Pertanika 12(1), 7-10 (1989)

A Rust Disease on Gendarussa vulgaris N ees. Caused by Pucciniathwaitesii Berk.

KAMARUZAMAN SIJAM and T.K LIMDepartment of Plant Protection,

Faculty of Agriculture,Universiti Pertanian Malaysia,

43400 UPM Serdang, Selangor DE Malaysia

Keywords: Leaf rust disease; medicinal plant; Puccinia thwaitesii.

ABSTRAKGendarussa vulgaris Nees., suatu tanaman herba perubatan yang biasa ditemui, telah didapati terukdijangkiti oleh penyakit karat. Ciri-ciri/pertanda penyakit ini dapat dilihat pada lesion-lesion cekung ataucembung yang berwama kelabu-ungu, dikelilingi oleh halo kuning yang luas di atas permukaan adaksialdaun dan lesion-lesion cembung atau cekung yang sepadan dipermukaan abaksial yang bertentangan. Daun­daun yang berpenyakit gugur sebelum matang. Agen penyebab telah dikenalpasti sebagai Puccinia thwaitesiiBerk. Kulat ini mengeluarkan kedua-dua uredospora dan teliospora di atas pustul yang sama dan adalahmerupakan karat autesius mikrosiklik (hemijorm).

ABSTRACTGendarussa vulgaris Nees., a common medicinal herb, was found to be severely infected lJy a rust disease. Thedisease was characterised lJy well defined, concave or convex, purplish-gray, discoloured lesions surrounded lJya wide yellow halo on the adaxial surface and corresponding convex or concave lesions on the opposite abaxialsurface. Infected leaves abort prematurely. The causal agent was identified as Puccinia thwaitesii Berk. Thefungus produced both uredospores and teliospores on the same pustule and is a microcyclic (hemijorm),

autoecious rust.

INTRODUCTIONGendarussa vulgaris Nees (syn. Justicia genda­russa L.), a monotypic genus of the familyAcanthaceae, and colloquially known as 'gandarusa' ('ghanda' in sanskrit meaning fragranceand 'rusa' in Malay meaning deer) is a commonmedicinal herb and is also used as anornamental hedge plant. The plant is renownas a traditional cure for many ailments, such asstomach swelling, lunacy, snake-bite, rheuma­tism, debility, and as a decoction for worms(Burkill 1966). It is also used as a protectivecharm to ward off evil by superstitious folks.The crop plant in the Universiti PertanianMalaysia (UPM) herbarium garden was recentlyfound to be severely infected by a leaf rustdisease. This paper reports on the symptomato­logy, identification and characterisation of the

pathogen. Some aspects of the epidemiology ofthe rust are also discussed.

MATERIALS AND METHODS

Rus tinfected leaves of G. vulgariswere collectedfrom the medicinal plant herbarium in UPMcampus for microscopic examination andhistopathological investigations. Histopatho­logical sections of the infected leaves withvarying degrees of rust pustule developmentwere made following standard histologicalmethods of Sass (1958). Adjacent plants andundergrowth which included weeds nearGendarussa host plants were also examinedthoroughly for rust incidence. Fallen diseasedleaves and plant host debris in the immediatevicinity were also collected for study.

KAMARUZAMAN SIJAM AND T.K. LIM

RESULTS AND DISCUSSION

SymptomatologyThe rust causes well-defined, discoloured, pur­plish-gray, necrotic lesions, 6-15 mm in diame­ter, surrounded by a distinct yellow halo on theupper leaf surface (Fig. 1). Such lesions may beconvex (bulged) or concave (sunken) on theupper leaf surface and correspondingly con­cave or convex on the opposite leaf surface.

Fig 1. Upper leaf surface showing the distinct concave orconvex, discoloured, necrotic ksions and yellow halo.

Severely diseased leaves often becomedistorted because of such lesions. When adja­cent lesions coalesce, the yellow peripheral areaenlarges. Subsequently the whole leaf turnsyellow with discrete pockets of purplish-grayislands (Fig. 2). One to 16 lesions can occur onanyone leaf. Infected leaves abort prematurelyin great numbers.

Fig. 2. Gendarussa plants sroerely infected by Pucciniathwaitesii.

Telia are most frequently observed on thelesions. They appear as minute, pin-size, pow­dery, brownish-black specks which are formedin well defined clusters on the undersurface ofthe lesions surrounded by a light green halo onthe abaxial leaf surface (Fig. 3). On some le­sions, \lredia can be seen surrounding the teliaforming tiny light-brown blisters usually in aconcentric ring or rings around the cluster oftelia on the same lesion or sometimes scatteredamongst the telia. Both telia and uredia arefrequently found to be overgrown by a Fusariummycoparasite which imparts a whitish, cottonygrowth over the purplish-brown rust pustules(Fig. 3). The parasitism of this mycoparasite willbe discussed in a separate paper.

Fig. 3. Lower leafsurface showing the purplish-brown rustpustules, some of which are parasitized by a Fusa­rium mycoparasite which produced a white turf ofmycelia over the pustuks.

