**1. Introduction**

Fungal biomass quantification is critical in understanding the interactions between the pathogen and susceptibility or resistance of the host plant in identification and competition in individual species of fungi in diseases progression [1].

The quantification and detection of biomass of fungi in plant host tissues have been conducted using polymerase chain reaction methods [2, 3]. Some authors, Sanzani et al. [2] showed that, the sensitivity of quantitative polymerase chain reaction (qPCR) can be applied to measure infections at very low volumes, thus, corresponding to the quantity of the pathogen that might be present during the latent or time of and or at asymptomatic infections. qPCR also enables the evaluation of stages of infection in plant tissues and the quantification of a fungal pathogen throughout the entire disease cycle [2].

Coninck et al. [1] developed a qPCR assay for detection and quantification of *Cercospora beticola* fungi in leaves of sugar beet. Moreover, Waalwijk and co-workers [4], using a gene involved in fumonisin biosynthesis developed a qPCR assay to quantify and detect fumonisin producing *Fusarium verticillioides* strains from maize obtained from South African subsistence farmers. These results were then compared to the fungal DNA content and with the fumonisin levels of the respective *F. verticillioides* strain. A qPCR assay was also developed by Nicolaisen et al. [5] using Ef1ɑ for quantification and detection of 11 *Fusarium* spp. isolated from field materials associated with wheat and maize. Similarly, Korsman and co-workers [6], demonstrated the use of qPCR assay for detection and quantification of Gray leaf spot disease in maize leaves using cytochrome P450 reductase gene. These studies demonstrated

the potential use of qPCR for detection and quantification of fungal pathogens and for probable selection of resistant plant cultivars in breeding lines. This also helps in understanding the processes involved in infection in a host-pathogen system and providing information on the bioecology [7, 8].

Mayer et al. [9] and Jurado et al. [10] used single copy mycotoxin biosynthetic genes to develop PCR assays for detecting mycotoxigenic fungi. Assay sensitivity increased when ITS1 and ITS2 spacer regions were included as, these regions have sufficient variability to enable discrimination of closely related species in the genus *Aspergillus* [11]. Subsequently, these regions have been successfully used for detection and identification of aflatoxigenic *Aspergillus* spp. [12, 13].

The objective of this study was to develop a sensitive, specific qPCR assay for quantifying *A. flavus* biomass in infected maize tissues. The assay was used to measure, the sensitivity of two dry land African maize lines grown in Kenya KDV1 and GAF4, when infected with an aflatoxigenic isolate (KSM014). Similar studies have been done with other fungal species, but this study is the first where the biomass of *A. flavus* from infected maize was detected and quantified with qPCR. This approach also could be used to discriminate between inbred maize lines that are sensitive or resistant to specific *A. flavus* strains and to help understand the mechanism of the maize defense response to *A. flavus*.
