Nelson Bortoletto

Fitorreguladores de crescimento e capação na cultura algodoeira

Estudaram-se, em dez experimentos de campo, os efeitos dos seguintes fitorreguladores de crescimento e da capacao na cultura algodoeira: cloreto de clorocolina, aplicado na dose de 50 g/ha; cloreto de chlormequat, 100 g/ha e cloreto de mepiquat, 100 g/ha. A capacao foi realizada manualmente, planta por planta, na mesma epoca da aplicacao dos fitorreguladores, aos 60-70 dias da emergencia das plantas. O delineamento estatistico foi de blocos ao acaso, com cinco tratamentos e seis repeticoes e, a variedade utilizada, a IAC 19. Para a avaliacao dos resultados de producao e altura de plantas, efetuaram-se dois agrupamentos de ensaios, sendo um com maior e outro com menor desenvolvimento, ou seja: plantas em parcelas testemunhas com altura superior e inferior a 100 cm respectivamente. As demais caracteristicas agronomicas e tecnologicas da fibra foram analisadas em um so grupo. Para o grupo de plantas com maior desenvolvimento, foi obtido, em media, um aumento de 16,3 e 8,4%, respectivamente, para o tratamento com capacao e aplicacao de fitorreguladores. O fitorregulador proporcionou, em media, reducao de 12,1% na altura das plantas e a capacao, em media, 20,8%. Os fitorreguladores, indistintamente, proporcionaram aumento de peso do tapulho e das sementes, enquanto, com a pratica da capacao, nao se verificou esse efeito. A aplicacao de cloreto de clorocolina resultou em menor porcentagem de fibra do que o cloreto de mepiquat.

Early selection for growth vigor in rubber tree genotypes in northwestern São Paulo State (Brazil)

Forty-five genotypes (clones) of rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.] of different origins were assessed for efficiency of early selection at the Votuporanga Experimental Station in northwestern Sao Paulo State, Brazil, using a randomized complete block design with three replications and six plants per plot. Girth at 120 cm above the highest point of the grafting union of each tree was taken at ages 12, 24, 36, 48, 60, 72, 84 and 96 months. Highly significant differences in girth were detected among the genotypes at all ages evaluated, except for 12 months. Estimates of genetic variance for two age sets showed a substantial increase with age, while the genotype variation decreased. Selection made at 24 months proved to be the most efficient, giving a superior gain per unit of time.

EFEITO DO NITROGÊNIO NO CULTIVO DE FEIJÃO IRRIGADO NO INVERNO

An experiment was conducted at three localities, namely, Ribeirao Preto (Latosolic B Terra Roxa), Votuporanga (Dark red latossol sandy phase) and Pindorama (Podzolic Lins-Marilia), in the State of Sao Paulo, Brazil. The objetive was to evaluate the response of nitrogen on irrigated dry beans during a two year period at Ribeirao Preto and Votuporanga (1990, 1991) and in Pindorama (1992, 1993). The experimental design was a complete randomized blocks design with five replications. The results showed that the yield of irrigated dry beans in the winter can be increased adding nitrogen. The sprint application is recommendable for the low fertility soil (Pindorama). The combination of N applied to the soil and on the leaves was more effective than that only on the leaves. The single dose applied at the 25th day after germination was more effective than the one aplied at the sowing date.

Genetic variability and selection for laticiferous system characters in Hevea brasiliensis

Six laticiferous system characters were investigated in 22 three-year-old, half-sib rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] progenies, evaluated at three sites (Votuporanga, Pindorama and Jau, all in the Sao Paulo State, Brazil). The traits examined were: average rubber yield (Pp), average bark thickness (Bt), number of latex vessel rings (Lv), average distance between consecutive latex vessel rings (Dc), density of latex vessels per 5 mm per ring averaged over all rings (Dd) and the diameter of the latex vessels (Di). The joint analysis showed that site effect and progeny x sites interaction were significant for all traits, except Lv. Estimates of individual heritabilities across the three sites were high for Bt; moderate for Lv, Pp and Dc; low for Dd and very low for Di. Genetic correlations in the joint analysis showed high positive correlations between Pp and the other traits. Selecting the best five progenies would result in genetic gains of 24.91% for Pp while selecting best two plants within a progeny would result in a Pp genetic gain of 30.98%.

