Advanced Biotechnological Interventions in Mitigating Drought Stress in Plants.

This comprehensive article critically analyzes the advanced biotechnological strategies to mitigate plant drought stress. It encompasses an in-depth exploration of the latest developments in plant genomics, proteomics, and metabolomics, shedding light on the complex molecular mechanisms that plants employ to combat drought stress. The study also emphasizes the significant advancements in genetic engineering techniques, particularly CRISPR-Cas9 genome editing, which have revolutionized the creation of drought-resistant crop varieties. Furthermore, the article explores microbial biotechnology's pivotal role, such as plant growth-promoting rhizobacteria (PGPR) and mycorrhizae, in enhancing plant resilience against drought conditions. The integration of these cutting-edge biotechnological interventions with traditional breeding methods is presented as a holistic approach for fortifying crops against drought stress. This integration addresses immediate agricultural needs and contributes significantly to sustainable agriculture, ensuring food security in the face of escalating climate change challenges.

In vitro and ex vitro propagation of Turkish myrtles through conventional and plantform bioreactor systems.

The myrtle (Myrtus communis) plant naturally grows in the temperate Mediterranean and subtropical regions and is used for various purposes; thus, it is among the promising species of horticultural crops. This study aimed to evaluate and compare the performance of different propagation systems, including rooting, solid media propagation, rooting, and with the Plantform bioreactor system, in achieving healthy and rapid growth of four myrtle genotypes with diverse genetic origins and well-regional adaptation. The selection of myrtle genotypes with distinct genetic backgrounds and proven adaptability to specific regions allowed for a comprehensive assessment of the propagation systems under investigation. Present findings proved that the Plantform system, the new-generation tissue culture system, was quite successful in micropropagation and rooting myrtle genotypes. We succeeded in vitro micropropagation and rooting of diverse wild myrtle genotypes, enabling year-round propagation without reliance on specific seasons or environmental conditions. The process involved initiating cultures from explants and multiplying them through shoot proliferation in a controlled environment. This contributes to sustainable plant propagation, preserving and utilizing genetic resources for conservation and agriculture.

Recovering triploid citrus hybrids from 2x × 2x sexual crosses with the aid of embryo rescue and flow cytometry in Turkey.

BACKGROUND: Turkey is one of the major exporters of mandarins in the Mediterranean region. Seedlessness in citrus, which is one of the most desired fruit quality traits, especially in fresh mandarin export markets, can be obtained via triploidy as in many fruit species. Triploid plants can be recovered by 2x × 2x hybridizations in citrus, as well as 2x × 4x and 4x × 2x crosses. Hence, we aimed to develop local triploid hybrids by using the embryo rescue technique in five crosses using eight different citrus varieties in the present study. METHODS AND RESULTS: Embryos isolated from abortive seeds derived by 135 days after pollinations were cultured on modified Murashige and Tucker (MT) medium by adding different levels of GA3 to achieve a high germination rate. A population of 574 plants was developed as a result of embryo rescue. After screening the ploidy levels of this 574-plant population with the aid of flow cytometry, 4 triploids from 'Encore' × 'Murcott', 8 triploids from 'Fortune' × 'Willow leaf', 1 triploid from 'Kiyomi' × 'Murcott', and 1 triploid from 'Ortanique' × 'Murcott' hybridization were recovered. Triploid hybrid plants and related parents were analyzed with SSR markers heterozygotic for parental mandarin varieties. In addition, we evaluated stomatal characteristics of diploid and triploid hybrids obtained from different crosses. Stomatal traits of diploid and triploid hybrids in all crosses significantly differed except the stomata index. CONCLUSIONS: Genotyping of triploid plants confirmed using Simple Sequence Repeat (SSR) molecular markers and five SSRs were able to identify three alleles of triploid hybrids. Selected triploid mandarin hybrids have been grafted on several rootstocks for field trials and are in the process of yield and quality performances.

In vitro drought stress and drought-related gene expression in banana.

