Temporal Dynamics of Enhanced Host Susceptible (EHS) Phase in Resistant and Susceptible Brassica juncea Accessions to Myzus persicae Infestation

Aim: To establish a standardised enhanced host susceptible (EHS) phase in resistant and susceptible genotypes based on aphid proliferation dynamics in Brassica juncea accessions infested with Myzus persicae. Study Design: Six replications per accession were used in a completely randomised design (CRD) in a controlled plant growth chamber. Place and Duration of Study: Performed at College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University (Imphal) School of Crop Improvement in Umiam, Meghalaya during, 2024. Methodology: Twenty Myzus persicae aphids per plant were infested on eight Brassica juncea accessions (four resistant and four susceptible) at 21 day seeding stage. For 60 hours, the number of aphids were counted every 12 hours. When a statistically significant increase in the aphid population was observed and it was referred to as the EHS phase. Results: Aphid populations in susceptible accessions (IC 491136, IC 491173, IC 491037, EC 400082) reached up to 75.3 after exhibiting an early EHS onset at 24 hours. While Pusa Mahak has shown the highest level of resistance with EHS onset at 48 hours, resistant accessions (PM 30, PBR 91, CS 2005 138) had delayed EHS at 36 hours. Aphid growth rates in resistant and susceptible lines differed statistically significant. Conclusion: The optimised EHS timing assay provides a quick and accurate way to test for aphid resistance by successfully differentiating between resistant and susceptible B. juncea accessions. Aphid-resistant mustard breeding efforts can benefit greatly from the identified resistant accessions, especially Pusa Mahak.