Journal of Plant Molecular Breeding
Volume:11 Issue: 2, Summer and Autumn 2023

The severe impact of drought and salinity on plant productivity presents a significant threat to worldwide food security. Plants exhibit the capacity to sense stimuli in their environment and adjust defense mechanisms through diverse regulatory networks to cope with abiotic stress. The complexities of drought and salinity tolerances can be deconstructed into contributing factors and mechanisms, classified under two categories: genetics and epigenetics. Epigenetic mechanisms play a role in partially attributing crop adaptation to the most formidable drought and salinity stresses. Plants respond to stress in part by undergoing stable alterations in gene expression, a process that involves the physical "marking" of DNA or its associated proteins, commonly called epigenetics. Plants utilize various epigenetic mechanisms to refine gene expression, vital for adaptation and phenotypic plasticity. These include DNA methylation, histone modifications, chromatin remodeling, epitranscriptomics, and gene silencing mediated by small RNAs. Notably, epigenetic modifications can be inherited or erased. Enhanced knowledge of epigenetics complements genetics and will aid in developing strategies to integrate them into crop improvement programs aimed at addressing adaptation to abiotic stress. This review highlights the latest and noteworthy findings regarding crop epigenetic responses to abiotic stress signals, particularly those pertinent to drought and salinity tolerance.

Plant chromosome manipulation is a powerful tool in plant breeding due to its significant impact on various genetic traits and diversity. To investigate the effect of polyploidy induction in anise (Pimpinella anisum L.), three different concentrations (0.01%, 0.5%, and 5%) of colchicine were tested. In this study, the seeds and terminal buds of five-week-old plants were treated with colchicine, and the process was repeated for three consecutive days. Subsequently, molecular, physiological, and morphological traits of both control (diploid) and induced (autotetraploid) plants were investigated. The results revealed that 0.01% colchicine had no significant effect on ploidy induction, while significant effects were observed at 0.5% and 5%.  Seedlings treated with concentrations higher than 0.5% colchicine exhibited larger stomatal size, lower stomatal density, and darker leaf color. In addition, the contents of DNA, RNA, and total protein increased in seedlings treated with concentrations of 0.5% and 5%. Karyotype observation confirmed polyploidy induction in plants treated with colchicine concentrations above 0.5%.  Overall, this study shows that  colchicine  can alter anise plants’ ploidy by 0.5% and 5% and  boostleaf size and pigments associated with photosynthesis, resulting in stronger plants.

Sustained availability of genetic resources is essential for successful plant breeding. Satureja bachtiarica Bunge is an endemic species to Iran, widely dispersed throughout the country. The rocky mountainous terrain between Asalem and Khalkhal, situated in the Ardabil province, is one of them. The current research focused on the genetic classification of 11 different ecotypes of S. bachtiarica collected from northwest Iran using RAPD molecular markers. A significant genetic diversity was observed among the ecotypes, with 64 bands displaying substantial polymorphism. These polymorphic bands served as the foundation for genetic analyses conducted using NTYSYS-pc (2.02e) software. The genetic distance between the ecotypes was determined using the Dice similarity coefficient. Subsequently, a dendrogram was constructed based on the similarity matrix data, employing the unweighted pair-group method with arithmetic averages (UPGMA). Genetic clustering analysis of the molecular marker data from 11 studied ecotypes revealed the lowest genetic similarity among the Khoy and Ardabil ecotypes. In contrast, the Khalkhal and Meshgin Shahr ecotypes exhibited the highest similarity. After examining the dendrogram, it becomes clear that most clusters consist of ecotypes sharing entirely similar or relatively similar climatic conditions. This suggests that the molecular diversity outcomes align with the geographical diversity of the ecotypes.

