HETEROSIS AND COMBINING ABILITY AMONG VARIETIES OF MAIZE IN ACID SOIL

Abstract

Maize (Zea mays L.) cultivars tolerant to acidity and resistant to diseases have made the crop feasible in ";cerrado"; (savanna) soil. The identification of potentially useful germplasm with the above mentioned characteristics for breeding purposes was the objective of this study. Ten maize varieties (populations), previously selected for resistance to Puccinia polysora, Phaeosphaeria maydis, Physopella zeae, Exserohilum turcicum and corn stunt complex, were evaluated under the diallel crossing scheme. Varieties and crosses were evaluated in acid and low fertility soil. Analyzed traits were: ear yield (EY), plant height (PH), and ear height (EH). Varieties PMI 8701, CMS 57NF, PMI 9401 CMS 58ND and AMARILLO DENTADO DMR showed the highest yields (above 3.5 t/ ha) per se representing more than 70% in relation to check yield. Heterosis showed significance for all traits, but among the components of heterosis only average heterosis was significant for EY and specific heterosis for EH. General combining ability effects (gi) were significant for all traits, and their highest EY estimates (t/ha) were for PMI 8701 (0.150), BR 105 (0.120), CMS 59 (0.106). The cross CMS 57NF x PMI 8701, with yield of 5.11 t/ha (above both hybrid checks) and heterosis of 23.7% above mid-parent, may be indicated as a potentially useful heterotic group. Varieties PMI 8701, CMS 57NF, PMI 9401 and CMS 58ND were considered the most promising intrapopulation breeding programs, for acid soils.

KEY-WORDS: Heterosis; acidity stress; combining ability; germplasm.