Salt Tolerance, Morphological and Anatomical Responses of in vitro Indigofera zollingeriana Miq. Seedling

The species belonging to genus Indigofera with high nutritional value and tolerance against abiotic stresses are widely distributed in the tropics to the subtropic areas world over. In this study, two years old stored seeds of I. zollingeriana, a potential forage used in Indonesia, were evaluated for their tolerance to salinity stress. In the first step, the morphology and anatomy of I. zollingeriana seedlings under in vitro salinity stress level of 20-120 mM NaCl were investigated after 14 days. In the second step, the 3 days old seedlings were transferred to several concentrations of NaCl (140-300 mM) to estimate Ld50 (lethal dose). Several concentrations of gibberalic acid (GA3) were applied to the previous estimated Ld50 (228 mM NaCl) medium for alleviating seedlings damage. It was estimated that the increasing concentration of NaCl caused reduction in the evaluated plant growth parameters and changed anatomy of the root and stem cross sections. The 100% mortality of the seedlings was noted after4 weeks on the medium containing 300 mM NaCl. Treatment of seedlings with <0.25 mg L-1 GA3 +228 mM NaCl (Ld50) in the culture medium was effective to reduce root damage for 4 weeks. Treatment of seedlings with >2.5 mg L-1 GA3 + 228 mM NaCl (Ld50) showed adverse effects in controlling damage by necrosis and blackening of roots and stems.

Mungbean germplasms tolerance to salinity stress correlated with age character and potential yield

Mungbean is of the important legume commodity in Indonesia, however the production is still encountering the abiotic salinity stress. Fifty mungbean accessions were evaluated for the salinity tolerance at Indonesian Legumes and Tuber Crops Research Institute (ILETRI). The experimental was arranged in Split Plot Design consisted of two factors and three replications. The main plot was two environments, normal and salinity stress that was applied using diluted seawater, while the subplot was mungbean accessions. The parameters including soil electrical conductivity, time to first flowering and seed maturation, plant height, leaf chlorophyll index, salinity toxicity score, and seed yield per plant were observed. Salinity stress decreased mungbean seed yield with ranged from 61.33 - 100%. The highest stress tolerance index (STI) were found in Vima 4-MLGV 1118 (STI=0.58) and MLGV 1065 (STI=0.53). Five accessions did not able to produce any seed. Mungbean accessions tolerance to salinity stress was negatively correlated with the time of first flowering and seed maturation, while it was positively correlated with potential yield both in normal and salinity stress. It is suggested that selection and evaluation of mungbean to salinity stress in the future should be categorized both by the plant age and potential yield.

Ecological adaptation and phylogenetic analysis of microsymbionts nodulating Polhillia, Wiborgia and Wiborgiella species in the Cape fynbos, South Africa

Polhillia, Wiborgia and Wiborgiella species are shrub legumes endemic to the Cape fynbos of South Africa. They have the ability to fix atmospheric N2 when in symbiosis with soil bacteria called ‘rhizobia’. The aim of this study was to assess the morpho-physiological and phylogenetic characteristics of rhizobia associated with the nodulation of Polhillia, Wiborgia and Wiborgiella species growing in the Cape fynbos. The bacterial isolates from root nodules consisted of a mixture of fast and intermediate growers that differed in colony shape and size. The isolates exhibited tolerance to salinity (0.5–3% NaCl) and pH (pH 5–10) and different antibiotic concentrations, and could produce 0.51 to 51.23 µg mL−1 of indole-3-acetic acid (IAA), as well as solubilize tri-calcium phosphate. The ERIC-PCR results showed high genomic diversity in the rhizobial population and grouped them into two major clusters. Phylogenetic analysis based on 16S rRNA, atpD, glnII, gyrB, nifH and nodC gene sequences revealed distinct and novel evolutionary lineages related to the genus Rhizobium and Mesorhizobium, with some of them being very close to Mesorhizobium australicum. However, the phylogenetic analysis of glnII and nifH genes of some isolates showed incongruency.

Identification of sources of tolerance to salinity stress in peas (Pisum sativum L.)

Salinity stress has become an important limiting factor for plant growth and productivity. To evaluate the effect of salinity on plant and root development three pea genotypes were grown under different concentrations of NaCl (50, 100 and 200 mM NaCI) in an in vitro and in vivo conditions. After two weeks of cultivation in culture medium the seedling emergence rate was not significantly affected by 50 mM NaCl. In culture medium containing 200 mM NaCl only in variety Prometei over 50% of the seeds developed to the plants. The data indicated that increasing NaCl level significantly reduced shoot and root lengths, and plant fresh weight. Six weeks (42 days) after sowing in vivo, a reduction in plant height and weight was observed at 200 mM NaCl concentration. A proven differences of the root traits were established only in variety Prometei. On the bases of the obtained results it can be concluded that variety Prometei was the most tolerant to applied salt stress.