Genetic Diversity and Combining Ability of White Maize Inbred Lines under Different Plant Densities

Mohamed M Kamara; Medhat Rehan; Khaled M Ibrahim; Abdullah S Alsohim; Mohsen M Elsharkawy; Ahmed M S Kheir; Emad M Hafez; Mohamed A El-Esawi

doi:10.3390/plants9091140

Genetic Diversity and Combining Ability of White Maize Inbred Lines under Different Plant Densities

Plants (Basel). 2020 Sep 3;9(9):1140. doi: 10.3390/plants9091140.

Authors

Mohamed M Kamara¹, Medhat Rehan^{2

3}, Khaled M Ibrahim⁴, Abdullah S Alsohim³, Mohsen M Elsharkawy⁵, Ahmed M S Kheir⁶, Emad M Hafez¹, Mohamed A El-Esawi⁷

Affiliations

¹ Department of Agronomy, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
² Department of Genetics, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
³ Department of Plant Production and Protection, College of Agriculture and Veterinary Medicine, Qassim University, Burydah 51452, Saudi Arabia.
⁴ Agronomy Department, Faculty of Agriculture, New Valley University, El-Kharga 72511, Egypt.
⁵ Department of Agricultural Botany, Faculty of Agriculture, Kafrelsheikh University, Kafr Elsheikh 33516, Egypt.
⁶ Soils, Water and Environment Research Institute, Agricultural Research Center, Giza 12112, Egypt.
⁷ Botany Department, Faculty of Science, Tanta University, Tanta 31527, Egypt.

Abstract

Knowledge of combining ability and genetic diversity are important prerequisites for the development of outstanding hybrids that are tolerant to high plant density. This work was carried out to assess general combining ability (GCA) and specific combining ability (SCA), identify promising hybrids, estimate genetic diversity among the inbred lines and correlate genetic distance to hybrid performance and SCA across different plant densities. A total of 28 F₁ hybrids obtained by crossing eight adverse inbred lines (four local and four exotic) were evaluated under three plant densities 59,500 (D1), 71,400 (D2) and 83,300 (D3) plants ha^-1 using spilt plot design with three replications at two locations during 2018 season. Increasing plant density from D1 to D3 significantly decreased leaf angle (LANG), chlorophyll content (CHLC), all ear characteristics and grain yield per plant (GYPP). Contrarily, days to silking (DTS), anthesis-silking interval (ASI), plant height (PLHT), ear height (EHT), and grain yield per hectare (GYPH) were significantly increased. Both additive and non-additive gene actions were involved in the inheritance of all the evaluated traits, but additive gene action was predominant for most traits. Inbred lines L₁, L₂, and L₅ were the best general combiners for increasing grain yield and other desirable traits across research environments. Two hybrids L₂ × L₅ and L₂ × L₈ were found to be good specific combiners for ASI, LANG, GYPP and GYPH. Furthermore, these hybrids are ideal for further testing and promotion for commercialization under high plant density. Genetic distance (GD) among pairs of inbred lines ranged from 0.31 to 0.78, with an average of 0.61. Clustering based on molecular GD has effectively grouped the inbred lines according to their origin. No significant correlation was found between GD and both hybrid performance and SCA for grain yield and other traits and proved to be of no predictive value. Nevertheless, SCA could be used to predict the hybrid performance across all plant densities. Overall, this work presents useful information regarding the inheritance of maize grain yield and other important traits under high plant density.

Keywords: combining ability; density tolerance; gene effects; genetic diversity; maize.