Early selection and genetic analysis of susceptibility to tapping panel dryness by applying an intense harvesting system to a segregating population in Hevea brasiliensis

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إنجليزي. Highlights: • First genetic study of Tapping Panel Dryness. • Different genetic bases for latex plugging at opening and Tapping Panel Dryness. • Intense harvesting system is an effective method to induce Tapping Panel Dryness. • Some genotypes show resistance to intensive harvesting system. • Identification of genes underlying QTLs linked to Tapping Panel Dryness.Abstract: Tapping Panel Dryness (TPD) is a physiological syndrome affecting natural rubber production in Hevea brasiliensis that is thought to be exacerbated by climate change stress. TPD is associated with high latex viscosity and agglutination of rubber particles. Although many studies have been carried out on the physiological and molecular mechanisms associated with TPD, little has been done in the way of genetic improvement. Intensive harvesting systems with high tapping frequency and ethephon stimulation of rubber trees are known to induce early TPD occurrence. A harvesting system with daily tapping and monthly ethephon stimulation was applied for one year to a segregating population of 189 individuals obtained from a cross between the TPD-susceptible clone PB 260 and the TPD-tolerant clone SP 217. This treatment induced a dramatic increase in dry cut length after six months for 26 % of the genotypes. Heritability also peaked at 88 % four months after treatment. Of the seven quantitative trait loci identified for the dry cut length, three were uniquely detected after application of the intensive harvesting system, and two quantitative trait loci were only observed after opening of trees under a standard harvesting system. Several genes underlying quantitative trait loci revealed functions previously identified through transcriptomic analyses. These results suggest a complex genetic basis of TPD.