IOI2 



The Brown Rot of the Tomato. [march, 



The Board have received the following note from Mr. 

 C. K. Bancroft, B.A., on certain investigations on which he 

 is engaged at the Jodrell Laboratory, 

 The Brown Rot Kew. 



of the Tomato. This disease is well-known to growers 



of tomatoes in this country, and during 

 the past two or three years many have suffered considerable 

 loss owing to the destructive nature of the pest. The fungus 

 appears to attack the fruits only, the other parts of the plant 

 show no external signs of infection. A fruit which is infected 

 first shows discoloured patches on its surface ; these usually 

 run together, so that the whole, or almost the whole, surface 

 of the fruit becomes discoloured. The pulp inside becomes 

 reduced to a dark-coloured mass. 



The seeds of infected fruits are of a darker colour than 

 those of healthy ones, and a microscopic examination shows 

 that, whereas the testa of the dark-coloured seeds is intact, 

 the tissues of the endosperm and embryo contain fungal 

 hyphae, which from their characters appear to be hyphae 

 of Phytophthora omnivora. In spite of the occurrence of 

 the hyphae, the cells of the endosperm and embryo appear 

 to be healthy. 



This infected seed or "brown seed," as it is sometimes 

 called, is known among the growers to be capable of ger- 

 minating, and is reported to produce plants which always 

 bear infected fruits. These facts, coupled with the results of 

 microscopic examination of the seed, suggest that the hyphae 

 may be capable of existing in the seed in a resting condition, 

 becoming active when the seed germinates, and keeping pace 

 with the growth of the plant until the fruit is formed. 



Whereas it is clear that "brown seed" always contains 

 fungal hyphae, the hyphae cannot be regarded as being in 

 a resting condition in the seed until they have been shown 

 to be capable of activity when the seed germinates. Attempts 

 are being made to ascertain whether this is so, that is, to 

 trace the growth of the hyphae in the seedling, and to 

 demonstrate their presence in the mature plant. 



