Evaluation of screening methods for anthracnose fruit rot resistance in chilli (Capsicum spp.)

Anthracnose fruit rot caused by Colletotrichum spp. is a serious production constraint causing severe marketable yield loss in chilli. Field evaluation of chilli accessions for resistance to Colletotrichum spp. depends on various factors affecting disease expression such as edaphic conditions, temperature, rainfall, humidity and other variables that are difficult to control, therefore considered less accurate. Also, high chances of cross contamination with different Colletotrichum species leads to inconclusive assays for specific pathogen species and isolate. To identify a stable and reliable screening method, various chilli accessions were subjected to in vitro pin-prick and non-wounding spray methods using a specific pathogen isolates. When chilli accessions were screened against C. gloeosporioides isolate 'IHRCg-1', the in vitro pin-prick method showed positive correlation with the non-wounding spray method, except in the accession PBC80. The change in bioassay influenced the disease reaction pattern in the accession PBC 80, probably the pin pricks break the basal cuticle defense mechanism that was retained in spray inoculation method indicating varied resistance pattern. However, in the accession PBC 81 stable resistance pattern was observed against isolates of both species viz., C. truncatum 'IIHR Ct-1' and C. gloeosporioides 'IIHR Cg-1' and in the accession PBC 80 against C. truncatum 'IIHR Ct-1' in both the inoculation methods that depicted the expression of resistance genes during both methods of inoculation. Based on disease development pattern, the red ripe chilli expressed a variant reaction to infection by C. truncatum and C. gloeosporioides. The peak anthracnose infection at 10 DAI and 14 DAI is an accurate duration to record 'IIHR Cg-1' and 'IIHR Ct-1' infection, respectively on chilli ripe fruit for assaying the resistance.