Initial development of IAC rubber clones in Sao Jose do Rio Preto, Sao Paulo State, Brazil/Desenvolvimento inicial de clones IAC de seringueira em Sao Jose do Rio Preto, SP

In this study the development of four clones (IAC 35; 40; 300 e 301) of rubber tree [Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.] selected by Instituto Agronomico de Campinas were evaluated during the first 24 months of cultivation. The experiment was laid out in randomized block design with three replications and four plants for parcel following the 1.5mx1.0m spacing at Sao Jose do Rio Preto, SP. The clone RRIM 600 was used as check. The variables analyzed were the trunk girth, the number of matured whorl, the photosynthesis rate and the concentrations of chlorophyll a, b, total and carotenoids. At the end of the experiment the values of trunk girth at 0.5m above the budgrafting union varied from 5.85 cm (IAC 301) to 10.53 cm (IAC 300) and the mean number of matured whorl varied from 2.58 (IAC 301) to 3.91 (RR1M 600). During the dry season, when the plants were 22 month old, the mean value of photosynthesis rate of IAC 40 and IAC 301 (12 [micro]mol [m.sup.2] [s.sup.-1]) were lower compared to the other clones (15 [micro] mol [m.sup.2] [s.sup.-1]). The chlorophyll a, b and total carotenoids concentrations were equal or superior to the check, never lower. Considering the variables analyzed, excluding the IAC 301, the other clones show performance comparable to RRIM 600. Key words: Hevea brasiliensis, trunk girth, photosynthetic rate, photosynthetic pigments. Neste estudo, acompanhou-se o desenvolvimento de quatro clones de seringueira [Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.] selecionados pelo Instituto Agronomico de Campinas (IAC 35; 40; 300 e 301) com relacao a testemunhaRR1M 600, durante os primeiros 24 meses de cultivo. O experimento foi instalado com espacamento 1,5x1,0m, em delineamento em blocos casualizados, com tres repeticoes e quatro plantas por parcela, em Sao Jose do Rio Preto, SP. Foram avaliados o perimetro do caule e o numero de lancamentos maduros; a taxa fotossintetica e o conteudo de pigmentos fotossinteticos. Ao final do acompanhamento, o perimetro medio do tronco, a 50cm do calo de enxertia, variou entre 5,85cm (IAC 301) e 10,53cm (IAC 300) e o numero medio de lancamentos maduros, de 2,58 (IAC 301) a 3,91 (RRIM 600). No periodo seco, em idade de 22 meses apos o plantio, os valores medios de taxa fotossintetica de IAC 40 e IAC 301 (12 [micro] mol [m.sup.2] [s.sup.-1]) foram inferiores aos dos demais clones (15 [micro]mol [m.sup.-2][s.sup.-1]). Os teores de clorofila a, clorofila b e carotenoides totais foram iguais ou