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Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat (Triticum spp.) in warm and humid wheat growing regions of the world. Area under the disease progress curve (AUDPC) in field experiment was used to find out the role of total phenol content (TPC), phenylalanine ammonia-lyase (PAL) activity and lignin deposition in the development of slow blight. Ten recombinant inbred lines (RILs) of spring wheat obtained from the cross between the susceptible parent 'Sonalika' and the resistant parent 'Yangmai 6' along with their parental genotypes were scored for disease severity (DS), AUDPC and lesion size in a field experiment on spot blotch. These lines were also evaluated for TPC, PAL and lignin deposition. The minimum DS, AUDPC and lesion size were recorded in the resistant parent 'Yangmai 6' (13%, 116.04 and 0.23 cm 2 , respectively) and RILs (18%, 113.3 and 0.27 cm 2 , respectively in RIL83 and RIL89) which associated with an elevated level of phenol content (395 mg g -1 fresh weight (wt) at 48 hours after inoculation (hai), PAL (928.41 μmoles cinnamic acid (cna) mg -1 fresh wt) and higher quantity of lignin (84%). While DS, AUDPC and lesion size were comparatively higher in the susceptible parent 'Sonalika' as well as susceptible RILs (100%, 938.27 and 3.43 cm 2 , respectively). Mean TPC (133.5 mg g -1 fresh wt 24 hai, respectively), PAL (248.8 μmoles cna mg -1 fresh wt) and lignin (10%) were significantly lower in the susceptible genotype 'Sonalika' and suscptible RILs. The study indicated that enhanced level of TPC, PAL and higher lignin deposition led to the development of slow blighting of spot blotch in terms of lower AUDPC and smaller lesion size in resistant RILs of wheat.

The initiation and prolonged growth of callus, from stem explants of young plants of Hevea brasilienies on solid medium yielded a heterogeneous callus, with areas which are the result of compact growth interspersed with brown necrotic tissue and soft white tissue formations. Subculturing this callus (O callus) to agitated liquid medium and returning it to solid medium resulted in the production of a homogeneous friable and rapidly growing callus (Rl callus) The two established lines O and Rl have remained stable over one year in culture and differ in gross morphology, anatomy, growth and auxin content. Both were maintained on Murashige and Skoog's medium, with 2 mg/1 2,4‐D and 0.5 mg/I kinetin. R 1 but not O showed enhanced growth at the lower 2,4‐D level of 0.2 mg/l: both lines failed to continue growing when 2,4‐D was omitted. It is suggested that the changes resulting from subculture in agitated liquid medium are related to those undergone by callus cultures which become habituated. Thus the Rl callus line is regarded as partially habituated. Subculture in agitated liquid medium also resulted in the production of large numberr of polyploid cells but these did not persist over the long periods of subsequent growth on agar medium, Enhanced auxin production by the establihed Rl callus line was thus observed in the absence of a detectable level of polyploidy.

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