BACKGROUND: Banana is largely grown in tropical and subtropical climates. It is rich in various food components and has quite a high economic value. Unavailable ecological and agricultural conditions cause quantitative and qualitative losses in banana cultivation. Along with global climate change, drought stress is becoming prominent day by day. METHODS AND RESULTS: Micropropagation and rooting performance of Azman and Grand Naine banana cultivars were investigated under in vitro drought stress conditions. The expression levels of four different genes of CDPK gene family in leaf and root tissues of the rooted plants were determined with the use of qRT-PCR. Greater expression levels of four MaCDPK genes were seen in Azman cultivar than in Grand Naine cultivar. MaCDPK9 and MaCDPK21 had greater expression levels in root tissue and MaCDPK1 and MaCDPK40 genes in leaf tissues. CONCLUSIONS: Response of different banana cultivars to in vitro drought stress was determined in this study. The expression levels of the genes of CDPK gene family with a significant role in drought stress had significant contributions in elucidation of banana plant response to drought stress.

Perspectives and recent progress of genome-wide association studies (GWAS) in fruits.

BACKGROUND: Earlier next-generation sequencing technologies are being vastly used to explore, administer, and investigate the gene space with accurate profiling of nucleotide variations in the germplasm. OVERVIEW AND PROGRESS: Recently, novel advancements in high-throughput sequencing technologies allow a genotyping-by-sequencing approach that has opened up new horizons for extensive genotyping exploiting single-nucleotide-polymorphisms (SNPs). This method acts as a bridge to support and minimize a genotype to phenotype gap allowing genetic selection at the genome-wide level, named genomic selection that could facilitate the selection of traits also in the pomology sector. In addition to this, genome-wide genotyping is a prerequisite for genome-wide association studies that have been used successfully to discover the genes, which control polygenic traits including the genetic loci, associated with the trait of interest in fruit crops. AIMS AND PROSPECTS: This review article emphasizes the role of genome-wide approaches to unlock and explore the genetic potential along with the detection of SNPs affecting the phenotype of fruit crops and highlights the prospects of genome-wide association studies in fruits.

Molecular Characterization of Cyclamen Species Collected from Different Parts of Turkey by RAPD and SRAP Markers.

The genus Cyclamen (family Myrsinaceae) contains about 20 species, most of which occur in the Mediterranean region. Turkey has critically important Cyclamen genetic resources. Molecular characterization of plant materials collected from different regions of Turkey in which Cyclamen species grow naturally, namely Adana, Antalya, Aydin, Mugla, Izmir, Denizli, Kahramanmaras, Osmaniye, Eskisehir, Trabzon, and Rize provinces, was performed using RAPD and SRAP markers. DNA was successfully amplified by 30 RAPD primers and 14 SRAP primer pairs. Among the 470 bands generated by the RAPD primers, 467 were polymorphic. The number of bands detected by a single primer set ranged from 11 to 22 (average of 15.6). The percentage polymorphism was 99.3 % based on the RAPD data. In the SRAP analysis, a total of 216 bands were generated, showing 100 % polymorphism. The number of bands detected by a single primer set ranged from 9 to 22 (average of 15.4). All data were scored and UPGMA dendrograms were constructed with similar results in both marker systems, i.e., different species from nine provinces of Turkey were separated from each other in the dendrograms with the same species being clustered together.

Genetic Characterization of Turkish Snake Melon (Cucumis melo L. subsp. melo flexuosus Group) Accessions Revealed by SSR Markers.

Snake melon is an important cucurbit crop especially in the Southeastern and the Mediterranean region of Turkey. It is consumed as fresh or pickled. The production is mainly done with the local landraces in the country. Turkey is one of the secondary diversification centers of melon and possesses valuable genetic resources which have different morphological characteristics in case of snake melon. Genetic diversity of snake melon genotypes collected from different regions of Turkey and reference genotypes obtained from World Melon Gene Bank in Avignon-France was examined using 13 simple sequence repeat (SSR) markers. A total of 69 alleles were detected, with an average of 5.31 alleles per locus. The polymorphism information content of SSR markers ranged from 0.19 to 0.57 (average 0.38). Based on cluster analysis, two major groups were defined. The first major group included only one accession (61), while the rest of all accessions grouped in the second major group and separated into different sub-clusters. Based on SSR markers, cluster analysis indicated that considerably high genetic variability exists among the examined accessions; however, Turkish snake melon accessions were grouped together with the reference snake melon accessions.

Genetic transformation in citrus.

Citrus is one of the world's important fruit crops. Recently, citrus molecular genetics and biotechnology work have been accelerated in the world. Genetic transformation, a biotechnological tool, allows the release of improved cultivars with desirable characteristics in a shorter period of time and therefore may be useful in citrus breeding programs. Citrus transformation has now been achieved in a number of laboratories by various methods. Agrobacterium tumefaciens is used mainly in citrus transformation studies. Particle bombardment, electroporation, A. rhizogenes, and a new method called RNA interference are used in citrus transformation studies in addition to A. tumefaciens. In this review, we illustrate how different gene transformation methods can be employed in different citrus species.

