Search

Genetic polymorphism amid plant species is a crucial factor for plant improvement and maintaining their biodiversity. Evaluation of genetic diversity amongst plant species is significant to deal with the environmental stress conditions and their effective involvement in the breeding programs. Hence, in present study, an attempt has been made towards the genetic assessment of individual and bulked populations of 25 watermelon genotypes, belonging to Citroides (citron watermelon) and Lanatus (dessert watermelon) group from Konya, Thrace, Turkmenistan, Saudi Arabia and Turkey. The employed Random Amplified Polymorphic DNA (RAPD) and Inter-Simple Sequence Polymorphism (ISSR) marker systems provided 69.4 and 95.4% polymorphisms, respectively. Different clustering methods showed clear grouping of the genotypes based on the geographical origin and species. Citron genotypes from Turkmenistan stood apart from all the Turkish Lanatus genotypes. However, Saudi Arab Lanatus genotype grouped with native Turkish varieties indicating the genetic linkage. Among all the Turkmenistan Citron genotypes, Turkmenistan-11 was the most distinct form. Moreover, sufficient genetic variation was found between the commercial and native Lanatus genotypes of Turkey as well as Citron genotypes of Turkmenistan. Hence, it will be beneficial to include these genotypes in the future breeding programs to transfer disease-resistant alleles from Citron to Lanatus genotypes.

In this study, strain PSBB1 isolated from Vicia fabarhizosphere was identified as Burkholderia cepacia, by 16S rDNA sequence analysis and characterized. Strain PSBB1 tolerated glyphosate up to 3200 μg ml−1and produced IAA (81.6 μg ml−1), ACC deaminase (69.3 mg−1protein h−1), SA (39.3 μg ml−1) and 2,3-DHBA (26.6 μg ml−1), solubilized insoluble P (50.8 μg ml−1) and secreted 29.4 μg ml−1exopolysaccharides, which decreased with increasing concentrations of glyphosate. Cell damage following glyphosate application was visible under SEM and CLSM. The phytotoxicity of glyphosate on chickpea was variable but significant. B. cepaciamitigated toxicity and enhanced the size, dry matter, symbiosis, seed attributes and nutritional contents of chickpea. Further, B. cepaciastrain PSBB1 declined the levels of CAT, POD, APX and GPX and MDA contents at 4332 μg kg−1soil glyphosate. Proline also increased under glyphosate stress but declined in B. cepaciainoculated plants. The ability to tolerate higher concentration of glyphosate, the capacity to secrete plant growth regulators even under herbicide stress and potential to reduce the level of proline and antioxidant enzymes makes B. cepaciaas an interesting choice for enhancing chickpea production in soils contaminated even with herbicides.

The role of exogenous nitric oxide (NO) application in alleviating drought stress responses by enhancing the antioxidant activities in plants is well established for several species. However, none of the studies reported its role in protecting the watermelon genotypes from drought stress. In this study, we aimed to observe the effect of NO application on the physiological and biochemical responses of the two watermelon (Citrullus lanatusvar. lanatus) genotypes grown under drought stress conditions by treating the plants with 15% polyethylene glycol 6000 (PEG 6000) and 100 µM sodium nitroprusside (SNP), which is a NO donor in Hoagland solution. Among the two genotypes, one genotype, KAR 98 was drought tolerant; while another, KAR 147 was drought sensitive. Drought stress showed a decrease in the growth parameters of both the genotypes; however, as expected it was higher in the susceptible genotype, KAR 147. NO application could not prevent the reductions in the growth parameters; however, it reduced the increment in malondialdehyde (MDA) content caused by the drought stress in both watermelon genotypes. Moreover, while drought stress condition reduced the ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), and peroxidase (POX) activities in both genotypes, NO + PEG application increased the APX activity in the tolerant genotype, KAR 98. Though the obtained results does not show the direct involvement of NO in increasing drought tolerance of watermelon plants, the increase in the APX antioxidant enzyme activity on NO application under drought stress confirmed its role in protecting the watermelon genotypes from the oxidative damage caused by the drought stress. Moreover, it can be concluded that the effect of NO application on watermelons’ responses towards drought stress condition may vary according to the specific genotypes. As to date none of the studies reported the effect of NO application on the antioxidant activity of watermelon genotypes under drought stress, the present study may provide information about the mechanisms that can be focused to improve drought stress tolerance of watermelon genotypes.