Abstract
Rootstocks and scions combinations of five rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) MuellArg.] clones were evaluated for rubber yield and growth vigor to detect the rootstock with the best general combining ability (GCA) and the best specific combining ability (SCA), using the method 1, suggested by Griffing. The clones (scions) involved were: IAN 873, RRIM 600, RRIM 701, PB 235 and GT 1 grafted in five different rootstocks from illegitimate seeds of the same clones. The ANOVA mean squares for GCA and SCA reciprocal effects were highly significant for both characters. The general GCA: SCA ratios were 24:1 and 4:1 for rubber yield and growth vigour, respectively. The rootstock of the RRIM 600 clone was the best general combiner for rubber yield (g i = 8.25), followed by the PB 235 (g i = 5.20).Although negative, the rootstock of the RRIM 600 clone showed the best GCA (g i = -0.0354) for growth vigour, followed by rootstock of the GT 1 clone which presented a g i = -0.5194 value. The maximum SCA effects for rubber yield (s ij = 5.55) was obtained by IAN 873 rootstocks combined with the RRIM 600 clone as scion, followed by the PB 235 (rootstock) combined with the RRIM 600 scions (s ij = 3.06). For growth vigour, the best specific combining ability effect of s ij = -1.64 was obtained by the IAN 873 clone in combination with the RRIM 701 clone, with their respective rootstock and scion. As for rubber yield, the RRIM 600 rootstocks were classified as the best general combination. In addition, the IAN 873 rootstocks combined with the RRIM 600 scion showed the best specific combining ability.
Highlights
The budded rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] plant comprises a root system provided by the stock plant and a shoot system supplied by the scion plant
Except for IAN 873 (23.75 g / tree / tapping), the yields obtained from the clonal rootstocks that received the scion of the same clones, such as GT 1, PB 235, RRIM 701 and RRIM 600, were very good, ranging from 41.25 to 58.84 g / tree tapping compared to 22.65 to 67.25 g / tapping for combinations arising from possible rootstocks combined with different clone scion
A similar or slightly lower values for growth vigour (Table 3) were observed for the five clonal rootstock combined with the same clone scion compared with rootstocks combined on different clone scions
Summary
The budded rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] plant comprises a root system provided by the stock plant and a shoot system supplied by the scion plant. Observations showed that the average yield of a clone budded on seedling rootstocks was usually somewhat inferior to that of its mother tree, which led to an investigation of the stock effects and of the possibility of selecting superior rootstocks to improve scion performance. The rootstock can influence the growth and rubber yield of the scion to varying degrees. Availability rather than the particular type of seedling dictates the selection of the rootstock used for budding. This situation arises not because there is no experimental information on rootstocks, but because the role of the rootstock has not been well emphasized and its benefits not clearly illustrated
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