**8. Screening of rootstocks for the Mi gene using molecular markers**

The resistance offered by plants to the damage caused by root-knot nematodes have been well researched and attributed to the presence of a single dominant gene (Mi gene). The Mi gene confers resistance to various root-knot nematode species (*M. incognita*, *M. javanica,* and *M. arenaria*) in addition to whiteflies and aphids [46]. *Solanum* spp., for example, *Lycopersicon peruvianum* and *S. torvum* have been reported to have this resistant gene, which enables the plant to tolerate the feeding activities and the reproductive abilities of root-knot nematodes [47]. The Mi gene was first discovered in an accession of a wild *L. peruvianum* in South America from which commercial F1 varieties were introgressed with the gene [48]. This process involves the extraction and detection of the gene using DNA markers and subsequent isolation of the gene for introgression. In other related research conducted using the positional cloning approach to isolate gene with linked traits and the subsequent sequencing of the DNA, Kaloshian et al*.* [49] reported that the sequencing analysis showed two genes, which were identical to each other (Mi-1.1 and Mi-1.2), which also confers resistance to three species of root-knot nematodes namely *M. arenaria, M. javanica,* and *M. incognita.*

**Author details**

Legon, Ghana

**References**

251-260

02.012

Seloame Tatu Nyaku1,2\* and Naalamle Amissah1,2

DOI: 10.1016/j.scienta.2010.09.023

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verticilium wilt of eggplant. Hortscience. 2003;**38**:183-186

\*Address all correspondence to: seloame.nyaku@gmail.com

Sciences (CBAS), University of Ghana (UG), Legon, Ghana

1 Department of Crop Science, College of Basic and Applied Sciences, University of Ghana,

Grafting: An Effective Strategy for Nematode Management in Tomato Genotypes

http://dx.doi.org/10.5772/intechopen.82774

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[8] Schwarz D, Rouphael Y, Colla G, Venema JH. Grafting as a tool to improve tolerance of vegetables to abiotic stresses: Thermal stress, water stress and organic pollutants.

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2 West Africa Centre for Crop Improvement (WACCI), College of Basic and Applied

Several DNA markers have been developed for the detection of the Mi gene in plants using polymerase chain reaction (PCR) amplifications. Devran et al. [50] screened for the Mi gene using gene specific primers C1/2 (5′-cagtgaagtggaagtgatga-3′) and C2S4 (5′-ctaagaggaatctcatcacagg-3′) for screening F2 tomato plants for the root-knot nematode resistance gene. A 1.6 kb amplification product was amplified in these containing the Mi-1.2 gene in the 3′ region; however, it was found to be absent in the susceptible F2 plants.

Similarly, in another study, the Mi-1.2 gene was introgressed into *S. melongena* to confer resistance to *M. javanica* and aphids. The study revealed that the transgenic eggplant was able to confer resistance to *M. javanica* but not aphids [51]. In confirming the presence of the Mi-1.2 gene in the transgenic eggplant, a reverse-transcription polymerase chain reaction assay with the Mi specific primers C2D1 (5′-ctagaa agtctgtttgtgtctaacaaagg-3′) and C2S4 (5′-ctaagaggaatctcatcacagg-3′) amplified a single PCR band of 915 bp, which was present but absent in the nontransgenic *S. melongena.*

A study in Morocco by Mehrach et al*.* [52] to detect the Mi-1.2 gene in 14 begomovirus-resistant breeding lines with known resistance was also undertaken using a two-step PCR approach. The primer pairs PM3Fb/PM3Rb and REX primers used in a multiplex PCR amplified a band of 720 bp for both susceptible and resistant varieties; however, the resistant varieties (Motelle and Better Boy) showed an additional band of 500 bp, indicating the presence of the Mi gene in those cultivars.

In distinguishing between heterozygous and homozygous plant cultivars with the Mi-1.2 gene, the primer pairs of PMiF3/PMiR3 amplified a single unique band of 350 bp for the susceptible cultivars (Moneymaker and Daniella). However, 550 and 350 bp fragments for both the homozygous and heterozygous plant resistant cultivars "Motelle" and "Better Boy" were amplified, respectively.
