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Fast track evaluation and selection of Hevea brasiliensis clones from a clonal nursery

Gireesh, T., Meenakumari, T., Mydin, Kavitha K.
Industrial crops and products 2017 v.103 pp. 195-201
Hevea brasiliensis, agronomic traits, bark, clones, crossing, females, genetic background, juveniles, parents, phosphorus pentoxide, plant growth, planting, progeny, rubber, seedlings, tree breeding, trees, South East Asia
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 2.5m×2.5m. 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 (4.9m×4.9m). The results indicated that one of the half-sib progeny of mother clone PB 86 (HS PB 86/57) registered significantly (P<0.05) superior dry rubber yield of 18g per tree per tapping (g/t/t), and vigorous trunk girth (43cm) at breast height in the 5th year after planting when compared to that of RRII 105 (11.9g/t/t; 34.1cm girth) and on par with RRII 430 (14.9g/t/t; 31cm girth) and RRII 414 (14g/t/t; 38cm girth), the best among the checks. The second best clone HS LCB 1320/30 also recorded comparable yield and growth with RRII 430 and was better than RRII 414. Three clones (HS PB 86/57, HS BD 5/27 and HS LCB 1320/30) could be selected based on the growth, yield and other secondary traits. None of the trees of HS PB 86/57showed incidence of pink disease and Tapping Panel Dryness (TPD) during field evaluation which deserves attention. The results support superior performance of new genotypes in CNT, saving time and space required to complete the breeding-evaluation cycle. Besides, these clones could be used as improved genetic stocks for initiating new breeding programmes to enrich the genetic base of natural rubber.