[ RNASeq transcripts ]
The coffee berry borer (Hypothenemus hampei; CBB; Coleoptera: Scolytidae) is considered one of the main pests of coffee cultivated in Brazil. CBB was first introduced in São Paulo, probably in 1913, together with seeds imported from Africa (place of origin of this insect species) and Java (Indonesia). From 1913 to 1924, the insect spread to many coffee fields in Campinas-SP (Brazil) and to several neighboring municipalities. In the 1924’s harvest, the first losses were observed. From then on, CBB spread to all Brazilian coffee regions. CBB is considered a monophagous coffee pest, even though reports have already shown this insect feeding on other plants, albeit occasionally, without its multiplication in seeds. All species of the Coffea genus are susceptible to the CBB attack, but in different scales, varying from one year to another and even during the same year. Depending on the CBB infestation level, the damage to coffee fields can reach 21%, just by the loss of the bean weight. In addition, the quality of coffee is impaired, since the percentage of brocated beans increases proportionally to the levels of pest infestation, resulting in a product with lower added commercial value. Beside that, exporters accept a maximum of 10% of brocade coffee beans. That is, the more brocade coffee the less profitable it will be.
This insect-pest undergoes complete metamorphosis (holometabola) passing through the egg, larva, pulp and adult phases. The cycle from egg until adulthood lasts between 27 and 30 days, and can vary according to environmental and biological conditions. After mating, the females leave the fruits lying on the ground or hanging on the plants where they spent the off-season, looking for "new" fruits, which is, fruits of the new harvest. CBB female only lays eggs inside the coffee seed. For this, the female opens a gallery, usually in the region of the crown of the fruit until reaching the seed. Perforated the seed, the gallery is enlarged and transformed into a chamber, in which the female lays its eggs. The laying is done on green fruits with the seed formed, ripe (cherries) and starts only when the fruits become very garnet. In fruits in the initial phase of growth, females can pierce them, but with a very watery content, they are abandoned without oviposition, and these fruits are compromised. The eggs are white, elliptical, with a milky and diminished shine, and the female lays about 2 eggs a day for 10-12 days, reaching an average of 75 eggs during 130 days of oviposition. After 4-10 days of laying, the larvae are born very small, with a curved, white, apophorous morphology, with brown head and mouth parts. The body of the larva is provided with sparse and long hair, directed backwards, with a visible median longitudinal suture. The average larval period is around 15 days (27ºC) and the number of ecdises varies with sex, with the female having two larval instars while the male has only one. When they are well developed and have consumed almost all of the coffee seed, the larvae form the pulp inside the seed, and this stage lasts around 8-10 days, when CBB is white in the first three or four days, head completely covered by the pronotum, antennas and mouthpieces free and distinct, with light brown color. Pulp length varies according to sex. The CBB adult is a shiny black beetle with cylindrical body slightly curved to the posterior region. The elytra are coated with characteristic filiform bristles and scales. The antennae, mouthpieces (except jaws) and legs are light brown. Males are much smaller than females, which have normal membranous wings and fly, while males do not fly, remaining in the seeds of the coffee fruits from which they were originated. In addition, adult males live about 40 days while females live more than 150 days. The ratio is 10 females for each male.
Currently, the growing search for healthy foods, concern for the health of the farmer and the environment requires the rational use of phytosanitary products. To produce coffee in a sustainable way is to cultivate with responsibility and respect for future generations. A well done harvest, with the removal of coffee fruits from the plant and from the ground reduces the possibility of CBB survival for the next harvest. In parallel, there are several CBB predators and parasitoids that assist in the biocontrol, among which stand out: Prorops nasuta, Cephalonomia stephanoderis, Beauveria bassiana, Heterospillus coffeicolla and Polynema sp. With regard to chemical control, the most used insecticide to control CBB for decades was endosulfan, which was banned from the market in 2013 due to its high toxicity. In addition, due to the CBB endophytic habit, the use of insecticides is not always effective, due to the fact that the coffee fruit can act as a barrier that protects the insect. In this sense, new molecules with the ability to control more efficiently and cheaply CBB populations, and at the same time be less harmful to the environment are needed. Thus, biotechnology plays an essential role in the development of new assets that have such characteristics. The RNA interference (RNAi)-mediated gene silencing has been shown to be an effective tool in the control of insect-pests, especially in species from Coleoptera order. The Plant-Pest Molecular Interaction Laboratory (LIMPP), together with the Bioinformatics Laboratory, both located at Embrapa Genetic Resources & Biotechnology (Brasilia-Brazil) and supported by Embrapa Café and University of Caldas (Manizales, Colombia), develop research aimed at identifying target genes (via RNA-Seq experiments) that, associated with nanotechnology can be applied in the H. hampei control, since transgenic coffee is not desirable by the market. Here is presented transcriptomes of three CBB developmental stages (larva, female and male) to increase the understanding of CBB life cycle in relation to molecular features.