DOI: 10.11648/j.ijaas.20261204.15 ISSN: 2469-7885

Phenotypic Differentiation and Yield-Component of Farmer-Recognized Black Pepper ( Piper nigrum L.) Genotypes in Selected Tanzanian Agroecosystems

Stephano Kayala, Luseko Chilagane, Ramadhani Majubwa
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Black pepper ( Piper nigrum L.) is an economically important perennial spice crop in Tanzania, but the identity, phenotypic distinctness and yield-component characteristics of farmer-maintained planting materials remain poorly documented. This study characterized farmer-recognized black pepper genotypes using integrated vegetative, leaf, spike, berry and reproductive-mass descriptors. An observational on-farm blocked characterization study was conducted across nine farms in Morogoro, Tanga and Unguja. A total of 138 mature vines were assessed for 28 descriptors, comprising nine qualitative and 19 quantitative traits. Vine-level quantitative data were analyzed using linear mixed-effects models that accounted for farm-level clustering. Qualitative descriptors were analyzed using Fisher’s exact tests with Monte Carlo simulation and Cramér’s V. Relationships among traits and integrated phenotypic structure were examined using correlation analysis, principal component analysis, factor analysis of mixed data, Gower-distance clustering and PERMANOVA. Soil variability among the nine farms was examined exploratorily using principal component analysis. Strong genotype-associated differentiation was observed for spike length (F = 171.94, p < 0.001, partial η 2 = 0.954), number of spikes per kilogram (F = 42.09, p < 0.001, partial η 2 = 0.927), berry length (F = 62.96, p < 0.001, partial η 2 = 0.901), berry-size index (F = 35.71, p < 0.001, partial η 2 = 0.813) and leaf-size index (F = 33.79, p < 0.001, partial η 2 = 0.796). BABUKUBWA expressed the longest spikes and largest leaves but comparatively light dry spikes. KATI had the greatest individual dry spike weight, BABUNDOGO had the greatest fresh weight of 100 spikes, ISMAILIA produced the most berries per spike, and NDEFU and KATI had the greatest 1,000-berry mass. Qualitative differentiation was strongest for spike shape (V = 0.909), spike setting (V = 0.806), leaf shape (V = 0.777), branching habit (V = 0.745) and leaf venation (V = 0.667). Multivariate analyses indicated that differentiation reflected integrated combinations of vegetative and reproductive traits, while farm-level clustering was pronounced for several vigour and reproductive-mass traits. Farmer-recognized black pepper genotypes in the surveyed production environments possessed coherent and multidimensional phenotypic profiles. Spike length alone did not predict reproductive mass, demonstrating that selection should integrate spike number, berry number, berry size, spike mass and dry recovery. The identified materials provide candidate germplasm for conservation and further evaluation, but morphological differentiation does not confirm genetic distinctness. Molecular characterization, and balanced multi-environment clonal trials are required before the materials can be recognized as distinct cultivars or recommended for formal release.

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