Fertility and pollen tube growth in polyploid melons (Cucumis melo L.)

The high sterility of tetraploid melon (Cucumis melo L.) plants is a serious inconvenient to obtain economically useful polyploid lines. In order to study the alterations on diploid pollen tube growth and their influence on sterility, in vitro and in vivo pollen tube growth from three commercial varieties and its tetraploids was observed. Polyploid pollen grains show a lower germination percentage in vitro and a slower germination rate than haploid pollen. Furthermore, diploid pollen grains producing two or three tubes and tube branchings were observed on diploid pollen; this seems to indicate a decrease in its functionality. In vivo and in vitro pollen behaviours are quite similar, but an interaction between the pollen and the pistillar tissues was detected in vivo. In the diploid × tetraploid cross, where fruits were not obtained, pollen tubes showed a slow growth rate at the base of the pistil. The possible effects of these alterations in sterility are discussed in terms of the factors that could affect fecundation.