Uromyces hobsoni Vize. is a rust fungus which infects Jasminum officinale var. grandiflorum. The fungus is mainly observed on the stem and leaves in the form of raised galls at the site of infection. Healthy and infected progressive disease stages on stem and leaves were collected directly from the field and were analysed for the activity of defence enzymes like peroxidase and polyphenol oxidase along with the estimation of total phenols. There was no significant alteration in the activity of polyphenol oxidase and peroxidase in stem tissues, although the leaves exhibited a significant increase in the activity of these enzymes at advanced disease stages. A significant increase in the amount of phenolics was observed at early and advanced stages of disease in leaves and stem, respectively. These studies correlate the susceptibility of the host with the concentration of preformed antimicrobial compounds and the temporal activity of defence enzymes during progress of the disease.

Ravenelia esculenta Naras. and Thirum. is a rust fungus which infects Acacia eburnea Willd. producing hypertrophy in the infected organs. We analysed the changes in the reaction patterns of peroxidase from the tissues at progressive disease stages. Peroxidases (POX) from the tissues were analysed for oxidation of reduced nicotinamine adenine dinucleotide (NADH), NADH-dependent hydrogen peroxide (H₂O₂) generation and polymerization of cinnamyl alcohol, a lignin precursor in plants. The effect of cofactors like Mn²⁺ and dichlorophenol (DCP) was also studied. Effect of externally added H₂O₂ on NADH oxidation and cinnamyl alcohol polymerization was analyzed. NADH oxidation and H₂O₂ generation are accelerated by supplement of cofactors. The cofactor requirements of the two reactions are different. The amount of H₂O₂ generated varies with disease stages, but the rate of NADH oxidation is comparable. Externally added H₂O₂ has an accelerating effect on NADH oxidation. Cinnamyl alcohol polymerizing activity of POX increased with disease progression and was strongly inhibited by H₂O₂. Stimulation of these reactions by cofactors has a physiological significance in terms of susceptibility of the host.

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Ravenelia esculenta Naras. and Thium. is a rust fungus, which infects mostly thorns, infl orescences, fl owers and fruits of Acacia eburnea Willd. Aecial stages of the rust produce hypertrophy in infected parts. DNA of the rust fungus was isolated from aeciospores by 'freeze thaw' method. 18S rDNA was amplifi ed and sequenced by automated DNA sequencer. BLAST of the sequence at NCBI retrieved 96 sequences producing signifi cant alignments. Multiple sequence alignment of these sequences was done by ClustalW. Phylogenetic analysis was done by using MEGA 3.1. UPGMA Minimum Evolution tree with bootstrap value of 1000 replicates was constructed using these sequences. From phylogenetic tree it is observed that Ravenelia esculenta and the genus Gymnosporangium share a common ancestry, though Ravenelia esculenta is autoecious on angiosperm and the genus Gymnosporangium is heteroecious with pycnia, aecia on angiosperm and uredia, telia on gymnosperm. Two major clades are recognized which are based on the nature of aecial host (gymnosperm or angiosperm). These clades were also showing shift from pteridophytes to angiosperms as telial hosts. The tree can be interpreted in the other way also where there is separation of 14 families of Uredinales depending upon nature of teliospores, nature of aeciospores and structure of pycnia. These studies determine the phylogenetic position of Ravenelia esculenta among other rust fungi besides broad separation of Uredinales into two clades. These studies also show that there is phylogenetic correlation between molecular and morphological data. This is fi rst report of DNA sequencing and phylogenetic positioning in genus Ravenelia from India.