A Vital Medicinal Trees Khaya senegalensis (Desr.) A. Juss. and Khaya grandifoliola C.DC., Native to African Savanna Region: Study of the Interspecific Variation in Morphology, Seeds Germination Characteristics, Early Growth Development of Seedlings and E

Abstract

Species of Khaya are exotic to Sudan and overexploited for its valuable wood and ethno-medicinal values. The study aimed to provide scientific and up-to-date data about commonly known species khaya senegalensis and Khaya grandifoliola, with special reference to their morphology and growth development at mature and seedlings stages, suitable seed germination techniques as affected by pre-sowing treatment methods and seasons. Materials were collected from established plantations in Abu Geili riverine forest reserved (13° 34' 41.51" N;  33° 35' 20.08" E) in Sennar state, Sudan. 10 trees (mature, dbh 25-30 cm) were randomly sampled in spacing not less than 100 m apart, and surveyed during time of vegetative growth (June-October), fruiting and seeding (March-May) for data collection.  Morphological characterization for each species assessed by evaluating 17 vegetative traits (11 Quantitative, 6 qualitative), 13 fruits’ traits (8 quantitative, 5 qualitative) and 11 seeds’ traits (9 quantitative, 3 qualitative). Analysis of variance performed to compare between the studied species (Ks and Kg). Germination experiments conducted during summer, autumn and winter and laid in completely randomized design with 4 replications using 6400 seeds (3200 seeds each species), and . The seeds per species (3200) were tested for germination under four pre-sowing treatments (800 seeds each treatment): i.e. immersion in hot water (100 °C, cooled overnight), cold water (4 °C, 24 h), and concentrated sulphuric acid (5 min) followed by soaking, in addition to untreated as control. The seeds were sown in polythene bags (10 seeds each), and monitored a nursery under controlled conditions, and germination indices (percentage, germination rate index “GRI”, mean germination time “MGT”), and shoot and root morphological characteristics and development at early ages were recorded. The data were analyzed using ANOVA (GLM, SAS v9.0). Significant differences (p = 0.0001) between species were observed in morphology at maturity Ks had the highest measures for leaflets number per leaf, while Kg had the largest leaves’ dimensions, as well as fruits’ and seeds’ dimensions. For both Ks and Kg, pre-sowing treatments significantly improved germination during different seasons (autumn, winter and summer) compared with controls. The highest germination success obtained during autumn season (July-October) from hot water treatment (80 °C for 10 min) 94% for Ks and 92% for Kg; followed by cold water (37 °C) treatment overnight 92% for Ks and 90% for Kg. Less success across all pre-sowing treatments was recorded for both species during winter season (December-February). Varying seedlings growth performance in roots’ and shoots’ morphological characteristics was reported between Ks and Kg. These savannah species Ks and Kg are native to Africa, this study highlighted its possibility to germinate by seeds in wide range of pre-treatment (tap water, hot water and cold water and H2SO4), and in different growing seasons (autumn, summer). In addition, the better growing performance and development from early seedling stage up to maturity indicates their adaptive potential to grow in different area and changing climates. These results are decision support tools for the regeneration of multipurpose, exotic forest species such as Ks and Kg that have high agroforestry potential, socio-economic importance and suitable for ecosystem restoration.