How an improved sorghum variety evolves in a traditional seed system in Mali: Effects of farmers’ practices on the maintenance of phenotype and genetic composition

Abstract

A B S T R A C TIn Africa, it is mostly the informal seed system that ensures farmers' seed supply. This is partly because the formal seed systems are not always effective in meeting demand for new seed varieties. Sometimes informal seed recycling and exchange of improved sorghum varieties will take place alongside formal initiatives, as is the case in southern Mali. Focusing on one particular village in the Dioïla district, we analyze the efficacy of farmers' strategies for preserving varietal seed purity and genetic integrity of an improved inbred-line (Soumba variety). Six seed lots of Soumba, recycled for two to six years by farmers using different practices, were collected and assessed in on-station trials in order to compare their agronomic performance and phenotypic purity (off-type plant frequencies) with control versions of the variety. Additionally, 30 panicle samples were randomly collected from five farmer fields sown with recycled Soumba and assessed for phenotypic purity in a progeny nursery and investigated for molecular diversity using 12 SSR markers. A total of 150 panicles from five other non-Soumba varieties were collected in the village in order to investigate eventual gene flow and its potential genetic consequences for the Soumba variety. In fields sown with recycled Soumba seed, between 2% and 14% of plants showed phenotypic deviations from the typical Soumba variety. The progeny nursery and SSR marker analysis verified the presence of the off-type plants observed in the field. The STRUCTURE program revealed admixtures with other varieties in 23% of Soumba plants, confirming the presence of gene flow. Gene diversity values in Soumba samples ranged from 0.006 for the commercial sample to 0.257 for recycled samples. Introgression and contamination were best minimized when (1) farmers had received specific training in seed production, (2) they could take advantage of isolated fields and (3) they could practise true-to-type panicle selection. Farmers were generally able to maintain the phenotype, as well as sustain or even improve yield performance of their Soumba variety while at the same time genetically enriching their seed stock.

Strengthening of the Formal Complementary Paddy Seeding System and Informal to Fulfill Demand of Quality Paddy Seeds and to Develop Seed Farming Business in West Java

“…The relevance of developing an informal paddy seed system is the implementation of the provisions in Other considerations in the development of informal paddy seed systems, are: (1) most of the use / application of paddy seeds by farmers in paddy fields are adhered to by the principles of informal relations that take place with adherence to social capital that has been built and applies for a long time to the local community; (2) the sizable contribution of farmers 'seed networks in the seed delivery shows that they currently serve farmers' needs quite well, and can benefit regarding choice, accessibility, costs, and noneconomic utility (for example, social value); (3) farmers' seed networks can provide quality planting material that is acceptable to farmers [35]; (4) that farmers' networks can maintain morphological characteristics and improved yield varieties for several seasons [36]; (5) farmer networks generally supply materials valued by the farmers, including varieties with traits not produced by formal breeding (such as tolerance of typical local stresses, or certain organoleptic qualities; [37,38] or neglected plants by formal research; (6) there is a plenty of room to improve quality in farmers networks, because the quality of formal seeds can also be poor due to improper standards or weak enforcement of regulations [39]; (7) The government will not be able to provide all certified paddy seeds or seeds needed by the farmers through the formal sector paddy seed industry, at any time;…”

Towards better metrics and policymaking for seed system development: Insights from Asia's seed industry

“…Similarly, Biemond et al (2013) found that Nigerian farmers' recycled seed was of poor quality but not more so than the seed being produced by public institutes such that neither passed the National Agriculture Seed Council's standards for certified seed. Deu et al (2014) have found that with proper training in seed production, farmers are generally able to maintain the phenotype of their varieties and minimize off-type plants.…”

Past and present dynamics of sorghum and pearl millet diversity in Mount Kenya region

“…Similar genetic differences among sorghum varieties on a local scale were described in many studies, resulting from limited pollen-mediated gene flow combined to farmers' conservative selection practices. For instance, genetic differences were found in northern Cameroon between varieties grown on a village scale (Barnaud et al, 2007), and limited creolization was observed by Rabbi et al (2010) in western Kenya and eastern Sudan, and by Deu et al (2014) in Mali.…”

“…; Busso et al., ; Robert et al., ; vom Brocke, Christinck, Weltzien, Presterl, & Geiger, ). On the contrary, for the mostly self‐pollinating sorghum ( Sorghum bicolor (L.) Moench), restricted cross‐pollination among varieties preserves their genetic distinctiveness on a local scale (Barnaud, Deu, Garine, McKey, & Joly, ), although admixture among varieties may occur (Deu et al., ).…”