Drought is one of the vital factors limiting maize production in sub-Saharan Africa. However, a rise in temperature above 30°C reduces crop yield by 1% under optimal rain-fed conditions and by 1.7% under drought conditions and up to 40% under both drought and heat stress (Meseka et al., 2018).

Maize is highly sensitive to drought than other cereals mostly at flowering stage. This is because the anthers and silks are separated by about 1 m, and pollen and stigma are exposed to environmental conditions (Monneveux et al., 2006). Maize is particularly sensitive to drought stress one week before and two weeks after flowering emergence ((Chapman and Edmeades, 1999; Campos et al., 2004) resulting in yield losses between 20 to 50% (Nielsen, 2007). Nevertheless, stress in maize is associated with temperatures rising above an optimum of 30°C which cause adverse physiological processes which results in increase in respiration, shorter life cycles, light interception, photosynthesis and increase in pollen sterility (Meseka et al., 2018; Nasser et al., 2020; Vani et al., 2001; Jagadish et al., 2011).

Water deficit is a common phenomenon in plants. It is accentuated when drought or lack of sufficient water in the rhizosphere occurs and the rate of evapo-transpiration is high (Bargali and Bargali, 2016; Dodd and Kudoyarova, 2021; Vibhuti et al., 2015). Drought may occur in any type of crop, irrigated or rain fed and may have a special impact in association with the prevalent farming system and environment. This fact has prompted agronomists, breeders, physiologists and physical scientists to study the nature of development and yield, management practices that would alleviate drought and to identify drought tolerant genotypes (Askari et al., 2019). Drought stress at grain filling period reduces grain yield in maize by 40% and this loss is of great concern to plant breeders (Prasad et al., 2011). However, much emphasis here is on yield performance under water deficit conditions (Lafitte et al., 2004). For this reason, it seems necessary to use appropriate criteria for selecting drought tolerant genotypes for breeding programs.

The drought tolerance indices provide a measure of drought based on loss of yield under drought conditions in comparison to normal irrigation condition, and have been used for screening drought tolerant genotypes (Naghavi et al., 2013). Several indices have been used to evaluate genotypes for drought tolerance based on grain yield such as Mean Productivity (Khalili et al., 2014), Stress Susceptibility Index (SSI) (Fischer and Maurer, 1978), Harmonic Mean Productivity (HAR) (Farshadfar et al., 2001), Stress Tolerance Index (STI) (Fernandez, 1992), Geometric Mean Productivity (GMP) and Tolerance (TOL). These indices have been studied by some researchers (Fernandez, 1992; Farshadfar et al., 2001; Shiri and Akhavan, 2005; Shirinzadeh et al., 2009).

Nass and Paterniani (2000) described and evaluated the genetic potential for races of maize in Brazil and adjacent areas. It is estimated that about 100,000 accessions of maize are maintained in germplasm banks around the world (Ortiz et al., 2008). In 1994, the International Maize and Wheat Improvement Center (CIMMYT) Maize Germplasm Bank had nearly 11,000 stored accessions in its base and active collections.

Maize germplasm is the total gene pool of a species consisting of landraces, advanced breeding lines, popular cultivars, wild and weedy relatives. It forms the raw material for any crop improvement program. Edaphic and climatic variations found among and within different regions, socioeconomic differences among the regions, as well as among farmers within these regions resulting in the evolution of specialized landraces (Nass and Paterniani, 2000). Diversity of cropping systems also contributes to variation and differentiation among landraces.

As is clear from the foregoing account, various institutes with different objectives are engaged in plant and/or germplasm collecting activities. Such Institutes include International Institute Of Tropical Agriculture (IITA), International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Institute for Agricultural Research (IAR) Samaru among others.

The objectives of this germplasm collection mission were to capture maximum variability of maize from maize producing areas in Burkina Faso, to include the germplasm in the breeding programmes to develop drought tolerant maize varieties for use by farmers in the savannah agro ecologies and to identify maize production constraints with the aim of suggesting possible solutions.

From the various centers and sites covered during the exploration and collection exercise, wide range of maize germplasm were collected and a very rich collection is now available in the seed storage facility of the Crop Science laboratory of  Kano University of Science and Technology, Wudil. From the social-economic information gathered and analyzed, it is recommended that drought tolerant   maize   varieties   should   be   developed    and  properly disseminated across the country for sustainable food security. It is also recommended that extension services should be improved, prices of fertilizers, pre- and post-emergence herbicides and pesticides be subsidized, and finally rural development programmes be improved so that rural urban migration among the youths could be discouraged.

The authors have not declared any conflict of interests.

The team wishes to acknowledge TETFUND for sponsoring the work and Microsoft Encarta 2009 Microsoft Corporation for utilizing its point mapping package as well as all the farmers who supplied the team with various maize samples and responded to our questionnaires. Many thanks to National Research Institute INERA in Burkina Faso for supplying vital information about the improved varieties.