Drought stress is one of the limiting factors for plant growth. To evaluate the effect of drought stress (0, 150, 250 g/L of Polyethylene glycol 6000 (PEG)) on the physiological characteristics of two wheat cultivars (‘Gonbad’ and ‘N8720’), a hydroponic experiment was conducted. A factorial experiment was used and arranged in a completely randomized design with three replications at the Pasteur Institute of Iran (North Research Center). The experimental results showed that the main effect of cultivars was significant for all studied traits except nitrogen and phosphorus in the stems (p ≤ 0.01). The main effect of drought stress, as well as the interaction effect of drought stress and cultivars were significant for all studied traits (p ≤ 0.01). The highest content of elements in root and shoot and the chlorophyll content was observed in N8720 cultivar under control treatment. Moreover, in N8720 cultivar, the amount of glycine betaine increased due to drought stress, reaching its maximum at 250 g/L PEG. The results of correlation analysis showed that there is a positive and significant correlation between all traits (p ≤ 0.01). The result of experiment showed that N8720 cultivar exhibited superior characteristics in terms of all studied traits.

To study the allelopathic effect of decomposed fresh aerial parts of Rapistrum rugosum on growth, physiological and biochemical traits of Hibiscus sabdariffa, a pot experiment was conducted as a completely randomized design with three replications under greenhouse condition at the Gonbad Kavous University. Treatments were different amounts of R. rugosum residues (0, 10, 20, 40, 80, and 160 g kg-1 soil). The results showed that increasing the amount of R. rugosum residues significantly reduced the growth traits of H. sabdariffa. The lowest amount of stem and root length, fresh and dry weight of the plant was observed in 160 g kg-1 of R. rugosum residues. The content of chlorophyll b and carotenoids, as well as malondialdehyde, decreased with increasing the amount of R. rugosum. However, the trend of changes in the content of catalase enzyme, soluble sugars content, proline, total phenol, and flavonoids increased with increasing the amount of R. rugosum residues. Consequently, our findings showed that with the increasing in the amount of R. rugosum residues, all the studied traits of H. sabdariffa decreased significantly. Therefore, it can be recommended to use H. sabdariffa weed as a natural herbicide in sustainable agriculture especially in medicinal plant production.

Heat shock proteins (HSPs), molecular chaperones with many activities, are essential to plant growth, development, and stress responses. To make crops more salt- and drought-resistant, plant breeders have considered halophytic plant. Aeluropus littoralis, a halophyte monocot grass, is one potential model species to discover new stress-response genes. Here, exon/intron structure, conserved motifs/ domains, and expression patterns of HSP100 gene family were identified in the genome of A. littoralis. This study found six unique AlHSP100 non-repetitive genes, revealing remarkable structural and physicochemical variations between the subfamilies. Phylogenetic and motif analyses revealed that proteins from the same subfamily (AlHSP100.1-4) and proteins from other subfamilies (AlHSP100.5-6) have similar types, ordering, and quantities of motifs. Finally, the expression of AlHSP100.3 gene was analyzed using RT-qPCR under dehydration, salt, cold, and phytohormone abscisic acid stress treatments, revealed that their expression patterns vary in response to abiotic stresses. The presence of stress-dependent regulation of the HSP100.3 gene, as evidenced by the early response to osmotic stress and the late response to cold stress, is likely associated with the cis-regulatory elements located upstream of this gene. This study provides more valuable information to deepen our understanding of the abiotic stress responses by HSP100 genes in A. littoralis.

The study utilized F2:5 lines derived from a cross between Kafiav N Zagora and Pusa Karishma cultivars to tag genomic regions controlling primary branches in Brassica juncea. One hundred and thirty F2:5 plants were used to characterize primary branch numbers, resulting in two pools of 12 genotypes for high (HPB) and low (LPB) branches. The average number of primary branches for HPB and LPB were 12.16 and 4.50, respectively. A set of 148 SSR (Simple Sequence Repeats) markers was used for parental polymorphism screening from which 14 polymorphic SSRs were used for molecular characterization of HPB and LPB bulks, tagging genomic regions. The allelic data scored for 14 polymorphic lines was tested using Student’s t-test analysis to understand relationships for primary branches with SSR markers and amplified alleles. Based on this, two B-genome markers (Ni2-C12 and Ni2-A11) were discovered to be strongly linked to the number of primary branches. Bioinformatic analysis located these two markers within a 9 Mb region on chromosome B5 of B. juncea. Utilising F2:5 lines of an inter-gene pool genetic cross, the current study was able to locate the loci regulating the number of primary branches on B. juncea's sub-genome chromosome B5. Before proceeding with fine-mapping investigations to dissect the genomic region (between 55.9 and 64.9 Mb) of sub-genome chromosome B5, it is imperative to emphasize the necessity of verifying these results across diverse genetic backgrounds.

