The use of participatory breeding and testing networks in maize varietal development for organic systems

Mujjabi, Christopher

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https://hdl.handle.net/2142/117714 Copy

Description

Title

The use of participatory breeding and testing networks in maize varietal development for organic systems

Author(s)

Mujjabi, Christopher

Issue Date

2022-09-06

Director of Research (if dissertation) or Advisor (if thesis)

Bohn, Martin O

Committee Member(s)

• Ugarte, Carmen M
• Wander, Michelle M

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Organic systems
• ExPVP germplasm
• Participatory breeding programs
• Variety testing networks.

Abstract

The high demand for organic foods has transformed organic agriculture from a niche industry into a well-developed alternative to conventional farming systems. However, regardless of the increase in organic acreage, the current domestic organic food supply does not satisfy the increasing demand, increasing organic food imports. The deficiency in organic produce is created by the failure of organic production systems to meet the demand due to the lack of high-yielding varieties adapted to organic growing conditions. Therefore, organic farmers need a germplasm that is better adapted to the inherent characteristics and challenges of organic cropping systems and breeding programs that address organic growers' traits of interest. Chapter 1 reviews how participatory breeding programs (PBP) can be a potential breeding tool in the U.S. to develop high-yielding crop varieties for organic systems with specific traits of interest for organic growers. The origin of participatory breeding programs (PPB) is discussed, and several examples of successful worldwide PPBs are given. Also, specific pitfalls associated with PPBs, and other decentralized breeding approaches are discussed. Chapter 2 provides the results of a Participatory Variety Testing (PVT) case study conducted with a variety testing network of organic farmers in the Midwest to evaluate the performance of exPVP-derived maize hybrids in organic conditions. The testing network was comprised of a total of eight certified organic farms in Illinois and four farms in Indiana from 2018 to 2020. Agronomic management practices such as crop rotation lengths, cover crop type, planting densities, weed management, and nitrogen sources varied across the participating farms. Each year, the participating farms evaluated a set of eight experimental hybrids developed by four breeding programs with varying breeding objectives using on-farm strip trials. The hybrids were evaluated for grain yield, moisture, test weight, kernel weight, plant height, ear height, protein, starch, and oil content in the grain. In addition, the reliability of each experimental hybrid was estimated as the probability of outperforming the check variety over a broad range of environments. The study showed that experimental hybrids differed significantly across farms for all agronomic performance traits. The grain yield across farms ranged from 1.6 t ha-1 to 14.8 t ha-1, with an average of 9.1 t ha-1 across the three years of the study. The mean protein, starch, and oil content across farms was 8.0%, 69.6%, and 4.0%, respectively. The UIUC hybrids developed from parental inbreds derived from base populations with exPVP background had higher grain yield and starch content than those developed from organic inbreds, whereas higher protein contents distinguished organic hybrids. Reliability estimates showed that UIUC hybrids had an increased probability of 50% of outperforming the commercial organic check across environments, while organic experimental hybrids had lower reliability (below 30%). The farm management practices such as cover crop types, nitrogen source, planting density, and crop rotation length significantly affected hybrids' performance, causing significant genotype-by-environment interactions. Due to the high yield response of the UIUC hybrids under on-farm conditions, the study demonstrates that the Illinois Elite Maize Association Mapping Panel derived from biparental crosses of exPVP inbreds can be a potential source for breeding superior maize hybrids for organic farming systems in the U.S. Corn Belt. However, all experimental hybrids lacked adequate tolerance to high weed pressure and performed poorly in farms with low nitrogen levels. Therefore, identifying and integrating new sources of genetic diversity for these traits would be beneficial for better adaptation to organic systems.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Christopher Mujjabi

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