Impact of salt stress on five varieties of Wheat( Triticum aestivum L.) cultivars under laboratory condition

Abstract

The impact of salt stress under different salinity level (0,25,50,75,100,125,150 mM NaCl) on five varieties of Wheat viz., HOW-234, HD-2689, RAJ-4101, RAJ-4123, and HD-2045 was conducted. The data showed that different level of salinity significantly affected the growth attributes by reducing root and shoot length for salinity below 125mM. Fresh weight and dry weight of root and shoot were reduced significantly with subsequent treatment. Regarding germination maximum germination was found in variety HD2689 in all the treatments and maximum inhibition was found to be in case of HOW234 variety at 150mM salinity level. Regarding biochemical analysis the sugar, proline content increased with increasing salinity level where as protein content decreased in the physiologically active leaves of different treatments for all the varieties of wheat. @ JASEM Wheat is a major cereal crop in many parts of the world and it is commonly known as king of cereals. It belongs to poaceae family and globally after maize wheat is the second most produced food among the cereal crops, rice ranks third. High substrate salinity is a major limiting factor for plants in coastal habitats that germination being one of the most critical periods in life cycle of halophytes (Gilles et.al, 2001; Rubio-Casal et.al., 2003). Salt stress affects germination percentage, germination rate and seedling growth in different ways depending on plant species (Ungar, 2005; Gul et. al., 1999). It was reported that maximum germination of the seeds of halophytic plants occurred in distilled water or under reduced salinity (Gul et. al.,1999;Khan et.al.,2003) and it has been found that germination percentage was reduced with a high NaCl concentrations (Tobe et al,2001; Pujol et al, 2000 ; Rubio-Casal et.al., 2003). Excess salinity with the plant root zone has a deleterious effect on plant growth and 8% germination at 1027mol/l level was reported by some workers (Mooring et al,1971). High level of salinity significantly reduced pigment content in leaves (Al-Sobhi et al., 2006). According to a report that seed germination of Suaeda salsa seeds decreased significantly with increased salinity. Subsequently it was observed that at low levels of salinity (0.05-0.1mol/l NaCl) seedling growth was increased , while high levels (>0.2mol/l NaCl) inhibited significantly and under salt stress, the leaves accumulated high levels of proline, whereas their soluble sugar content decreased with an increase in salinity level (Duan et al.,2007). The effect of salinity on plants may cause disturbances in plant metabolism (El-Tayeb, 2005). Salinity induced oxidative stress could be a reason for germination inhibition (Amor et al, 2005). Adaptation of plants to salt stress (i.e., resumption of growth after exposure to high soil salinity) requires cellular ion homeostasis involving net intracellular Na + and Cl-uptake and subsequent vacuolar compartmentalization without toxic ion accumulation in the cytosol (Niu et al, 1995; Blumwald et al., 2000; Hasaewaga et al., 1980; Gaxiola et al,2001). Therefore the aim of the present study were i) to assess the impact of salt stress on different varieties of wheat ii) to screen out best salinity resistant wheat variety and iii) to assess the various biochemical and morphological changes associated with the plants under different salinity gradient. MATERIALS AND METHODS Seeds were collected in November 2007 from Field Crop Research Station, Department of Agriculture, Government of West Bengal. Five varieties of Wheat included HOW-234, HD-2689, RAJ-4101, RAJ 4123 , and HD-2045. Seeds were sterilized by 0.1% HgCl 2 for 30seconds and then washed with fresh water, followed by distilled water. Germination trials were carried out in sterilized petridishes containing a sheet of blotting paper, and thin layer of cotton and moistened with distilled water or saline solution (25,50,75,100,125,150mM Nacl). Each of the three replicates contained 10seeds. Each treatment was carried out for 12 days. Germinated seeds were counted, then these seeds were removed from petridishes. Seeds were considered germinating with the emergence of the radicle. Three parameters of germination were determined which includes i) final germination percentage ii) Germination rate: is a measure of rapidity of germination, with lower values indicating faster germination. It is calculated as follows :GR = (n 1 t 1)+(n 2 t 2) + ……………. + (n x t x) / X n where n1 is the number of germinants at the first day of germination , t 1 is the days from start to fist germination , and X n is the total number of seeds germinated (Rubio-Casal et al.,2003) iii) Mean Daily Germination MDG = Final germination percentage / number of days to final germination (Rubio-Casal et al., 2003) Regarding