Genetic trends in the Zimbabwe’s national maize breeding program over two decades

Monitoring genetic gains within breeding programs is a critical component for continuous improvement. While several national breeding programs in Africa have assessed genetic gain using era studies, this study is the first to use two decades of historical data to estimate genetic trends within a national breeding program. The objective of this study was to assess genetic trends within the final two stages of Zimbabwe’s Department of Research & Specialist Services maize breeding pipeline between 2002 and 2021. Data from 107 intermediate and 162 advanced variety trials, comprising of 716 and 398 entries, respectively, was analyzed. Trials were conducted under optimal, managed drought stress, low nitrogen stress, low pH, random stress, and disease pressure (maize streak virus (MSV), grey leaf spot (GLS), and turcicum leaf blight under artificial inoculation. There were positive and significant genetic gains for grain yield across management conditions (28–35 kg ha-1 yr-1), under high-yield potential environments (17–61 kg ha-1 yr-1), and under low-yield potential environments (0–16 kg ha-1 yr-1). No significant changes were observed in plant and ear height over the study period. Stalk and root lodging, as well as susceptibility to MSV and GLS, significantly decreased over the study period. New breeding technologies need to be incorporated into the program to further increase the rate of genetic gain in the maize breeding programs and to effectively meet future needs

Improving maize (Zea mays L.) growth and yield using Jatropha (Jatropha curcas L.) seed cake under Zimbabwean soil condition

A research study exploring the use of jatropha seed cake as a sole source of nutrients and used in combination with inorganic N fertilizer was conducted on station at Henderson Research Station on sandy and clayey soils during the rainy season of 2006/2007. Two experiments were conducted to determine the effect of jatropha seed cake on maize dry matter and grain yield and its effect on weed density and biomass. Experiment 1 explored the use of jatropha seed cake rates ranging from 767kg/ha to 3835kg/ha in maize production. Included in the experiment were three other treatments viz extension recommendation for inorganic fertilizer, farmer¡¦s practice of applying cattle manure and a control. A Randomized Complete Block Design (RCBD) was used and a total of 8 treatments were assessed. Jatropha seed cake application rate and inorganic fertilizer had higher yields (P „T 0.05) on maize dry matter yield at 4, 8 and 12wace on the sandy soil site. Application of 2301kg/ha of jatropha seed cake and the extension recommendation resulted in maize dry matter yields of 3059kg/ha and 3399kg/ha respectively at 12wace. There were no differences noted in maize dry matter yields on the clayey soil site. Weed densities of the following species F exilis and Eragrostis spp (sandy soil site ) and T. annua, C. rotundus, and L. martinicensis (clayey soil site) were significantly reduced (P<0.05) where jatropha seed cake was applied. Weed biomass on the sandy soil site was reduced by 30% along the maize rows. In experiment 2, three levels of jatropha seed cake were tested (0, 767kg/ha and 1534kg/ha) in combination with 3 levels of inorganic nitrogen levels (0, 25kg/ha and 50 kg/ha N) The N was applied as topdressing at 6wace. The other treatments included use of 200kg/ha Compound D (N: 7%, P:14% and K: 7%) as basal fertilizer in combination with the three inorganic N fertilizer rates. 12 treatments were tested in this experiment and it was laid out as a 3 x 3 factorial arranged in an RCBD design. The jatropha seed cake levels performed equally as well as the inorganic fertilizer treatment in terms of dry matter yield at 4 and 8 wace. The maize grain yield was significantly higher (P0.05). The results from this study suggest that smallholder farmers can apply jatropha seed cake at a rate of 767kg/ha in maize production and 25kg/ha inorganic N can be used as a top dressing fertilizer