Abstract:

The risk of exposure to aflatoxin in tropical agricultural systems is high due to factors
that favour fungal growth and toxin production. Maize is among the staple crops with
high aflatoxin contamination in Uganda. An understanding of host, pathogen and
resistance to infection facilitates the development of germplasm with elevated
resistance to infection. The objective of the study was to contribute to maize ear rots
management and the associated mycotoxins through host resistance. A various levelled
testing method was utilized to haphazardly collect 247 diseased maize cob samples in
maize fields in 16 districts for aflatoxin quantification and Aspergillus flavus isolations
and characterization. Also, 25 SSR markers were used to fingerprint 41 inbred lines to
determine genetic diversity and their relationship, 35 lines were used to evaluate
aflatoxin accumulation using High-Performance Liquid Chromatography and 19 inbred
lines generated 90 F1 using North Carolina Design II mating scheme to understand the
gene action controlling kernel infection resistance by Aspergillus flavus and also to
estimate additive and dominance genetic variances. Results showed significant
differences among areas of study for A. flavus incidence and severity. Utmost incidence
and severity of Aspergillus flavus was recorded in Pallisa (74.2% and 4.8, respectively).
Among agro-ecological zones, the utmost incidence and severity of Aspergillus flavus
were in the eastern region at 62.4% and 4.6% respectively. At all the loci, 184 alleles
were recorded with an average of 7.36 and a range: 2-19. The gene diversity average
was 0.65 and ranged from 0.18 to 0.92. Percentage heterozygosity was 4% on average
and ranged from 0.0% to 2.0%. Average polymorphism information content recorded
was 0.61. In understanding the inheritance of resistance to kernel infection: The environment plus, Year x Environmental interaction was significantly high (P < 0.001) for percent kernel infection at 7 days after inoculation, percent kernel infection at 14 days
after inoculation, percent kernel infection at 21 days after inoculation, mean percent
kernel infection and Kernel texture. Inbred parents WL 118-3, WL 429-18, WL 429-14,
combiners for Aspergillus ear rot while inbred CML247 and WL118-10 emerged as best
combiners for aflatoxin accumulation. The non-additive effects were slightly greater than
additive genetic effects for percent kernel infection and aflatoxin accumulation. Maize
Inbred lines with good general combining ability effects for resistance to Aspergillus
flavus kernel infection and aflatoxin accumulation save as good candidates to use in
breeding resistant varieties. These results provide information on Aspergillus flavus
strain prevalence and distribution in maize growing agro-ecological zones. It’s prudent
standard bureau to observe levels of aflatoxin in grain to set up legitimate aflatoxin
administration rules. Results from kernel screening of material show that significant
reduction in grain damage can be enhanced through host plant resistance by
hybridization with resistant parents; therefore the materials eye marked in the study
provides candidates for breeding for resistance to Aspergillus flavus.