Variação somaclonal da resistência à brusone em arroz nas gerações iniciais derivadas de panículas imaturas

Somaclones derived from immature panicles of the rice cultivars Bluebelle and Maratelli susceptible to blast and their F1's from crosses with resistant donors (Araguaia, Basmati-370 and Ramtulasi) were compared in the R2 (plants from self-pollinated seed from primary R1 regenerants) and R3 generations in the greenhouse and field for blast resistance. In the greenhouse the R2 plants and R3 lines were inoculated with the races IB-1 and IB-9 of Pyricularia grisea. The frequency of plants resistant to both races ranged from 16 to 42% in the F1 derived somaclones, whereas no resistant plant was recovered from the susceptible parents when inoculated with IB-1. The means of the leaf blast rating of R2 and R3 populations of F1's were significantly lower than those derived from susceptible parents. Similar results were obtained in field trials. However, the performance of the F1 derived somaclones varied depending on the resistant donor parent. In field trials, the mean visual ratings for leaf blast of regenerants from F1 derived R2 and R3 populations were significantly lower than those regenerants derived from the parental genotypes Maratelli and Basmati-370.Somaclones derivados de panículas imaturas das cultivares de arroz Bluebelle e Maratelli suscetíveis à brusone, e seus respectivos F1's de cruzamentos com doadores de resistência (Araguaia, Basmati-370 e Ramtulasi) foram comparados em R2 (plantas obtidas de autofecundação de sementes de regenerantes primários) e na geração R3, em casa de vegetação e no campo com relação à resistência à brusone. Em casa de vegetação, as plantas R2 e linhas R3 foram infectadas com as raças IB-1 e IB-9 de Pyricularia grisea. A freqüência de plantas resistentes a ambas raças variou de 16 a 42% nos somaclones derivados de F1's, enquanto nenhuma planta resistente foi encontrada nos pais suscetíveis quando inoculados com a raça IB-1. As médias de notas de brusone nas folhas das populações R2 e R3 foram significativamente menores do que as derivadas dos pais suscetíveis. Resultados semelhantes foram obtidos nos experimentos de campo. Contudo, o comportamento dos somaclones derivados de F1 variou dependendo do pai doador de resistência. Nos experimentos de campo, as médias de notas visuais de brusone nas folhas dos regenerantes derivados de F1 das populações R2 e R3 foram significativamente menores do que os regenerantes derivados dos genótipos Maratelli e Basmati-370

Poliembrionia no milho "Dentado Composto"

The frequency of polyembryony in "Dent Composite" maize was studied during three generations of controlled progeny self-pollination. Following established norms for seed testing, the seeds were placed in germinators. Seeds with multiple coleoptiles and primary roots were transplanted to Mitscherlich pots in the greenhouse and later to field plots. The increase of the multiple seedling frequency from S0 to S2, greater than 500 times, indicates the hereditability of the character. Correlation between polyembryony and prolificness and with oil and balanced protein content are suggested as new areas of research of interest for corn breeding.A frequência de poliembrionia no milho Dentado Composto foi estudada em três gerações de autofecundação com controle de progênie. As sementes foram colocadas em germinadores, de acordo com as normas para análise de sementes. As sementes com coleóptilos e raíses primárias múltiplas foram transplantadas para casos na casa de vegetação e dois para canteiros. O aumento de frequência de plântulas múltiplas de S0 S2, de mais de 500 vezes, indicada a hereditariedade do caráter. Correlação de poliembrionia com prolificidade e com teor de óleo e proteína equilibrada são indicados como novas áreas de pesquisas, de interesse para o melhoramento do milho

Desenvolvimento de somaclones da cultivar Araguaia resistentes à brusone em arroz de sequeiro

