Evaluation of orange-fleshed sweet potato (Ipomoea batatas L.) genotypes for salt tolerance through shoot apex culture under in vitro NaCl mediated salinity stress conditions

Abstract

Fifteen genotypes of sweet potato were evaluated for salinity stress tolerance under in vitro NaCl mediated salinity stress conditions (MS, MS + 0.5% and MS + 1.0% NaCl). The growth parameters such as number of leaves, number of shoots, number of roots, length of plantlets and length of roots decreased significantly among the genotypes with increase in level of salinity. Of the 15 genotypes tested, six genotypes (108X1, 90/606, 90/696, CIP 8, S-30X15 and SP-61) were unable to sprout even at 0.5% NaCl and were characterized as susceptible to salt stress, three genotypes (CIP 6, 90/774 and CIP 3) which could tolerate 0.5% NaCl as moderately tolerant and six genotypes (CIP 12, CIP 13, JO 14, JP 13, and Gouri) as tolerant to salinity at 1.0% NaCl. Amongst the six genotypes showing tolerance to 1.0% NaCl, the exotic genotypes--JP 13, CIP 12 and indigenous one SB-198/115 continued to exhibit significant higher values for growth parameters over the susceptible one. Based on the performance under NaCl mediated salinity stress (1.0%), the pattern of salinity tolerance in the genotypes through shoot apex culture was JP 13 . The effect of salt stress on the activity of antioxidative enzymes was studied in leaves of 8-week-old plantlets of those six genotypes, which responded at higher NaCl stress along with a susceptible genotype 90/606. In leaves of salt stressed plants, superoxide dismutase (SOD), guaiacol peroxidase (GPX) and catalase (CAT) activities increased when compared with the stress free control. The increase was more pronounced in the tolerant genotypes than that in the susceptible one. These results indicate that oxidative stress may play an important role in salt stressed sweet potato plants and that the greater protection of tolerant plants from salt induced oxidative damage results, at least in part, through the increase in the activity of antioxidant enzymes.

Oxidative Stress Studies in Plant Tissue Culture

“…CAT is also important in the removal of H2O2 generated in peroxisomes during the -oxidation of fatty acids, photorespiration, and purine catabolism (Ahmad et al, 2008;Gill and Tuteja, 2010;Karuppanapandian et al, 2011). Various abiotic stresses induced CAT activities under in vitro conditions in different plants, including hyperhydricity, salinity, drought, and gamma radiation (Saher et al, 2004;Chakrabarty et al, 2005;Rahnama and Ebrahimzadeh, 2005;Dewir et al, 2006Niknam et al, 2006Erturk et al, 2007;Dasgupta et al, 2008;Sivritepe et al, 2008;Shehab et al, 2010;Yang et al, 2010;Zamora et al, 2010;El-Beltagi et al, 2011;Sen and Alikamanoglu, 2011;Helaly and El-Hosieny, 2011;Patade et al, 2012) in contrast, Fe-deficiency stress reduced activity of CAT (Lombardi et al, 2003;Mohamed and Aly, 2004). CAT activities also induced in Medicago sative clones, which were improved with in vitro selection method, under PEG-treatment (Safarnejad, 2004).…”

“…The Mn-SOD is resistant to both inhibitors; Cu/Zn-SOD is sensitive to both inhibitors whereas; Fe-SOD is resistant to KCN and sensitive to H2O2 (Ahmad et al, 2008;Gill and Tuteja, 2010;Karuppanapandian et al, 2011). There have been many reports of the increased activities of SOD under abiotic stresses induced with tissue culture techniques in a wide range of plant species, including heavy metals, such as Al, Cd, Cr, and Cu, hyperhydricity, salinity, gamma radiation, and drought (Gallego et al, 2002;Saher et al, 2004;Dewir et al, 2006;Israr et al, 2006;Erturk et al, 2007;Dasgupta et al, 2008;Sivritepe et al, 2008;Gupta and Prasad, 2010;Shehab et al, 2010;Yang et al, 2010;El-Beltagi et al, 2011;Helaly and El-Hosieny , 2011;Lokhande et al, 2011;Sen and Alikamanoglu, 2011;Xu et al, 2011;Patada et al, 2012) on the other hand, Fe-deficiency stress reduced activity of SOD (Lombardi et al, 2003). Advanced-antioxidant defense systems play an important role in plants not only to tolerate environmental stress but also to improve plants against these stresses.…”

“…POX prefers aromatic electron donors such as guaiacol and pyragallol to catalyze H2O2, and many researchers reported that excess POX activities were measured in a wide range of plant varieties under abiotic stress conditions induced with in vitro culture techniques (Saher et al, 2004;Chakrabarty et al, 2005;Rahnama and Ebrahimzadeh, 2005;Dewir et al, 2006;Niknam et al, 2006;Erturk et al, 2007;Dasgupta et al, 2008;Kumar et al, 2008;Sivritepe et al, 2008;Zamora et al, 2010;Sen and Alikamanoglu, 2011, ;Helaly and El-Hosieny, 2011). POX also decomposes indole-3-acetic acid (IAA) and has a role in the biosynthesis of lignin and defense against biotic stresses by consuming H2O2 in the cytosol, vacuole, and cell wall as well as in extracellular space (Gill and Tuteja, 2010;Karuppanapandian et al, 2011).…”

Improving salinity tolerance in crop plants: a biotechnological view

“…Field screening procedures in saline soils are confronted by spatial heterogeneity of soil chemical and physical properties as well as seasonal fluctuations in rainfall . Hence, many screening experiments for salttolerant genotypes were conducted either under in vitro (Barakat and Abdel Latif 1996;Arzani and Mirodjagh 1999;Dziadczyk et al 2003;Lee et al 2003;Dasgupta et al 2008) or under controlled environmental conditions (Kingsbury and Epstein 1984;Rawson et al 1988;Munns et al 2000;Mohammadi-Nejad et al 2008).…”

Approaches to Increasing Salt Tolerance in Crop Plants

“…Haploid culture, double haploidy, somaclonal variation, and in vitro-induced mutagenesis has been used to create variability to improve salinity tolerance in crop plants. Cell and tissue culture techniques have been used to obtain salttolerant plants through in vitro culture approaches: selection of mutant cell lines from cultured cells and subsequent plant regeneration (Zair et al 2003 ;Gandonou et al 2006 ;Lu et al 2007 ;Queirs et al 2007 ) and in vitro screening of plant germplasm for salt tolerance (Arzani and Mirodjagh 1999 ; Dziadczyk et al 2003 ;Lee et al 2003b ;Wheatley et al 2003 ;Dasgupta et al 2008). Cereal tissue culture is of great economic importance for selection of improved cell lines under in vitro condition ( Fig.…”