Relative performance of testers to identify elite lines of corn (Zea mays L.)

Tesrcross evaluarion is used to determine the relative potential of corn (Zea mays L.) lines in a hyhrid hreeding program. Choice o f rester is important fo r effi­ cient selection :IITIong lines for their potential in hybrids. Testcrosses among 21 lines and seven testers were evalUat­ ed at se ven environments in Guatemala. The experimental des ign was a randomized complete block with a split-plot arrangement. where lines were assigned to whole plots and testel.'> to subplots. The objectives of the study w ere to ohtain informatio n for choice o f testers and to identify the more convenient tester to use in early tes ting for a hyhrid program in which three-way and double-cross hybrids ,He commonly used . Data for yield and agronomic traits were recorded. but the combined analysis for yield (r/ ha) was th e main trait of interest. Differences among lines and :lmong testers across environments w ere highly significant (I' :s; 0.01). Highly significant differences t()r the testers x lines interaction indicateci that the te sters ranked the lines differently. Coefficient of concordance (\1(1) and Pea rson correlations (I') suggested that the ranking of lines across testers was relatively consistent. Testcrosses with a single cross had the greatest average yield (6.48 t/ ha). Based on the v:niance among testcrosses. estimates of general C0111­ hining ability. correlatio n with the other testers, and ac­ cept:lble performance itself, the single c ross tester was sug­ gested as the tester for the hybrid breeding program in Guatemala. Lines with good general combining ability for different hybrid combinations were identified. Three-way testcrosses superi or to the hes t check (lCTA HB-85) w ere icientified for further evaluat ion as potential new hybrids for release. Significant correlations between yield and dis­ eases (Southern corn rust caused hy Puccinia po~ysorct L:nclerw. and Northern corn lelf hlight caused by Exserohi­ /11111 lurcicul1I Pass. = Helmintbo.,poriul1l t"rcicllm Pa ss.)