The degree of blast resistance of upland rice (Oryza sativa L.) cultivar Araguaia has decreased over time causing significant yield losses. The major objective of this study was to obtain blast (Pyricularia grisea) resistant somaclones, adapting greenhouse and field selection procedures. Rice blast resistance and agronomic traits were assessed in R2 to R6 generations derived from regenerant plants (R1) from immature panicles of Araguaia. The evaluation and selection procedures include testing of early segregating populations and fixed lines in the advanced generations, under natural field conditions, and artificial inoculations in the greenhouse, with prevalent races IB-1 and IB-9 of P. grisea. Somaclones with both vertical resistance and slow blasting resistance were obtained. Twenty of 31 somaclones developed with a high degree of vertical resistance and fan shaped plant type maintained resistance in field and blast nursery tests in the R6 generation. Greenhouse selection with two specific physiologic races yielded 44 somaclones with slow blasting resistance, similar plant type and yield potential as that of Araguaia.O grau de resistência à brusone da cultivar de arroz (Oryza sativa) Araguaia tem decrescido ao longo dos anos, resultando em prejuízos significativos na produtividade. O objetivo principal deste estudo foi obter somaclones resistentes à brusone (Pyricularia grisea), adaptando os métodos de seleção em casa de vegetação e de campo. Foram avaliadas plantas regeneradas (R1) de panículas imaturas da cultivar Araguaia nas gerações R2 a R6 para resistência à brusone e características agronômicas. O método de avaliação e seleção de plantas envolveu avaliações de populações segregantes e linhagens fixadas, em condições naturais de infecção no campo, e infecções artificiais em casa de vegetação com duas raças prevalecentes de P. grisea IB-1 e IB-9. Foram obtidos somaclones com resistência vertical e progresso lento de brusone. Vinte de 31 somaclones desenvolvidos com alto grau de resistência vertical e tipo de planta em leque apresentaram estabilidade da resistência no campo e nos viveiros de brusone na geração R6. No procedimento de seleção em casa de vegetação com duas raças específicas, foram obtidos 44 somaclones com progresso lento de brusone, as quais não diferiram da Araguaia quanto ao tipo de planta e potencial de produtividade

Micropropagation of rubber trees (Hevea brasiliensis Muell. Arg.)

Tissue cultures were established from newly expanded leaves and axillary buds of rubber trees (Hevea brasiliensis Muell. Arg.). Calli formed from these explants, but no regeneration occurred. Shoots were obtained from axillary buds cultured on Murashige and Skoog's (MS) medium (Physiol. Plant. 15: 473-497, 1962) supplemented with 1.0 mg/l kinetin, 1.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D), 20 g/l sucrose and 4 g/l Difco agar. Formation of a root similar to a tap root was induced on MS medium supplemented with 5.0 mg/l naphthaleneacetic acid (NAA), 3.0 mg/l indolylbutyric acid (IBA), 50 g/l sucrose and 4 g/l Difco agar. Several types of explants were used in attempts to recover complete rubber tree plants with well-developed tap roots. Leaf explants and axillary buds formed calli on MS basic medium with different combinations of kinetin, benzylaminopurine (BAP), 2,4-D, IBA, NAA and indolylacetic acid (IAA). The antibiotic tetracycline was also used to control possible bacterial infections. However, no antibiotic effect was noted. Calli formation was abundant, but no regeneration was observed when the calli from different media was transferred to MS medium without growth hormones. On this basic medium, callus cultures became necrotic and died. Shoots developed from axillary buds, rooted vigorously when cultured on MS medium with NAA, IAA, and IBA. Based on these results, further studies with commercially important clones should lead to a feasible micropropagation technique.Culturas de tecidos in vitro foram estabelecidas de folhas recém-expandidas e de gemas axilares de seringueira (Hevea brasiliensis Muell. Arg.). Houve formação de calos nestes explantes mas a regeneração destes calos em embrióides não ocorreu. Brotos foram obtidos de gemas axilares cultivadas no meio de cultura básico de MS (Murashige and Skoog (Physiol. Plant. 15: 473-497, 1962)), suplementado com 1,0 mg/l de cinetina, 1,0 mg/l de ácido 2,4-diclorofenoxiacético (2,4-D), 20 g/l de sacarose e 4 g/l de ágar Difco. Para o desenvolvimento do sistema radicular com raiz pivotante o meio de cultura usado foi o MS, suplementado com 5,0 mg/l de ácido naftalenoacético (NAA); 3,0 mg/l de ácido indolilbutírico (IBA); 50 g/l sacarose e 4,0 g/l ágar Difco