A reference genetic map of C. clementina hort. ex Tan.; citrus evolution inferences from comparative mapping.

BACKGROUND: Most modern citrus cultivars have an interspecific origin. As a foundational step towards deciphering the interspecific genome structures, a reference whole genome sequence was produced by the International Citrus Genome Consortium from a haploid derived from Clementine mandarin. The availability of a saturated genetic map of Clementine was identified as an essential prerequisite to assist the whole genome sequence assembly. Clementine is believed to be a 'Mediterranean' mandarin × sweet orange hybrid, and sweet orange likely arose from interspecific hybridizations between mandarin and pummelo gene pools. The primary goals of the present study were to establish a Clementine reference map using codominant markers, and to perform comparative mapping of pummelo, sweet orange, and Clementine. RESULTS: Five parental genetic maps were established from three segregating populations, which were genotyped with Single Nucleotide Polymorphism (SNP), Simple Sequence Repeats (SSR) and Insertion-Deletion (Indel) markers. An initial medium density reference map (961 markers for 1084.1 cM) of the Clementine was established by combining male and female Clementine segregation data. This Clementine map was compared with two pummelo maps and a sweet orange map. The linear order of markers was highly conserved in the different species. However, significant differences in map size were observed, which suggests a variation in the recombination rates. Skewed segregations were much higher in the male than female Clementine mapping data. The mapping data confirmed that Clementine arose from hybridization between 'Mediterranean' mandarin and sweet orange. The results identified nine recombination break points for the sweet orange gamete that contributed to the Clementine genome. CONCLUSIONS: A reference genetic map of citrus, used to facilitate the chromosome assembly of the first citrus reference genome sequence, was established. The high conservation of marker order observed at the interspecific level should allow reasonable inferences of most citrus genome sequences by mapping next-generation sequencing (NGS) data in the reference genome sequence. The genome of the haploid Clementine used to establish the citrus reference genome sequence appears to have been inherited primarily from the 'Mediterranean' mandarin. The high frequency of skewed allelic segregations in the male Clementine data underline the probable extent of deviation from Mendelian segregation for characters controlled by heterozygous loci in male parents.

Micropropagation of banana.

Banana (Musa spp. AAA) is propagated vegetatively and can be rapidly and efficiently propagated by micropropagation. Conventional micropropagation techniques, however, may be too costly for commercial purposes. Our laboratory has found that depending on the combination of culture vessel and gelling agent more economic methods can be chosen for successfully micropropagating banana.

Somatic hybridization for citrus rootstock breeding: an effective tool to solve some important issues of the Mediterranean citrus industry.

The prevalence of sour orange rootstock in the southern and eastern part of the Mediterranean Basin is presently threatened by the spread of Citrus Tristeza Virus (CTV) and its main vector Toxoptera citricida, combined with abiotic constraints such as drought, salinity and alkalinity. The search for alternative CTV-resistant rootstocks that also withstand the other constraints is now considered an urgent priority for a sustainable citrus industry in the area. Complementary progenitors can be found in citrus germplasm to combine the desired traits, particularly between Poncirus and Citrus genera. The production of somatic hybrids allows cumulating all dominant traits irrespective of their heterozygosity level, and would appear to be an effective way to solve the rootstock challenge facing the Mediterranean citrus industry. This paper presents the results obtained during a regional collaborative effort between five countries, to develop new rootstocks by somatic hybridization. New embryogenic callus lines to be used for somatic hybridization have been created. Protoplast fusions have been performed at CIRAD and IVIA laboratories, focusing on intergeneric combinations. Analysis of ploidy level by flow cytometry and molecular markers confirmed the acquisition of new interesting tetraploid somatic hybrids for six combinations. Diploid cybrids with intergeneric (Citrus × Poncirus) nucleus and C. reticulata or C. aurantifolia mitochondria were also identified for four combinations. The agronomical performance of a pre-existing somatic hybrid between Poncirus trifoliata and Citrus reticulata was validated in calcareous soils in Morocco. Somatic hybridization is now integrated into the breeding programs of the five Mediterranean countries.