Analysis of an intraspecific RIL population uncovers genomic segments harbouring multiple QTL for seed relevant traits in lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> L.)

Improving seed related traits remains key objective in lentil breeding. In recent years, genomic resources have shown great promise to accelerate crop improvement. However, limited genomic resources in lentil greatly restrict the use of genomics assisted breeding. The present investigation aims to build an intraspecific genetic linkage map and identify the QTL associated with important seed relevant traits using 94 recombinant inbreds (WA 8649090 × Precoz). A total of 288 polymorphic DNA markers including simple sequence repeat (SSR), inter simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) were assayed on mapping population. The resultant genetic linkage map comprised 220 loci spanning 604.2 cM of the lentil genome, with average inter-marker distance of 2.74 cM. QTL mapping in this RIL population uncovered a total of 18 QTL encompassing nine major and nine minor QTL. All major QTL were detected for seed related traits viz., seed diameter (SD), seed thickness (ST), seed weight (SW) and seed plumpness (SP) across two locations. A considerable proportion of the phenotypic variation (PV) was accounted to these QTL. For instance, one major QTL on LG5 controlling SW (QTL 15) explained 50% PV in one location, while the same QTL accounted for 34.18% PV in other location. Importantly, the genomic region containing multiple QTL for different seed traits was mapped to a 17-cM region on LG5. The genomic region harbouring QTL for multiple traits opens up exciting opportunities for genomics assisted improvement of lentil.     

Endophytic colonization of Typha australis by a plant growth-promoting bacterium Klebsiella oxytoca strain GR-3

AIMS: To isolate and characterize endophytic diazotrophic bacteria from a semi-aquatic grass (Typha australis) which grows luxuriantly with no addition of any nitrogen source. METHODS AND RESULTS: Ten endophytic diazotrophic bacteria from surface-sterilized roots and culm of T. australis were isolated and screened for plant growth-promoting activities employing standard methods. Based on the rate of nitrogenase activity, indole acetic acid (IAA) production and phosphate (P) solubilization, one root isolate namely GR-3 was found to be the most efficient one. This isolate was identified as Klebsiella oxytoca on the basis of 16S rDNA sequence analysis. Amplification of nifH by polymerase chain reaction (PCR) and detection of dinitrogenase reductase by western blot confirmed the diazotrophic nature of GR-3. It was tagged with gusA fused to a constitutive promoter and the resulting transconjugant was inoculated onto endophyte-free rice variety Malviya dhan-36 seedlings to express cross-infection ability which resulted in a significant increase in root/shoot length and chlorophyll a content. CONCLUSIONS: Roots and culm of T. australis harbour several endophytic diazotrophic bacteria. One root isolate, identified as K. oxytoca GR-3, seems to be an efficient plant growth-promoting bacterium. SIGNIFICANCE AND IMPACT OF THE STUDY: Plant growth-promoting properties of GR-3 suggest that this promising isolate merits further investigations for potential application in agriculture.     

Growth Enhancement of Chickpea in Saline Soils Using Plant Growth-Promoting Rhizobacteria

Bacterial isolates with the ability to tolerate salinity and plant growth-promoting features were isolated from the saline areas of Gujarat, India, that is, Bhavnagar and Khambat. A total of 176 strains of rhizobacteria were isolated out of which 62 bacterial strains were able to tolerate 1 M NaCl. These were then further studied for their potential plant growth-promoting rhizobacteria characteristics like phosphate solubilization, siderophore production, and IAA production. Twenty-eight isolates of the 62 strains showed good tricalcium phosphate solubilization in solid medium in the range of 9–22 mm and 15 isolates showed good phosphate solubilization in liquid medium in the range of 9–45 μg/ml. Siderophore production was checked in all 15 isolates, and 13 were screened out that produced the hydroxamate type of siderophore in the range of 11–50 mM. Among the 13 isolates, 10 were able to produce indole acetic acid in the range of 10–26 μg/ml after 72 h of incubation. Pot trials were carried out on chickpea under 300 mM NaCl stress using the best five isolates. Plants inoculated with MSC1 or MSC4 isolates showed an increase in the parameters that evaluate plant growth when compared to uninoculated controls. Strains MSC1 and MSC4 were identified as Pseudomonas putida and Pseudomonas pseudoalcaligens, respectively, according to sequence analysis of the 16S rRNA gene.     

