Development of southern corn leaf blight (SCLB) resistant and high-popping volume composite popcorn using phenotypic and marker-assisted selection (MAS)

Popcorn ( Zea mays L.), the most popular snack in the world, is known for being high fiber and healthy food. Most popcorn cultivars have low yields and are highly susceptible to various diseases. Southern corn leaf blight (SCLB) or Maydis Leaf Blight (MLB) caused by Bipolaris maydis cause significant yield losses in maize throughout the world including some parts of the Indian subcontinent. A low popping volume (LPV) composite (Bajaura popcorn developed by HPKV, Palampur, Himachal Pradesh, India) grown in the foothills and hilly region of Himachal Pradesh is resistant to SCLB and a high popping volume (HPV) inbred line introduced from the USA and commercially utilized in India has a high popping volume (HPV) but is highly susceptible to SCLB. The SSR molecular markers bnlg1331, bnlg1520 and bnlg1836 linked to three popping volume QTLs qPVEU-1, qPVEU-2 and qPVEU-5 located on chromosomes 1, 2 and 5 had additive gene action with the positive alleles for popping contributed by HPV were used in marker-assisted selection. The disease severity or percent disease index (PDI) was calculated from the SCLB rating score at intervals of 15 days up to 45 days of second inoculation. The PDI was varied from 12 to 80% among the BC 2 F 2:3 populations. The parent HPV and LPV showed disease severity of 80% and 20%, respectively. A total of 27 lines of the BC 2 F 3 population showed a disease severity up to 42%. The area under disease progress curve (AUDPC) values were calculated from PDI at different intervals after inoculation and ranged from 480–1890% for parents and 1080–2040% among the BC 2 F 2 population for SCLB. The mean for 27 BC 2 F 3 lines was 999 ± 32.57 with 16% of the coefficient of variance. The parent LPV was resistant to SCLB and its AUDPC was up to 480% while HPV was highly susceptible with 1890% AUDPC. From 27 BC 2 F 2:3 self-progenies, 144 plants were screened for high-popping volume QTLs using linked molecular markers. Out of 144 BC 2 F 2:3 plants, 62 were selected based on molecular markers linked to popping volume QTLs and disease reaction for SCLB. All the 62 selfed BC 2 F 2:3 families (cobs) were harvested separately and evaluated for popping volume along with yield contributing traits. Out of 62 plants, 19 were homozygous for all three popping volume QTLs markers with high popping volume and the remaining 43 plants were segregating for popping volume QTL markers. These segregating plants were advanced in the subsequent Kharif season to evaluate in a larger area to screen homozygous plants for high-popping volume QTLs. The homozygous lines of BC 2 F 3 progenies with three high popping volume QTLs and resistance to SCLB were selfed. The selected plants from the selfed BC 2 F 3 population were allowed for open pollination to develop a composite variety with high popping volume and SCLB resistance.