Infection response is an effective tool in selecting spot blotch resistance in wheat- a case study

A total of 49 entries showing different levels of resistance against spot blotch caused by Bipolaris sorokiniana along with two susceptible checks, Sonalika and Raj 4015 were screened against artificially inoculated conditions in poly house maintaining temperature in the range of 27–30°C and relative humidity ranging from 85–90% during 2008–09 crop season. The record on infection responses (R, MR, MS and S type) and spot blotch score in 0–9 double digit scale was taken on test entries as well as susceptible checks. The number of leaves dried after inoculations at tillering and flowering stages were also counted along with total leaves per tiller. Out of these, ten numbers of genotypes, HRLSN 14, HRLSN 15, HRLSN 21, HRLSN 23, Chirya 7, Ning 8201, SW 89–5422, 7th EGPSN 101, LBRL 6 and LBRL 13 were showing resistant (R) type infection response against spot blotch pathogen and adult plant score ranging from 00–12 only against 79 score of susceptible checks. The entries showing moderately resistant (MR) types infection response were HRLSN 22, BW/SH 6, BW/SH 16, Chirya 3, Ning 8319, PC-OE-BW-22, YM#6, Sanghai 7, BL 1724, LBRL 11 and LBRL 12 with spot blotch score up to 24. The percentage of dried leaves per tiller was in the range of 8.0–39.1 in case of genotypes showing R and MR type of infection responses as compared to 66.6% in case of susceptible checks at milk stage. The most promising genotypes showing only 8% dried leaves were, SW 89–54422 and LBRL 13. The above study indicated a strong relationship between infection responses, adult plant score and number of leaves dried at different crop stages and genotypes showing R and MR types of infection responses were showing clear advantage in terms of spot blotch resistance and retaining green leaves till grain filling stage and may be used a criterion for selection of promising lines.