Analysis of diallel cross for the evaluation of maize populations acrossenvironments
Pedro Mário de Araújo and José Branco de Miranda Filho
Eleven open-pollinated maize (Zea mays L.) populations were crossed in a diallel scheme and evaluated in five locations in the State of Paraná: [1] Ponta Grossa, [2] Pato Branco, [3] Palotina, [4] Londrina and [5] Guarapuava. Two commercial hybrids (P 3230 and BR 201) were included as checks in the experiments, thus completing 68 entries (11 parents, 55 hybrids and 2 checks). Plots were represented by single rows 5 m long spaced 0.9m with 25 plants per plot after thinning. The following traits were analyzed: GY- total plot grain yield expressed in kg/ha after adjustment to 14.5% grain moisture; PH- plant height (cm); EH- ear height (cm); and FF- days for female flowering. Plant height and EH were not included in location [2]; FF was not include in locations [2] and [3]. The joint analysis of variance showed significance for all traits, only for the variation among location, entries, variety effects and average heterosis. For yield the total heterosis in mid-parent percentage varied from –0.96% (PMI 8403 x PMI 9304) to 32.4% (PMI 9302 x PMI 9307). Variety effects (vi) and general combining ability (gi) effects were in the range of –1483 to 772 kg/ha and from –847 to 448 kg/ha, respectively. Both gi (for yield) and vi (for the other traits) were used to select two populations to be used in a reciprocal recurrent selection program. BR 106 showed the highest estimates for both gi and vi for yield but also showed undesirable traits (tall plants and late flowering). Some outstanding populations for yield potential per se did not show a good performance in crosses. Other populations with outstanding performance in crosses exhibited lower variety effects for yield or high variety effects for the other traits. Some introduced populations who showed shorter plants and earliness should be submitted to selection for yield, adaptation and other agronomic traits before being indicated for crossing. However, they should be recommended as source populations for short architecture and early flowering. An overall analysis led to the decision of choosing the population IAPAR 26 to be used as contrasting parent of BR 106 in a reciprocal recurrent selection program at IAPAR (Londrina, State of Paraná).