Rice fall by 10 % and wheat

Rice (Oryza sativa L.) hold
about one fifth to the total land area covered by cereals and it is the
principal staple food for more than 50% of the world’s population (Chakravarthi
et al. 2006; Ram et al. 2007). Rice is cultivated under diverse
eco-geographical conditions in assorted tropical and subtropical countries like
Bangladesh and other Asian countries. Salt stress is a foremost restriction to
cereal production worldwide (Tuteja 2012). In Bangladesh, about 2.8 million
hectares of coastal soil has become saline due to dense withdrawal of surface
and groundwater for irrigation and intrusion of seawater. The total saline area
customs a third of the 9 million hectares of total cultivated lands in
Bangladesh (ABSPII 2006). The coastal saline soils are distributed unevenly in
64 upazilas of 13 districts, covering portions of eight agro-ecological zones of
the country (Seraj and Salam 2000). Agriculture is the main sector for
Bangladesh’s economy and the coastal area of Bangladesh is very fertile for producing
rice. Increase in salinity intrusion and expansion in soil salinity will have severe
harmful effects on agriculture. The food production appears to face a pronounced
alarm in near future due to climate change. In Bangladesh, rice production may
fall by 10 % and wheat by 30 % by 2050 (IPCC 2007).

Assessment of genetic diversity is important in plant breeding if there
is to be improvement by selection. For the assessment of genetic diversity molecular
markers have been generally superior to morphological, pedigree, heterosis and
biochemical data (Melchinger et al., 1991). Genetic diversity is commonly
measured by genetic distance or genetic similarity, both of which imply that
there are either differences or similarities at the genetic level (Weir, 1990).
Molecular Marker based Genetic Diversity Analysis (MMGDA) also has potential
for assessing changes in genetic diversity over time and space (Duwick, 1984). Deoxyribonucleic
acid (DNA) is the genetic material that presents the sign to identify the
potentiality and diversity among different plant genotypes (Semagn et al. 2006).
Though, rice genome sequence is available (The Rice Genome Mapping Project 2005),
most researchers are trying to identify particular segment of DNA or gene in a definite
chromosome (Semagn et al. 2006). Molecular markers are the molecules
that can trace a required gene in observed genotypes. Molecular markers deliver
evidence that can help to define the distinctiveness of germplasms and their
ranking according to the number of close relative and their phylogenetic
position. DNA-based SSR markers were co-dominant and highly polymorphic; deal
an easy, perfect, and measurable degree of the genetic variation within crop
plants (Sunnucks 2000; Collard 2008). SSR markers have been proved to be ideal
for making genetic maps (Islam 2004; Niones 2004), assisting selection (Bhuiyan
2005) and studying genetic diversity in germplasms. SSR markers play an significant
role while recognizing gene for salt tolerance or in introgressing the genes to
develop new cultivars. For rice, there are nearly about 15,000 SSRs now
available (www.gramene.org) and are currently being used to develop high density
genetic maps, genotype rice accessions, determine the genetic structure and
diversity patterns, optimize the assembly of core collections, and for
marker-assisted breeding (McCouch et al. 2002; Yu et al. 2003; Garris et al. 2005).
Microsatellites, mentioned to as simple sequence repeats (SSR), are a suitable marker
for genome analysis, because of the suggestive level of allelic diversity that
may be discovered (Ishii et al. 2001). Polymorphisms in the microsatellite
region are pondered to result from misreplication of repeated sequences
(Richards and Sutherland 1994), and the polymorphisms detected by PCR, using
pairs of primers specific to the sequences flanking the microsatellite repeats.

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Hence, the objective of the study was undertaken to screen rice genotypes
under salinized conditions at the seedling stage and to identify salt tolerant
rice genotypes using microsatellite markers at seedling stage.