Inheritance pattern of okra enation leaf curl disease among cultivated species and its relationship with biochemical parameters.

Okra production in eastern India at present is severely threatened by whitefly-mediated okra enation leaf curl disease (OELCuD). Identification of resistant genotype and understanding the genetic control and biochemical relationship of OELCuD resistance are prerequisite for developing an effective breeding strategy. This study was conducted employing six populations (P1, P2, F1, F2, BC1 and BC2) of two selected (resistant x susceptible (RxS)) crosses. Associationship between severity of OELCuD and biochemical parameters of parents and hybrids at preflowering and flowering stages was studied. Segregation pattern of the genotypes in F2 generation showing OELCuD reaction of two crosses suggested that two duplicate recessive genes was operative for resistance to OELCuD. Generation mean analysis revealed involvement of both additive and nonadditive effects in the inheritance of disease resistance. Hence, postponement of selection in later generations or intermating among the selected segregates followed by one or two generations of selfing to break the undesirable linkage and allow the accumulation of favourable alleles could be suggested for the development of stable resistant genotype against this disease. Higher peroxidase activity and total phenol content in leaf emerged as reliable biochemical markers for early selection of genotype resistant to OELCuD.

Seed biopriming with P- and K-solubilizing Enterobacter hormaechei sp. improves the early vegetative growth and the P and K uptake of okra (Abelmoschus esculentus) seedling.

Limited information is available that seed biopriming with plant growth-promoting Enterobacter spp. play a prominent role to enhance vegetative growth of plants. Contrary to Enterobacter cloacae, Enterobacter hormaechei is a less-studied counterpart despite its vast potential in plant growth-promotion mainly through the inorganic phosphorus (P) and potassium (K) solubilization abilities. To this end, 18 locally isolated bacterial pure cultures were screened and three strains showed high P- and K-solubilizing capabilities. Light microscopy, biochemical tests and 16S rRNA gene sequencing revealed that strains 15a1 and 40a were closely related to Enterobacter hormaechei while strain 38 was closely related to Enterobacter cloacae (Accession number: MN294583; MN294585; MN294584). All Enterobacter spp. shared common plant growth-promoting traits, namely nitrogen (N2) fixation, indole-3-acetic acid production and siderophore production. The strains 38 and 40a were able to produce gibberellic acid, while only strain 38 was able to secrete exopolysaccharide on agar. Under in vitro germination assay of okra (Abelmoschus esculentus) seeds, Enterobacter spp. significantly improved overall germination parameters and vigor index (19.6%) of seedlings. The efficacy of root colonization of Enterobacter spp. on the pre-treated seedling root tips was confirmed using Scanning Electron Microscopy (SEM). The pot experiment of bioprimed seeds of okra seedling showed significant improvement of the plant growth (> 28%) which corresponded to the increase of P and K uptakes (> 89%) as compared to the uninoculated control plants. The leaf surface area and the SPAD chlorophyll index of bioprimed plants were increased by up to 29% and 9% respectively. This report revealed that the under-explored species of P- and K-solubilizing Enterobacter hormaechei sp. with multiple plant beneficial traits presents a great potential sustainable approach for enhancement of soil fertility and P and K uptakes of plants.

Chemical composition, nutritional value and antioxidant properties of Mediterranean okra genotypes in relation to harvest stage.

The aim of the present study was to determine the effect of fruit size on nutritional value, chemical composition and antioxidant properties of Mediterranean okra genotypes. For this purpose, pods from four okra cultivars and local landraces commonly cultivated in Greece, as well as pods from four commercial cultivars from North America were collected at two sizes (3-5 and>7cm). Significant differences were observed between the studied genotypes for both nutritional value and chemical composition parameters. Small fruit had a higher nutritional value, whereas chemical composition differed in a genotype dependent manner with most of the studied cultivars showing better results when harvested in small size. In conclusion, fruit size has a genotype dependent impact on chemical composition and nutritional value of okra pods and the common practice of harvesting okra fruit while they still have a small size helps to increase nutritional value for most of the studied genotypes.

The chemical composition, nutritional value and antimicrobial properties of Abelmoschus esculentus seeds.