Transverse sections of the infected leavesreveal that the hyphae of the fungus proliferatebetween the cells of the mesophyll and palisade.The rust pustules protrudes through the lowerleaf surface through stomatal openings.

PathogenThe rust fungus is identified as Puccinia thwai­tesii Berk. Two stages of the rust fungus canbe observed on some necrotic lesions on theleaves viz. teliospores (Fig. 4) and urediospores(Fig. 5). However, teliospores are more fre­quently and abundantly produced. Teliosporesare dark-brown, two-celled, ellipsoidal, orclavate, slightly constricted at the septum andslightly attenuated below, 36.8 ± 4.8 x 19.7 ± 1.7/lm. The teliospore wall is smooth and very

8 PERTANIKA VOL. 12 NO.1, 1989

A RUST DISEASE ON GhNDARUSSA VUCG4RJS NEES. CAUSED BY PUCCINIA THWArrESII BERK.

Fig. 4. Micrograph of a telia showing the thick-walled,two-celled teliospores. Note the two nuclei (arroweda) and the pore (arrowed b). Bar = 18 Jlm.

finely reticulate of approximately 2.6 ± 0.2 /lmthick at the side and 3.65 ± 1.1 /lm thick above,with one or more pores; pedicels are basal andpersistent, paler than the spores, smooth, withvariable length of 74.2 ± 17.0 /lm. Teliosporesalways give rise to basidiospores (Laundon1967). However, this was not observed on thehost lesions. Uredia are amphigenous, occur­ring in concentric rings in association with teliaon some lesions. Urediospores are pale-brown,ellipsoidal to obovoidal, unicellular, andechinulate, 21.2 ± 2.0 x 24.4 ± 2.5 mm, usually2 pores at the equatorial region. The uredosporewall is amber, and 1.5 /lm thick. Uredosporesare borne singly on pedicels which arise incompact clusters.

This rust was first reported by Parandekarand Ajrekar (1932) in India on the same host.They observed that this rust fungus producedonly teliospores which germinated immediately.This was also reported by Laundon (1963).Payak (1952) reported that the diploidisationprocess in the telial primodia of Puccinia thwai­tesii occurred through cell fusion rather than bynuclear migration. However, in rusts, telia canoriginate from aeciospores or uredospores(Laundon, 1967).

EpidemiologyThe rust fungus has a microcyclic life cycle(Hawksworth et aL 1983), producing ure­dospores and teliospores which will producebasidiospores. No pycnial or aecial stages werepresent. Using the terminology of Peterson

Fig. 5. Micrograph of a uredia showing the echinulatedthin-walled uredospores borne on closely-packedpedicels. Bar = 42 Jlm.

(1974), this rust can be regarded as hemi-formas it possesses stage II (uredospores), stage III(teliospores) and stage IV (basidiospores) . Sinceonly G. vulgaris was infected and not the weedspecies in the immediate vicinity, the fungusappears to be autoecious without an alternatehost. Teliospores were more abundantly pro­duced than urediospores. Most of the diseasedleaves which fell to the ground contained moreteliospores than .urediospores indicating telio­spores to be more important in disease spread.Fallen infected leaves appeared to serve as animportant inoculum source. Disease spreadwithin plants was observed to be by water splashand crawling insects, but between plants, windmay be more important.

Many of the telia and uredia were foundto be naturally parasitized by a mycoparasitewhich formed whitish tufts of mycelia over therust pustules. The Fusarium mycoparasite mayplay an important role in the secondary spreadof the rust pathogen. However, further studiesare needed to confirm the identity of themycoparasite and its relationship and impor­tance to the epidemiology of the rust disease.

REFERENCES

BURKILL, I.H. 1966. A Dictionary of the EconomicProducts of the Malay Peninsula. Vol. 1. Ministry ofAgriculture and Cooperatives, Kuala Lumpur,Malaysia.

HAWKSWORTH, D.L., B. C. SUTTON and G.C.AINSWORTH. 1983. Dictionary of the Fungi,

PERTANIKA VOL. 12 NO.1, 1989 9

KAMARUZAMAN SIJAM AND T.K LIM

Seventh Edition. Commonwealth MycologicalInstitute, Kew, Surrey.

LAuNDON, G.F. 1963. Rust Fungi I: On Acan­thaceae. Mycowgical Papers no. 89. CommonwealthMycological Institute, Kew, Surrey, England.

LAUNDON, G.F. 1967. Terminology in the RustFungi. Trans. Br. Mycol. Soc. 60: 189-194.

PARANDEKAR, SA and S.L. AJREKAR. 1932. Observ­ations on Puccinia thwaitesii Berk. Jour. Indian Bot.

Soc. 11: 127-131.

PAYAK, M.M. 1952. Diploidisation in Uromyces holrsoni Vize and Puccinia thwaitesii Berk. Indian Phyt(}­pathoL 5: 104-109.

PETERSEN, R.H. 1974. The Rust Fungus Life Cycle.The Botanical Review 40: 453-513.

SASS, JE. 1958. Botanical microtechnique. Ames,Iowa: Iowa State University Press.

(Received 15 September, 1988)

10 PERTANlKA VOL. 12 NO. 1,1989