seed supply

Seed Systems Research Abstracts from the Biotechnology, Breeding and Seed Systems Conference

Striga weed control in maize using herbicide seed coating technology

F.K. Kanampiu, J.K. Ransom, D.K. Friesen & J. Gressel

During the past eight years, CIMMYT, in collaboration with the Weizmann Institute of Science (Israel), has developed a unique approach for Striga control in maize. It combines low-dose of a systemic acetolactate synthase (ALS)-inhibiting herbicide seed coating applied to imidazolinone-resistant (IR) maize seed that leaves a field virtually clear of emerging Striga flower stalks season-long. This maize allows application of high localized herbicide levels on or near the crop seed, but at one-tenth the rate that would be used as a spray application. On-station and on-farm studies over several seasons in Eastern and Southern Africa demonstrate that 30 - 45 g/ha imazapyr (or some other ALS inhibiting herbicides) are optimal for seed coating for effective Striga control in various environments. Low-dose herbicide seed dressing on IR-maize also controls Striga without impacting sensitive intercrops when they are planted 15 cm or more from maize hills. This allows small-scale farmers to continue intercropping while using maize seed treated to control Striga. This technology increases yields in Striga-infested fields greater than three-fold at a cost of less than US $4 per hectare. The added cost of this 1 ton/ha added yield is equivalent to about 25-50 kg/ha maize yield, depending on market prices, suggesting potential benefit:cost ratios >25:1. This technology, coupled with pulling rare Striga escapes (some of which could be resistant to the herbicide) can deplete the Striga seedbank, reduce infestation of susceptible rotation crops, delay the evolution of resistant populations, and can be used as a stop gap until genetic crop resistance becomes available. CIMMYT initiated a breeding program originally in Harare and later in Kenya to incorporate adaptation of IR maize to the local environment. This has focused on improving IR maize germplasm for resistance to turcicum blight and leaf rust diseases, reducing the proportion of Pioneer hybrid germplasm to less than 12.5%, increasing seed stocks. High-yielding and disease-resistant IR-maize inbred lines, hybrids, and open pollinated varieties adapted to Striga-infested agro-ecologies in sub-Saharan Africa will soon be available from CIMMYT. Our goal is to deliver this product to farmers in all major agro-ecologies in sub-Saharan Africa where Striga is endemic. To achieve this goal, CIMMYT is collaborating with BASF and with seed producers to commercialize the technology and make seed-treated maize available to farmers.