Advanced Statistical Methods in Biometric Research.

Thirty crop species provide 90% of our food, most of which display severe yield losses under moderate salinity. Securing and augmenting agricultural yield in times of global warming and population increase is urgent and should, aside from ameliorating saline soils, include attempts to increase crop plant salt tolerance. This short review provides an overview of the processes that limit growth and yield in saline conditions. Yield is reduced if soil salinity surpasses crop-specific thresholds, with cotton, barley and sugar beet being highly tolerant, while sweet potato, wheat and maize display high sensitivity. Apart from Na+ , also Cl- , Mg2+ , SO4 2- or HCO3 - contribute to salt toxicity. The inhibition of biochemical or physiological processes cause imbalance in metabolism and cell signalling and enhance the production of reactive oxygen species interfering with cell redox and energy state. Plant development and root patterning is disturbed, and this response depends on redox and reactive oxygen species signalling, calcium and plant hormones. The interlink of the physiological understanding of tolerance processes from molecular processes as well as the agronomical techniques for stabilizing growth and yield and their interlinks might help improving our crops for future demand and will provide improvement for cultivating crops in saline environment.

Salinity and crop yield

Salt stress reduces land and water productivity and contributes to poverty and food insecurity. Increased salinization caused by human practices and climate change is progressively reducing agriculture productivity despite escalating calls for more food. Plant responses to salt stress are well understood, involving numerous critical processes that are each controlled by multiple genes. Knowledge of the critical mechanisms controlling salt uptake and exclusion from functioning tissues, signaling of salt stress, and the arsenal of protective metabolites is advancing. However, little progress has been made in developing salt-tolerant varieties of crop species using standard (but slow) breeding approaches. The genetic diversity available within cultivated crops and their wild relatives provides rich sources for trait and gene discovery that has yet to be sufficiently utilized. Transforming this knowledge into modern approaches using genomics and molecular tools for precision breeding will accelerate the devel...

Genomics, Physiology, and Molecular Breeding Approaches for Improving Salt Tolerance.

Identification of genes for quantitative traits is difficult using any single approach due to complex inheritance of the traits and limited resolving power of the individual techniques. Here a combination of genetic mapping and bulked transcriptome profiling was used to narrow down the number of differentially expressed salt-responsive genes in rice in order to identify functional polymorphism of genes underlying the quantitative trait loci (QTL). A population of recombinant inbred lines (RILs) derived from cross between salt-tolerant variety CSR 27 and salt-sensitive variety MI 48 was used to map QTL for salt ion concentrations in different tissues and salt stress susceptibility index (SSI) for spikelet fertility, grain weight, and grain yield. Eight significant QTL intervals were mapped on chromosomes 1, 8, and 12 for the salt ion concentrations and a QTL controlling SSI for spikelet fertility was co-located in one of these intervals on chromosome 8. However, there were total 2,681 genes in these QTL intervals, making it difficult to pinpoint the genes responsible for the functional differences for the traits. Similarly, transcriptome profiling of the seedlings of tolerant and sensitive parents grown under control and salt-stress conditions showed 798 and 2,407 differentially expressed gene probes, respectively. By analyzing pools of RNA extracted from ten each of extremely tolerant and extremely sensitive RILs to normalize the background noise, the number of differentially expressed genes under salt stress was drastically reduced to 30 only. Two of these genes, an integral transmembrane protein DUF6 and a cation chloride cotransporter, were not only co-located in the QTL intervals but also showed the expected distortion of allele frequencies in the extreme tolerant and sensitive RILs, and therefore are suitable for future validation studies and development of functional markers for salt tolerance in rice to facilitate marker-assisted breeding.

Combining QTL mapping and transcriptome profiling of bulked RILs for identification of functional polymorphism for salt tolerance genes in rice (Oryza sativa L.).

Rice (Oryza sativa L) is an important staple crop that feeds more than one half of the world’s population and is the model system for monocotyledonous plants However, rice is very sensitive to salinity and is the most salt sensitive cereal crop with a threshold of 3 dSm−1 for most cultivated varieties Despite many attempts using different strategies to improve salinity tolerance in rice, the achievements so far are quite modest This review aims to discuss challenges that hinder the improvement of salinity stress tolerance in rice as well as potential opportunities for enhancing salinity stress tolerance in this important crop

https://www.mdpi.com/2073-4395/6/4/54/pdf

Improvement of salinity stress tolerance in rice: Challenges and opportunities

http://r4d.dfid.gov.uk/PDF/Outputs/GenerationChallenge/Thomson_2007_poster.pdf

QTL mapping and marker-assisted backcrossing for improved salinity tolerance in rice

Twenty eight genotypes of potato representing different sources collected from TCRC, BARI, Gazipur were tested for genetic divergence utilizing multivariate analysis. The genotypes were grouped into five clusters. No relationship was found between genetic divergence and geographic distribution. Number of tubers per plant and yield contributed maximum, while average weight of a tuber and weight of tubers per plant contributed high towards total divergence which offered due attention to these characters while selecting for increased tuber yield. The inter-cluster distance (D 2 ) was maximum (36.29) between III and IV. The highest and the lowest intracluster distances (D 2 ) were 9.64 and 2.48 in cluster III and II, respectively. Keywords: Potato; selection; genetic divergence; cluster analysis; tuber yield. DOI: http://dx.doi.org/10.3329/bjar.v36i1.9240 BJAR 2011; 36(1): 165-172

/pdf/genetic-divergence-in-potato-solanum-tuberosum-l-bddev6epfb.pdf

Genetic Divergence In Potato ( Solanum Tuberosum L.)

BRRI Dhan 47: A salt tolerant rice variety for Boro season isolated through participatory variety selection

Breeders are habituated to develop rice varieties on the centralized breeding approach. Varieties recommended in this method are popular to farmers at favorable rice production systems and often they are not suitable for stressed soil like saline prone land. To develop varieties suitable for saline prone areas, farmers’ participation are directly involved to choice variety as they want. A large range of salt tolerant improve genotypes was grown in mother and baby system trials of participatory variety selection (PVS) at five coastal areas of Bangladesh. Experiments in farmers fields with farmers participation based on their needs has helped identify high yielding varieties for their lands. The success of PVS in the five coastal localities has convinced researchers and partner organizations to mirror the appreciation for this approach of rice variety development in risk prone environment. Among 234 genotypes the chosen five for both of Boro and T. Aman seasons of PVS were included in the national variety release system.

/pdf/participatory-variety-selection-for-salt-tolerant-rice-38mo64s5je.pdf

Rahman

Papers

QTL mapping and marker-assisted backcrossing for improved salinity tolerance in rice

Genetic Divergence In Potato ( Solanum Tuberosum L.)

BRRI Dhan 47: A salt tolerant rice variety for Boro season isolated through participatory variety selection

Participatory variety selection for salt tolerant rice

BRRI dhan47: a salt tolerant variety for Boro season, IRRN, IRRI, Philippines.