Genetic diversity of maize genotypes on the basis of morpho-physiological and simple sequence repeat (SSR) markers

In this investigation, an attempt was made to assess the genetic diversity among 91 maize (Zea mays L.) genotypes using morpho-physiological and molecular markers. Variability was observed for six morpho-physiological traits namely, SPAD chlorophyll meter reading, canopy temperature, plant height, yield per plant, fodder yield and plant biomass as well as with simple sequence repeat (SSR) markers. All the amplification products with 40 SSRs were in the range of 58 to 410 bp. A total of 124 alleles were generated and the number of alleles scored for 40 SSR loci ranged from 2 to 5 with a mean of 3.1 alleles per locus. Polymorphism information content ranged from 0.054 to 0.82 with a mean of 0.55 suggesting that all the selected genotypes possessed high level of polymorphism. The study indicates that five genotypes, RJR-247, RJR-159, NSJ-179, RJR-55 and Z101-15 were most diverse, so it is suggested that they may be used as genetic resources for maize improvement programme in future quantitative trait loci (QTL) mapping for different agronomic traits and for developing new varieties with adaptation to a broad range of environments.Key words: Maize, SSR markers, genetic diversity, dendrogram

Modulation of host cell processes by T3SS effectors

Two of the enteric Escherichia coli pathotypes-enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC)-have a conserved type 3 secretion system which is essential for virulence. The T3SS is used to translocate between 25 and 50 bacterial proteins directly into the host cytosol where they manipulate a variety of host cell processes to establish a successful infection. In this chapter, we discuss effectors from EPEC/EHEC in the context of the host proteins and processes that they target-the actin cytoskeleton, small guanosine triphosphatases and innate immune signalling pathways that regulate inflammation and cell death. Many of these translocated proteins have been extensively characterised, which has helped obtain insights into the mechanisms of pathogenesis of these bacteria and also understand the host pathways they target in more detail. With increasing knowledge of the positive and negative regulation of host signalling pathways by different effectors, a future challenge is to investigate how the specific effector repertoire of each strain cooperates over the course of an infection

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Not AvailableHigh temperature is an important environmental stress that influences the growth and development of crop plants thus adversely affecting their production and productivity. An experiment was carried out to investigate the protective role of bioregulators viz., Putrescine (Put), Thiourea (TU) and Hydrogen Peroxide (H2O2) against high temperature stress in maize at early vegetative stage. Maize genotypes earlier identified as heat tolerant (NSJ 221 and NSJ 189) and heat sensitive (RJR 270 and PSRJ 13099) were chosen for the present study. Independent foliar spray of Put (4 mM), TU (20mM) and H2O2 (1.2 mM) was observed to have significant difference (P>0.01) between genotypes, treatments and their interaction when applied 72 hrs prior to heat exposure. High temperature stress led to disruption of cellular membrane by increasing cell membrane injury, lipid peroxidation and H2O2 contents. It led to decrease in total chlorophyll content, soluble proteins, quantum yield and POD activity. Increased SOD activity in heat stressed seedlings was recorded with genotypes NSJ 189 and NSJ 221. Foliar application of Put, TU and H2O2 ameliorated heat-induced damages by stimulating the antioxidant enzyme system through decrease in lipid peroxidation, membrane injury and H2O2 contents in all the genotypes when compared with untreated heat stressed seedlings. Spray with these chemicals resulted in an increase in chlorophyll content, quantum yield and activities of anti-oxidative stress enzymes. Genotypes RJR 270 and PSRJ 13099 recorded improved heat tolerance with spray either of these chemicals by enhancing their biochemical potential. Spray of Put or TU was observed to be more effective of improving heat stress tolerance of maize seedlings.Not Availabl

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Not AvailablePigeon pea (Cajanus cajan L. Millsp.) is an important grain legume crop of the semi arid tropics and is a major dietary protein source. The extra short duration cultivar of pigeon pea ICPL 88039 was evaluated at ambient (370 μmol/mol) and twice the ambient (700 μmol/mol) concentrations of CO2 in open top chambers (OTCs). The results showed that the crop recorded a significant positive enhanced response for total biomass, fodder yield, grain yield, number of pods and seeds per plant, test weight and HI at elevated CO2. The ANOVA revealed significant differences in response of the characteristics to CO2 concentrations. Under elevated CO2 the total biomass recorded an improvement of 91.3%, grain yield 150.1%, fodder yield 67.1%. The major contributing components for improved grain yield under elevated CO2 were number of pods, number of seeds and test weight which recorded an increase of 97.9%, 119.5% and 7.2%, respectively. The crop maintained a significant positive increase of harvest index (HI) at elevated CO2 with an increment of 30.7% over ambient values. This increase in HI was due to its improved pod set and seed yield under enhanced CO2 concentration thereby emphasizes this crop for sustained food with nutritional security under climate change scenario.AP-Cess, ICA

Microarray analysis of the Ler regulon in enteropathogenic and enterohaemorrhagic Escherichia coli strains

The type III protein secretion system is an important pathogenicity factor of enteropathogenic and enterohaemorrhagic Escherichia coli pathotypes. The genes encoding this apparatus are located on a pathogenicity island (the locus of enterocyte effacement) and are transcriptionally activated by the master regulator Ler. In each pathotype Ler is also known to regulate genes located elsewhere on the chromosome, but the full extent of the Ler regulon is unclear, especially for enteropathogenic E. coli. The Ler regulon was defined for two strains of E. coli: E2348/69 (enteropathogenic) and EDL933 (enterohaemorrhagic) in mid and late log phases of growth by DNA microarray analysis of the transcriptomes of wild-type and ler mutant versions of each strain. In both strains the Ler regulon is focused on the locus of enterocyte effacement – all major transcriptional units of which are activated by Ler, with the sole exception of the LEE1 operon during mid-log phase growth in E2348/69. However, the Ler regulon does extend more widely and also includes unlinked pathogenicity genes: in E2348/69 more than 50 genes outside of this locus were regulated, including a number of known or potential pathogenicity determinants; in EDL933 only 4 extra-LEE genes, again including known pathogenicity factors, were activated. In E2348/69, where the Ler regulon is clearly growth phase dependent, a number of genes including the plasmid-encoded regulator operon perABC, were found to be negatively regulated by Ler. Negative regulation by Ler of PerC, itself a positive regulator of the ler promoter, suggests a negative feedback loop involving these proteins