Long‐term on‐farm participatory maize breeding by stratified mass selection retains molecular diversity while improving agronomic performance

Abstract

Modern maize breeding programs gave rise to genetically uniform varieties that can affect maize's capacity to cope with increasing climate unpredictability. Maize populations, genetically more heterogeneous, can evolve and better adapt to a broader range of edaphic–climatic conditions. These populations usually suffer from low yields; it is therefore desirable to improve their agronomic performance while maintaining their valuable diversity levels. With this objective, a long‐term participatory breeding/on‐farm conservation program was established in Portugal. In this program, maize populations were subject to stratified mass selection. This work aimed to estimate the effect of on‐farm stratified mass selection on the agronomic performance, quality, and molecular diversity of two historical maize populations. Multilocation field trials, comparing the initial populations with the derived selection cycles, showed that this selection methodology led to agronomic improvement for one of the populations. The molecular diversity analysis, using microsatellites, revealed that overall genetic diversity in both populations was maintained throughout selection. The comparison of quality parameters between the initial populations and the derived selection cycles was made using kernel from a common‐garden experiment. This analysis showed that the majority of the quality traits evaluated progressed erratically over time. In conclusion, this breeding approach, through simple and low‐cost methodologies, proved to be an alternative strategy for genetic resources’ on‐farm conservation.

A method for obtaining flexible broccoli varieties for sustainable agriculture

“…Our genetic results were similar to those found by [23] (comparing two open-pollinated maize populations undergone to stratified mass selection for 19 and 25 years) and to those found by [20] (comparing two maize synthetic varieties after two cycles RRS) who found that the genetic differentiation among versions of the same population was very low.…”

“…Of course, a longer breeding period or a different selection method than implemented in this study could have allowed a greater differentiation among populations. For example, as suggested by results of [23], in which the final versions of two maize populations showed low differentiation from the original populations, mass selection resulted less selective than a RRS implemented for a similar period [18]. In addition, in both maize mass and RSS, a long breeding program increased the genetic differentiation among original and final breeding populations [18,49], probably as a consequence of allele fixation [18,50].…”

“…Although several experiences of evolutionary breeding for autogamous species have been reported by different authors [8, 12 and references therein, 45,46], a few EBP have been registered for allogamous species like broccoli [23,47,48].…”

“…were analyzed by using Restriction Fragment Length Polymorphism (RFLP) [17,18], Simple Sequence Repeats (SSR) [19][20][21] and Single Nucleotide Polymorphism (SNP) [22]. SSR were also used in order to evaluate the genetic changes in different maize populations obtained after about 20 years of stratified mass selection on two historical Portuguese populations [23]. Considering autogamous species, the genetic evolution over time and space of wheat composite cross populations (CCP) was assessed by RFLP [24,25] and by SSR [26] and that of a barley CCP by using SSR [13].…”

A method for obtaining flexible broccoli varieties for sustainable agriculture

“…For example, genetic changes in maize composite populations under Reciprocal Recurrent Selection (RRS) were analyzed by using Restriction Fragment Length Polymorphism (RFLP) [17,18], Simple Sequence Repeats (SSR) [19][20][21] and Single Nucleotide Polymorphism (SNP) [22]. SSR were also used in order to evaluate the genetic changes in different maize populations obtained after about 20 years of stratified mass selection on two historical Portuguese populations [23]. Considering autogamous species, the genetic evolution over time and space of wheat CCP was assessed by RFLP [24,25] and by SSR [26] and that of a barley CCP by using SSR [13].…”