Madigasekara MMSK1, Withanage SP2*,
Liyanage KK2, Dharmarathne TTD1 and
Meegahakumbura MK1*
1Department of Export Agriculture, Faculty of
Animal Science and Export Agriculture, Uva Wellassa
University, Badulla 90000, Sri Lanka
2Genetics and Plant Breeding Division, Rubber
Research Institute, Agalawatta 12200, Sri Lanka
Abstract
The hybridization and selection in rubber (Hevea brasiliensis)
aim to produce superior genotypes. The perennial nature of
Hevea is the major limitation in rubber breeding. Early
selection is crucial for strengthening and shortening the breeding
program. Therefore, 20 randomly selected individuals of the 2014
hand-pollinated progeny were used for the current morphological,
anatomical, biochemical, and gene expression study to identify superior
genotypes for future recommendations. The average yield, girth, and bark
thickness were measured as morphological characteristics, while sucrose,
inorganic phosphorus, thiol, and polyphenol were measured as biochemical
characteristics. Dry rubber and total solid content were also measured
as diagnostic indicators of latex. The bark anatomical analysis was done
with a modified staining protocol. Gene expression analysis was
performed using the Catalase (HbCAT) and Superoxide dismutase (HbSOD)
genes to evaluate the proneness for Tapping Panel Dryness (TPD). Results
indicated that girth (79.8%), bark thickness (60.8%), bark anatomical
parameters such as the diameter of latex vessels (60.1%) and the number
of latex vessels per unit area (density) (89.2%) positively correlated
with rubber yield. The genotypes 2014HP-11, 2014HP-42, 2014HP-78,
2014HP-25, 2014HP-102, 2014HP-35, 2014HP-39, and 2014HP-21 showed
comparatively higher morphological characteristics. The genotypes
2014HP-56 and 2014HP-57 showed potential for stimulation due to their
high sucrose and low inorganic phosphorus contents. All other genotypes
showed below-average performance for commercial recommendations. The
optimized bark anatomical screening protocol of the current study
clearly stained the secondary latex vessels. Genotypes 2014HP-21 and
2014HP-98 showed higher TPD traits morphologically. Therefore,
expression of HbCAT and HbSOD genes was tested. The fold difference
value was upregulated in the genotypes 2014HP-21 and 2014HP-98. As a
result, these two genotypes are possibly prone to TPD. In conclusion,
this study optimized the bark anatomical screening protocol, identified
promising high-yielding genotypes and pinpointed the possible
vulnerability of two genotypes (2014HP-21 and 2014HP-98) to TPD.
Keywords: Bark
anatomical staining, Catalase (CAT), Gene expression, Rubber
breeding, Super-oxide Dismutase (SOD), Tapping panel dryness
(TPD)
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* - Corresponding Author
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