Response of Selected Maize Inbred Germplasm to Maize Lethal Necrosis Disease and Its Causative Viruses (Sugarcane Mosaic Virus and Maize Chlorotic Mottle Virus) in Kenya

Abstract

Background:Maize lethal necrosis (MLN) disease continues to reduce the productivity of maize drastically threatening food security in the affected regions. It continues to cause yield loss of 30-100 percent in farmers' fields, depending on the time of infestation which is valued at $198 million in Kenya. This has not only threatened regional trade, but also seed industry. It has been reported in the major maize belts of Uasin Gishu, Trans-Nzoia, Bomet, Narok and Nandi Counties. MLN is caused by the synergistic interaction between Sugarcane Mosaic Virus (SCMV) and Maize Chlorotic Mottle Virus (MCMV). The disease has then spread to other Eastern and Central African countries with devastating food security and economic consequences. Objectives:This study highlights result after screening selected maize inbred lines for resistance to MLN, SCMV and MCMV in identifying promising lines for integration into the breeding program for MLN resistance. Methods:Sixty-five (65) maize genotypes were artificially inoculated using virus strains collected from Bomet County in Kenya at 3-4 leaf stage. Data on disease severity and incidence, AUDPC and flowering were recorded. Results:From the result, the inbred lines had significant differences for SCMV, MCMV and MLN reactions. Based on Area Under Disease Progress Curve (AUDPC) score and ELISA analysis, genotypes MLN001 and MLN006 have the lowest score of 270, whereas OH28 had a maximum at 1259 under MCMV. Genotypes MLN042 and MLN041 were identified as the most promising sources of resistant against SCMV. However, no genotype was identified to have acceptable levels of tolerance to MLN, but MLN001 and MLN013 were identified as the best performers under MLN. This study also validated the presence of MLN tolerance in MLN013 (CKDHL120312) and MLN001 (CKDHL120918) as earlier reported by CIMMYT. These tolerant genotypes are now serving as donors in the introgression of the tolerance into the Kenyan adapted maize backgrounds and development of improved MLN tolerant varieties. This will go a long way in restoring and ensuring sustainable maize productivity in improving the livelihoods of the smallholder farmers who form 75% of the major maize producers in Kenya.The identified inbred lines would be recommended for use in varietal development, MLN management and to enhance maize productivity, in the MLN endemic regions and further research in understanding the mode of gene action for MLN tolerance.

Factors Affecting Yield of Crops

“…It is caused by the synergistic interaction between Sugarcane Mosaic Virus (SCMV) and Maize Chlorotic Mottle Virus (MCMV). It causes yield reduction ranging from 30 to 100% in farmers' fields depending on the time of infestation [44]. MLN is transmitted by beetles, rootworms, thrips, stem borers, several species of aphids in non-persistent manner, infected soil, infected seeds and any tools or materials used in the infected field [45].…”

Genotype by environment interaction (GEI) of maize varieties resistant to maize lethal necrosis for mid altitudes of Rwanda

“…The AUDPC and its derivative rAUDPC, and the standardized AUDPC noted sAUDPC (Simko and Piepho 2012) have been used to correctly measure the level of susceptibility to diseases in various crops (Mukherjee et al 2010;Forbes et al 2014;Kebede and Golla 2020) including MLN (Karanja et al 2018).…”

“…They have been found to be specifically useful in the identification of MLN-resistant maize germplasm (Karanja et al 2018;Nyaga et al 2020).…”

Status of maize lethal necrosis disease in seed production system in Kenya

“…Out of the eight varieties observed, only two maize varieties, namely, DH04 and Duma 43, were not affected by MLN-causing viruses based on the absence of symptoms and laboratory confirmation. The absence of incidence and severity of diseases in DUMA 43 and DH 04 could be due to an effective production management approach as most Kenyan varieties are susceptible to MLN disease (Karanja et al, 2019). Previous studies by Zambrano et al (2014) have also reported the presence in the potyviridae family of some resistance to several viruses.…”