Application of meta-Analysis to yield performance of rubber (Hevea brasiliensis,) clones

In hevea,so far no attempt has been made to conduct a meta-analysis on yield performance of clones from many studies. with the objective to demonstrate the application of meta-analysis in hevea research,yield performance of twelve clones repeated across many trials were subjected to meta-analysis. two effect-size measures namely,standardised mean difference as hedge's g and log response ratio were used for combining results. standardised mean difference in different studies ranged from -3.76 to 6.83. random effect mean standardised mean difference in gt1 wo? 0.38. all the standardised mean difference values in rrim 600 were negative. in clones rrii203,pb 235,pb 260,pb 217 and pb 311,standardised mean difference values were all positive while in other clones they were mostly negative. random effect,model mean standardised mean difference's were significantly higher in clones rrii 203 and pb 235. in effect sizes,the percentage change in yield of gt 1 over rrii 105 ranged from negative 13 percent to positive 39 percent. among eight studies,four studies gave positive while the other four gave negative change in yield over the control rrii 105. random effect overall yield was about 10 percent. in rrii 600. all the six studies produced negative change in yield. rrii 203 and pb 235 produced significantly higher yield over rrii 105 with percentage increases ofabout 20 and 36 percent respectively among the other clones,pb 260 produced a significantly higher yield of about 22 percent. clear general patterns were identified in yield performance of treatment clones over the control. clones rrii 203,pb 235 and pb 260 showed clear superiority in yield performance. results of clones pb 217 and pb 311 indicated that further testing needs to be undertaken for taking a clear stand on the usefulness of these clones for the region. comparison of standardised mean difference and the log response ratio effect size indices indicated that the log response ratio maybe more informative for quantifying the treatment effect in meta-analytic studies with hevea brasilicnsis.