Microgametogenesis Tolerant to Heat Stress in Some Maize Crosses

A field experiment was conducted on the farm of Res. Sta. Coll. of Agric. Univ. of Baghdad during 2018-2020. The experiment involved 26 recently developed maize crosses plus an adopted check hybrid. Fall planting of maize in Iraq gives higher yield than spring planting, but it is confronted with high grain moisture at harvest (30-40%) through the rain season. The main goals of this experiment were; to have crosses of low grain moisture, high grain yields, and harvesting before rain season. Seeds were planted about 10 days earlier than recommended, and harvested at mid-October. There were heat tolerant, semi-tolerant and sensitive crosses. The top five heat tolerant crosses were;1-pio3×60L, 2-60 frc × J1, 3-17A×J2, 4-Pio3 × B74 and 5-4f6×B74. Other crosses were either semi-tolerant or heat sensitive. It was concluded that high heat temperatures (45-55c) has negative impact on many growth parameters, enzyme activity, DNA damage, and microsporogenesis and/or microgametogenesis. Maize genotypes still have excellent opportunity to breed for high temperature and other abiotic stresses. Gene transfer will not be helpful as evaluation and screening if genetically diversed genotypes. Such plants characteristics could be controlled by hundreds of not thousands of genes. Cycles of reselection on some individual unique plants inbred population will be helpful to have new genetic variations in maize germplasm.