Geo-climatic factors co-drive the phenotypic diversity of wild hemp (Cannabis sativa L.) in the Potohar Plateau and Lesser Himalayas

Abstract

Hemp (Cannabis sativa L.) is an annual, and dioecious herb belonging to the Cannabaceae family. This plant is native to Central and Southeast Asia. The wild races of this species are commonly growing in Khyber Pakhtunkhwa and Punjab provinces, as well as in Islamabad, Pakistan. This study provides crucial insights into how environmental variables influence the wild hemp populations, which can be utilized in for conservation and breeding. The present study was aimed at evaluating the effects of key environmental factors such as altitude, geographical location, precipitation, relative humidity, maximum, minimum, and average temperature on 16 morpho-agronomic traits of a wild population of hemp growing in the Potohar Plateau and Lesser Himalayas. Our findings indicated that high relative humidity (> 64%), low average temperature (< 15 °C), intermediate average temperature (19-22 °C), and high average temperature (> 22 °C) played significant roles in determining the distribution pattern of the wild hemp. Correlation analysis demonstrated that average annual temperature contributed a higher percentage of variation in phenotypic diversity than geographic variables. Additionally, cluster analysis indicated three groups for the selected 35 populations. Clustering and Principal Component Analysis (PCA) of the morpho-agronomic traits indicated that group 1 from the Lesser Himalayas showed high relative humidity (> 64%) and low average temperature (< 15 °C). Conversely, Group 2 populations from the Potohar Plateau demonstrated intermediate average temperature (19-22 °C). There is an existence of Group 3 in the Potohar Plateau with a high average temperature (> 22 °C) compared to Group 1 and Group 2. Our examination highlights the complex interplay between ecological factors, and morphological attributes in native landraces of Cannabis sativa, giving significant insight into knowledge for preservation and breeding initiatives. A study of genetic diversity could complement morpho-agronomic traits in future research to learn more about how genetic variation affects environmental adaptation.

Keywords: Cannabis sativa; Environmental variables; Himalayas; Morpho-agronomic traits; Population diversity; Wild hemp.

Fig. 1

Location of the collected samples, covering the geographical distribution of hemp (Cannabis sativa L.) in the Himalayas, Pakistan

Fig. 2

Wild hemp plant, A) female plant with trichrome, B) different population, C) stem diversity and D) compound leaf

Fig. 3

Phenotypic divergence of wild Cannabis between Lesser Himalayas (G1) and Potohar Plateau (G2 and G3). The box and whisker plot represents the observed measures for each region, with the centre bar indicating the median value

Fig. 4

Diversity of Stem and petiole colors observed in the wild population of Hemp

Fig. 5

Pearson Plot of morpho-agronomical, climatic, and geographical correlation coefficients for sixteen agronomic traits of 35 locations of wild hemp across the Lesser Himalayas and Potohar Plateau. Legend: Lat: Latitude, long: Longitude, Alt: Altitude, rh: Relative Humidity, tmax: Maximum Temperature, tmin: Minimum Temperature, tavg: Average Temperature, prec: Precipitation, htf.pl: Plant height female, htm.pl: Plant height male dia.st: stem diameter, nm.lf: number of leaves, nm.br: Number of branches, len.cl: Central leaflet length, wid.cl: Central leaflet width, ara. lf: leaf area, len.pet: Petiole Length, ser.pr: Primary serration, ser.sc: Secondary Serrattion, len. Intr: Internode length, lfl. shp: leaflet shape, den.lf: leaf density

Fig. 6

Principal component analysis of morphological parameters of wild hemp. Legends: htf.pl: Plant height female, htm.pl: Plant height male, dia.st: stem diameter, nm.lf: number of leaves, nm.br: Number of branches, len.cl: Central leaflet length, wid.cl: Central leaflet width, ara. lf: leaf area, num.lfl: No of leaflets, len.pet: Petiole Length, ser.pr: Primary serration, ser.sc: Secondary Serrattion, len. Intr: Internode length, lfl. shp: leaflet shape, den.lf: leaf density

Fig. 7

Cluster dendrogram analysis of morphological traits of wild Hemp and the number represents the study sites shown in Table 1