Expression of transformation in cell hybrids. I. Isolation and application of density-inhibited Balb/3T3 cells deficient in hypoxanthine phosphoribosyltransferase and resistant to ouabain.

A cell line, THO2, was isolated from Balb/3T3 clone A31 after sequential nitrosoguanidine treatments and selection for resistance to 6-thioguanine and ouabain. THO2 retains the properties of density-dependent inhibition of growth and serum dependence of DNA synthesis characteristic of 3T3. The codominant expression of ouabain resistance and inability of THO2 to utilize exogenous hypoxanthine in the presence of aminopterin allows isolation of somatic cell hybrids involving THO2 and any ouabain-sensitive, hypoxanthine phosphoribosyltransferase-positive cell line. Hybrid clones derived from THO2 and SV40-transformed cells show dominant expression of the transformed phenotype with respect to multilayered arrangement of cells and ability to synthesize DNA in 1% calf-serum medium.     

Bufadienolides in different chromosomal races of Indian squill

Scilliphaeoside and anhydroscilliphaeosidin have been isolated from tetraploid Indian squill. The absence of scilliphaeoside in all populations of diploids and hexaploids and anhydrophaeosidin in diploids, triploids and hexaploids might be one of the reasons why they were not detected in previous studies.     

Heavy-metal toxicity in the cyanobacterium Nostoc Linckia

The effects of HgCl₂, NiCl₂ and CoCl₂ on Nostoc linckia (Roth) Born. et Flah. were studied. Low level (0.2 p.p.m.) of mercury increased heterocyst frequency, stimulated nitrate reductase and ammonium uptake, but significantly inhibited acetylene-reducing and glutamine-synthetase activities. In contrast, NiCl₂ and CoCl₂ greatly inhibited all of the above processes.     

Occurrence of Arbuscular Mycorrhizal Fungi in Rhizosphere of Jatropha curcas L. in Arid and Semi Arid Regions of India

A study was conducted to identify common arbuscular mycorrhizal (AM) fungi present in rhizosphere of Jatropha curcas L., an important bio-diesel crop, from different arid and semi arid regions of India viz., Jodhpur (Rajasthan), Hissar (Haryana), Jhansi and Lalitpur (Uttar Pradesh) and Hyderabad (Andhra Pradesh). A total of 20 AM species were recorded, which consisted of two species of Acaulospora and 18 species of Glomus. The highest frequency of occurrence was recorded for Glomus intraradix (100%), followed by Acaulospora scrobiculata (83%), G. etunicatum (50%) and Glomus 1 (50%). Maximum species richness was recorded at Jodhpur, followed by Jhansi, Hissar, Hyderabad and Lalitpur. The results seem to suggest that species richness was more in arid regions as compared to semi arid areas.     

Polyamine metabolism and lipoxygenase activity during Fusarium oxysporum f. sp. ricini -Castor interaction

Polyamine oxidase and lipoxygenase enzymes are key players for hyper sensitive reaction (HR) during incompatible interaction of host-pathogen. Thus, the role of lipoxygenase and polyamines was studied in the wilt pathogen infected and non infected tissues of resistant and susceptible genotypes of castor at 0 days after infection (DAI), 5 DAI and 10 DAI (30 days after sowing). The lipoxygenase (LOX) and polyamine oxidase (PAO) activities were higher in the incompatible interaction at all the stages of analysis. The constitutive level of malondyaldehyde (MDA) content, a product of lipid peroxidation was higher in susceptible genotypes (VP-1 and VI-9), while induced level was higher in resistant genotypes (48–1 and SKP-84) at 5 DAI and 10 DAI . Polyamine profiling using HPTLC showed higher spermidine and spermine content in resistant genotypes at 10 DAI. Furthermore, spermidine was detected only in the roots of resistant genotypes at 10 DAI. These results suggest the role of high titers of polyamines, LOX and PAO in disease resistance possibly through HR induction.