Seed and seedling diversity delimitation and differentiation of Indian populations of Melia dubia cav.

Abstract

Melia dubia is one of the most important industrial tree species in the South East Asia . In last few decades, the populations of M. dubia has rapidly expanded in the Indian sub-continents, leading to an increase in the genetic diversity of species. However, very less information is available on intra-specific variation in Melia under the Indian subcontinent. Therefore, a present investigation was undertaken, to assess the level of diversity in seed and saplings of the Melia populations (ecotypes) collected from three agro-ecological regions of India. Results revealed that the seed and saplings of all the ecotypes are significantly different for all the traits, except for number of branches per plant, and the maximum variability was recorded in germination percentage, seed weight, internodal length, and sapling height of the species. The high heritability for seed weight (0.99), length (0.99), and width (0.97), and germination percentage (0.99) indicated that selection and genetic gain for these traits would be effective during the commencement of improvement program. Trait association analysis explained that higher seed weight significantly reduced sapling height, collar diameter, number of leaves per plant, internodal length, petiole length, and germination percentage (r = −0.86; p < 0.001) that ultimately reduced the seedling vigor in Melia dubia . Interestingly, the number of branches per plant were not associated with any of the morphological traits. The first principal component explained 50.09% of the entire variation and all the traits contributed greatly to the variation for this principal component, except for number of branches, leaf width and seed length. The clustering approach assorted geographic variation of M. dubia populations into three main sub-clusters i.e. South, North, and North East populations each consisting of five, seven and one populations (including cultivar), respectively. Among different ecotypes, Bahumukhi, Varsha and US Nagar seed sources outperformed all others in seedling vigour (sapling height) and rest of the growth parameters. Overall, findings explained that considerable scope exists for the development of superior planting material of M. dubia through exploration of seeds and selection at the early seedling stage.

Pre-Sowing Treatments on Seeds of Forest Tree Species to Overcome the Germination Problems

“…Seed germination constitutes the process through which the embryo evolves into a seedling under favourable conditions. It involves a series of physiological, biochemical, and morphological changes that collectively lead to germination [36,56,57,58]. This intricate process can be delineated into three major phases: Phase I, characterized by rapid water imbibition; Phase II, dominated by the reactivation of metabolism, cell elongation, and chitting; and Phase III, marked by rapid cell division coinciding with radicle growth.…”

“…Genetic makeup, seed viability and dormancy are internal factors inherited from parent plants, influencing germination potential and subsequent growth. Seed source variations among species can significantly affect seed quality and growth [46,47,57,58]. External factors consider the growing environmental conditions, including temperature, moisture, light, and soil properties, also influence germination and seedling establishment [76,99].…”

Genetic diversity of Melia dubia as revealed by molecular markers

“…Due to the increase in populations of M. dubia in the Indian sub-continent, the genetic diversity of the species has increased. However, very less data is available on intra-speci c variation in Melia under the Indian subcontinent [5]. As suggested by evolutionary evidence, high levels of genetic diversity are depicted by the species with diverse ecotypes and broad distribution [6].…”