Variation in wood density and strength properties among Markhamia lutea (sprague) half sib families from western Kenya

Abstract

Wood samples of forty two (42) half sib families of Markhamia lutea were drawn from a 4-year old progeny test at Kakamega and assessed for variation in wood properties. The mother plus trees had been selected from partially isolated populations in the Lake Victoria belt of Kenya. The main objective of the progeny trial was to test breeding values for various traits, including wood properties, of the selected trees for advanced breeding and to estimate genetic parameters. Incomplete block design in 3 replications with 8 tree line plots was used. Results on growth performance and stem straightness revealed significant variations in diameter and height and no significant variation in stem straightness among the progenies, (ICRAF,1996) The study reported here involved analysis of wood specific gravity, bending strength (modulus of elasticity [MOE] and modulus of rupture [MOR]), compression (crushing) strength. Wood samples for specific gravity determinations were obtained at 1.3 m height. Other properties were based on the butt logs. Specific gravity was determined using the water displacement method (Brown et al, 1952) while the other properties were determined according to British Standard No. 373:1957. No significant differences (P < 0.05) were obtained for all the properties studied. Averages for specific gravity were highest for South Nyanza provenance and lowest for Busia provenance. The range in specific gravity was 0.37-0.44 (18.9%) while the ranges in strength values were: MOR 67.7-85.3 MPa (26.0%) and compression 31.9 - 40.9 MPa (28.2%). It was concluded that at 4 years selection can be done for height and diameter but little gain may be expected from provenance and individual tree selection for specific gravity and strength properties, although it was recognised that the reported results relate to juvenile assessments (rotation age for this species is about 40 years). It is therefore recommended that these studies be repeated at later ages towards half rotation age.