Anatomical characterization of leaves from coffee plants resistant and susceptible to leaf miner

The leaf miner Leucoptera coffeella (Guérin-Méneville, 1842) (Lepidoptera: Lyonetiidae) is the major pest of coffee culture, being responsible for significant production losses as result of premature leaf fall, and consequent reduction of the photosynthetic area. The Coffee Breeding Program of the Agronomic Institute (IAC) has transferred through crossing genes that confer resistance to leaf miner from Coffea racemosa to the susceptible species C. arabica. The main objective of this study was to characterize leaf tissues, at histological level, from the parental species C. racemosa and C. arabica, and also from hybrids exhibiting different resistance levels. Histological analyses were performed in leaf transversal sections, and included measurements of cuticles and epidermis thickness, total palisade and spongy parenchyma, total leaf thickness, and percentage of the palisade parenchyma from total mesophyll. Results revealed that there were significant differences in leaf thickness between parental species C. arabica and C. racemosa. However, in hybrids no such difference could be observed between resistant and susceptible progenies, suggesting that the anatomical differences of parental genotypes are not related to resistance mechanisms to L. coffeella. When leaf lesions caused by insect attack were measured one and four days after larvae eclosion a slow insect development was observed in resistant plants, which could be related to a presence of specific chemicals in the palisade parenchyma.

Coffee; Leucoptera coffeella; insect resistance; palisade parenchyma