Breeding for purple blotch resistance in garlic and shallot
1997
Pascua, M.F. | Kik, C. | Patena, L.F. | Badar, A.J. (Mariano Marcos State Univ., Batac, Ilocos Norte (Philippines))
Purple blotch caused by Alternaria porri is one of the major disease of Allium species in tropical areas. The fungus can cause a reduction in yield from 30 to 50 percent if left uncontrolled. The cheapest and simplest means of minimizing crop losses is the planting of disease resistant cultivar. It is therefore the aim of this research work to 1) develop a quick and reliable screening test for A. porri in garlic and shallot under controlled conditions, 2) to identify possible sources of resistance under laboratory conditions, and 3) verify the level of resistance of garlic genotypes under field conditions. Field evaluation of AVNET 2 shallot accessions in 1995 identified 6S, a collection from Sumenep, Indonesia as resistant to the pathogen. Results of laboratory screening further confirmed the resistance of this genotype. To develop the screening test, five experiments were performed in the phytotron, using four accessions of two-week old shallot plants and 11 accessions of one-week and one-month old garlic plants. These were inoculated with different types of inoculum at varying temperature. An average of 4.43 and 3.12 lesions/plant were observed in the shallot plants inoculated with an inoculum from pure culture and infected leaves, respectively. There was better disease development at 26 deg C and at high relative humidity (95-100 percent). However, the use of spores as inoculum and not mycelia was better in garlic plants. It was also noted that one-week old garlic plants were more susceptible to the pathogen than one-month old plants. Laboratory screening identified Acc. Nos. 95116, 95117, 95121 and 95122 as resistant. Field evaluation confirmed the resistance of garlic Acc. Nos. 95119 and 95121
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