Use of Rank Indexing for Comparative Evaluation of All-male and Other Hybrid Types in Asparagus

Abstract

Abstract Numerous asparagus (Asparagus officinalis L.) hybrids have been developed worldwide during the past 20 years. Most are clonal hybrids. The French (INRA) breeding program has successively introduced double, clonal, three-way all-male, and F1 (mixed or all-male) hybrids. Because these hybrids are evaluated at different locations during different years, a composite comparison of all cultivars is not feasible. A ranking index has been developed to make useful the huge volume of heterogeneous data that has been accumulated from the many trials during the past 10 years. This index is based for each hybrid on 2 years of comparative harvest data at four locations from about 40 hybrids and check cultivars at each location and each year. Using these rank indexes, the different types of hybrids can be compared one with another and with foreign hybrids. These indexes show that 1) all-male F1 and three-way hybrids tend to have high total yield and earliness; 2) F1 mixed hybrids are likely to have relatively large spear diameter; 3) double, clonal, and foreign hybrids produce the most attractive spears; 4) the general superiority of all-male hybrids is confirmed; 5) the four characters that are the major breeding objectives—early yield, high total yield, large spear size, and attractive spear appearance—are difficult, but not impossible, to combine into one hybrid. The indexes also show that, in spite of general trends, individual hybrids outstanding in all characteristics can be found in each type of hybrid.