Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Williams, W. Paul

Committee Member

Smith, Jesse

Committee Member

Baldwin, Brian

Committee Member

Shan, Xueyan

Committee Member

Tiwari, Khusi

Other Advisors or Committee Members

Warburton, Marilyn Louise

Date of Degree

8-7-2020

Document Type

Dissertation - Open Access

Major

Agronomy

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Maize, Zea mays L., is the largest cereal grain crop grown in United States. Its yield and grain quality are adversely impacted by diseases every year. Aspergillus ear rot, caused by the fungus Aspergillus flavus, received little interest until its carcinogenic secondary metabolites, aflatoxins, were discovered. The objectives of this study were to introgress the quantitative trait loci (QTL) 2.04 from Mp313E and 5.03 from Mp715 into two commercial inbred lines, MonF and MonM; and evaluate their near isogenic lines (NILs) and testcrosses for preharvest aflatoxin accumulation and secondary agronomic traits. Marker assisted selection to create NILs and the testcross production was conducted by Bayer Company between 2015 and 2018. Field trials were conducted in summer 2019 as randomized complete block trials at three locations. The entry list of inbred trials included two donor parents (DP), two recurrent parents (RP), and their 58 NILs, and that of hybrid trials included 114 NIL testcrosses and 8 parental testcrosses. The top ear of each plant in every plot was inoculated with a 3.4 ml of A.flavus conidial suspension 13 days after mid-silk. All the inoculated ears were harvested at maturity, dried, machine shelled, ground, and aflatoxin concentration was determined by plot. Separate hybrid yield trials were conducted in four locations to measure the grain yield including an additional commercial check. Data on aflatoxin and other secondary traits was analyzed using SAS software. Overall, MonF NILs improved significantly more than MonM NILs in terms of their resistance to aflatoxin accumulation with the introgression of QTL 2.04 from Mp313E, but there were no differences with the introgression of QTL 5.03 from Mp715. Overall, Mp313E NILs improved more than Mp715 NILs when the recurrent parent was MonF, but the response was opposite when the recurrent parent was MonM. Compared to their respective recurrent parents, there were at least two NILs from each of the three out of four RP x DP crosses that significantly improved their resistance to aflatoxin accumulation with a minimal loss of their agronomic performance and testcross grain yields. These NILs could be considered as parents in future introgression projects.

URI

https://hdl.handle.net/11668/18003

Comments

Introgression||Maize||Aflatoxin||Near Isogenic Lines||Testcrosses||Mp313E||Mp715

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