304 research outputs found
Differential Solute Regulation in Leaf Blades of Various Ages in Salt-Sensitive Wheat and a Salt-Tolerant Wheat x Lophopyrum elongatum (Host) A. Love Amphiploid
Salt tolerance in chickpea: Towards an understanding of sensitivity to salinity and prospects for breeding for improved resistance
Chickpea (Cicer arietinum L.) is sensitive to salinity, although genotypes showsignificant variation in tolerance. The reproductive phase appears to be particularly salt-sensitive. Importantly, recent screening experiments have been conducted to maturity with evaluation of seed yield under saline conditions, The genetic variation appears to be sufficient to breed for improved salt tolerance, but heritability of tolerance requires further study, only minor QTLs for salt tolerance have been identified, and the physiological basis of genotypic differences in tolerance is unclear; so, screening and selection of progeny will likely be a bottleneck in improvement of salt tolerance in chickpea
Domesticating Australian Native Legumes for Pastures: A Case Study in \u3ci\u3eCullen\u3c/i\u3e
Regulation of intracellular pH during anoxia in rice coleoptiles in acidic and near neutral conditions
Rice coleoptiles, renowned for anoxia tolerance, were hypoxically pretreated, excised, ‘healed’, and then exposed to a combination of anoxia and pH 3.5. The putative acid load was confirmed by net effluxes of K+ to the medium, with concurrent net decreases of H+ in the medium, presumably mainly due to H+ influx. Yet the coleoptiles survived the combination of anoxia and pH 3.5 for at least 90 h, and even for at least 40 h when the energy crisis, inherent to anoxia, had been aggravated by supplying the coleoptiles with 2.5 mM rather than 50 mM glucose. Even in the case of coleoptiles with 2.5 mM glucose, an accumulation ratio of 6 for Cl– was attained at 4 h after the start of re-aeration, implying plasma membrane integrity was either maintained during anoxia, or rapidly restored after a return to aerated conditions. Cytoplasmic pH and vacuolar pH were measured using in vivo 31P nuclear magnetic resonance spectroscopy with 50 mM glucose in the basal perfusion medium. After 60 h in anoxia, external pH was suddenly decreased from 6.5 to 3.5, but cytoplasmic pH only decreased from 7.35 to 7.2 during the first 2 h and then remained steady for the next 16 h. During the first 3 h at pH 3.5, vacuolar pH decreased from 5.7 to 5.25 and then stabilized. After 18 h at pH 3.5, the initial values of cytoplasmic pH and vacuolar pH were rapidly restored, both upon a return to pH 6.5 while maintaining anoxia and after subsequent return to aerated solution. Summing up, rice coleoptiles exposed to a combination of anoxia and pH 3.5 retained pH regulation and cellular compartmentation, demonstrating tolerance to anoxia even during the acid load imposed by exposure to pH 3.5
Vegetative and reproductive growth of salt-stressed chickpea are carbon-limited: sucrose infusion at the reproductive stage improves salt tolerance
Reproductive processes of chickpea (Cicer arietinum L.) are particularly sensitive to salinity. We tested whether limited photoassimilate availability contributes to reproductive failure in salt-stressed chickpea. Rupali, a salt-sensitive genotype, was grown in aerated nutrient solution, either with non-saline (control) or 30mM NaCl treatment. At flowering, stems were either infused with sucrose solution (0.44M), water only or maintained without any infusion, for 75 d. The sucrose and water infusion treatments of non-saline plants had no effect on growth or yield, but photosynthesis declined in response to sucrose infusion. Salt stress reduced photosynthesis, decreased tissue sugars by 22-47%, and vegetative and reproductive growth were severely impaired. Sucrose infusion of salt-treated plants increased total sugars in stems, leaves and developing pods, to levels similar to those of non-saline plants. In salt-stressed plants, sucrose infusion increased dry mass (2.6-fold), pod numbers (3.8-fold), seed numbers (6.5-fold) and seed yield (10.4-fold), yet vegetative growth and reproductive failure were not rescued completely by sucrose infusion. Sucrose infusion partly rescued reproductive failure in chickpea by increasing vegetative growth enabling more flower production and by providing sucrose for pod and seed growth. We conclude that insuffcient assimilate availability limits yield in salt-stressed chickpea.The work was financially supported by the Australia–India
Strategic Research Fund Grand Challenge Project (Project GCF010013)
of the Australian Government Department of Industry. HAK received an
Endeavour Postgraduate Award from the Australian Government and some
operating funds from the School of Plant Biology at The University of
Western Australia
Salt sensitivity of the vegetative and reproductive stages in chickpea (Cicer arietinum L.): Podding is a particularly sensitive stage
Soil salinity is an increasing problem, including in regions of the world where chickpea is cultivated. Salt
sensitivity of chickpea was evaluated at both the vegetative and reproductive phase. Root-zone salinity
treatments of 0, 20, 40 and 60mM NaCl in aerated nutrient solution were applied to seedlings or to
older plants at the time of flower bud initiation. Even the reputedly tolerant cultivar JG11 was sensitive
to salinity. Plants exposed to 60mM NaCl since seedlings, died by 52 d without producing any pods; at
