Bulent Uzun

Identification of molecular markers linked to determinate growth habit in sesame

This is the first report on molecular studies and tagging of the dt gene regulating determinate growth habit in sesame. The development of determinate cultivars has become an objective of high priority in sesame breeding programmes. Random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) techniques were investigated for the development of molecular markers for this induced mutant character. In order to identify molecular markers linked to determinate growth habit, a segregating F2 population was developed from a cross between determinate mutant line, dt-1 and an indeterminate Turkish cultivar, Muganlı-57. Using the F2 segregating population and bulked segregant approach, two ISSR marker loci originated from a (CT)8AGC primer were detected. The association was confirmed by analysing the ISSR profile from single plants originating from a F2 segregating population for the trait. This marker is potentially useful for assisting sesame breeding programmes by marker assisted selection and can facilitate the integration of determinate growth habit into new genetic backgrounds.

Heterosis for agronomic traits in sesame hybrids of cultivars×closed capsule mutants

Closed capsule is a mutant character, which may be useful in mechanised harvesting of sesame (Sesamum indicum L.). The capsules bearing the seeds of these useful mutants, unlike those of normal types, do not shatter at harvest. However, the direct use of induced mutations is very limited due to unwanted side-effects associated with the trait. It is therefore strongly recommended that such mutants should be crossed with commercial varieties to remove the undesirable side-effects. Apart from eliminating side-effects of mutants for pure line improvement, mutant heterosis is an active area of research (Maluszynski et al., 2002). It is a generally accepted approach that high levels of heterosis are obtained when the parents of hybrids are from very divergent origins (Ashri, 1998). On the other hand, many authors for many crop plants observed heterosis in a very narrow genetic base in crosses between mutants derived from the same parent variety and crosses of mutants with parent varieties (Maluszynski et al., 2002). Although, it is still unknown why high levels of heterosis can be obtained in mutant /mutant or mutant /wild type crosses, the interaction of mutated genes seems to play a key role. Heterosis in sesame has been studied by many researchers (Mazzani et al., 1981; Osman, 1985, 1989; Goyal & Kumar, 1991; Reddy & Haripriya, 1993; Padmavathi et al., 1993; Fatteh et al., 1995; Mishra & Sikarvar, 2001; Sankar & Kumar, 2001), although sesame is considered to be a self-pollinated crop and there are no hybrid varieties. The common purpose of all these studies was to investigate the heterotic performance of sesame lines with dehiscent capsules. However, there is no information available on heterotic effects between induced closed capsule mutants and normal shattering types. The aim of this study was therefore to investigate the heterotic performances of F1 hybrids in the generated population using novel mutants and traditional cultivars.

Multiplex Real-Time qPCR Assay for Simultaneous and Sensitive Detection of Phytoplasmas in Sesame Plants and Insect Vectors

Phyllody, a destructive and economically important disease worldwide caused by phytoplasma infections, is characterized by the abnormal development of floral structures into stunted leafy parts and contributes to serious losses in crop plants, including sesame (Sesamum indicum L.). Accurate identification, differentiation, and quantification of phyllody-causing phytoplasmas are essential for effective management of this plant disease and for selection of resistant sesame varieties. In this study, a diagnostic multiplex qPCR assay was developed using TaqMan® chemistry based on detection of the 16S ribosomal RNA gene of phytoplasmas and the 18S ribosomal gene of sesame. Phytoplasma and sesame specific primers and probes labeled with different fluorescent dyes were used for simultaneous amplification of 16SrII and 16SrIX phytoplasmas in a single tube. The multiplex real-time qPCR assay allowed accurate detection, differentiation, and quantification of 16SrII and 16SrIX groups in 109 sesame plant and 92 insect vector samples tested. The assay was found to have a detection sensitivity of 1.8 x 102 and 1.6 x 102 DNA copies for absolute quantification of 16SrII and 16SrIX group phytoplasmas, respectively. Relative quantification was effective and reliable for determination of phyllody phytoplasma DNA amounts normalized to sesame DNA in infected plant tissues. The development of this qPCR assay provides a method for the rapid measurement of infection loads to identify resistance levels of sesame genotypes against phyllody phytoplasma disease.

Traits for Phenotyping

The term plant phenotyping has been regenerated with the contribution of sensors, system technologies, and algorithms. This new plant describing concept allows multi-trait assessment with automatic measurements. Uniform structure, nondestructive measurements, precise results, and direct storage are the advantages of digital phenotyping. The hyper-spectral spectroradiometers and imaging technologies lead the way of new plant phenotyping applications. This high-throughput technique therefore requires lots of traditional and novel traits to present new characterization. Digital-based phenotyping in plants is new and still a developing area of research. The most often used traits of digital phenotyping are canopy temperature, chlorophyll fluorescence, stomatal conductance, chlorophyll content, leaf water potential, leaf area, fruit color, carbon isotope discrimination, light interception, senescence, and root traits which have been discussed in this chapter together with their advantages, limitations, and plant breeding potentials.

Screening, selection and real-time qPCR validation for phytoplasma resistance in sesame (Sesamum indicum L.)

Phyllody is one of the most destructive diseases of sesame and causes serious yield losses worldwide. The present research was conducted to identify phyllody resistant genotypes in sesame. A total of 542 sesame genotypes were screened for the disease resistance in the field using a disease incidence scale of 1–5 in the year 2012. Three hundred four genotypes showing high disease intensity were eliminated under artificially infected field conditions. In the year 2013, only 30 out of 238 accessions were determined as potential resistant genotypes based on the disease incidence scale. These selected genotypes were further evaluated for confirmation of the resistance in greenhouse conditions using the phytoplasma-infected vector insects under choice and no-choice conditions. Furthermore, real-time qPCR was employed for detection and quantification of phytoplasmas to select true resistant genotypes. The sesame accessions ACS38 and ACS102 were identified as resistant to the disease after evaluation in field, greenhouse and qPCR assays. This work is one of the most comprehensive studies to select genotypes resistant to the diseases caused by phytoplasmas.