An investigative study of the drought tolerance of F1 maize (Zea mays L.) single crosses derived from PANNAR and CIMMYT inbred lines.
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Drought is the most devastating abiotic stress limiting the production of maize (Zea mays L.) worldwide. The effect of drought stress is greatest in sub-Saharan Africa (SSA) where most small scale farmers rely on open pollinated varieties (OPVs); rather than certified hybrid seed grown under dryland1 conditions. Small scale farmers perceive OPVs to be drought tolerant and yet the yields are as low as 1-2 t ha-1 . In many parts of SSA, therefore, hybrid adoption rate is still below 20%. With the projected population growth in SSA, food insecurity is likely to worsen. However, the development of drought tolerant maize hybrids to help address declining food security is a relevant strategy in SSA. This is so because, drought tolerant hybrids will out yield OPVs. The main objective of this study was to investigate the drought tolerance of F1 single cross maize hybrids developed from CIMMYT drought tolerant donor inbred lines and PANNAR elite inbred lines. The hybrids were tested under random and managed drought stress environments. The first set of F1 hybrids was produced using a 12x12 North Carolina factorial mating design during winter (April-August 2012) and the second set of hybrids was produced in summer (November 2012-March 2013). Seventy F1 hybrids were tested during the summer season (November 2012- April 2013) under random drought stress (RDS) environments in South Africa and Zimbabwe. One hundred hybrids were tested during the winter season (April – September 2013) in Zimbabwe at CIMMYT experimental stations in Save Valley and Chisumbanje under managed drought stress (MDS). The main traits measured included grain yield (GY), ear plant-1 (EPP), anthesis-silking interval (ASI) and days to anthesis (DTA). Statistical analysis of collected data was conducted using GenStat 16th edition. Significant differences between hybrids and environments for grain yield and secondary traits were obtained. The genotype x environment (GxE) interactions was significant under both RDS and MDS environments indicating the differential performance of hybrids across environments. Using stability indices, the relatively stable hybrids were identified. General and specific Combining ability (GCA and SCA) analysis revealed lines that could be used as potential parents in development of hybrids. However, the presence of GCAxE and SCAxE interactions indicated that selection of inbred lines and their hybrid crosses should be done at target environments. Under RDS and MDS, EH79 and EH24 appeared to be the best performing hybrids, respectively, whereas inbred lines DT2, DT7 and UT8 had the best GCA and SCA under both RDS and MDS. Further efforts are required to develop potential drought tolerant hybrids and test for adaption in target environments.