Controlled Condition Testing (CCT): An Ideal High-Throughput Method for Screening of Pre-Release Clones and Progenies for Red Rot Resistance in Sugarcane

Abstract

Resistance to red rot, a fungal disease caused by Colletotrichum falcatum is an important trait in sugarcane varietal development and commercial release. All the varieties in the advanced varietal trials are artificially screened for red rot resistance in the field on standing canes following plug method. However, rejection of the varieties at this stage due to red rot susceptibility causes huge losses in the selection process for 5–6 years. Hence, there was a need to screen progenies at an early stage of selection to overcome the rejection of promising sugarcane clones due to red rot susceptibility at later stages. ICAR-SBI has developed controlled condition testing (CCT), a rapid screening method to identify more number of red rot-resistant clones before the advanced varietal trial. In this study, we compared the effectiveness of plug and CCT methods in categorizing about 654 sugarcane clones over a period of 10 years. In both the methods, the clones were categorized into resistant (R), moderately resistant (MR), moderately susceptible (MS), susceptible (S) and highly susceptible (HS) and the frequencies were 3.52%, 44.50%, 26.45%, 13.46% and 12.08% in the plug method and 13.91%, 41.44%, 17.28%, 20.80% and 6.57% in the CCT method, respectively. The clones showed similar reactions of 56.52, 57.73, 27.17, 51.14 and 34.18% in both the methods, respectively. In general, the plug method favoured more MR reactions whereas the CCT method showed more of R reactions. In about 500 population from bi-parental crosses, both the methods had shown similar categorization for red rot reactions and the results are encouraging and favoured the usage of CCT method for rapid screening of large populations during early stages of sugarcane varietal development programme. The utilization of CCT method hastens the selection process for red rot resistance and indirectly increases the selection frequency of good quality varieties.