Plant breeding can be made more efficient by having fewer, better crosses

Abstract

BackgroundCrop yields have to increase to provide food security for the world’s growing population. To achieve these yield increases there will have to be a significant contribution from genetic gains made by conventional plant breeding. However, the breeding process is not efficient because crosses made between parental combinations that fail to produce useful varieties consume over 99% of the resources.ResultsWe tested in a rice-breeding programme if its efficiency could be improved by using many fewer, but more judiciously chosen crosses than usual. In a 15-year programme in Nepal, with varietal testing also in India and Bangladesh, we made only six crosses that were stringently chosen on complementary parental performance. We evaluated their success by the adoption and official release of the varieties they produced. We then modelled optimum cross number using assumptions based on our experimental results.Four of the six crosses succeeded. This was a fifty-fold improvement over breeding programmes that employ many crosses where only about one, or fewer, crosses in 200 succeed. Based on these results, we modelled the optimum number of crosses by assuming there would be a decline in the reliability of the breeder’s prediction of the value of each cross as more crosses were made (because there is progressively less information on the traits of the parents). Fewer-cross programmes were more likely to succeed and did so using fewer resources. Making more crosses reduced the overall probability of success of the breeding programme.ConclusionsThe efficiency of national and international breeding programmes would be increased by making fewer crosses among more carefully chosen parents. This would increase the number of higher yielding varieties that are delivered to farmers and hence help to improve food security.

Exploring the Realm of Possibilities: Trying to Predict Promising Crosses and Successful Offspring through Genomic Mating in Barley

“…In many selfing crops, pure-breeding varieties are developed from populations resulting from crosses made between two parents. Testing large numbers of parents leads to an excessively high number of biparental populations to test [15]. Even though breeders try to take into account all potential information about parents to design crosses, many crosses are eliminated each year because they do not produce superior progeny [16,17].…”

Strategies for Selecting Crosses Using Genomic Prediction in Two Wheat Breeding Programs

“…Crossing is one of the main decisions of a breeding program. The number of possible crosses is orders of magnitude larger than the number of feasible crosses (Witcombe et al, 2013). Although breeders attempt to take into consideration all available information on the potential parents to determine which crosses to make, many crosses are discarded in subsequent years, as they do not deliver superior progeny (Koebner and Summers, 2003; Heslot et al, 2015).…”

Transforming Rice Breeding: Re-Designing the Irrigated Breeding Pipeline at the International Rice Research Institute (IRRI)

“…Crosses that would have a high chance of producing progeny that did not match profile targets (e.g., both parents with high amylose when low or medium was required) were not made. In other words, our paradigm regarding the number of crosses shifted from quantity to quality, which had been previously advocated by other rice breeders [27].…”