RESPONSE OF WHEAT GENOTYPES TO SALT STRESS
Md. Mustafa Khan Registration No. 98 -05-704
A DISSERTATION
Submitted to
Bangabandhu Sheikh MujiburRahman Agricultural University in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
DEPARTMENT OF AGRONOMY
BANGABANDHU SHEIKH MUJIBUR RAHMAN AGRICULTURAL UNIVERSITY SALNA, GAZIPUR-1706, BANGLADESH
SUMMER 2016
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DISSERTATION ABSTRACT
RESPONSE OF WHEAT GENOTYPES TO SALT STRESS by
Md. Mustafa Khan
Four experiments were conducted to identify wheat genotypes that can tolerate salt stress to a considerable extent and to understand the mechanisms of salt tolerance through analyzing yield performance, dry matter production and distribution, pattern of mineral ions accumulation and some physiological and biochemical parameters. To satisfy these objectives wheat plants were grown in the research field of Regional Wheat Research Centre, BARI Gazipur and in the research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur during winter seasons, 2011- 2013. In the first experiment 50 wheat genotypes were evaluated under 15 dS m-1 NaCl salinity from 15 days after sowing, employing randomized complete block design (RCBD) with three replications in pucca seed beds. Visually poor growth was observed and a wide range of variation was found among the genotypes in the production of biomass, yield and yield attributes. The 50 genotypes were ranked into four groups based on grain yield per plant.
Also four clusters of same genotypes were made following cluster analysis. From these groups 12 wheat genotypes namely BAW 1135, BAW 1142, BAW 1147, Shatabdi, BARI Gom 25, BAW 1120, G13 BAW 1140, BAW 1143, BAW 1150, BAW 1157, BAW 1159 and BAW 1141were selected considering the mean value of groups and clusters related to yield and yield attributes.
The selected 12 genotypes were grown in pucca seed bed irrigated with normal water (control), sea water of 5 and 10 dS m-1 salinity levels. The experiment was laid out with split plot design with three replications. Salt stress condition caused an overall reduction in morphological, phenological and yield and attributes but the reduction was very little under 5 dS m-1salinity level compared to control in most of the cases. The highest relative value of
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yield was maintained by genotype BAW 1147 together with the highest relative values of plant height, flag leaf breadth, flag leaf length, flag leaf area, days to heading, days to anthesis, days to physiological maturity, grain filling duration, tiller number plant, spike number plant, spike length, spikelet number per spike, grain number spike, 1000-grain weight, biological yield and harvest index under higher i. e. 10 dS m-1 levels though a little deviation occurred at 5 dS m-1salinity level in some characters. BAW 1147 also maintained the highest flag leaf SPAD value after anthesis stage especially in latter part of the grain filling stage. BARI Gom 25 also expressed the second highest relative value in all the characters except grain filling duration and tiller number plant under both the salinity levels.
BARI Gom 28 was the most sensitive to increasing salinity level which reflected in the lowest relative values of all the characters except a little deviation in days to heading, spikelet per spike and biological yield. The flag leaf SAPD value of BARI Gom 28 was the lowest with some others in latter growth stages. Thus these three genotypes were selected for conducting the next experiment in order to understand physiological mechanisms of salinity tolerance.
The effects of salinity on dry matter production and distribution of different mineral ions in various plant organs of the selected three wheat genotypes viz. BAW 1147, BARI Gom 25 and BARI Gom 28 were assessed with control and sea water of 5 and 10 dS m-1 salinity levels applied throughout the life cycle from 15 days after sowing in pot culture. The study was comprised with factorial completely randomized design (CRD) with three replications.
Salinity reduced the dry matter production and influenced the pattern of distribution and ion accumulation in nine plant organs in three wheat genotypes. The reduction was larger at higher salt concentration. BAW 1147 and BARI Gom 25 showed greater tolerance, while BARI Gom 28 was susceptible in terms of both dry matter production and distribution in nine plant parts. Salt stress conditions increased the Na+ uptake and decreased the accumulation of K+, Ca2+ and Mg2+ in the shoot together with genotypic variation where BAW 1147
accumulated the lowest content of Na+ and highest content K+, Ca2+, Mg2+ and maintained the highest K:Na ratio followed by BARI Gom 25 and BARI Gom 28. Moreover, BAW 1147 maintained remarkable lower concentration of Na+ in flag leaf blade and grain followed by in BARI Gom 25. Whereas, the highest concentration of Na+ was obtained in the flag leaf and grain of BARI Gom 28 under salt stress conditions. The experiment four was carried out for further clarification of physiological and biochemical mechanisms of salt tolerance of wheat.
It was found that higher salt tolerance in BAW 1147 and BARI Gom 25 was associated with better water relations probably due to higher accumulation of proline, soluble sugar and soluble protein than that of BARI Gom 28 under salt stress conditions. Furthermore, the faster photosynthetic rate with higher stomatal conductance and least degradation of chlorophyll, minimum cell membrane injury with low H2O2 accumulation and high antioxidant enzyme activities in genotype BAW 1147 followed by BARI Gom 25 contributed to their high salt tolerance than BARI Gom 28.
