Resposta de acessos de arroz (Oryza sativa L.) ao ataque da broca-do-colmo (Diatraea saccharalis Fabr., 1794)
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Data
2011-02-15
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Universidade Federal de Goiás
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Among the biotic stresses, insect pests are considered a major threat to to increasing world rice production and the stem borers are one of the most destructive pests. Due to the behavior of the caterpillar in D. saccharalis in staying inside the stems of rice plants and the difficulty to be controlled by chemicals, the use of cultivars resistant to this
pest is in a viable method of controlling this not imposed because of production costs and is environmentally safe. This study had as main objective to observe the response of 34
accessions of rice to the attack of stem borer D. saccharalis, assessing and describing the morphological characteristics of plants associated with resistance to this rice-stem borer
and analyze, using microsatellite markers, the genetic diversity of these accessions. The experiment was conducted in greenhouse condition at Embrapa Rice and Beans Research
Center using randomized complete block design with four replications. During the assessment of some plants were determined quantitative and qualitative characters of rice
accessions related to the attack of larvae of D. saccharalis. The quantitative characters were the number of living larvae/stem, weight of surviving worms, the inner diameter of
the stem, stem attacked number and percentage of stems attacked. The qualitative characters were the kind of ligule and pubescence of the leaf. Accesses more favorable
survival of larvae IAC 47 and Ti Ho Hung showed that on average 10.37 and 10.25 larvae. Larvae with greater weight (0,0986 g e 0,0862 g) were found in two VT "Canela de Ferro"
(CA 780099 and CA 790164). The highest inner diameter of the stem was found in two VT "Canela de Ferro" (CA 790164 and CA 980007) that showed 3.18 mm. The accessions
introduced Ti Ho Hung and Chiang an Tsao Pai Ku showed an average in the most
damaged stalks (7,04 stems for both cultivars). The percentage of attack between the LCI ranged from 49% to 93% in accesses C 409 and Ti Ho Hung. Among the hits that make up the stratum of the LCB the percentage of attack ranged from 45% to 88% at Bonança and IAC 47. Among the VT "Canela de Ferro", the hits that showed the values smaller and larger numbers of stems were damaged CA 790167 and CA 810055 (95 and 57% respectively). The number of surviving worms showed significant positive correlation with
the average weight of larvae and number of stems attacked. The inner diameter of the stem showed a significant positive correlation with the average weight of larvae. In this sense,
the larvae were found in the heaviest hits with the largest stem diameter, showing the
positive effect of this feature. The qualitative characters that predominated among accessions of rice was pubescence of the leaf type flat and shape of ligule type split. For molecular analysis of rice accessions were used 24 microsatellite markers. The PIC identified by this set of markers ranged from 0.10 (RM 171) to 0.87 (OG 106), averaging 0.63. The number of alleles was between four (RM 171) and 28 (RM 14), totaling 243 alleles with an average of 10.12 alleles/locus and between alleles 92 were private. The marker that detected the highest number of private alleles was RM 14 with thirteen alleles and the accessions with the highest numbers of private alleles were IR 42 and TKM 6. The combined value of PI was 1.005 x10-18 and by correspondence factor analysis (CFA)
showed the spatial distribution of genetic variation within the set of accessions analyzed and verified that the LCI IR 42 and TKM 6 were distinguished from other accesses. The other cultivars and lines introduced formed a group with high genetic similarity between them, the same way, the traditional varieties and cultivars in Brazil found themselves
closer. The dendrogram produced a cophenetic coefficient r = 0.82 and the average genetic distance of Rogers-W was 0.62 and this value was used as the cutoff point for identifying
groups most similar. We observed the formation of five distinct groups. However, despite the presence of these five groups, four accessions remained non-grouped or isolated, which were Primavera, "Canela de Ferro - CA 220268, Su Yai 20 and TKM 6. With the exception of access Ti Ho Hung, the other LCI morphological traits (hairy leaves and stem inner diameter smaller than 2.5 mm) remained similar and grouped into the molecular analysis. Overall, the VT "Canela de Ferro" were similar for response to attack D. saccharalis. Plants of these accessions have smooth leaves and stems with an internal diameter larger than 2.5 mm. Only one access (CA 220268) had an inner diameter of the stem smaller than 2.5 mm and not associated with the group of "Canela de Ferro" in the molecular analysis. The LCB were less attacked the VT "Canela de Ferro". However, the morphological characteristics of plants of some accessions of LCB were similar to those of VT "Canela de Ferro", as in access IAC 47, Caiapó and Confiança showed that inner diameter greater than 2.5 mm stem and leaves with pubescence of the leaf type flat. The present results indicate that the morphological and molecular analysis were able to separate the accessions of rice in different groups. With respect to morphological characteristics, we separated the accessions into groups that responded differently to the attack of stem borer D. saccharalis. Molecular analysis of the access allowed to evaluate high degree of detail the level of genetic variability among accessions, and allows the determination of the
genetic relationship between them. The verification of the presence of significant genetic variability among 34 accessions provides evidence that these can be used by the rice breeding programs in Brazil as a way to increase the genetic base of Brazilian accessions of rice, allowing the emergence of new allele combinations and adaptations to specific environments, which can provide, for example, a reduction of vulnerability to insect pests.
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NASCIMENTO, Jacqueline Barbosa. Response of accessions of rice (Oryza sativa L.) to attack of stem borer (Diatraea saccharalis Fabr., 1794). 2011. 67 f. Dissertação (Mestrado em Ciências Agrárias) - Universidade Federal de Goiás, Goiânia, 2011.