Protein Kinase), Rboh (NADPH oxidases).</p

Schematic representation of predicted functional domains in Pi54of protein (a) and the frequency of amino acid residues found in four <i>Pi54</i> orthologue proteins; b: orthologue proteins; c: LRR region of all orthologue proteins.

<p>Schematic representation of predicted functional domains in Pi54of protein (a) and the frequency of amino acid residues found in four <i>Pi54</i> orthologue proteins; b: orthologue proteins; c: LRR region of all orthologue proteins.</p

Sub-cellular localization analysis of Pi54of protein.

<p>Panel a: Schematic representation of construct used. Panel b: GFP alone under the control of <i>CaMV 35S</i> promoter; Panel c: GFP-Pi54of fusion protein under the control of <i>CaMV 35S</i>; Panel d- non bombarded onion cells.</p

Phylogeny and alignment of amino acid residues from ORF of <i>Pi54, Pi54of</i> and <i>Pi54rh</i> orthologues.

<p>a: Phylogenetic relationship among the cloned rice blast resistance genes. Tree was generated using neighbor-joining method by MEGA.6 software with bootstrap value 1000 replications. The unit of branch length is 0.1 nucleotide substitutions per site, and is indicated by a bar at the bottom left corner of the tree. b: Aligned sequences of Pi54 protein orthologues using BioEdit tool.</p

Molecular docking of Pi54 proteins.

<p>Predicted tertiary structures of Pi54 orthologue protein Pi54 (a); Pi54rh (b); Pi54of (c); Pi54tp (d) and AVR-Pi54 protein (e) generated by <i>ab initio</i> modeling using I-TASSER server. Various secondary structure; Alpha helices (blue), β-sheets (red), Coils (green) have been depicted. Docked AVR-Pi54 with protein Pi54 (f); Pi54rh (g); Pi54of (h) and Pi54tp (i) using Z-DOCK server in Discovery studio 3.5. In the interaction, AVR protein is depicted in pink color and R-protein in blue color.</p