Identification and fine-mapping of Xa33, a novel gene for resistance to Xanthomonas oryzae pv. oryzae

Broadening of the genetic base for identification and transfer of genes for resistance to insect pests and diseases from wild relatives of rice is an important strategy in resistance breeding programs across the world. An accession of Oryza nivara, International Rice Germplasm Collection (IRGC) accession number 105710, was identified to exhibit high level and broad-spectrum resistance to Xanthomonas oryzae pv. oryzae. In order to study the genetics of resistance and to tag and map the resistance gene or genes present in IRGC 105710, it was crossed with the bacterial blight (BB)-susceptible varieties 'TN1' and 'Samba Mahsuri' (SM) and then backcrossed to generate backcross mapping populations. Analysis of these populations and their progeny testing revealed that a single dominant gene controls resistance in IRGC 105710. The BC(1)F(2) population derived from the cross IRGC 105710/TN1//TN1 was screened with a set of 72 polymorphic simple-sequence repeat (SSR) markers distributed across the rice genome and the resistance gene was coarse mapped on chromosome 7 between the SSR markers RM5711 and RM6728 at a genetic distance of 17.0 and 19.3 centimorgans (cM), respectively. After analysis involving 49 SSR markers located between the genomic interval spanned by RM5711 and RM6728, and BC(2)F(2) population consisting of 2,011 individuals derived from the cross IRGC 105710/TN1//TN1, the gene was fine mapped between two SSR markers (RMWR7.1 and RMWR7.6) located at a genetic distance of 0.9 and 1.2 cM, respectively, from the gene and flanking it. The linkage distances were validated in a BC(1)F(2) mapping population derived from the cross IRGC 105710/SM//2 × SM. The BB resistance gene present in the O. nivara accession was identified to be novel based on its unique map location on chromosome 7 and wider spectrum of BB resistance; this gene has been named Xa33. The genomic region between the two closely flanking SSR markers was in silico analyzed for putatively expressed candidate genes. In total, eight genes were identified in the region and a putative gene encoding serinethreonine kinase appears to be a candidate for the Xa33 gene.     

Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite

The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption of hexadecyltrimethylammonium (HDTMA) and octadecyltrimethylammonium (ODTMA) on montmorillonite was studied above and below their critical micelle concentrations (CMC). At concentrations above the CMC, the loading exceeded the clay's cation exchange capacity (CEC) and indicated higher affinity of the cation with the longer alkyl chain. An adsorption model could adequately simulate adsorption at concentrations below the CMC, and yield fair predictions for the effect of ionic strength. The model indicated that above the CMC adsorbed micelles contributed significantly to the amount of ODTMA adsorbed. Evidence for adsorption of ODTMA micelles on montmorillonite was provided by X-ray diffraction, freeze-fracture electron microscopy, and dialysis bag measurements. SFM was not adsorbed directly on the clay mineral, and adsorbed at low levels, when the organic cation was adsorbed as monomers. In contrast, a large fraction of SFM adsorbed on the clay mineral when incorporated in micelles that adsorbed on the clay.     

Bioactivities of <Emphasis Type="Italic">Cocos nucifera</Emphasis> L. (Arecales: Arecaceae) and <Emphasis Type="Italic">Terminalia catappa</Emphasis> L. (Myrtales: Combretaceae) leaf extracts as post-harvest grain protectants against four major stored product pests

Compounds extracted from the leaves of coconut palm, Cocos nucifera L. (Arecales: Arecaceae) and the Indian almond, Terminalia catappa L. (Myrtales: Combretaceae) were assessed as potential grain protectants against four major pests of stored grains, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), and Callosobruchus chinensis (L.) (Coleoptera: Bruchidae). The crude leaf extracts and their fractions were obtained by solvent elution and bioassayed in the laboratory, focusing on (a) the duration of protection and (b) their effects on progeny production. Results showed that adults of C. chinensis, S. oryzae, and T. castaneum were equally susceptible to the fumigant toxicity of C. nucifera and T. catappa crude extracts as well as their column eluted fractions. On the contrary, adults of R. dominica showed tolerance to all the extracts tested in both fumigation and contact mode bioassays. Cocos nucifera crude extracts were highly effective in offering long-term protection in residual toxicity trials and along with the crude extracts of T. catappa showed strong repellent properties against the tested species except for R. dominica in a Y-tube olfactometer. Generally, the chromatographic fractions of crude leaf extracts eluted with ethyl acetate were significantly more effective than methanol, chloroform or hexane-eluted fractions. Further, all the tested plant extracts demonstrated a negative impact on several biological parameters such as feeding activity and progeny production of the tested species. These results highlight the potential of C. nucifera and T. catapa extracts as potent insecticides, feeding deterrents and progeny production inhibitors and consequently are suitable for the control of pests in stored commodities.     

