Assessed Line by Tester Analysis of Maize Inbreds for Northern Leaf Blight and Other Yield Components in Selected Counties, Kenya

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Ndung’u, Ferista Wanjiku
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Kenyatta University
Northern Leaf Blight (NLB) also known as Turcicum Leaf Blight (TLB) is a foliar disease of maize caused by Exserohilum turcicum. It is a great challenge in many maize production regions worldwide. It has a growing season characteristic of high humidity and moderate temperatures ranging from 17-270C. The disease can result to great yield losses in maize ranging at 40-70% in the case where there is disease presence 2-3 weeks after the crop silks. The main aim of this study was to assess the combining ability of the maize lines to NLB and other yield related traits, to determine the heterotic orientation of the lines and to establish the yield potential of the crosses across different environments. The lines were introductions and the study was aimed to determine the performance of the lines prior to further development. Forty nine lines used in the study were obtained from a segregating population in the F4 were crossed to two CIMMYT testers Tester A (CML312/CML442) and Tester B (CML395/CML444). The 98 crosses were planted in 3 mid-altitude agro-ecological zones of Kenya (Kakamega, Muranga and Embu). The heterotic orientation was determined for the lines and that differed across the 3 sites. The 3 sites were treated as independent environments due to genotype x environment interactions. Data was analyzed using REML, META-R and AGD-R tools. The results indicated significant GCA and SCA of some of the lines to NLB and different yield related traits including AD (days to anthesis) and SD (days to silking). The lines expressing significant GCA and SCA for NLB tolerance and high yield, the lines are recommended for further testing and development of NLB tolerant and high yielding maize hybrids in the mid-altitude agro-ecological zones of Kenya. The lines will recommended for use in breeding following further segregation hence could be used to develop hybrids that could be further subjected to trialing to obtain hybrids that are resistant to NLB, early maturing and high yielding. For the lines that could not be classified to their heterotic groups using Tester A and Tester B, these could be subjected to further tests with different testers in order to determine their heterotic groups and the knowledge could later be used in development of crosses.
A thesis Submitted in Partial Fulfillment of the Requirement for the Award of a Degree in Master of Science in Plant Breeding in the School of Agriculture and Enterprise Development, Kenyatta University, January, 2021
Assessed Line, Tester Analysis, Maize Inbreds, Northern Leaf Blight, Other Yield Components, Selected Counties, Kenya