Discovering new genes for alfalfa (Medicago sativa) growth and biomass resilience in combined salinity and Phoma medicaginis infection through GWAS

Salinity and Phoma medicaginis infection represent significant challenges for alfalfa cultivation in South Africa, Europe, Australia, and, particularly, Tunisia. These constraints have a severe impact on both yield and quality. The primary aim of this study was to establish the genetic basis of traits associated with biomass and growth of 129 Medicago sativa genotypes through genome-wide association studies (GWAS) under combined salt and P. medicaginis infection stresses. The results of the analysis of variance (ANOVA) indicated that the variation in these traits could be primarily attributed to genotype effects. Among the test genotypes, the length of the main stem, the number of ramifications, the number of chlorotic leaves, and the aerial fresh weight exhibited the most significant variation. The broad-sense heritability (H²) was relatively high for most of the assessed traits, primarily due to genetic factors. Cluster analysis, applied to morpho-physiological traits under the combined stresses, revealed three major groups of accessions. Subsequently, a GWAS analysis was conducted to validate significant associations between 54,866 SNP-filtered single-nucleotide polymorphisms (SNPs) and seven traits. The study identified 27 SNPs that were significantly associated with the following traits: number of healthy leaves (two SNPs), number of chlorotic leaves (five SNPs), number of infected necrotic leaves (three SNPs), aerial fresh weight (six SNPs), aerial dry weight (nine SNPs), number of ramifications (one SNP), and length of the main stem (one SNP). Some of these markers are related to the ionic transporters, cell membrane rigidity (related to salinity tolerance), and the NBS_LRR gene family (associated with disease resistance). These findings underscore the potential for selecting alfalfa genotypes with tolerance to the combined constraints of salinity and P. medicaginis infection.

Improving productivity and soil fertility in Medicago sativa and Hordeum marinum through intercropping under saline conditions

BACKGROUND AND AIMS

Intercropping is an agriculture system used to enhance the efficiency of resource utilization and maximize crop yield grown under environmental stress such as salinity. Nevertheless, the impact of intercropping forage legumes with annual cereals on soil salinity remains unexplored. This research aimed to propose an intercropping system with alfalfa (Medicago sativa)/sea barley (Hordeum marinum) to explore its potential effects on plant productivity, nutrient uptake, and soil salinity.

METHODS

The experiment involved three harvests of alfalfa and Hordeum marinum conducted under three cropping systems (sole, mixed, parallel) and subjected to salinity treatments (0 and 150 mM NaCl). Agronomical traits, nutrient uptake, and soil properties were analyzed.

RESULTS

revealed that the variation in the measured traits in both species was influenced by the cultivation mode, treatment, and the interaction between cultivation mode and treatment. The cultivation had the most significant impact. Moreover, the mixed culture (MC) significantly enhanced the H. marinum and M. sativa productivity increasing biomass yield and development growth under salinity compared to other systems, especially at the second harvest. Furthermore, both intercropping systems alleviated the nutrient uptake under salt stress, as noted by the highest levels of K+/Na+ and Ca2+/Mg2+ ratios compared to monoculture. However, the intercropping mode reduced the pH and the electroconductivity (CEC) of the salt soil and increased the percentage of organic matter and the total carbon mostly with the MC system.

CONCLUSIONS

Intercropped alfalfa and sea barely could mitigate the soil salinity, improve their yield productivity, and enhance nutrient uptake. Based on these findings, we suggest implementing the mixed-culture system for both target crops in arid and semi-arid regions, which further promotes sustainable agricultural practices.

Pod, seed traits and cytotaxonomic studies of some Vicia narbonensis L. accessions (Fabaceae)

This study aimed to characterize eight accessions of Vicia narbonensis L. originated from different Mediterranean countries. The cytology of these species is rarely known despite the fact of its great socio-economical and ecological interest in these arid and semi-arid zones. This work aimed mainly to characterize the karyotype, morphological pod and seed traits of the species. Karyotypes of all accessions were similar to a diploid number of 2n = 2x = 14. All the accessions have submetacentric chromosomes with a secondary constriction attached to the long arm of pair VII close to the centromere. Variation in chromosome size was observed; it ranged from 5.86 μm to 7.62 μm. Indices of karyotype asymmetry were calculated as the total form percentage (TF%) and symmetric indices (Syi) which ranged from 33.75% to 35.42% and from 51.01% to 54.85%, respectively. The predominance of submetacentric chromosomes indicated that the karyotype is symmetrical and can be considered as primitive. However, the analysis of quantitative parameters measured on pods and seeds showed a significant variation between accessions. A relationship between centromeric index and the pod beak length was found. Estimation of phenotypic diversity using the Shannon diversity index (H') showed that the length, the seed color and the number of seeds per pod are the most polymorphic traits with respectively, H' = 0.92, 0.80 and 0.83. Cluster analysis of karyological, pod and seed traits showed four groups of accessions. This clustering is partially due to the geographical origin of the studied accessions. The variation in chromosome size, pod and seed traits could offer potentially valuable genetic resources for the improvement of V. narbonensis which is considered as neglected and underutilized crop species (NUCS).

Pheno-morphological variation, genetic diversity and population structure of Tunisian Echinus Medic (Medicago ciliaris L.)

Medicago ciliaris L., considered as a valuable genetic resource, is a good candidate for the improvement of marginal or degraded lands with low fertility or high salinity. In this study, the pheno-morphological and genetic diversity were investigated in 14 Tunisian populations of M. ciliaris for the first time. Fourteen morphological traits showed significant differentiation between populations and high levels of diversity. Two amplified fragment length polymorphism primer combinations (E-AGC/M-CAA; E-AAG/M-CTG) were analyzed using an automated capillary electrophoresis system. A total of 528 loci were generated, of which 54% were polymorphic. Allelic polymorphism ranged from 0.02 to 0.5. Significant variation between populations was found for gene diversity, mean number of alleles per locus and Shannon index for which mean values were 0.17, 0.26, and 1.57, respectively. Analysis of molecular variance revealed a high rate of genetic variation within populations. Principal component analysis and genotypic clustering discriminated M. ciliaris populations according to their geographical origin. M. ciliaris clustered into three main groups. The first group was associated with high inland and cold areas, the second was defined by low areas with mild winters while the third described low coastal areas. Similarity of morphological and molecular results indicated that either markers could be used for the study of genetic diversity in this species.