Genetic diversity and resistance assessment among maize genotypes against banded leaf and sheath blight (caused by Rhizoctonia solani f. sp. sasakii) utilizing SSR markers

A field investigation was carried out during the consecutive kharif seasons of 2021 and 2022 to assess the resistance response of 38 maize genotypes against banded leaf and sheath bight (BLSB). The trials were conducted at CCS Haryana Agricultural University, Regional Research Station, Karnal (India) under artificial epiphytotic conditions. Throughout both seasons, six genotypes (HKI 163, HKI 193-2, HKI 488, IQPMH-18-2, HKI 194-7 and HKI 1128) exhibited resistant reactions, one genotype (HM 8) showed susceptible reaction, whereas 19 genotypes showed moderately resistant response to BLSB. To analyse molecular aspects of BLSB resistance, genomic DNA was extracted and PCR amplification was performed using 22 SSR markers. Ten SSR markers (bnlg238, bnlg161, bnlg127, bnlg339, bnlg615, bnlg1272, phi077, phi080, phi035 and umc1275) revealed distinct banding patterns in resistant and susceptible genotypes. Among these, marker bnlg339 exhibited a band size of 120 bp across 14 genotypes, with six (HKI 163, HKI 193-2, HQPM 5, IQPMH-18-2, HKI 194-7 and HKI 1128) classified as resistant and eight (HKI 193-1, HKI 1657, HKI 1378, HPQM 1, HKI 1659, HPQM 2, T Bio 259 ER and HKI 191-2-5) as moderately resistant, resembling the amplified profile of the resistant check genotype (HKI 163). Similarly, the markers phi080 and bnlg1272 exhibited differential amplified profile of approximately 150 bp and 240 bp, respectively, in 10 (five resistant and five moderately resistant) and 12 (four resistant and eight moderately resistant) maize genotypes throughout the study. The percentage of polymorphism for the SSR markers varied from 0 to 100%, with an average value of 95.45% per primer among all genotypes. The identification of resistant and moderately resistant genotypes and characterization of specific SSR markers associated with resistance offer practical tools for breeders to develop BLSB-resistant maize varieties, ultimately enhancing crop resilience and food security.