Translocation of cyanogenic glycosides in rubber tree crown clones resistant to South American leaf blight

Abstract

-The objective of this work was to assess the possible transport of cyanogenic glycosides from leaves of rubber tree crown clones (Hevea spp.) resistant to South American leaf blight to the trunk of the panel clones in which they are grafted. The cyanogenic potential (HCNp) of the crown clones was determined in the trunk bark, at different distances from the cambium, and its gradient was evaluated along the trunk. The correlation between the HCNp of the crown leaves and that of the trunk bark was also evaluated. HCNp determined in leaves showed a wide range variation in the species studied as crown clones, with the lowest values registered in H. nitida clones, and the highest ones in H. rigidifolia. In the trunk bark, the tissue layer nearer the cambium showed higher HCNp values. A positive basipetal gradient was observed along the trunk, i.e., there was an increase in HCNp from the apex toward the base. Although the grafted crowns influence the cyanogenic potential of the trunk bark of panel clones, the absence of correlation between the HCNp of the leaves and trunk bark indicates that the crown is not the main source of the cyanogenic glycosides found in the trunk.Index terms: Hevea, Microcyclus ulei, crown budding, HCNp, linamarin. Translocação de glicosídeos cianogênicos em clones de copa de seringueira resistentes ao mal-das-folhasResumo -O objetivo deste trabalho foi avaliar o possível transporte de glicosídeos cianogênicos de folhas de clones de copa de seringueira (Hevea spp.) resistentes ao mal-das-folhas para o tronco dos clones de painel em que estão enxertados. O potencial cianogênico (HCNp) dos clones de copa foi determinado na casca do tronco, a diferentes distâncias do câmbio, e o seu gradiente foi avaliado ao longo do tronco. Avaliou-se, também, a correlação entre o HCNp das folhas das copas e o da casca do tronco. O HCNp determinado nas folhas apresentou ampla faixa de variação nas espécies estudadas como clones de copa, com os menores valores registrados em clones de H. nitida e os maiores em H. rigidifolia. Na casca do tronco, a camada de tecido mais próxima ao câmbio apresentou valores mais elevados de HCNp. Um gradiente basípeto positivo foi observado ao longo do tronco, ou seja, houve aumento do HCNp do ápice para a base. Apesar de os clones de copa influenciarem o potencial cianogênico na casca do tronco dos clones de painel, a ausência de correlação entre o HCNp das folhas e o do tronco indica que a copa não é a fonte principal dos glicosídeos cianogênicos encontrados no tronco.

Relationship between cyanogenesis and latex stability on tapping panel dryness in rubber trunk girth

“…In a trial under the same edafoclimatic conditions, Moraes et al (2012) also reported significant differences of HCNp in the trunk bark under different crowns, even if the lack of correlation between HCNp in the crown and in the trunk invalidated their hypothesis that the crown budded with different species of Hevea is the main source of cyanogenic glycosides in the trunk. Kongsawadworakul et al (2009) and Moraes et al (2011) affirmed that the presence of cyanogenic glycosides in the trunk of rubber tree is related to the reserves of nitrogen and energy (glucose), which can be used by these plants to produce latex.…”

The Diseases and Pests of Rubber Tree and Their Natural Control Potential: A Bibliometric Analysis

“…Although efforts to control rubber diseases have been taken since 1910, rubber farmers continue to suffer a great deal of crop failure [1]. During this long history of investigation, researchers have proposed various disease control strategies, for example, the use of modern chemical fungicides, breeding of rubber resistant clones, application of biocontrol agents, and searching for growing zones suitable for rubber and with adverse climatic condition for disease development [10][11][12][13]. However, how to integrate these control strategies to achieve upgraded and improved disease control effectiveness remains a challenge.…”