Okra is a vegetable crop usually used for its immature pods. The harvest stage (fruit size) depends on consumers' preferences and the fruit that does not meet market requirements is being disposed of. Considering the short time interval from the setting of the fruit to the harvest stage, the present study evaluates the nutritional value, chemical composition, and antioxidant and antimicrobial properties of okra seeds from genotypes cultivated under Mediterranean conditions, as an alternative end-use product. For this purpose, seeds from four okra cultivars and local landraces commonly cultivated in the Mediterranean basin, as well as seeds from four commercial cultivars from North America were collected at the maturity stage. A significant variation between the studied okra genotypes was observed for all the evaluated parameters. Okra seeds of cv. "Silver Queen" are a significant source of proteins and minerals, such as Ca, K, Fe and Zn. Seeds of all the genotypes contained significant amounts of gamma-tocopherols, liposoluble pigments, and linoleic and palmitic acid. The total phenol content differed between the studied genotypes and correlated with the EC50 values of the Reducing Power assay. Seed extracts exhibited significant antibacterial properties, especially against Listeria monocytogenes, Salmonella enteritidis and S. typhimurium, while fungistatic and fungicidal properties were better than ketoconazole in a genotype dependent manner. The antifungal properties of seeds were noticed towards all tested fungi, where Aspergillus versicolor and Caldosporium cladosporioides were the most sensitive species. Moreover, two of the tested genotypes ("Boyati" and "Clemson Spineless") exhibited higher fungistatic and fungicidal properties than ketoconazole. In conclusion, okra seeds could be considered as innovative okra products and could be proposed for alternative end-uses in the food and pharmaceutical industries, especially for functional foods with antimicrobial and bioactive properties.

Genetic bottlenecks in Turkish okra germplasm and utility of iPBS retrotransposon markers for genetic diversity assessment.

Lack of requisite genetic variation in Turkish okra has necessitated the use of different types of markers for estimating the genetic diversity and identifying the source of variation. Transposable elements, present abundantly in plant genomes, generate genomic diversity through their replication and are thus an excellent source of molecular markers. We hypothesized that inter-primer binding site (iPBS)-retrotransposons could be the source of variation because of their genome plasticity nature. In the present study, genetic diversity of 66 okra landraces was analyzed using iPBS-retrotransposon markers. iPBS-retrotransposons detected 88 bands with 40.2% polymorphism and an average of 6.8 bands per primer. Gene diversity and Shannon's information index ranged from 0.01 to 0.13 and 0.02 to 0.21 for iPBS-retrotransposons and from 0.06 to 0.46 and 0.14 to 0.65 for simple sequence repeat (SSR) markers, respectively. Polymorphism information content value for retrotransposons varied between 0.12 and 0.99, while that for SSR was from 0.52 to 0.81. Neighbor joining analysis based on retrotransposons and SSRs divided all the accessions into four clusters; however, SSR markers were more efficient in clustering the landraces based on their origin. Using the STRUCTURE software for determining population structure, and two populations (at the number of hypothetical subpopulations, K = 2) were identified among the landraces. Low genetic diversity in Turkish okra highlights the need for the introduction of plants from countries with greater genetic diversity for these crops. This study also demonstrates the utility and role of iPBS-retrotransposons, a dominant and ubiquitous part of eukaryotic genomes, for diversity studies in okra.

Abelmoschus esculentus (L.) Moench. and Abelmoschus moschatus Medik: seeds production and analysis of the volatile compounds.

Nine accessions of Abelmoschus esculentus (L.) Moench. and three of Abelmoschus moschatus Medik were both grown in Central Italy for the evaluation of the production of seeds. Furthermore, the volatiles emitted by the mature seeds were sampled by mean of SPME. Seventy compounds were detected in the headspace of the seeds of A. esculentus. The principal constituents common to all the nine accessions were isopentyl 2-methyl butanoate (24.5-59.1%) and heptanoic acid 2-methylbutyl ester (6.6-13.5%). In the headspace around the seeds of A. moschatus 93 components were detected. Among the main volatiles shared by the three accessions, n-tridecane (1.5-26.9%), isopentyl 2-methyl butanoate (0.2-14.3%) and decanal (1.6-5.7%) should be mentioned. Many differences were present in the volatiles emitted by the various accessions and between the two Abelmoschus species.