The relative performance of inbreds and open-pollinated populations of spring-sown onions

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Abstract
SUMMARY: First (I1), second (I2) and third-generation (I3) inbreds were compared with openpollinated spring-sown onion populations in field trials at five sites over 2 years. The open-pollinated populations were earlier maturing and gave higher yields and a lower proportion of bullnecked plants than the inbreds but the latter had a lower proportion of unmarketable double bulbs. The mean level of expression of each character differed considerably between individual trials. The effect on sprouting within each year resulted from factors operating prior to storage; bulbs from all sites were stored at Wellesbourne in a common environment yet large differences in the proportion of sprouted bulbs from different sites occurred by the following spring.Interactions were found between the type of population (inbred and open-pollinated) and the macro-environment. Inbred populations showed a greater linear response to environment for yield, skin colour and proportion of bullnecked plants, but were less responsive for percentage of double bulbs.The results are discussed in relation to the evaluation procedures for inbreds.