Ration restriction,compensatory growth and pituitary growth hormone gene expression in Labeo rohita

An experiment to investigate the compensatory growth (CG) response of Labeo rohita was conducted in two phases: a first phase (6 weeks) in which triplicate groups of fish were subjected to feed restriction (5, 25, 50 and 75 % of satiation) or satiation feeding (control) and a second phase (6 weeks) of satiation feeding for all treatment groups. CG in body weight occurred in groups which were under moderate feed restriction (50–75 % of satiation) under phase 1, but more severe feed restrictions resulted in lower weight gain. Improved feed conversion ratio (FCR) (1.6 ± 0.05 and 1.9 ± 0.03) relative to control (2.1 ± 0.06) was observed in the fish that displayed CG following moderate feed restriction (50–75 % of satiation). At the end of the experiment, body moisture, lipid and protein content were not significantly different between moderately restricted fish and the control. After the first phase, there was no significant difference in the expression of pituitary growth hormone (GH) gene between groups, but at the end of the experiment, significantly lower GH expression was observed in the fish subjected to a restriction of 25 and 50 % of satiation during phase 1. Exploiting the ability of fishes to undergo CG in terms of weight gain and improved FCR without major changes in body composition can be considered as an effective management practice.     

Surface modifications of natural Kanchipuram silk (pattu) fibers using glow discharge air Plasma

Experimental investigations have been carried out to modify the surface properties of natural Kanchipuram silk (pattu) fibers using a low temperature DC glow discharge air Plasma. Silk is an externally spun fibrous protein secretion formed into fibers. Plasma treatment is an eco-friendly, dry, and clean process over wet chemical method and does not suffer from any environmental and health concerns. Experiments have been performed considering three parameters such as discharge current, treatment time, and working pressure. The structural, thermal, morphological, optical, and mechanical studies of raw and plasma treated silk fibers have been obtained out using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), thermo gravimetric analyzer (TGA), scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS), diffuse absorbance spectroscopy, and tensile test. A comparative study has been done for the untreated and different treated fibers. Various characterization analyses reveal that surface roughness of the plasma treated silk fiber is increased and also crystallite size of treated samples is enhanced, plasma treated silk fibers maintain the whiteness effect and it is observed that UV transmittance region (A & B) is more for the treated fiber which signifies enhanced UV protection.     

Do cannibalistic fish possess an intrinsic higher growth capacity than others? A case study in the Asian redtail catfish Hemibagrus nemurus (Valenciennes, 1840)

This study relied on the day‐by‐day analysis of bioenergetics and prey size preference in larvae and juveniles of Hemibagrus nemurus selected at random, held in isolation (28.5°C, 12L:12D) and feeding ad libitum on conspecifics [21 fish, 12–46 mm total length (TL), dry mass (DM) of 1–145 mg]. Several traits concur to make young H. nemurus highly cannibalistic: (1) high predation capacities (largest prey = 88% and 70% TL in fish of 8 and >40 mm TL, respectively), (2) opportunistic feeding behaviours with no marked size preference and (3) an unusual combination of high food intake (>100% DM at 1 mg DM) and very high gross conversion efficiency (>0.70). A growth model was constructed from the top performances of fish feeding maximally (16 of 21 fish) and indicated that the risk of cannibalism would be high and permanent except for meal frequencies over five daily meals. Cannibals emerging spontaneously under communal rearing (6 fish L^?1, three daily meals) grew more slowly or just at the same rate as predicted by the growth model constructed from siblings selected at random. This indicates that the individuals that become cannibals do not possess higher intrinsic capacities for growth than others.     

Marker assisted introgression of bacterial blight resistance in Samba Mahsuri,an elite indica rice variety

Samba Mahsuri (BPT5204) is a medium slender grain indica rice variety that is very popular with farmers and consumers across India because of its high yield and excellent cooking quality. However, the variety is susceptible to several diseases and pests, including bacterial blight (BB). We have used PCR based molecular markers in a backcross-breeding program to introgress three major BB resistance genes (Xa21, xa13 and xa5) into Samba Mahsuri from a donor line (SS1113) in which all the three genes are present in a homozygous condition. At each backcross generation, markers closely linked to the three genes were used to select plants possessing these resistance genes (foreground selection) and microsatellite markers polymorphic between donor and recurrent parent were used to select plants that have maximum contribution from the recurrent parent genome (background selection). A selected BC₄F₁ plant was selfed to generate homozygous BC₄F₂ plants with different combinations of BB resistance genes. The three-gene pyramid and two-gene pyramid lines exhibited high levels of resistance against the BB pathogen. Under conditions of BB infection, the three-gene pyramid lines exhibited a significant yield advantage over Samba Mahsuri. Most importantly, these lines retain the excellent grain and cooking qualities of Samba Mahsuri without compromising the yield as determined in multi-location trials. This work demonstrates the successful application of marker-assisted selection for targeted introgression of multiple resistance genes into a premium quality rice variety. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. R. M. Sundaram and M. R. Vishnupriya have contributed equally to this work.     

