394 



SHERRET S. CHASE 



PARTHENOGENESIS 



A number of interesting facts have come out of studies of the frequency of 

 reduced parthenogenesis in maize. One unanticipated fact has been that of 

 the effect of the male (pollen) parent on parthenogenesis. Although this 

 parent does not contribute its genes to the maternal monoploid, the particu- 

 lar pollen parent used in any cross does have an effect on the rate of occur- 

 rence of maternal monoploids (Chase, 1949a). In Table 25.1 the results of 



TABLE 25.1 



FREQUENCIES OF OCCURRENCE OF MONOPLOIDS FROM SEVERAL 



INBREDS AND HYBRIDS WHEN INBREDS A385 AND 



38-11 WERE USED AS THE POLLEN PARENTS 



Known to be too low. 



paired crosses involving two different pollen i)arents, inbreds A385 and 

 38-11, are summarized. Both of these inbreds carry the purple plumule 

 marker system. From the genetic point of view A385 is the more satisfactory 

 of the two. That is, in its hybrids the marker phenotype is generally well 

 developed. In the hybrids of 38-11 the phenotype is often obscure. Conse- 

 quently few monoploids were lost by misclassification in the progenies of 

 A385, whereas a considerable number may have been lost in those of 38-11. 

 In spite of this the data show 38-11 to be ten or more times as effective as 

 A385 as a stimulator of parthenogenesis. This effect seems to be general. That 

 is, the several dent stocks and also the sweet corn hybrid show about the 



