Morphological Characterisation of Safflower (Carthamus tinctorius L.) Genotypes in Relation to Resistance against Aphid (Uroleucon compositae Theobald)

Abstract

The present investigation was conducted during the rabi seasons of 2023-24 and 2024-25 under field conditions to identify morphological traits associated with resistance to the safflower aphid, Uroleucon compositae (Theobald), in safflower (Carthamus tinctorius L.) genotypes. Twenty safflower varieties/genotypes were evaluated in a randomised complete block design with three replications, without adopting plant protection measures. Observations were recorded for quantitative traits, including plant height, days to 50 per cent flowering and days to maturity, and for qualitative traits, including leaf colour, leaf nature, flower colour, plant type and stem nature. Aphid infestation was assessed using foliage drying grade and Aphid Infestation Index. Considerable variation was observed among the tested genotypes for aphid response and morphological characters in both years. Based on pooled resistance classification, fourteen genotypes, namely PBNS 184, PBNS 40, SSF 1371, PBNS 12, PBNS 86, PBNS 154, GMU 4429, GMU 6026, GMU 1765, GMU 1603, GMU 3095, GMU 5032, GMU 3852 and SSF 1565, were categorised as moderately resistant. Four genotypes, namely GMU 1059, GMU 1287, GMU 3929 and GMU 774, were categorised as susceptible, while GMU 2944 and C-4 were highly susceptible. Quantitative traits did not show a consistent association with aphid resistance. In contrast, qualitative traits showed a clearer relationship with resistance behaviour. Moderately resistant genotypes were generally characterised by pale green, shiny and thin leaves, a spiny plant type, and hard and thick stems, whereas susceptible and highly susceptible genotypes generally possessed dark green, leathery thick leaves, succulent stems and predominantly non-spiny plant type. The findings indicate that qualitative morphological traits may be useful selection criteria in breeding programmes aimed at improving safflower resistance to aphids.