LAUSR

Abstract Ten female parents of natural rubber (Hevea brasiliensis), introduced from two Southeast Asian countries were allowed to natural cross breeding. After a primary culling of seedlings based on growth and test tap yield in juvenile stage, 20 half-sib (HS) progenies were cloned and evaluated in a clonal nursery trial (CNT) laid out (RCBD, plot size 6 with 3 replication) in a close spacing of 2.5 m × 2.5 m. Four established precocious high yielding clones (RRII 430, RRII 414, RRII 105 and PB 235) were included as control. Superior clones were identified based on the important agronomic traits viz., growth, juvenile yield, tolerance to pink disease and bark thickness within a short span of five years, instead of fifteen years in conventional small scale trials (SST) with a wide spacing (4.9 m × 4.9 m). The results indicated that one of the half-sib progeny of mother clone PB 86 (HS PB 86/57) registered significantly (P