Uma RaoZirwal Yogiraj Namdeo2017-06-122017-06-122014http://krishikosh.egranth.ac.in/handle/1/5810019523t-9026Root knot nematodes (Meloidogyne species) are the most economically important group of plant parasitic nematodes worldwide attacking nearly more than 2000 host plants. The inadequacy and limitations of current control measures demand the development and designing of novel management strategies. The most cost effective and sustainable method for combating their damage is to develop resistant plants that suppress nematode development and reproduction. Recent developments in the sequencing of several eukaryotes including M. incognita and other plant parasitic nematodes provide an invaluable wealth of potential target gene sequences that can be used for disrupting the nematode life cycle which in turn can help in their management. RNA interference (RNAi) has proved to be a very promising tool for understanding the role of these genes in the nematode physiology and pathogenesis so that they could be the possible targets for designing nematode resistant crops. The FMRFamide-like peptides (FLPs) are the most diverse and widely studied group of nematode neuropeptides. FLPs play a significant role in the nematode nervous system as a neurotransmitters or neuromodulators and proposed to be one of the important targets. The present study was undertaken to examine the stability of transgenic brinjal expressing dsRNA of flp-18 against different population densities of M. incognita. T1 plants of transgenic brinjal carrying a single copy of flp-18 were challenged with 1, 2, 4 and 8 second stage juveniles per gram of soil along with wild type for comparison. Bioefficacy studies performed revealed 40–70% reduction in host invasion compared to wild type plants. Likewise, reproduction and multiplication was also reduced considerably by 41–50 and 60- 75% respectively irrespective of the population density. Molecular analyses by PCR and qRT-PCR of the T1 transgenic plants used in the bioefficacy confirmed both for the presence of transgene and its expression. Comparison of total proteins of transgenic and wild type plants did not show any difference. This is a pioneer study to demonstrate the performance of host delivered RNAi based transgenics against various population densities. Generally, nematode populations under field conditions are not evenly distributed and quite variable. The population density in given field could be either at economic threshold level or ii below or above these levels (i.e. under ETL, ETL and above ETL). In view of this, the present study suggests that transgenic brinjal plants expressing dsRNA of flp-18 gene could provide stable resistance to M. incognita at various population densities. It may prove promising for the management of M. incognita under field conditions with varying population densities.en-USnullThesis