Successful development of a new tomato cultivar "Al-First" immune to stem canker using host-selective toxin [Japan].
1987
Nishimura S. | Ieda T.
Stem canker of tomato caused by a distinct pathotype of Alternaria alternata became a problem in Japan since 1977. It affected only tomato plants of cv. "First" and its derivatives, which are the most popular ones for glasshouse production. The causal pathogen produced in culture a host-selective toxin (al-toxin) that is highly toxic only to susceptible tomato cultivars. Elegant tests using al-toxin revealed that the susceptibility (or sensitivity) of tomato to the disease (or al-toxin) was controlled by a major single gene locus, expressed as incompletely dominant, however, cv. "First" tomato was found to have homozygous susceptible gene and highly sensitive to both the toxin and stem canker. Using the toxin solution as a screening agent, mass screening for stem canker resistant in "First" tomato seeds was performed. The seedlings that survived the toxin treatment showed some degree of damage, indicating that mutation might have occurred from susceptible homozygote to heterozygote. A quarter of S1 progenies of the mutant was confirmed to be completely resistant to both toxin and stem canker, and hold almost useful characters which existed in "First" tomato, those named as new cv. "Al-First" homozygously resistant to stem canker.
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