Journal of Biochemistry International

Barley (Hordeum vulgare L.) is one of the most important food and feed crops in the world, which infested with several insect pests, the main economic pest is aphid which causes direct damage and indirect damage in barley production. The integrated pest management (IPM) programs are requirement to reduce aphids’ damages, by using chemical substances extracts obtained from plants as an alternative to synthetic chemical control for its satisfactory effectiveness in pest control. The insecticidal effect of the aqueous extract of hot pepper and quinoa’s saponin on aphids controlling were evaluated on ten Egyptian barley cultivars to determine their susptability and resistance to aphids’ infestation through studying their agro-phycological behavior for aphids’ infestation under Malawi station, during two growing seasons 2021/2022 and 2022/2023. The results showed that Egyptian   barley cultivar Giza 137 was the lowest infested cultivars with aphids   which had lowest No. of aphids (9.777insects/tiller) with lowest percentage infestation of aphids was 29.638%/plant, lowest cultivars in Chlorophyll content (ChLa &Chl b) with values (4.17 and 1.65 µg ml^-1), with highest values for flavonoids and total phenolic with values were (2.37 and 79.82) and high grain yield was 19.17 ard fad¹. However, the Egyptian barley cultivar Giza 136 was the highest cultivar that infested by high No. of aphids (33.167 insects/tiller) with highest percentage infestation with aphids which was 71.833%/plant, which displayed highest ChLa and ChL b with values (7.54 and 3.04 µg ml^-1), and had lowest values for total flavonoids contents and total phenolic content with values (0.14 and 44.04 mg/g) and had  grain yield was 18.47 ard fad¹  . The low aphids’ infestation cultivars under Malawi station were Giza 123, Giza 133, Giza 134 and Giza 130 which were (35.027, 39.111, 39.388 and 40.834%/plant according their physiological behavior after infestation. The Pearson correlation coefficients showed that high aphid insect infestation had high positive and significantly correlated with cha and ChL b, while had had high negative and significantly correlated with T-phenol and flavonoids The results showed that the first and second principal components accounted 78.3% of the total changeability, which PCA2 clarified 15.3  % of the total variability influenced by T-phenol and flavonoids which placed in the left side (negative) of the horizontal axis according to its negative significant correlations with other characters. Treated barley plants by hot pepper and quinoa extract due to decreasing the aphid’s infestation percentage on all cultivars after spray, the results showed that Giza 136 which was recorded the highest infested percentage 71.87 % was reduce to 35% after treated and also had a significant increasing grain yield of the ten barley cultivars.