Combined Genetic Analysis of Brown Spot (Helminthosporium oryzae) Disease for Developed Hybrid Combinations and their Parental Lines in Hybrid Rice

Abstract

This experiment was carried out at the Farm of Rice Research and Training Center, Sakha, Kafrelsheikh, Egypt during three rice grown seasons from 2014-2016. Three cytoplasmic male sterile lines, two wild abortive type (WA); IR69625A, IR70368A and one (K-type) K17A as females were tested with seven rice genotypes Giza 178, Giza 179, Giza 181,Giza 182, Sakha 105, GZ 6296-12-1-2-1-1 and HR195R as testers using line x tester model of hybridization. The parental lines and their resulting (21F1 crosses) were evaluated in Randomized Complete Block Design (RCBD) experiment having three replications during 2015 and 2016 growing seasons and surrounded by susceptible rice varieties i.e. Giza 171, Giza 177 and Giza 159 as natural infection to brown spot (Helminthosporium oryzae). Three brown spot acceptability traits; disease severity (%), infected leaves (%) and infected grains/panicle (%) were observed during this investigation. The combined data was calculated over both seasons to test the interaction of the different genetic components. According to the results, the male parents Giza178, Giza179, HR195, Giza 181 and Giza 182 could be utilized either for producing new hybrid combinations or for developing new parental lines in brown spot resistance program. The female line K17A was found to have a good combiner to brown spot resistance. Evaluation of hybrids for heterosis breeding based on mean performance, better-parent (BP %) and mid-parent heterosis (MP %) indicated that, out of 21F1 hybrid rice combinations, one hybrid K17A x Giza182 found significantly desirable values for most brown spot traits and can be utilized as commercial hybrids resistant to brown spot disease.