THE BAY STATE TOMATO 7 



It is interesting to note here that Langford (9) originally repotted four distinct 

 physiologic forms of leaf mold to which Vetomold is resistant. Bay State and 

 Globelle share the same measure of resistance to these forms, since each derived 

 its resistance to the fungus from Red Currant which in widely scattered centers 

 throughout the world has shown a high degree of immunity. The new form to 

 which Vetomold and other derivatives of Red Currant are susceptible is regarded 

 by Bailey and Langford (4) as a fi^th physiologic form. 



VARIABILITY OF REACTIONS OF LYCOPERSICON TO INFECTION 



Alexander (1) recognized five arbitrary classes of resistance: excellent and good 

 grouped together as resistant; and fair, poor, and none grouped together as sus- 

 ceptible. These pathological reactions to infection on various species and va- 

 rieties of tomatoes were used by Langford in the classification of five strains of the 

 fungus. Cultural studies also have revealed numerous strains of the fungus which 

 produce different pathological reactions. 



A completely susceptible type of infection is characterized by a progressive 

 browning and necrosis of the foliage and profuse molding and sporulation when 

 humidity is relatively high. Infected foliage Is destroyed progressively and 

 comparatively early. Under relatively dry conditions, the progress of infection 

 is characterized by slowly expanding brown necrotic spots with only a limited 

 amount or no sporulation on the lower surface. Reactions within this range are 

 found on Ailsa Craig, Potentate, VValtham Forcing, Kondine, Comet, Michigan 

 State. 



In contrast, a partial resistance or less virulent type of infection is manifested 

 on other varieties. Infections are restricted to a smaller area and they are con- 

 spicuously yellow on the upper surface. Both necrosis and sporulation occur 

 eventually but to a comparatively slight degree, and they are restricted to the 

 center of the spots. The surrounding yellow areas are more conspicuous above 

 than below. In a continued moist atmosphere the final reaction may be com- 

 parable to complete susceptibility, but under conditions of relatively low humidity 

 there is little or no sporulation. This type of infection is shown by Norduke, 

 Maincrop, Up-to-Date, Stirling Castle, Bay State, Vetomold, Globelle. 



A similar reaction expressing a still greater degree of resistance or extreme re- 

 sistance is manifested by progressively enlarging 3'ellowish infection areas. The 

 centers ultimately become necrotic and sporulation occurs in and from the centers 

 only in a moist atmosphere. This resistance is manifested by Lycopersicon hir- 

 sutiini Humb. and Bonpl. and L. pimpinellifolmm (Jusl.) Mill. 



Immunity or complete resistance to the fungus is offered by L. peruvianum (L.) 

 Mill. The macroscopic symptoms of infection are of an expanding yellowish 

 type, indefinitely outlined, extremely rare, and non-sporulating. This type of 

 reaction was originally exemplified by Red Currant, L. pimpinellifolium (Jusl.) 

 Mill., to all of the known forms of Cladosporium fulvum Cke. Attempts to hybrid- 

 ize L. peruvianum and L. esculentum have failed completely. Pollination of 

 "esculentum" flowers with pollen from L. peruvianum gives rise to tomato fruits 

 of good size but no seed is ever produced. 



Langford (9) described a kind of partial resistance manifested by progressively 

 enlarging, necrotic, non-sporulating infection areas developing under high atmos- 

 pheric moisture conditions and resembling symptoms following inoculation with 

 the commc>n virulent strain of the fungus on susceptible varieties under con- 

 ditions of relatively low humidity. 



Confirmation of the identity of the several reported strains of Cladosporium 

 fulvum Cke. is desirable. In view of the difficulty and uncertainty ol providing 

 and maintaining at Waltham pure culture atmospheres for infection purposes, 