Seleção combinada univariada e multivariada aplicada ao melhoramento genético da seringueira

The objective of this paper was to estimate the heritability coefficients by the univariate method and genetic prediction by the multivariate method, as well as to compare the genetic gain obtained by individual and combined selection between and within progenies, in rubber tree (Hevea brasiliensis Willd. ex Adr. de Juss.) Muell. Arg.). Twenty two half-sib progenies were established at the Experimental Station, in Votuporanga, Sao Paulo State, Brazil, following the randomized block design, with five replications and ten plants per plot. Three years after planting, number of latex vessel rings (NR), yield of dry rubber (YB), bark thickness (BT) and stalk circunference (SC) were evaluated. The results showed significant variability among progenies for YB, BT and SC characters. The heritability coefficients and genetic prediction to progenies level were high, with expressive values for the genetic prediction coefficients. Additional genetic gains were obtained by combined selection. Although the genetic gains had been small, this method is recommended, because it gives a better improvement and genetic gain. The most expressive values of improvement and genetic gain were estimated by multivariate method.

Root-system depth of field beans and wheat under center pivot

O estudo foi realizado na Estacao Experimental de Votuporanga, do Instituto Agronomico, em solo podzolizado com as culturas de feijao e trigo irrigadas por pivo central no inverno de 1989. O objetivo for a determinacao da profundidade efetiva do sistema radicular, como um dos parâmetros fundamentais no manejo das irrigacoes. Estas eram realizadas quando a tensao da agua no solo atingia 0,05 a 0,06 MPa, controlada por tensiometro a 15cm de profundidade. Foram feitas tres medicoes quinzenais de raizes em cada cultura, utilizando-se trado tipo caneca de 7cm de diâmetro. As amostragens foram tomadas na linha de plantio, de 10 em 10cm ate a profundidade de 60cm. Os resultados indicam que, para o manejo adequado da irrigacao, a profundidade do sistema radicular a ser considerada deve ser de 30 e de 40cm, respectivamente, nas culturais de feijao e de trigo no solo em questao.

Genetic variation in growth traits and yield of rubber trees (Hevea brasiliensis) growing in the Brazilian state of São Paulo

Analysis of variance and covariance was preformed on growth traits (stem girth, bark thickness, total height gain and rubber yield) of 22 open-pollinated progenies of the rubber tree Hevea brasiliensis from an Asian Hevea collection introduced to Agronomic Institute (Instituto Agronomico, Campinas, Sao Paulo, Brazil; IAC) in 1952. This progeny trial was replicated at three sites in Sao Paulo state and it was found that at three years from sowing there was statistically significant variation for girth, bark thickness, height and rubber yield. An individual test sites, values of individual plant heritability for girth ranged from h= 0.36 to h= 0.89 whereas values for heritability for progeny means ranged from h= 0.77 to h= 0.87. These moderate and high heritabilities suggest that a combination of progeny and within-progeny selection would be effective at increasing girth in this population at individual sites. Across sites, values of individual-plant heritability for girth ranged from h= 0.36 to h= 0.47, whereas values for heritability of progeny means girth ranged from h= 0.77 to h= 0.87. There were high positive genetic correlations between increased girth and bark thickness suggesting that breeding aimed at increasing girth would also increase bark thickness and possibly height.

