Genotypic Influences on in vitro Fertilization and Kernel Development of Maize1

Abstract

A study was conducted to determine the performance of maize (Zea mays L.) genotypes in a procedure for in vitro fertilization and kernel (caryopsis) development. The influence of sampling and crossing methods on in vitro fertilization and kernel development were examined as part of a continuing effort to improve the procedure for use in genetic and developmental studies. Segments of maize ears containing 10 unfertilized intact pistillate spikelets were pollinated after placement on a defined agar‐based medium in petri dishes. Fertilization percentage, frequency and extent of kernel development, and germination percentage were obtained for 31 female genotypes each sibbed and crossed by four inbred‐line males. Average percent fertilization of 11 single‐cross females (42%) was higher than for 20 inbred‐line females (18%). Fertilization ranged from 0 to 84% and significant effects were attributable to female genotype; male genotype; female ✕ male combinations; crossing date interactions with females, males, and female ✕ male combinations; age of ears (from silking); and the time of day that pistillate spikelets and pollen were collected in the field for crossing. Full kernel development lot crosses involving single‐cross females averaged 12% of the initial ovary number and was influenced mainly by female genotype. For a 10‐ovary block, differences in development were evident among fertilized ovaries beginning 10 to 15 days after pollination. Two fully developed kernels was the average maximum per 10‐ovary block. Germination of full kernels developed from single‐cross and inbred‐line females was 95 and 85%, respectively. The above effects should be considered when designing in vitro fertilization studies with maize.