Early selection for flowering time in almond breeding programs

Abstract

Late flowering to reduce the risk of late frosts is one of the main objectives of almond breeding programs. Breeders have to wait at least three years, however, to know the flowering time of newly obtained seedlings. Although some trials have been conducted correlating the chilling requirements for seed germination with leafing and flowering times, the results have not shown high correlations between these characteristics. In this work we studied the correlation between germination, leafing and flowering in four families created in 2009 between very early and very late progenitors with a broad phenotypic segregation for flowering time. In winter, the seeds obtained were stratified without shells for germination. Once a week notes of germination date were taken. The plants obtained were taken to the greenhouse in pots, where they were left to grow up until the summer. The plants were then moved to a cold room, where the number of buds sprouted was noted on a weekly basis as the leafing time in controlled conditions. Finally, the plants were taken to the definitive plots, and the leafing and flowering times were noted for three years. The results showed a strong maternal effect for germination time and also indicated that germination time was not correlated with any other trait. Correlations between the first leafing time in the cold chamber and the flowering time in the field four to six years later were intermediate, raising doubts about the use of this correlation as an early selection criterion for flowering time in almond.