Plant Domestication: Wild Date Palms Illuminate a Crop's Sticky Origins

Pathological Characterization and Management of Lasiodiplodia theobromae, a Hemibiotroph with an Interkingdom Host Range

Heart rot disease, caused by Lasiodiplodia theobromae, is destructive for date palms and other woody plants. The disease was reported in several oases in Egypt, and the pathogen was found in association with infected trees suffering dieback and rachis blight. Seven phylogenetically distinct fungal isolates were selected, and their pathogenicity was confirmed on date palms. The isolates exhibited variable degrees of virulence on inoculated leaves, which confirms the variation. We examined the antifungal effect of microbial bioagents and plant extracts on heart rot disease. The isolates of Trichoderma spp. gave moderate reduction of the pathogen's linear growth (40 to 60%), whereas their exudates were ultimately ineffective. Bacillus spp. isolates, except for B. megaterium, were more effective against spore germination, giving 80 to 90% reduction on average. Among the examined plant extracts, garlic sap gave 98.67% reduction of linear growth followed by artemisia (15.5%) and camphor (24.8%). The extraction methods greatly influenced the antifungal efficiency of each extract because exposure to organic solvents significantly decreased the efficiency of all extracts, whereas hot water extraction negatively affected garlic sap only. Successful bioagents and plant extracts were further assayed for the suppression of heart rot disease on date palms. Both T. album and T. harzianum gave comparable degrees of suppression as by commercial fungicides. In addition, treatment before or during pathogen inoculation was the most effective because it significantly enhanced the expression of defense-related enzymes. Our findings suggest biopesticides possess a dual role in disease suppression and defense boosters for date palms suffering heart rot disease.

Phoenix phylogeny, and analysis of genetic variation in a diverse collection of date palm (Phoenix dactylifera) and related species

Date palm (Phoenix dactylifera), one of the most ancient crops, is grown commercially in >30 countries. Using whole plastome assemblies, phylogenetic analyses revealed that cultivated date palm accessions share the same clade with P hoenix sylvestris, P hoenix pusilla and P hoenix acaulis, which are native to the Indian subcontinent, and Phoenix caespitosa that is native to the Arabian Peninsula and the deserts of Somalia. Analysis of genetic diversity and genetic relationships among date palm accessions from 13 producing countries involved 195 date palm accessions that were genotyped at 19 microsatellite loci. Extensive genetic diversity was observed, with many accessions heterozygous for most markers in this clonally propagated crop. The average number of alleles per locus (42.1), expected heterozygosity (0.8), observed heterozygosity (0.47) and fixation indices (FST = 0.42) demonstrated substantial genetic diversity and population structure. Iraqi accessions were found to have the richest allelic diversity, and the most private alleles. The model-based Bayesian method indicated that these accessions could be broadly divided into two structure groups, one group with predominantly African accessions and another predominantly Asian. Some germplasm, especially from Tunisia and Iraq, deviated from this generalization. Many accessions in the STRUCTURE-derived groups were found to be genetic admixtures, with gene flow between Asian and African groups. Indian and Pakistani date palms were found to be most closely related to North African germplasm.