Comparison of rice lines derived through anther culture and the pedigree method in relation to blast (Pyricularia grisea) resistance

Rice blast (Pyricularia grisea) is considered the most important disease of rice worldwide. Development of resistant cultivars has been the most effective method to control it; the pedigree method (PM) has been used in this regard but recently, the production of double-haploids through anther culture (AC) has been proposed as an effective, and economic breeding tool. The objectives of this study were to generate rice lines by PM and AC and to compare their efficiency in relation to blast resistance. Crosses were made between the rice cultivar Fanny (highly susceptible to blast), and 11 cultivars with different degrees of resistance/susceptibility to blast. Using PM, the F2, F3, F4, F5, and F6 generations were evaluated and selected for blast resistance through subsequent semesters. Via AC, AC-R2 (from F1 plants), and AC-F2 (from F2-blast susceptible plants) lines were obtained using a liquid potato-medium for callus induction and an MS medium for plant regeneration. Three sets of lines (F6, AC-R2 and AC-F2) were planted together and evaluated for blast resistance under upland conditions in a blast prone environment. Rice blast reactions were evaluated on a 0-9 scale and analyzed as a discrete variable following the multinomial distribution. Three response variables, leaf and neck blast, and general reaction to blast (maximum score between the first two variables), were considered. Stratified analysis using the Cockran-Mantel-Haenszel statistic was performed to test the association between methods and blast resistance, and resistance stability across crosses; all data processing and analysis was performed through SAS version 6.07. The percentage of resistant lines as well as stability of resistance was significantly (P=0.01) greater in PM-derived lines, with a lower mean blast score, suggesting that PM is more efficient than AC in relation to selection for blast resistance. Nevertheless, in Fanny/Ceysvonni, and Fanny/LAC 23 crosses the percentage of stable-resistant lines was greater in the case of AC. Crosses between susceptible cultivars (Fanny/CICA4, and Fanny/Colombia 1) yielded resistant lines by either method (PM or AC). This excludes somaclonal variation as a possible mechanism and indicates that recombination of possibly minor genes took place and was fixed through either method. However, the stability of the resistance was greater in PM-derived lines