ABSTRACT
Pink stem borer, Sesamia inferens (Walker, 1856) (Lepidoptera: Noctuidae) is reported to infest many graminaceous crops and cause significant losses. S. inferens cause damage by killing the central shoot and producing a characteristic symptom called "dead heart". Since graminaceous crops are an important source of food for humans and their livestock, impetus should be given on designing efficient management strategies against pink stem borer. The study of genetic variability of pest populations enables to interpret the ecological investigations correctly and also helps to comprehend the dissimilar response of pest to management tactics. The present study was undertaken to evaluate the diversity in S. inferens populations using mitochondrial cytochrome oxidase subunit I sequences from India, Pakistan, China and Indonesia. Analysis revealed a very low nucleotide diversity in Indian populations (π = 0.00981), as compared to a high nucleotide diversity in the sequences outside India (π = 0.4989). The phylogenetic analysis also did not show any clustering among populations within India and Pakistan. However, the nearest neighbour for the Indian and Pakistan population is a sequence from Indonesia followed by China indicating possible ancestral background. This is the maiden attempt to assess the molecular diversity of Indian populations in comparison to populations from other Asian countries. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02678-y.
ABSTRACT
Shoot fly (Atherigona naqvii) is one of the major insects affecting spring maize in North India and can cause yield loss up to 60 per cent. The genetics of insect resistance is complex as influenced by genotypic background, insect population and climatic conditions. Therefore, quantitative trait loci (QTL) mapping is a highly effective approach for studying genetically complex forms of insect resistance. The objective of the present study was to dissect the genetic basis of resistance and identification of genomic regions associated with shoot fly resistance. A total of 107 F2 population derived from the cross CM143 (resistant) x CM144 (susceptible) was genotyped with 120 SSR markers. Phenotypic data were recorded on replicated F2:3 progenies for various component traits imparting resistance to shoot fly at different time intervals. Resistance to shoot fly was observed to be under polygenic control as evidenced by the identification of 19 putative QTLs governed by overdominance to partial dominance and additive gene actions. The major QTLs conditioning shoot fly resistance viz., qDH9.1 (deadheart) and qEC9.1 (oviposition) explaining 15.03 and 18.89 per cent phenotypic variance, respectively were colocalized on chromosome 9. These QTLs are syntenic to regions of chromosome 10 of sorghum which were also accounted for deadheart and oviposition suggesting that the same gene block may be responsible for shoot fly resistance. The candidate genes such as cysteine protease, subtilisin-chymotrypsin inhibitor, cytochrome P450 involved in synthesis of alleochemicals, receptor kinases, glossy15 and ubiquitin-proteasome degradation pathway were identified within the predicted QTL regions. This is the first reported mapping of QTLs conferring resistance to shoot fly in maize, and the markers identified here will be a valuable resource for developing elite maize cultivars with resistance to shoot fly.
