Confirmation of Induced Tolerance to Alternaria Blight Disease in Indian Mustard (Brassica juncea L.).

Indian mustard (Brassica juncea L.) is an important edible oilseed crop in India. Low productivity is the major concern which is adversely affected by biotic stresses. Alternaria blight (Alternaria brassicae) is one among major diseases that has no resistant cultivar until now. Keeping in view, an experiment was conducted for isolation of Alternaria blight-tolerant mutants in Indian mustard using gamma radiation and EMS mutagens during four consecutive years in Rabi (winter season). Furthermore, the morphologically and economically superior mutants of Brassica juncea were screened artificially at cotyledonary and adult stage against Alternaria blight. Tolerance to Alternaria blight is observed in DRMR-M-163 (11.7%), DRMR-M-158 (13.1%), DRMR-M-174 (13.8%) and DRMR-M-177 (18.6%) with minimum conidia in infected cotyledons. Mutant DRMR-M-178 (19.8%) had the highest radical scavenging activity, while DRMR-M-162 (104.9 mg/g AAE), DRMR-M-169 (96.9) and DRMR-M-161 (96.9) had higher antioxidant capacity that appears to act as defence to pathogen. DRMR-M-168 (8.4%), DRMR-M-173 (8.3), DRMR-M-171 (7.9), DRMR-M-165 (7.4), DRMR-M-175 (7.2) and DRMR-M-172 (6.9) had higher phenol content which may be responsive for resistance, although DRMR-M-161 (192.7 mg/g), DRMR-M-163 (187.7 mg/g), DRMR-M-164 (132.7 mg/g), DRMR-M-167 (149.3 mg/g), DRMR-M-173 (196.0 mg/g) and DRMR-M-178 (192.7 mg/g) mutants are found to contain low levels of total soluble sugar compared with susceptible Rohini (379.3). Based on biochemical parameter's similarity, mutants are grouped in 4 major clusters. Cluster 4 contained significantly different mutant DRMR-M-172. Relative expression of mitogen-activated protein kinase 3 (MAPK3) gene was found highest in DRMR-M-177, DRMR-M-174, DRMR-M-175, DRMR-M-178, DRMR-M-170, DRMR-M-176, DRMR-M-172 and DRMR-M-173 which resulted the better response to AB stress. Based on biochemical analysis, realtime PCR and cluster analysis, DRMR-M-172 mutant appears more tolerant to Alternaria. DRMR-M-178, DRMR-M-167 and DRMR-M-177 mutants seem tolerant and could be utilized for further breeding programme.

Morphological, Histobiochemical and Molecular Characterisation of Low Lignin Phloem Fibre (llpf) Mutant of Dark Jute (Corchorus olitorius L.).

Lignin is a versatile plant metabolite challenging high-end industrial applications of several plant products including jute. Application of developmental mutant in regulation of lignification in jute may open up door for much awaited jute based diversified products. In the present study, a novel dark jute (Corchorus olitorius L.) mutant with low lignin (7.23%) in phloem fibre being compared to wild-type JRO 204 (13.7%) was identified and characterised. Unique morphological features including undulated stem, petiole and leaf vein distinguished the mutant in gamma ray irradiated mutant population. Histological and biochemical analysis revealed reduced lignification of phloem fibre cells of the plant. RT-PCR analysis demonstrated temporal transcriptional regulation of CCoAMT1 gene in the mutant. The mutant was found an extremely useful model to study phloem fibre developmental biology in the crop besides acting as a donor genetic stock for low lignin containing jute fibre in dark jute improvement programme.