40mM NaCl plants died by 75 d with few pods formed; and at 20mM NaCl plants had 78–82% dry mass
of controls, with slightly higher flower numbers but 33% less pods. Shoot Cl exceeded shoot Na by 2–5
times in both the vegetative and reproductive phase, and these ions also entered the flowers. Conversion
of flowers into pods was sensitive to NaCl. Pollen from salinized plants was viable, but addition of 40mM
NaCl to an in vitro medium severely reduced pollen germination and tube growth. Plants recovered
when NaCl was removed at flower bud initiation, adding new vegetative growth and forming flowers,
pods and seeds. Our results demonstrate that chickpea is sensitive to salinity at both the vegetative
and reproductive phase, with pod formation being particularly sensitive. Thus, future evaluations of salt
tolerance in chickpea need to be conducted at both the vegetative and reproductive stages
Silicon enhances suberization and lignification in roots of rice (Oryza sativa)
The beneficial element silicon (Si) may affect radial oxygen loss (ROL) of rice roots depending on suberization of the exodermis and lignification of sclerenchyma. Thus, the effect of Si nutrition on the oxidation power of rice roots, suberization and lignification was examined. In addition, Si-induced alterations of the transcript levels of 265 genes related to suberin and lignin synthesis were studied by custom-made microarray and quantitative Real Time-PCR. Without Si supply, the oxidation zone of 12 cm long adventitious roots extended along the entire root length but with Si supply the oxidation zone was restricted to 5 cm behind the root tip. This pattern coincided with enhanced suberization of the exodermis and lignification of sclerenchyma by Si supply. Suberization of the exodermis started, with and without Si supply, at 4–5 cm and 8–9 cm distance from the root tip (drt), respectively. Si significantly increased transcript abundance of 12 genes, while two genes had a reduced transcript level. A gene coding for a leucine-rich repeat protein exhibited a 25-fold higher transcript level with Si nutrition. Physiological, histochemical, and molecular-biological data showing that Si has an active impact on rice root anatomy and gene transcription is presented here
Two key genomic regions harbour QTLs for salinity tolerance in ICCV 2 × JG 11 derived chickpea (Cicer arietinum L.) recombinant inbred lines
Background
Although chickpea (Cicer arietinum L.), an important food legume crop, is sensitive to salinity, considerable variation for salinity tolerance exists in the germplasm. To improve any existing cultivar, it is important to understand the genetic and physiological mechanisms underlying this tolerance.
Results
In the present study, 188 recombinant inbred lines (RILs) derived from the cross ICCV 2 × JG 11 were used to assess yield and related traits in a soil with 0 mM NaCl (control) and 80 mM NaCl (salinity) over two consecutive years. Salinity significantly (P < 0.05) affected almost all traits across years and yield reduction was in large part related to a reduction in seed number but also a reduction in above ground biomass. A genetic map was constructed using 56 polymorphic markers (28 simple sequence repeats; SSRs and 28 single nucleotide polymorphisms; SNPs). The QTL analysis revealed two key genomic regions on CaLG05 (28.6 cM) and on CaLG07 (19.4 cM), that harboured QTLs for six and five different salinity tolerance associated traits, respectively, and imparting either higher plant vigour (on CaLG05) or higher reproductive success (on CaLG07). Two major QTLs for yield in the salinity treatment (explaining 12 and 17% of the phenotypic variation) were identified within the two key genomic regions. Comparison with already published chickpea genetic maps showed that these regions conferred salinity tolerance across two other populations and the markers can be deployed for enhancing salinity tolerance in chickpea. Based on the gene ontology annotation, forty eight putative candidate genes responsive to salinity stress were found on CaLG05 (31 genes) and CaLG07 (17 genes) in a distance of 11.1 Mb and 8.2 Mb on chickpea reference genome. Most of the genes were known to be involved in achieving osmoregulation under stress conditions.
Conclusion
Identification of putative candidate genes further strengthens the idea of using CaLG05 and CaLG07 genomic regions for marker assisted breeding (MAB). Further fine mapping of these key genomic regions may lead to novel gene identification for salinity stress tolerance in chickpea
Selecting Grassland Species for Saline Environments
In Australia, around 5.7 million hectares of agricultural land are currently affected by dryland salinity or at risk from shallow water tables and this figure is expected to increase over the next 50 years (LWRA, 2001). Most improved grassland species cannot tolerate the combined effects of salt and waterlogging and, therefore, the productivity of sown grasslands in salt-affected areas is low. However, there is potential to overcome the lack of suitably adapted fodder species by introducing new, salt and waterlogging-tolerant species and by diversifying the gene pool of proven species. Potential species include exotic, naturalised and native Australian grass, legumes, herb and shrub species that are halophytes and non-halophytes. A collaborative national project in southern Australia commenced in 2004 with the objective of evaluating a range of forage species for saline environments
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