THE RELATIVE CONSTANT TO ESTIMATE F ̅2 OF 3–WAY AND DOUBLE CROSSES OF MAIZE

Abstract

A field experiment was conducted at the field of the Dept. of Field Crop Sci. / College of Agriculture / University of Baghdad . The objective was to determine the values of relative constant of three – way and double crosses of maize . Ten inbreds were used and crossed during spring and fall seasons of 2009 to produce three - way and double crosses , and ten hybrids were taken from each group . The ten hybrids were grown and selfed during spring 2010 to produce F2 seed . Three way and double crosses were sown with their parents and F2 seed during fall 2010 in RCBD with four replicates . Leaf area , total dry matter , row/ear , grain/ear , grain weight and grain weight/plant of hybrids , parents and F2 plants were taken . Results showed that the relative constant obtained was applicable to estimate F ̅2 of hybrids . However , leaf area was different in values of F ̅2 , as compared to that observed in the field . The relative constant values were different as trait and parent number of crosses differ . The obtained relative constant of grain weight/plant was (0.576) and (0.556) , grain weight (0.521) and (0.516) , grain /ear (0.571) and (0.554) , raw / ear (0.509) and (0.502) , total dry matter . plant -1 (0.553) and (0.541) and leaf area (0.508) and (0.495) in three way and double crosses , respectively . It was concluded that the application of relative constant , to predict parent means (P ̅), F ̅2 and parent number (n) was fit as compared to Wright's equation [ F ̅2= F ̅1 – (F ̅1 - P ̅)/n ] . Accordingly , it was recommended to use the formula [F ̅2 = χ (F ̅1 + P ̅)] to predict F ̅2 of hybrids , [(P ) ̅= ( F ̅2 / χ ) – F ̅1] to predict P ̅, and [ n = ( F ̅1 - P ̅ ) / ( F ̅1 - F ̅2 ) ] to predict number of inbreds included in the hybrid .