Identification and differentiation of Orseolia species in Nigeria as revealed by SCAR-PCR analysis

Identification and differentiation of Orseolia species in Nigeria was carried out using SCAR-PCR analysis. Twenty-three insects from 9 localities in Nigeria and three reference insects (Orseolia bonzii, Orseolia nwanzei and Orseolia oryzivora) were analyzed. Out of the 60 SCAR primers screened, only four produced clear amplified DNA fragments at annealing temperature of 55°C that differentiated all the 26 Orseolia species. Cluster analysis revealed two major insect genotypes (OSG-1 and OSG-2). The OSG-1 was further divided into two subgroups (OSG-1a and OSG-1b). Eleven insects were genotyped as OSG-1a, 14 as OSG-1b and one as OSG-2. Only NG1 and NG2 were identical among the insects of OSG-1a genotype. OSG-1b genotype produced two different groups of identical insects. While O. bonzii and O. oryzivora were genotyped as OSG-1b along with other twelve insects, only O. nwanzei was genotyped as OSG-2. OSG-1b genotype constitutes about 54% O. bonzii and O. oryzivora in Nigeria, OSG-2 genotype represents 4% of O. nwanzei in Nigeria while OSG-1a genotype covers 42% of yet unknown Orseolia species in Nigeria. This information would strongly assist breeding programmes aiming at effective development of cultivars with durable resistance to African rice gall midge (AfRGM) in Nigeria.