Researchers at the National Horticultural Research Institute (NIHORT) in Ibadan set out to assess the genetic diversity of fifteen avocado accessions conserved in the institute’s genebank. The seeds behind these accessions were originally collected from smallholder farmers across four states in south-eastern Nigeria — Imo, Enugu, Anambra and Abia — during successive collection missions, and were registered with NIHORT accession numbers upon entry into the genebank. Because avocado is highly heterozygous and predominantly outcrossing, with a protogynous–protandrous flowering system that promotes cross-pollination, the seedlings raised from these seeds represent open-pollinated half-sib progenies rather than clones of the maternal trees, and were treated as independent accessions in the analysis.

The team, led by Omolara I. Akinyoola and published in the journal Discover Plants, employed two complementary DNA marker systems: inter-simple sequence repeats (ISSR) and start codon targeted (SCoT) markers. ISSR primers amplify DNA fragments lying between simple sequence repeats in the genome and require no prior knowledge of the species’ DNA sequence, making them accessible and inexpensive. SCoT markers, first developed in rice by Collard and Mackill, target regions surrounding the start codons of genes, giving them a functional bias that often makes them more informative. After a pilot screen of twenty ISSR and fifteen SCoT primers on three representative accessions, the researchers selected five primers of each type based on band clarity, polymorphism and reproducibility.

The laboratory work began with fresh young leaflets collected from the field and preserved in liquid nitrogen. Genomic DNA was extracted from approximately 100 milligrams of leaf tissue per accession using a modified CTAB protocol, in which polyvinylpyrrolidone and 2-mercaptoethanol were added to suppress polyphenols and oxidation, and the chloroform–isoamyl alcohol extraction step was repeated twice to remove residual protein and lipid. DNA was precipitated overnight with ice-cold isopropanol, washed with 70 percent ethanol and re-suspended in buffer containing RNase A. Quality checks on 1 percent agarose gels confirmed sharp, high-molecular-weight bands with no shearing, and Nanodrop spectrophotometry gave A260/A280 purity ratios between 1.80 and 2.00 before samples were diluted to a working concentration of 30 nanograms per microlitre.

Polymerase chain reactions were carried out in 25-microlitre volumes on an Applied Biosystems GeneAmp 9700 thermal cycler. ISSR amplification used a touchdown profile in which the annealing temperature dropped from 65 to 56 degrees Celsius over ten cycles before thirty standard cycles at 55 degrees, while SCoT amplification used thirty-five cycles with a 50-degree annealing temperature. Amplified fragments were separated on 2 percent agarose gels, visualised under ultraviolet transillumination and scored manually against a 50-base-pair ladder, with faint or ambiguous bands excluded. The convergence of results across two independent marker systems, and across multiple analysis platforms, provided a form of internal validation that strengthens confidence in the findings.

The results revealed a moderate but meaningful reservoir of variation. The ten loci detected a total of 41 polymorphic alleles, averaging 4.1 alleles per locus — higher than the 3.1 alleles per locus reported in a previous avocado study using EST-SSR primers. The polymorphism information content, a measure of a locus’s discriminating power, ranged from 0.509 to 0.825 with a mean of 0.654, and gene diversity averaged 0.708 across the ten loci. Genetic similarity coefficients between accessions ranged from 0.59 to 0.84. Notably, SCoT markers outperformed ISSR markers, generating a higher mean number of alleles per locus (4.4 versus 3.8) and higher mean PIC values (0.671 versus 0.637), leading the authors to recommend the combined use of both systems rather than either alone.

When the researchers clustered the accessions using the unweighted pair group method with arithmetic mean (UPGMA) on Jaccard dissimilarities, supported by 1000 bootstrap resamplings, the fifteen accessions split into two main clusters — one containing six accessions and the other nine — with membership broadly reflecting the south-eastern states of origin. A factorial coordinate analysis performed in DARwin software resolved four geographic groups along the first two factorial axes, with groups dominated respectively by accessions from Imo, Enugu and Anambra, while the single Abia accession stood apart. Some accessions, however, were interwoven between groups, a pattern the authors attribute to informal farmer-to-farmer seed exchange across state boundaries.