Stabilization of tannery sludge amended soil using Ricinus communis,Brassica juncea and Nerium oleander

Purpose

Characterization of tannery sludge (TS) for its plausible use in amelioration and phytoremediation of heavy metal rich TS treated soil by growing economically important plants (Ricinus communis, Brassica juncea and Nerium oleander).

Materials and methods

Treatments were prepared by amalgamation of TS (0, 5, 10, 20, 30, 50, 75, 100 %) with garden soil (GS). All treatments were analysed for chemical properties, total and DTPA (Diethylene triamine pentaacetic acid) extractable heavy metals (Cr, Pb, Cu, and Mn). Seed germination experiment was conducted; unvarying saplings were selected and planted in concerned pots and allowed to grow for 90 days in green house. At harvest, plant samples were washed with distilled water and used for determination of growth parameters (biomass of root, shoot and total biomass on dry weight basis) and metal accumulation in different parts of the plant. Translocation factor (TF) and bioconcentration factor (BCF) have been calculated to check the phytostabilization capability of studied plants.

Results and discussion

Application of TS in fixed quantity as an amendment resulted in significant improvements of GS characteristics (alkaline pH with high electrical conductivity, organic carbon, available NPK and heavy metals) and in treatments. DTPA extractable heavy metal concentrations were found very low and total heavy metal concentrations were also found under allowable range in control and treated soil (T-I to T-VI). The maximum seed germination percentage, plant growth, biomass production for all plant species were observed in T-III treatment (20 % TS + 80 % GS) with majority of the metal accumulation in underground part (BCF >1) and meagre translocation in aerial part (TF <1). From T-IV to T-VII treatment, accumulation of heavy metals in plant parts has generally increased; however, biomass has been tremendously decreased.

Conclusions

TS was found rich in NPK content with significant concentration of heavy metals. Pot growth experiment suggested amelioration of GS with specific quantity of 20 % TS can tremendously enhance the plant growth, help in the utilization of TS and can act as a substitute of synthetic fertilizer. Majority of the metals was accumulated in root part (BCF >1) and meagre translocation (TF <1) in aerial part, concludes R. communis and B. juncea could be suitable plant species to be grown in heavy metal rich TS treated soil, vis-à-vis for phytostabilization of heavy metals. In addition, these oil yielding and medicinal plants can also be used for phytoremediation of moderately contaminated tannery soils.

     

Marker‐assisted introgression of bacterial blight and blast resistance into IR 58025B,an elite maintainer line of rice

IR 58025A is a very popular wild‐abortive cytoplasmic male sterile (WA‐CMS) line of rice and is extensively used for hybrid rice breeding. However, IR 58025A and many hybrids derived from it possess mild aroma (undesirable in some parts of India) and are highly susceptible to bacterial blight (BB) and blast diseases. To improve IR 58025A for BB and blast resistance, we have introgressed a major dominant gene conferring resistance against BB (i.e. Xa21) and blast (i.e. Pi54) into IR 58025B, the maintainer line of IR 58025A. An introgression line of Samba Mahsuri (i.e. SM2154) possessing Xa21 and Pi54 genes in homozygous condition and fine‐grain type was used as donor parent, and backcross breeding strategy was adopted for targeted introgression of the resistance genes. PCR‐based molecular markers tightly linked to Xa21 and Pi54 were used for selection of BB‐ and blast‐resistant lines, while closely linked markers were used for identification of backcross‐derived plants devoid of Rf4 and aroma. At BC₂F₅, four backcross‐derived lines possessing resistance against BB and blast, devoid of aroma, high yield, short plant stature, long‐slender grain type and with recurrent parent genome recovery ranging from 88.8% to 98.6% were selected and advanced for further evaluation. The improved versions of IR 58025B, viz. SB54‐11‐143‐9‐44‐5, SB54‐11‐143‐9‐44‐98, SB54‐11‐143‐9‐44‐111 and SB54‐11‐143‐9‐44‐171, behaved as perfect maintainers when test‐crossed with WA‐CMS lines. Agronomically superior lines of improved IR 58025B are being converted to CMS line through backcrossing for developing high‐yielding and biotic stress‐resistant rice hybrids.