Abstract
The characteristics of the pectic enzyme polygalacturonase (PG) of Phytophthora meadii isolates from petioles of rubber (Hevea brasiliensis) genotypes were compared in relation to (i) aggressiveness (virulence) in infecting detached petioles of a susceptible rubber genotype (PB86) or (ii) in relation to the availability of purified rubber petiole cell walls (obtained from a Phytophthora-resistant clone, RRIC100) in the growth medium, as the sole carbon source. The four most highly aggressive isolates produced PG forms varying within mw 48-60 kDa, while, the highly aggressive MAD86 isolate produced two PG forms of mw 48 and 70 kDa. Moderately or weakly aggressive isolates produced PG forms within the range of 62-66 kDa. With rubber petiole cell walls in the growth medium, the four most highly aggressive isolates produced PG forms of mw 42-62 kDa, while, MAD86 produced a much smaller PG form of 21 kDa. Weak or moderately aggressive isolates produced similar PG forms in both cell wall and pectin media. Quite smaller PG molecules produced in rubber cell wall medium could be due to elicitor molecular fragments bound to rubber cell walls, which may induce P. meadii to secret specific PG forms via signal transduction pathway. None of the isolates produced pectin lyase (PL) in any growth medium. Neither PG nor PL activity was detected in P. meadii-infected petioles. Key Words: Cell wall degrading enzymes, resistance, Hevea brasiliensis, leaf disease doi: 10.4038/cjsbs.v36i2.485 Cey. J. Sci. (Bio. Sci.) 36 (2): 108-114, 2007
Highlights
Phytophthora species are ubiquitous in rubber [Hevea brasiliensis
A previous study (Jayasuriya et al, 1999) has indicated that P. meadii isolates obtained from different rubber genotypes had markedly different degrees of virulence (Dv) in infecting petioles of a susceptible genotype PB86
None of the isolates produced pectin lyase (PL) enzymes in any liquid medium used in this experiment, and the lack of PL confirmed the earlier findings of Ann and Ko (1989), that described the entire genus of Phytophthora as poor producers of pectolytic enzymes
Summary
Phytophthora species are ubiquitous in rubber [Hevea brasiliensis (A. Juss.) Muell.Arg.] plantations causing diseases such as leaf fall, bark rot, shoot die-back and pod rot, of which the first two cause direct yield losses. Phytophthora species are ubiquitous in rubber [Hevea brasiliensis Arg.] plantations causing diseases such as leaf fall, bark rot, shoot die-back and pod rot, of which the first two cause direct yield losses. In. Sri Lanka, these diseases are caused mainly by. (Danthanarayana et al, 1984). A previous study (Jayasuriya et al, 1999) has indicated that P. meadii isolates obtained from different rubber genotypes had markedly different degrees of virulence (Dv) in infecting petioles of a susceptible genotype PB86.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
