Adaptability of four-year old eucalyptus species and clones in Kenya.

Abstract

Eucalyptus is the third most commonly grown tree genus in Kenya, after pine and cypress. The most common species are E.grandis, E. saligna, and E. camaldulensis. These species are fast-growing, adapted to many agro-ecological zones and have numerous uses. Due to their importance, breeding strategies have been developed to improve productivity. One of the major concerns is assessing their adaptability across sites. Fifteen Eucalyptus grandis x Eucalyptus camaldulensis (GCs) and three Eucalyptus grandis x EucalyPtus urophyla (GUs) hybrid clones were introduced to Kenya from Mondi Forest, South Africa (SA).These clones and local land-races of E. grandis (EG), E. camaldulensis (EC), E. saligna (ES), E. tereticomis (ET) and E. urophyla (EU) were used to establish trials on four high and three low altitude sites in Kenya. The trials were established in complete randomized block design replicated two to four times. Assessments were done on height, diameter at breast height (DBH),stemform and branching habit at four years. The objective of this paper was to determine adaptability of the four-year-old eucalyptus species and clones in Kenya. Additive Main effect Multiplicative Interaction (AMMI) was used to determine adaptability and stability of the genotypes across the sites. Orthogonal comparisons on the growth were done using ANOVA and generalized linear modeling procedures. Results showed that performance of clones and local land-races was not consistent over all sites. There was a high significant (p < 0.01) difference in height, DBH, stemform and branching habit within and between sites. In high altitude sites, GC1S had highest height and DBH of 18.2 m and 14.Ocm,respectively, in Machakos. In low altitude sites, GCS81and GC167 had highest height of 14.2and 14.3m, respectively. Overall, none of the genotypes was stable across high altitude sites. On the other hand, GCS81, GU21 and GC784 were stable across the low altitude sites. The results suggest that, on sites above 2000m, the local land-races, EG and ES, would perform better than clones. It is recommended that GC581, GU21 and GC784 could be used for further wide scale in Kenya across the low altitude sites.