M. C. Poltronieri

High-throughput sequencing of black pepper root transcriptome

BackgroundBlack pepper (Piper nigrum L.) is one of the most popular spices in the world. It is used in cooking and the preservation of food and even has medicinal properties. Losses in production from disease are a major limitation in the culture of this crop. The major diseases are root rot and foot rot, which are results of root infection by Fusarium solani and Phytophtora capsici, respectively. Understanding the molecular interaction between the pathogens and the host’s root region is important for obtaining resistant cultivars by biotechnological breeding. Genetic and molecular data for this species, though, are limited. In this paper, RNA-Seq technology has been employed, for the first time, to describe the root transcriptome of black pepper.ResultsThe root transcriptome of black pepper was sequenced by the NGS SOLiD platform and assembled using the multiple-k method. Blast2Go and orthoMCL methods were used to annotate 10338 unigenes. The 4472 predicted proteins showed about 52% homology with the Arabidopsis proteome. Two root proteomes identified 615 proteins, which seem to define the plant’s root pattern. Simple-sequence repeats were identified that may be useful in studies of genetic diversity and may have applications in biotechnology and ecology.ConclusionsThis dataset of 10338 unigenes is crucially important for the biotechnological breeding of black pepper and the ecogenomics of the Magnoliids, a major group of basal angiosperms.

Caracterização de acessos de pimenta-do-reino com base em sistemas enzimáticos

Seventy and eight accessions of black pepper, including some wild species, were analyzed through isozyme electrophoresis in polyacrylamide gel, aiming to distinguish phenotypic differences to discriminate and select accessions. The enzymatic systems SKDH, GOT, ACO, ACP, PGI, FUM, 6PGDH and G6PDH were studied. The polymorphism of isozymes was evaluated based on number of alozymes with different mobility for each enzymatic system, the frequencies of alozymes within each enzymatic system in relation to the total of bands of the system and, the analysis of the genetic similarity, based on the absence or presence of bands. All the enzymatic systems presented good resolution and definition of bands, with emphasis on SKDH, 6GPDH, PGI and the ACP. All the systems presented sufficient polymorphism to characterize and to identify accessions or groups with little number of accessions, where the GOT system presented better variability of alozymes. On the other hand, FUM system revealed only three alozymes and four profiles. Fifty seven percent of alozymes are efficient to characterize and to identify clones or groups of clones. About sixty four percent of the analyzed accessions can be identified per one to six individual phenotypes of enzymatic systems. The analysis of similarity indicated the G1, G2 and G3 groups as the most divergent, being appropriate for intra or interspecific crossings aiming to obtain superior clones.

Diversidade e similaridade genéticas em clones de pimenta-do-reino

Seventy eight black pepper clones (Piper nigrum L.) were analyzed by means of isozyme electrophoresis for the systems ACP, GOT, SKDH, ACO, G6PDH, PGI, 6PGDH and FUM, in order to evaluate the diversity through the percentage of polymorphic loci, mean number of alleles per locus and mean heterozigosity. Genetic similarity was calculated by simple matching coefficient and summarized in the group average phenogram. Fourteen loci and 35 alleles were detected. The loci that presented larger diversity were G6pdh-1, Acp-1 and Skdh-1. The percentage of polymorphic loci ranged from 3.57% to 64.29%; the mean number of alleles ranged from 0.04 to 1.64 and; the mean heterozigosity varied from 0.036 to 0.321. The lower values observed in the interval of variation of the average heterozigosity are consistent with the narrow genetic basis and the width of this interval can be related to the natural or forced hybridization degree of each clone. The genetic similarity ranged from 65% to 100%, and 70 clones were ranked into the interval of 85% to 100%, which confirms the narrowing of the genetic basis of the species and thereby resulting in the homogeneity of the cultivated clones.

Cylindrocladium pteridis leaf spot of apricot tree in the State of Para, Brazil.

The apricot (Mammea americana L.) is a fruit-bearing tree growm throughtout the entire Amazon region, especially in the state of Para, hence the name abrico-of-Para (Cavalcante. Frutas Comestiveis da Amazonia, 1996). The fruits are used in salads, and in the forms of liquor, jelly and compote, all which keep the taste and flavor for long periods of time. The bark latex and the seed powder of apricot are reported to have an insecticidal effect that efficiently control of ticks, other insects, and animal parasites. Its wood tannins are used in the leather industry (Coral. O Abricoteiro, uma opcao de investimento para o Estado do Para. Boletim Tecnico, SAGRI, 1998). In April 2002, during a routine plant pathological inspection of orchards in Marituba, PA, a generalized attack of a leaf spot disease was observed. Small light brown leaf spots, surrounded by a dark brown halo eventually resulted in the blight of the entire leaf (Figure1 A) and defoliation of the trees. Isolations were made from the lesions by cutting tissues fragments from the lesion margins, which after disinfections in 2% sodium hypochlorite for 1 min and washing in sterile water, were placed on 2% water agar. After a seven-day incubation at 26 + 2 C, the fungal growth showed morphometric characteristics of Cylindrocladium pteridis Wolf (telemorph Calonectrica pteridis Crous et al.). The conidiophores are penicillate, with clavate vesicle and the conidia are cylindrical, hyaline, uniseptate, 65-76 x 4.6-5.5 μm (mean 70 x 4.9 μm) (Figure 1B). For the pathogenicity tests, a 5 mm mycelial disc was placed on healthy apricot seedling leaves, while the PDA discs without the fungus served as control. All seedlings were placed in a moist chamber for 72 h. Symptoms similar to the natural infection appeared on the leaves five days after inoculation while the control seedlings remained healthy. The fungus was reisolated from the lesions. Cylindrocladium pteridis has been reported from Brazil causing lesions on aciculae of Pinus caribea Morelet var. hondurensis ( Senecl.) W.H.G. Barret & Golfari (Hodges et al. Brasil Florestal 6:8. 1975), in Cocus nucifera L. (Silva & Souza. Fitopatologia bras. 6:515. 1981; Ponte & Silveira Filho. Fitopatologia bras. 22:67. 1997; Trindade et al. Fitopatologia bras. 23:412. 1998), in Mauritia flexuosa L. (Silva. Fitopatologia bras. 21:523. 1996) and in Eucaliptus spp. (Ferreira et al. Fitopatologia bras. 17:226.1992). No previous report was found in the literature regarding the occurrence of C. pteridis and symptoms of the foliar lesions on apricot; thus this is the first record of the pathogen on apricot in Brazil.