Pineapple stands as a cornerstone among Benin's vital fruit crops, playing a pivotal role in enhancing both household food security and income. This delectable fruit is prominently featured among the key crops advocated for cultivation within the country. Despite the critical role this crop plays, our understanding of the diversity within genetic resources is remains limited. This study aimed to assess genetic variation and infer the population structure of 57 pineapple accessions collected from Benin's national core collection, using 10 simple sequences repeat (SSR) markers. The result showed a total of 23 alleles, ranging from 2 to 4, with a mean of 2.3 alleles per locus. The polymorphic information content was 0.34 whereas the mean expected heterozygosity was 0.43. The UPGMA dendrogram revealed two main clusters. The collection was determined to exhibit a structured composition comprising two distinct groups based on genetic analysis. This grouping was further validated by AMOVA, affirming its existence. Our work offers valuable insights into the genetic diversity within Beninese pineapple germplasm, thereby guiding strategic conservation efforts. Moreover, these findings open avenues for leveraging the genetic variation present in Benin’s pineapple germplasm for future pineapple breeding programs, thereby enhancing pineapple cultivation and resilience.

Onion is one of the widely consumed vegetables in most food preparations. The present study aims to evaluate the genetic diversity of onion cultivars in southern Benin in 2023. DNA isolation of the fourteen (14) morphotypes collected was carried out using the CTAB protocol and amplified by PCR using five RAPD markers. The observed polymorphism rate was 100%. A total of 35 alleles were scored with an average of 7 per locus. The Polymorphism Information Content (PIC) of loci varies from 0.734 to 0.806 with an average of 0.784. The loci OPA08 (Na = 8 alleles, PIC = 0.806) was the most polymorphic and the most discriminating. OPB08 (Na = 6 alleles, PIC = 0.734) was the least polymorphic and the discriminating loci. The rate of rare alleles was Ra = 31.42%. The lowest genetic distance (D = 0.09) was observed between PVOV and PVAL but the highest (D = 0.94) was between FPAL and BQOV genotypes. The dendrogram classified the morphotypes into four genetic groups with a dissimilarity coefficient of 40% confirmed by the Principal Coordinate Analysis. These results are globally significant for the definition of strategies for the improvement, conservation and sustainable use of onion genetic resources in Benin.

Heat shock protein of 90 kDa or HSP90 plays an important dynamic role in regulating biotic and abiotic stresses through multiple functional mechanisms. The present study aimed to perform a comprehensive analysis of the HSP90 gene family in soybean. In total, 20 HSP90 genes from soybean were identified and showed unequal distribution on the 13 chromosomes. The evolutionary tree divided these genes into three main groups based on their subcellular localization. In Group I, nearly all of the HSP90 genes are distributed in the nucleus or cytoplasm. In Group II, the HSP90s were mostly classified in the endoplasmic reticulum. HSP90 genes were exclusively found in the mitochondria or chloroplast in Group III. Phylogenetic relationships have shown that genes in similar subgroups have the same exon-intron structure and number of introns. Glyma14g219700, Glyma17g258700, and Glyma07G207600 were identified as hub proteins based on their high degrees of interaction. In addition, Glyma02g302500, Glyma08g332900, Glyma14g219700, Glyma17g258700, and Glyma18g074100 genes displayed high expression levels in all of the tissues at different developmental stages. These findings provide a complete overview of the GmHSP90 gene family classification and evolution, which can help to identify the functional properties of the HSP90 genes in soybean growth and development.