The most striking result came from the analysis of molecular variance. AMOVA partitioned 99.3 percent of the genetic variation within the UPGMA clusters and only 0.7 percent between them, with a Phi statistic of 0.007 that was statistically non-significant (P = 0.395, based on 9999 random permutations). Cross-validation in a second R package yielded an essentially identical result (P = 0.390), confirming the robustness of the partitioning. In other words, the two clusters represent dissimilarity gradients within a single, largely panmictic gene pool rather than genetically isolated subpopulations. The authors attribute this to two interacting forces: avocado’s strongly outcrossing reproductive biology, which maintains high heterozygosity within genotypes, and widespread informal seed exchange among smallholder farmers, which has homogenised allele frequencies across the sampled states.

The study is not without limitations, which the authors acknowledge candidly. The sample of fifteen accessions, while reflecting the current holdings of the NIHORT avocado germplasm at the time of sampling, is modest for inferring fine-scale population structure and limits the statistical power of subgroup analyses. Marker-trait associations were not pursued, and the dominant nature of ISSR and SCoT markers means each accession had to be treated as a single haploid genotype. Future work, the team suggests, should integrate SNP-based platforms such as genotyping-by-sequencing with phenotypic and biochemical fruit characterisation, to link the genetic variation documented here to agronomically relevant traits such as fruit quality, pest resistance and climate resilience.

Even so, the significance of the work extends well beyond a single genebank. Nigeria’s avocado industry is growing rapidly and holds considerable potential in the global market, but it faces threats from pests including the avocado lace bug, the Persea mite and the western avocado leaf roller, as well as diseases such as anthracnose and avocado black streak. The moderate diversity documented in the NIHORT collection provides a baseline molecular dataset for future curation, hybridisation and selection, and underscores a broader truth for crop science: genetic diversity is the raw currency of breeding, and knowing exactly what a genebank holds is the first step towards spending it wisely. The identified variation can now be deployed in breeding programmes aimed at developing better varieties with desirable traits, while the finding that most variation lies within rather than between geographic groupings offers a caution against assuming that provenance alone guarantees genetic distinctiveness in conserved germplasm.

Subject of Research: Genetic diversity assessment of avocado germplasm using ISSR and SCoT molecular markers

Article Title: Genetic diversity assessment of avocado (Persea americana Mill.) germplasm from NIHORT genebank

Article References: Akinyoola, O. I., Olagunju, Y. O., Matthew, J. O., Akin-Idowu, P. E., & Ajayi, E. O. (2026). Genetic diversity assessment of avocado (Persea americana Mill.) germplasm from NIHORT genebank. Discover Plants, 3(1), Article 414. https://doi.org/10.1007/s44372-026-00866-9

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00866-9

Keywords: avocado, Persea americana, genetic diversity, ISSR markers, SCoT markers, germplasm, genebank, Nigeria, NIHORT, molecular markers, AMOVA, plant breeding

The research was driven by a persistent and growing global problem. Across much of the developing world, rapid population growth, urbanization, industrial expansion, and intensified agriculture have multiplied the discharge of untreated wastewater into rivers and streams. Suspended solids, organic matter, pathogenic microorganisms, and toxic metals accumulate in these waters, degrading ecosystems and raising the risk of waterborne disease. Conventional treatment plants rely heavily on chemical coagulants—typically aluminium and iron salts—which excel at clumping suspended particles together so they can settle out. But these chemicals carry well-documented downsides: they generate chemically complex sludge that does not biodegrade, they can disturb the delicate pH balance of treated water, they add cost, and they leave behind residual metal species that have been linked in some studies to neurological harm.

