Growth and disease tolerance in selected progenies of pinus radiata(D.Don) in Kenya.

Abstract

Five progeny trials of Pinus radiata were established at Timboroa, Nabkoi, Sabor and Kaptagat areas in the Rift Valley between 1985 and 1996. The objective of these trials was to determine the growth and disease tolerance levels among selected germplasm at different sites. One trial at Timboroa was 22 years and comprised 59 progenies introduced from Australia and one general collection seedlot. The trials at Sabor and Nabkoi were 17 years and comprised 38 progenies introduced from New Zealand and 6 progenies from local selections. The other trial at Timboroa was 16 years and comprised 24 progenies from New Zealand and one progeny from local selection. The 11 year old triid at Kaptagat comprised 12 locally selected progenies. In each of these trials, randomised block design was used with four blocks. Six trees from each progeny were planted per plot. Analysis of the data collected in 2007 show a significant variation in diameter at breast height (dbh), height and disease score in four out of five trials (p=0.5). Ranking of progeny performance was done on the basis of height growth. The best performing of the 22 year old Australian material at Timboroa was progeny number 9 with a mean height and dbh of 27.8 m and 31.6 cm respectively. Mean disease score on this progeny was 1.8 on a scale of 1-5 where 1 is least infected and 5 is most infected. The best result among the New Zealand material at 17 year was shown by progeny number 24 at Nabkoi where the mean height, dbh and disease score was 29 m, 31.6 cm and 1.3 respectively. The eleven year old trial at Kaptagat with local material did not show statistically significant difference among the progenies but the best performing group was progeny 7 with mean height, dbh, and disease score of 20.2 m, 19.4 cm and 1.8 respectively. Ranking of growth performance and disease tolerance levels of the progenies enabled the identification of the best performers at each site and recommendations made on their inclusion in further tree improvement programmes and germplasm/site matching to achieve maximum productivity of the species for supply of industrial wood.