QTL Mapping of Traits Associated with Dual Resistance to the African Stem Borer (Busseola fusca) and Spotted Stem Borer (Chilo partellus) in Sorghum (Sorghum bicolor).

Phyllis W Muturi,James K Mwololo,Patrick Rubaihayo,Mary Mgonja

doi:10.1155/2021/7016712

Phyllis W Muturi, James K Mwololo + Show 2 more

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https://doi.org/10.1155/2021/7016712

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Abstract

Sorghum (Sorghum bicolor (L.) Moench) is an important food crop in semi-arid tropics. The crop grain yield ranges from 0.5 t/ha to 0.8 t/ha compared to potential yields of 10 t/ha. The African stem borer Busseola fusca Fuller (Noctuidae) and the spotted stem borer Chilo partellus Swinhoe (Crambidae), are among the most economically important insect pests of sorghum. The two borers can cause 15% - 80% grain yield loss in sorghum. Mapping of QTLs associated with resistance traits to the two stem borers is important towards marker-assisted breeding. The objective of this study was to map QTLs associated with resistance traits to B. fusca and C. partellus in sorghum. 243 F9:10 sorghum RILs derived from ICSV 745 (S) and PB 15520-1 (R) were selected for the study with 4,955 SNP markers. The RILs were evaluated in three sites. Data was collected on leaf feeding, deadheart, exit holes, stem tunnels, leaf toughness, seedling vigour, bloom waxiness, and leaf glossiness. ANOVA for all the traits was done using Genstat statistical software. Insect damage traits and morphological traits were correlated using Pearson's correlation coefficients. Genetic mapping was done using JoinMap 4 software, while QTL analysis was done using PLABQTL software. A likelihood odds ratio (LOD) score of 3.0 was used to declare linkage. Joint analyses across borer species and sites revealed 4 QTLs controlling deadheart formation; 6 controlling leaf feeding damage; 5 controlling exit holes and stem tunneling damages; 2 controlling bloom waxiness, leaf glossiness, and seedling vigour; 4 conditioning trichome density; and 6 conditioning leaf toughness. Joint analyses for B. fusca and C. partellus further revealed that marker CS132-2 colocalised for leaf toughness and stem tunneling traits on QTLs 1 and 2, respectively; thus, the two traits can be improved using the same linked marker. This study recommended further studies to identify gene(s) underlying the mapped QTLs.

Highlights

Sorghum (Sorghum bicolor (L.) Moench) is an important food crop in drought prone areas in the tropics
The combined results for the two borer species suggested that plant damage and agro-morphological traits evaluated in this study were influenced significantly (P < 0:01) by borer species tested, genotype, and the environment where the experiment was conducted (Table 1)
Heritability estimates for deadheart formation, leaf feeding damage, exit holes, stem tunneling, bloom waxiness, and seedling vigour tested for B. fusca at Embu and Kabete were low to high and ranged between 0.21 and 0.65

Summary

Introduction

Sorghum (Sorghum bicolor (L.) Moench) is an important food crop in drought prone areas in the tropics. The African stem borer, Busseola fusca Fuller (Noctuidae) and the spotted stem borer Chilo partellus Swinhoe (Crambidae), are among the most economically important insect pests of sorghum and maize in Eastern and South Africa [3]. Stem borers are associated with grain yield loss of 15% - 80% depending on borer species population and variety phenological stage at the time of attack [4]. Management approaches such as cultural practices and use of synthetic chemical pesticides have

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