in diameter. The plant is an annual, 

 slender, and weak-stemmed, with 

 no economic value, although cas- 

 ually it may be cultivated as an 

 oddity. The species is quite variable 

 in its reaction to infection and plant 

 characters. A type obtained from 

 the U.S.D.A. Plant Introduction 

 Program provided the souice of high 

 resistance to the disease in our 

 breeding program. 



The immunity of the variety 

 Waltham Mold-Proof Forcing to 

 the leaf mold pathogen is derived 

 from the Andean tomato. Lye ope r- 

 sieon peruviannm, a perennial, de- 

 cumbent plant with slender, weak 

 stems, and greenish-white fruits 

 about one-half inch in diameter. 

 The species is native to the Peru- 

 vian Andes Mountains and has no 

 economic value. 



The fruits of these resistant and 

 immune ancestors, although small 

 and of insignificant weight, remain 

 but a memory as larger fruit size, 

 desirable horticultural plant type, 

 and resistance or immunity to dis- 

 ease were linked by progressive 

 hybridization and selection for suc- 

 cessive generations to develop the 

 acceptable edible commercial tomato 

 botanically known as Lycopersicon 

 esculentum. 



Improved Bay State, in commer- 

 cial production for several years, 



has improved yields significantly. 

 Our Mansfield, Massachusetts, to- 

 mato growers have jocosely called 

 it a "mortgage lifter." Waltham 

 Mold-Proof Forcing, introduced in 

 1952, is considered commercially 

 acceptable and is being grown rather 

 widely. The fruits of both varieties 

 number three to five to the pound, 

 whereas those of the wild resistant 

 and immune ancestors number about 

 450 to the pound. 



Control Simplified 



Research has simplified the con- 

 trol of the disease. The customary 

 method of controlling tomato leaf 

 mold in practice has always been 

 uncertain and costly. Now, it is old 

 and something of the past. The need 

 for heating, careful greenhouse man- 

 agement, and cultural practices for 

 controlling the disease as in the past 

 is no longer so important. Induced 

 resistance and immunity to tomato 

 leaf mold by breeding have oflfered 

 the grower security against loss and 

 less investment in costs of culture. 

 Thus the new concept of disease 

 control in tomato culture under 

 glass has replaced the old to im- 

 prove the grower's income. It is 

 hoped that no new strains of the 

 fungus will appear to upset the re- 

 sults of our long history of effort. 



Inflorescence and fruits of highly resistant currant tomato, lycopersicon pimpinellifolium, 

 ancestor of the Improved Bay State tomato at right. 



