Predicting hybrid performances from interploidy crosses in Musa species

Models for predicting hybrid performance of progenies from crosses have been developed and genetic parameters for different Musa populations would have to be estimated from experimental data. Determination of these parameters would be dependent on defining the relationships of progeny to parents in different crosses and identifying parental contributions to offspring. The objective of this work was to estimate genetic relationships based on meiotic mechanisms in parents, and redefine models for predicting hybrid performance for different inter-ploidy crosses in Musa. The study was carried out at the High Rainfall Station of the International Institute of Tropical Agriculture in Onne (443' N, 701'E, 10 m above sea level). A breeding population of approximately 2150 individuals was developed from crosses involving tetraploid (4x) and diploid (2x) parental lines. The diameter of pollen grains from parental lines was measured under a light microscope, while the ploidy status of the breeding populations was determined by flow cytometry (FCM) analysis. Tetraploid lines had a higher mean pollen diameter than diploids. However, there were no differences between the diameter of "n" pollen of the 4x and 2x lines. 4x - 2x crosses produced predominantly 3x progenies, whereas 2x - 4x crosses gave mostly 2x progenies, suggesting a pattern of unequal contribution of the parents with respect to 3x progeny from 4x - 2x crosses, but equal parental contribution to 2x progeny from 2x - 4x crosses. The knowledge of parental contributions to progeny was used to redefine models for predicting hybrid performance from interploidy crosses in Musa.

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