In vitro germination and pollen tube growth of maize (Zea mays) pollen. III. The effect of pollen genotype and pollen source vigor

Abstract

Pollen grains from three inbreds (H49, H55, and H50) and two of their single cross hybrids (H49 × H55 and H49 × H50) were cultured on an artificial medium containing 15% sucrose and 0.6% bactoagar supplemented with all possible combinations of two levels (0.00 and 0.03%) of calcium nitrate (Ca) and two levels (0.00 and 0.01%) of boric acid (B). For all characteristics measured (germination percentage, germination with more than one pollen tube percentage, rupturing percentage, length and growth rate of the pollen tubes), significant differences between inbreds were obtained on most combinations of Ca and B. Since the inbreds were presumably homozygous and, as a result, each produced pollen grains of only one genotype, these differences in germination characteristics were apparently produced by the genetic differences between the inbreds. Therefore, the in vitro germination characteristics of pollen grains are associated with pollen genotype. The response of the hybrids could not be accurately predicted from the behavior of their inbred parents. In general, the hybrid mean was in the range between the means for the two inbred parents. However, the value of the mean for the hybrid relative to the values of the parental means depended on which hybrid combination was involved. The results indicated that the germination characteristics of pollen grains on various combinations of Ca and B are influenced in large part by pollen genotype but that the genetic expression is quite complex. Vigor of the pollen source per se was not a factor.