4, MASS. EXPERIMP:NT station bulletin 225. 



The Relation of Fruit Set to the Development of Yellow Pickle 



A cucumber plant grows in cycles with reference to producing pistillate 

 flowers. After a large number of pistillate flowers have been produced, 

 that is, one on each node up to the first ten nodes of the stem, only stam- 

 inate flowers are produced for a number of new nodes higher up, fol- 

 lowed by another group of pistillate flowers. Thus a "set" usually fol- 

 lows the removal of a number of large cucumbers from the vine. Usually 

 more pistillate flowers are produced in one set than the plant will mature, 

 and some of them must be sacrificed. Under greenhouse conditions, where 

 all the flowers are in a favorable position to be visited by bees, a very 

 large percentage of the female flowers set fruit. If conditions are ideal 

 for good growth, the plant may be able to mature a complete set. Usually, 

 however, a few of the cucumbers formed on the first few nodes of the 

 plant are a day or two ahead of the others and develop normally, while 

 the later pollinated pistillate flowers make very little growth until the 

 first formed cucumbers have been picked. If growing conditions are un- 

 favorable so that several weeks are required to grow the market size cu- 

 cumber, the pickle becomes stunted and, even though conditions later be- 

 come favorable, it does not grow. Instead a newly pollinated flower may 

 start and as a result the small pickle is prematurely ripened. It may have 

 a few viable seeds or it may not have grown suflficiently to develop any 

 seed. Tlie pickle turns yellow, a condition which many growers have at- 

 tributed to a parasitic disease. y\n infection of a plant by an organism is 

 prol)ably the most important cause of yellow pickle on normal plants. 



The condition cited above very definitely manifested itself in self-pol- 

 linating work on old plants which had set a number of fruits. A study 

 was undertaken of certain characters existing in a mixed lot of cucumbers 

 grown in the station greenhouse. Self-pollinated flowers, on plants al- 

 ready having a number of pickles set, in\ ariably developed yellow pickle; 

 and not until every pollinated flower and developing cucumber were removed 

 from the plant was it possible to get the plant to produce any self-fer- 

 tilized fruit. On the other hand, when the first flowers of the plant were 

 self-pollinated the fruit developed and matured. Indicating that self-pol- 

 lination was not the determining factor. 



Yellow pickle was very much in evidence on plants used for seed pro- 

 duction in breeding work. As many as eight pistillate flowers on a plant 

 were selfed, but only three or four matured while the others remained 

 for .several weeks without growing, and then turned yellow. It was not 

 uncommon to find five or six yellow pickles on these plants because of the 

 time required to mature the early pollinated fruit. 



Since, in the production of seed, the mature cucumber must remain on 

 the vine much longer than that which is picked for market, nuich more 

 food material is required and the plant is not able to carry as much 

 maturing fruit as if all were picked green. Under such conditions yellow 

 ])ickle is ver\ much in evidence. 



Generally yellow pickle is associated with old vines, but the plants in 

 the above ex])eriment were in their first set. This brought out the fact 

 that yellow pickle is a premature ripening of pollinated flowers at a time 

 when the plant is carrying a heavy load. The second set came along after 

 the mature seed cucumbers were removed. The fruits from this .set produced 

 good marketable cucumbers while the yellow pickles were .still hanging 