Scientists have long sought greener alternatives, and plant-derived coagulants have emerged as front-runners. Seed extracts of Moringa oleifera, for example, have achieved turbidity removal of 80 to 99 percent in prior research, while papaya seed extracts and watermelon seed preparations have delivered removal efficiencies of 70 to 90 percent for suspended solids. The active ingredients in these plants—proteins, polysaccharides, and polyphenols—work through charge neutralization, adsorption, and inter-particle bridging, destabilizing colloidal particles so that they aggregate into settleable flocs. What has been largely overlooked, however, are plant leaves, despite being chemically rich in tannins, flavonoids, alkaloids, and saponins, compounds known for their metal-chelating and adsorptive properties. Soursop and avocado leaves, both abundant and widely available across the tropics, seemed ideal but untested candidates.

To test that hypothesis, a team led by S. M. Ajiboye of Bamidele Olumilua University of Education, Science and Technology, in Ekiti State, Nigeria, collected fresh leaves from trees in Ado-Ekiti, washed them repeatedly in distilled water, sun-dried them for five to seven days until crisp, and ground them into a fine powder. The powder was sieved into precise fractions between 0.144 and 0.145 microns using a rotary sieve shaker and stored in airtight containers. The test water itself came from the Ureje River, a surface freshwater body that receives runoff from surrounding residential, commercial, and agricultural activities. Samples were collected during the rainy season, when surface runoff drives suspended particle levels and turbidity to their highest, providing a realistic and demanding medium for evaluating coagulation performance.

The experimental design was straightforward but rigorous. Dried leaf powders were applied to raw water samples at dosages ranging from 0.1 to 0.4 grams, after which the researchers measured a full panel of physicochemical parameters using standard analytical methods. Turbidity was quantified with a HACH 2100P nephelometer, pH with a calibrated digital meter, total hardness by EDTA titration with Eriochrome Black T indicator, total suspended solids by filtration and gravimetric drying, and electrical conductivity, salinity, temperature, and total dissolved solids with calibrated meters and probes. Heavy metals—chromium, copper, and iron—were digested in concentrated nitric acid and analyzed with a HACH DR 1900 spectrophotometer following APHA Method 3111 B. All results were reported as means with standard deviations, and differences among treatment groups were tested statistically using analysis of variance with Duncan’s multiple range post hoc test at the 0.05 significance level.

The results revealed a clear dose-dependent pattern with an important twist: less proved to be more. The best contaminant removal occurred at the lowest dosages of 0.1 to 0.2 grams, where charge neutralization and floc formation were most efficient. Turbidity fell by approximately 56 percent in soursop-treated water and 51 percent with avocado leaf powder, with values dropping from an initial range of 2.59 to 5.90 NTU. Color removal followed a similar trajectory, reaching about 56 percent for soursop and 47 percent for avocado, as humic substances and other chromophoric compounds adsorbed onto the surfaces of the bio-coagulant flocs. At higher dosages, however, performance degraded: turbidity and color crept back up, a phenomenon the researchers attribute to overdosing effects that restabilize colloids, and to the leaching of fine organic particles and natural pigments from the plant material itself—a cautionary signal that dosage optimization is essential to avoid secondary contamination.

Perhaps the most striking results involved heavy metals, where the leaf extracts outperformed expectations. Chromium concentrations dropped by up to 87.5 percent, copper by 97.6 percent, and iron was removed almost entirely—approaching 100 percent—under optimal conditions. The researchers attribute this exceptional metal capture to adsorption, complexation, and co-precipitation mechanisms, in which dissolved metal ions bind to functional groups such as hydroxyl, carboxyl, and phenolic moieties abundant in the leaves’ bioactive constituents. Notably, these removal efficiencies are comparable to those reported for Moringa oleifera, the most celebrated of plant-based coagulants, which achieves up to 90 percent removal for certain metals. The finding positions soursop and avocado leaves as serious contenders in the biocoagulant arena, particularly for treating metal-contaminated surface water in settings that cannot afford advanced treatment infrastructure.

