POLLEN STERILITY IN GRAPES 



Some Varieties Self-sterile — Study of Pollen Shows That It Becomes Worthless 



through Degeneration of Cell-nucleus — Remedy in the Planting 



of a Mixture of Varieties in the Vineyard. 



M. J. Dorse Y 



University of Minnesota Agricultural Experiment Station, University Farm, 



St. Paul, Minn. 



A 



NUMBER of varieties of grapes 

 fail to set fruit when pollinated 

 with their own pollen. This 

 fact has been observed by 

 grape growers for some time, especially 

 when large blocks of certain varieties 

 have been grown in more or less isolated 

 positions. The reason for this has been 

 given careful study by Beach ('98 

 and '99) and Booth ('02) working at 

 the New York State Experiment Sta- 

 tion. Munson ('09) in Texas and 

 Whitten ('99) in Missouri have also 

 contributed much in this work. Later, 

 working in North Carolina with some 

 of the southern grapes, Reimer and 

 Detjen ('10) showed that a similar 

 condition with respect to sterility existed 

 in a number of these varieties. These 

 have been the important attempts to 

 determine which varieties will fruit when 

 standing alone. 



Testing Sterile Varieties : A brief state- 

 ment, setting forth the main facts 

 developed in their work will be inter- 

 esting in this connection. Tests were 

 made of the ability of a large number of 

 varieties to set fruit when pollinated 

 with their own pollen, by enclosing 

 clusters in paper bags before the 

 blossoms opened. In those varieties 

 which are self sterile, pollen is produced 

 in the usual quantities so that the 

 failure to produce pollen is eliminated 

 as a reason for sterility. An interesting 

 fact developed in this bagging work was 

 that pollen from those varieties which 

 failed to set fruit when self pollinated 

 also failed as an effective pollcnizer 

 when used on other varieties. These 

 facts show that sterility in the grape 

 is due to a lack of functioning in the 

 pollen rather than in the pistil. 



To illustrate from the work of Beach, 

 when 143 clusters of Brighton were 

 covered with bags and self pollinated, 

 the average rating of the clusters 

 formed, counting 100 as a perfect 

 cluster, was approximately one, and, 

 when thirty-two clusters distributed 

 among 8 other varieties were pollinated 

 with Brighton pollen, the average rating 

 was three, showing Brighton, for those 

 varieties used, as well as for itself, to 

 be a poor pollenizer. On the other 

 hand, when 116 clusters of Catawba 

 were selfed, the average rating on the 

 same basis as above was eighty-six, 

 as compared with one in Brighton. 

 When thirty-three clusters of eight 

 other varieties were pollinated with 

 pollen from Catawba, the average 

 rating was sixty-seven, showing a 

 marked difference between the Brighton 

 pollen and the Catawba pollen when 

 used either in selfing or crossing. 



EXPERIMENTAL EVIDENCE 



Beach worked with a large number of 

 varieties and by means of the bagging 

 method classified them with respect 

 to their abiUty to fertilize themselves 

 and also as cross pollcnizers. Figs. 

 1 and 2 show two mature clusters of 

 Brighton, illustrating the result when 

 this variety is self -pollinated and when 

 it is fecundated with the pollen of 

 some other variety. 



Reimer and Detjen ('10) extended this 

 information and showed a similar_ con- 

 dition to exist in a number of varieties 

 of Vitis rotundi folia grown in the South. 



Booth ('02) showed that the pollen 

 from self sterile varieties was markedly 

 different, when dusted upon a slide and 

 examined with a microscope, frcm the 



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