Bhutan Journal of Natural Resources and Development

Evaluation of Antifungal Activities of Trichoderma spp. Against Phytophthora spp.: In- Vitro Bioassay

Karma Wangchuk, Ugyen Dendup, Peljor Wangdi — Tue, 30 Jun 2026 00:00:00 +0000

This study evaluated the antifungal potential of native Trichoderma spp. in inhibiting the growth of Phytophthora spp. Trichoderma spp. and Phytophthora spp. were isolated from rhizospheric soil and diseased chilli plants, respectively. The isolates of Trichoderma spp. and Phytophthora spp. were subjected to in-vitro laboratory bioassay under controlled environmental conditions following the dual culture method. The pathogenic Phytophthora spp. were isolated, purified using the hyphal tip method and identified based on key morphological features. The virulence of the Phytophthora spp. isolates was tested on detached leaves of the chilli plant. The Trichoderma spp. were isolated following serial dilution and characterized based on key morphology features. The in-vitro experiment to evaluate the antifungal properties of Trichoderma spp. against Phytophthora spp. was designed in randomized complete block design in three replicates. Three isolates of Trichoderma spp. namely, TCP1, TCP2 and TCP3 were tested for antagonistic activity against four different isolates of Phytophthora spp., namely, PP1, PP2, PP3 and PP4. Results revealed that TCP3 exhibited the highest inhibition, reaching 61.49% (PP1), 62.10% (PP2), 60.19% (PP3), and 36.11% (PP4). TCP1 also showed strong antagonism with inhibition percentages of 56.48% (PP1), 59.11% (PP2), 56.63% (PP3), and 34.07% (PP4). In contrast, TCP2 displayed lower inhibition values: 44.44% (PP1), 45.18% (PP2), 39.63% (PP3), and 32.41% (PP4). A two-way ANOVA revealed a statistically significant interaction between Trichoder-
ma and Phytophthora isolates (F (30, 82) = 7.261, p = 0.001), confirming variation in inhibitory efficacy.

Wild Edible and Medicinal Plants: A Case Study of Community Perceptions, Gendered Roles, and Pathways for Sustainable Management in Yagang and Gengu Villages, Darla Gewog, Chhukha

karma Orong, Sangay Dorjee, Wangdi — Tue, 30 Jun 2026 00:00:00 +0000

Wild edible and medicinal plants (WEMPs) play a critical role in the livelihoods of forest-adjacent communities, yet integrated village-level evidence from Bhutan remains limited. This study examined WEMP diversity, household dependence, gendered roles, knowledge transmission, and perceived threats in Yagang and Gengu villages, Darla Gewog, Chhukha District. Data were collected through semi-structured interviews and field-based plant-use records, yielding 58 valid respondent records and 101 plant records. A total of 101 species were documented, including 48 medicinal-only, 38 edible-only, and 15 dual-use species. Household reliance on WEMPs was nearly universal (98.3%), primarily for medicine (96.5%), food (80.7%), and nutrition (80.7%), with minimal contribution to income (1.8%). Knowledge was transmitted predominantly through grandparents (98.2%), indicating strong intergenerational continuity. Gendered roles were evident, with men more frequently involved in plant collection and women primarily. Responsible for preparation and storage. Most respondents (94.1%) perceived a decline in WEMP populations, attributing this trend to multiple interrelated pressures, including cattle grazing, unsustainable harvesting, and land-use change. Despite these perceived declines, respondents expressed strong support for the domestication of WEMPs and their integration into agroforestry systems. These findings are based on respondents’ perception rather than direct ecological measurements and are therefore specific to the two villages. The results highlight the importance of localized, gender-responsive, and agroforestry-based strategies for sustaining WEMP systems while maintaining their ecological and socio-cultural function.

Habitat and Distribution Pattern of Threatened Freshwater Fishes found along the Drangmechhu River and its Tributaries in Pemagatshel District, Eastern Bhutan

Tandin Wangchuk, Dhan Bdr. Gurung, Ugyen Dorji, Karma Wangchuk — Thu, 02 Jul 2026 00:00:00 +0000

The distribution of freshwater fishes is primarily determined by physical and chemical water parameters and human activities. However, a complete understanding of how these factors relate to threatened species in the study area is still lacking. This study assessed the habitat association and distribution pattern of three threatened species Tor putitora Hamilton, 1822, Neolissochilus hexagonolepis McClelland, 1839, and Schizothorax richardsonii Gray, 1832, along the Drangmechhu River and its five tributaries in Pemagatshel District,

Bhutan. The field data was collected in March 2025 from 33 sampling plots, with each plot covering a 500 m stretch. Fishes were sampled using electrofishing and cast nets. A significant difference in fish abundance was detected across habitat types (H = 16.64, df = 2, p = .000), with riffles supporting the highest abundance (58.4%), followed by pools (30.1%), and runs (11.5%). The species exhibited distinct habitat association with respect to velocity, depth, and substrate composition. These threatened species preferred varying velocities, depths, and substrates. N. hexagonolepis favored higher velocities (0.5 m/s), shallower depths (0.44 m), and fine substrates, while S. richardsonii preferred lower velocities (0.3 m/s), moderate depths (0.56 m), and coarse substrates. Ecological models revealed highly suitable zones (>0.6) for N. hexagonolepis and S. richardsonii with strong predictive accuracy (AUC = 0.88–0.996), whereas models for T. putitora showed low accuracy (AUC = 0.547–0.569). Conservation implications from the study highlight the importance of habitat-specific management for threatened freshwater fishes along the Drangmechhu River system and its tributaries. Conservation should focus on protecting and restoring riffle habitats.

Leucas lavandulifolia Sm. (Lamiaceae): The Correct Name for Leucas indica of the Flo- ra of Bhutan

Phub Gyeltshen, Sangay Choden, Kezang Wangmo, Kezang Tobgay — Tue, 30 Jun 2026 00:00:00 +0000

Five Leucas species are reported in the Flora of Bhutan. During a floristic survey, specimens of Leucas lavandulifolia were collected from a subtropical forest in Sarpang District. The collected specimens were identified as Leucas indica (L.) Vatke, an illegitimate name as treated in the Flora of Bhutan. The correct name for the Linnaean species Leonurus indicus L. is Leucas lavandulifolia Sm. The species is placed in sect. Plagiostoma, which is characterised by an oblique calyx, a fan-shaped corolla lip, pedicellate nutlets, and distinctive exocarp cells. Leucas lavandulifolia can be distinguished from other closely related species in the genus by its obconical calyx, a puberulous and strongly oblique mouth, 8–10 calyx teeth with the apical tooth larger than the others, and oblong to oblong-obovate nutlets. It occurs in a wide range of habitats, including dry areas and roadsides, disturbed and agricultural fields, as well as moist sites, riverbanks, and thickets at forest margins. A key to the genus is also provided to facilitate accurate identification for conservation and management purposes.