Equally significant was what the natural coagulants did not do: they did not destabilize the water’s chemistry. Treated water maintained pH values between 6.5 and 8.5 throughout the experiments, squarely within the WHO’s recommended range. This contrasts sharply with conventional chemical coagulants, which often require pH adjustment before or after dosing and can leave treated water too acidic or too alkaline. The researchers suggest the pH stability stems from the buffering capacity of hydroxyl and carboxyl functional groups in the extracts. Meanwhile, total dissolved solids and electrical conductivity showed moderate reductions at optimal dosages, total hardness declined through partial removal of calcium and magnesium ions, and total suspended and total solids fell measurably, improving both water clarity and aesthetic quality. Slight increases in dissolved solids at high dosages likely reflect the dissolution of soluble organic compounds from the leaf powders themselves.

The broader implications are considerable. Both plant species grow abundantly across tropical regions, their leaves require only washing, sun-drying, and grinding to become active treatment agents, and the resulting coagulants are fully biodegradable and low in toxicity. For communities and small industries that depend on rivers degraded by urban runoff, agricultural activity, and wastewater discharge, the study points toward a treatment approach that is simultaneously cheap, sustainable, and locally sourced. The authors are careful to frame their work as a foundation rather than a finish line. They recommend further research into optimizing extraction methods, evaluating microbial removal efficiency, and assessing the long-term stability and scalability of the leaf coagulants in real-world treatment systems, along with direct comparative trials against conventional chemical coagulants. But the core message is clear: two trees that millions of people pass every day may hold an accessible, green answer to one of the world’s most pressing public health challenges, transforming fallen leaves into a first line of defense for cleaner water.

Beyond the headline removal efficiencies, the study offers practical lessons for how plant-based coagulants behave under real-world conditions. The observation that lower doses outperformed higher ones mirrors a well-known feature of coagulation chemistry: particle destabilization depends on achieving the right balance of surface charge, and excess coagulant can actually coat particles and restore their repulsive forces. For operators considering leaf-derived treatments, this suggests that small, carefully calibrated additions—not generous handfuls—are the key to both performance and avoiding the secondary contamination that can arise when organic material from the plant powder dissolves into the water.

The choice of test water also strengthens the findings. Because the Ureje River samples were collected during the rainy season, when runoff carries peak loads of suspended sediment, the coagulants were evaluated against genuinely challenging conditions rather than artificially prepared turbid water. This matters for communities in tropical regions, where seasonal rains routinely push surface water beyond the capacity of simple sedimentation or cloth filtration, and where a locally harvestable treatment aid could bridge the gap until conventional infrastructure arrives.

Another advantage worth emphasizing is the nature of the waste stream. Conventional alum and iron salt treatment produces sludge laden with hydroxide precipitates that resists degradation and complicates disposal. Flocs formed from leaf extracts, by contrast, are predominantly organic and should decompose far more readily, reducing the environmental burden of sludge handling—a significant ongoing cost for small treatment facilities.

The researchers also note that the leaves’ rich content of tannins, flavonoids, alkaloids, and saponins likely underpins both the coagulation and the metal-binding behavior, since these compound classes carry functional groups capable of chelating dissolved ions. Future work, the authors suggest, should isolate which biomolecules drive performance, verify microbial removal, and confirm that treated water is safe for long-term consumption—steps needed before leaf powders can move from promising laboratory results to routine household or industrial practice.

Subject of Research: Plant-based natural coagulants derived from soursop and avocado leaves for sustainable water treatment

Article Title: Performance of Annona muricata (Soursop) and Persea americana (Avocado pear) Leaves as Natural coagulants in water treatment

Article References: Ajiboye, S. M., Aduloju, M. O., & Pii, B. T. (2026). Performance of Annona muricata (Soursop) and Persea americana (Avocado pear) Leaves as Natural coagulants in water treatment. Discover Green Chemistry, 1(1), Article 24. https://doi.org/10.1007/s44509-026-00026-y

Image Credits: AI Generated

DOI: 10.1007/s44509-026-00026-y

Keywords: natural coagulants, water treatment, Annona muricata, Persea americana, turbidity removal, heavy metals, green chemistry, sustainable technology, surface water, biocoagulation, Performance, Annona