Field Inoculation and Classification of Maize Ear Rot Caused by Fusarium verticillioides

Background

Maize ear rot is a fungus-induced ear disease that occurs widely in Europe, America, Africa, Asia and Oceania (Desjardins et al., 2000; Pamphile and Azevedo, 2002; Hussain et al., 2005; Anjorin et al., 2008; Görtz et al., 2008; Rahjoo et al., 2008; Dorn et al., 2009; Eckard et al., 2011; Scauflaire et al., 2011; Madania et al., 2013). In 1977, maize ear rot swept through the state of Meghalaya, India. In 1988, maize ear rot was prevalent in the USA, and became a key biological control factor in maize production of African, resulting in a 48% reduction in maize yield (Vigier et al., 2001). Moreover, the infected maize ears also produced mycotoxins such as fumonisin and deoxynivalenol, which seriously threatened human and animals’ health (Gelderblom et al., 1988; Wild and Turner, 2002; Zhou et al., 2010).

At present, it is generally and internationally considered that Fusarium is the main pathogen causing ear rot in maize. However, different countries or different regions of the same country may have different types of pathogens, and the dominant pathogen may also be different in different regions. The dominant pathogen is Fusarium graminearum in the USA, Austria and Germany (Schaafsma et al., 1997; Goertz et al., 2010; Mesterházy et al., 2012), but Fusarium verticillioides in France, South Africa, Croatia, Iran, Argentina, Brazil and China (Presello et al., 2004; Aliakbari et al., 2007; Ivić et al., 2008; Folcher et al., 2010; Small et al., 2012; Stumpf et al., 2013; Qin et al., 2014). No matter what the pathogen is, it is very important to have an effective artificial inoculating method in order to get the accuracy resistance evaluation.

To date, a total of four inoculation methods were reported in publications, silk channel injection method, silk spray method, prick ear method and toothpick method. A large number of maize germplasms with resistance to maize ear rot were screened by prick ear method and the genetic basis of the resistance were elucidated in our previous study (Chen et al., 2002; Dong et al., 2006; Li et al., 2008; Sun, 2009; Chen, 2012; Li, 2012; Wang et al., 2016). This method that can easily control the inoculation dose together with the suitable inoculation time can accurately reflect the underlying resistance in the maize materials.