Micropropagation of rubber trees (Hevea brasiliensis Muell. Arg.)

Tissue cultures were established from newly expanded leaves and axillary buds of rubber trees (Hevea brasiliensis Muell. Arg.). Calli formed from these explants, but no regeneration occurred. Shoots were obtained from axillary buds cultured on Murashige and Skoog's (MS) medium (Physiol. Plant. 15: 473-497, 1962) supplemented with 1.0 mg/l kinetin, 1.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D), 20 g/l sucrose and 4 g/l Difco agar. Formation of a root similar to a tap root was induced on MS medium supplemented with 5.0 mg/l naphthaleneacetic acid (NAA), 3.0 mg/l indolylbutyric acid (IBA), 50 g/l sucrose and 4 g/l Difco agar. Several types of explants were used in attempts to recover complete rubber tree plants with well-developed tap roots. Leaf explants and axillary buds formed calli on MS basic medium with different combinations of kinetin, benzylaminopurine (BAP), 2,4-D, IBA, NAA and indolylacetic acid (IAA). The antibiotic tetracycline was also used to control possible bacterial infections. However, no antibiotic effect was noted. Calli formation was abundant, but no regeneration was observed when the calli from different media was transferred to MS medium without growth hormones. On this basic medium, callus cultures became necrotic and died. Shoots developed from axillary buds, rooted vigorously when cultured on MS medium with NAA, IAA, and IBA. Based on these results, further studies with commercially important clones should lead to a feasible micropropagation technique

Utilização de fósforo e características do sistema radicular e da parte aérea da planta de arroz Phosphorus utilization and characteristics of root and top of rice plant

A seleção de plantas mais eficientes no uso do fósforo é importante para tornar mais econômica a cultura do arroz e, assim, maximizar a produção de grãos. Conduziu-se este trabalho com o objetivo de estudar as inter-relações que possam ocorrer entre a eficiência no uso do P e outras características da planta do arroz (Oryza sativa L.). Foram avaliados 25 genótipos de terras altas cultivados em solo e in vitro, nos níveis baixo (0 mg de P dm-3) e alto (150 mg de P dm-3, em solo, e 17 mg de P dm-3 em meio de cultura). Em solo com nível baixo de P, a altura e o número de raízes da planta foram as caraterísticas que tiveram maior efeito direto na eficiência de utilização do P. No nível alto de P, o número de folhas e comprimento das raízes da planta foram as caraterísticas que tiveram maior efeito direto. In vitro, tanto no baixo como no alto nível de P, o teor de P acumulado e o volume da raiz foram as caraterísticas que tiveram maior efeito direto na eficiência de utilização do P.<br>The improvement of rice plants (Oryza sativa L.) for better P use efficiency is important to decrease the cost of rice production and maximizing yields. The objective of the present study was to understand the relationship among root and shoot characteristics with P use efficiency and other characteristics of the rice plant. Twenty-five genotypes of rice were grown in soil and in vitro under two level of P: low (0 mg of P dm-3) and high (150 mg of P dm-3) in soil, and 0 and 17 mg of P dm-3 in vitro. In soil at low level of P, the plant height and number of root per plant had the highest direct effect on P use efficiency. At high P level, the number of leaves per plant and root length had the highest direct effect on P use efficiency. In vitro, under all conditions of evaluation and levels of P, the level of P accumulation in the plant and root volume had the highest direct effect on P use efficiency