NITROGÊNIO E POTÁSSIO NA FIXAÇÃO SIMBIÓTICA DE N2 POR SOJA CULTIVADA NO INVERNO

The objective of these experiments was to study the effect of nitrogen and potassium fertilizations on the response to nodulation, nitrogen fixation, nitrogen seed content and yield of two soybean cultivars planted during the winter season. They were installed on the following soils: Eutric Lixisol (Mococa) and Rhodic Ferralsol (Ribeirao Preto and Votuporanga, SP, Brazil). The treatments consisted of three rates of nitrogen (0, 50 and 100 kg.ha-1 of N) as urea, three of potassium (0, 30 and 60 kg.ha-1 of K2O) as chloride and two soybean cultivars (IAC-8 and IAC-14). The experimental design was a random factorial with four replications. Soybean seeds of all treatments were inoculated with a commercial inoculant. At flowering, plants were sampled to evaluate nodulation and nitrogenase activity. At maturity, plants were harvest and seeds weighed.The results showed that inoculation did not provide the amount of nitrogen required to maximize soybean yield in the winter. The nitrogen treatment reduced nodulation and nitrogen fixation, but increased seed yield at the three localities. Potassium fertilization did not have any significant effect on nodulation, nitrogen fixation and yield of soybeans. Increased however dry matter weight and number of nodules of the cultivar IAC-14.

Phenotypic stability and genetic gains in six-year girth growth of Hevea clones

7 ABSTRACT - Rubber tree (Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.) budgrafts of seven clones were evaluated on five contrasting sites in the plateau region of the Sao Paulo State, Brazil. The objective of this work was to study the phenotypic stability for girth growth. The experimental design was a randomized block design with three replications and seven treatments. Analysis of variance of girth at six-year plant growth indicated a highly significant clone x site interaction. Only linear sites and clone x site components of clone x year interaction were significant, indicating that the performance of clones over sites for this trait could be predicted. The clones GT 1 and PB 235 showed the greatest stability in relation to girth growth, with foreseen responses to change, introduced in the sites. The clones PB 235 and IAN 873 showed significative difference in relation to regression coefficient, representing clones with specific adaptability on favorable and unfavorable sites respectively. The clone GT 1 became the most promissory one in the study of stability and adaptability even showing low girth growth. Expected genetic gains from planting sites, along with estimates of clonal variance and repeatability of clonal means are generally greatest or close to the greatest when selection is done at the same site.

Desempenho de novos clones de seringueira: III. seleções promissoras para a região de Votuporanga, Estado de São Paulo

6 RESUMO - E apresentado o resultado da primeira selecao de 25 clones de seringueira ( Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.), a maior parte constituida de introducoes de diferentes origens. Apos multiplicados, foram avaliados em experimentos do tipo pequena escala, obedecendo ao deline- amento de blocos ao acaso, instalado na Estacao Experimental de Votuporanga, SP. Os caracteres avaliados foram: producao de borracha seca, vigor expresso pelo perimetro do caule, espessura de casca e numero de aneis de vasos laticiferos. Com relacao a producao de borracha seca, destacaram-se os clones IAN 3156, IAC 40, 7/6, 3/5 e 3/1, produzindo 124%, 105%, 27%, 26% e 19% superiores em relacao ao RRIM 600, recomendando-se seu plantio em pequena escala na regiao de Jau. Caracteres secundarios tais como o vigor, espessura de casca e numero de aneis de vasos laticiferos dos clones testados sao tambem discutidos. Sugere-se sua avaliacao em experimentos do tipo grande escala com o objetivo de avaliar, alem da producao, outros caracteres secundarios para futuras recomendacoes no Estado de Sao Paulo. ABSTRACT - The present paper shows the results of the first selection of 25 rubber tree clones (Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.). Most of them are introductions, originated in selections obtained from different places. After multiplied, the clone evaluation was conducted in a small scale trial under a randomized complete block design established at Votuporanga Experimental Station in Sao Paulo State, Brazil. The evaluated characters were yield, vigour expressed by stem girth, bark thickness and number of latex vessel rings. The clones IAN 3156, IAC 40, 7/6, 3/5 e 3/1 were classified as high yielding in the first year of tapping. They produced 124%, 105%, 27%, 26% and 19% higher compared with the RRIM 600. The secondary characteristics, such as stem girth, bark thickness, and number of latex vessel rings of the tested clones are discussed. A complementary evaluation in large scale trials is suggested, aiming to evaluate besides yielding other secondary char- acters with purpose of future recommendation of planting materials to the industry.