First, second and third generation maize hybrids (Fl, F2 and F3) were evaluated against local farmers' maize (LFM) and Chitedze Composite C (CCC), an improved open pollinated variety (OPV). Three levels of nitrogen, O, 40, and 80 kg/ha were applied for two seasons, 1992/93 and 1993/94, in on- farm trials at 5 sites across Malawi. The hybrids were two single crosses (MH12 and MH16), two top- crosses (MH17 and MH18), and one three-way cross (NSCM41). The objectives of the study were: I) to assess the degree of yield decline of the different types of hybrids due to inbreeding depression, and 2) to compare the performance of recycled hybrids with LFM and CCC and assess economic implications. The first season results showed that for ON applied, inbreeding depression was large for all types of hybrids. At high N, however, top-crosses showed smaller inbreeding depression (15-20%) compared to single crosses (30-40%). Recycled top-cross hybrids performed much better than LFM at all N levels. MH17F2 yielded 2.4t/ha compared to 1.8t/ha for LFM. In the second season, recycled top-cross hybrids consistently did better than CCC, and LFM, even without nitrogen. An economic analysis showed that recycled top- cross hybrids had higher Marginal Rate of Returns than CCC and LFM. This study indicates that these top- crosses tend to tolerate recycling better than the single crosses. Inbreeding depression was more critical at low N than at high N. If farmers have to recycle maize hybrids, some fertilizer needs to be applied in order to get reasonable yield.

English

9712|AGRIS 9702|anterior|R97-98PROCE|FINAL9798|3

Jose Juan Caballero

CIMMYT Staff Publications Collection