INHERITANCE IN THE 

 SUMMER SQUASH 



Edmund W. Sinnott 



AND 



George B. Durham 



Connecticut Agricultural College, Storrs, Conn. 



OUR KNOWLEDGE of inheritance 

 in Cucurbita pepo, that inckisive 

 species under which are grouped 

 the summer squashes, pumpkins, and 

 most gourds, is not extensive. In pre- 

 MendeHan days Naudin and others 

 studied Cucurbita but their results are 

 not of great value in constructing a 

 modern genetic analysis of the group. 

 Many of the workers on squashes have 

 bfeen more interested in the demarka- 

 tion of species and varieties and in the 

 possibility of making crosses between 

 the various forms than in determining 

 the inheritance of the particular char- 

 acters displayed by the plants. 



Two recent papers, however, should 

 be especially noted. Drude^ has re- 

 ported the results of a long series of 

 crosses in the Cucurbitaceae, chiefly 

 among forms of Cucurbita pepo. He 

 states that some characters show Men- 

 delian inheritance but makes no ex- 

 tended analysis. His results show that 

 white fruit color is evidently dominant 

 over yellow or green and that wartiness 

 is dominant over smoothness. He 

 believes that many characters are not 

 inherited in a Mendelian fashion and 

 that reciprocal crosses are frequently 

 dissimilar. A thorough mixture of the 

 six types of summer squash with which 

 he worked shows that certain of these 

 types tend to persist in the offspring 

 whereas others are entirely lost. Lotsy- 

 reviews the work of previous writers 

 and has made some extensive crosses 

 among certain of the forms of Cucurbita 

 pepo as well as in other species. He 



does not present much information as 

 to the behavior of particular charac- 

 ters, but is especially concerned with 

 interfertility among the different spe- 

 cies and varieties. He confirms 

 Drude's statement that in certain 

 cases the results of reciprocal crosses 

 are dissimilar. 



All workers call attention to the 

 extreme difficulty of effecting self- 

 fertilization in the squash and to the 

 sterility and lack of vigor shown by 

 plants grown from inbred seed. In 

 no case, therefore, have pure lines been 

 established, or material known to be 

 homozygous used in hybridization ex- 

 periments. This fact of course casts 

 a certain degree of doubt over the 

 results heretofore reported in squash 

 breeding experiments. 



In 1916 the senior author grew sev- 

 eral hundred plants of summer squash 

 including all the commoner commercial 

 varieties — croockneck, yellow and 

 white scallops (patty-pans), Fordhook, 

 marrow, and cocozelle. Seeds were 

 obtained from four prominent seed 

 firms. As is often found to be the 

 case with summer squash, the plants 

 showed a marked degree of variability 

 and many of them did not come true 

 to name. Some preliminary hybridiza- 

 tions were made, but it soon became 

 clear that until reasonably pure types 

 had been isolated, the results of hy- 

 bridization experiments would be 

 valueless. In something over one 

 hundred plants of the types which 

 seemed to be the most constant, per. 



' Drude, Q., Erfahrungen bei Kreuzungsversuchen mit Curcurhita pepo. Ber. Deiitsch. Bot. 

 Ges., XXXV:26-57. 1918. 



" LOTSY, J. P., Curcurbita-Strijdvragen. De soort-quaestie. Het gedrag na kruising. Par- 

 thenogenese? I. Historisch overzicht. II. Eigen onderzoekingen. Genetica, I: i97-531. 1919: 

 II: 1-21. 1920. 



