Interaction of seed coat color and seed hardness: An effective relationship which can be exploited to enhance resistance to the safflower fly (Acanthiophilus helianthi) in Carthamus spp.

Soraya Karami, Mohammad R. Sabzalian*, Mehdi Rahimmalek, Ghodratollah Saeidi,
Sareh Ghasemi,. 2017. Crop Protection.98 (2017) 267-275.

Abstract:

A choice test study was conducted in the field from 2014 to 2016 to determine the mechanism(s)
involved in resistance to the safflower fly (Acanthiophilus helianthi, Diptera, Tephritidae) in germplasm of
the wild safflower species with pigmented (Carthamus oxyacanthus, C. lanatus, and C. glaucus) and white
(C. palaestinus) seed coats, some white-seeded cultivated genotypes, and a novel breeding line (A82) with
black seeds obtained through interspecific hybridization of C. tinctorius
C. oxyacanthus. The choice test
in 2014 revealed the significantly higher values of infested heads per plant and seed yield loss per plant
of the white-seeded cultivated safflower (26.3e48.7% and 37.3e73.2%, respectively) compared with
those recorded for the color-seeded wild accessions (3.0e10.9% and 3.8e11.4%, respectively) and line A82
(15.9% and 19.3%, respectively). Similar results were obtained in the two consecutive years of 2015 and
2016 as the black seed coated genotype A82 exhibited significantly lower seed loss per head and seed
yield loss per plant than the other four cultivated genotypes. The highly significant correlations found
between resistance to the safflower fly and each of the two parameters of seed hardness and seed coat
color indicated that these latter parameters strongly affected plant response to the safflower fly; that is,
harder seeds with darker seed coat colors made greater contributions to plant's resistance against the
safflower fly while the white-seeded lines were generally found to be more susceptible to the fly. In
short, the color-seeded wild species and the black-seeded line A82 exhibited a higher resistance while
the white-seeded cultivars showed little or no resistance at all. Scanning electron microscopy was also
used to investigate the morphological differences in seed coat among the color-seeded wild genotypes,
black-seeded line A82 (resistant), and white-seeded cultivars (susceptible). The color-seeded genotypes
and the white-seeded cultivars exhibited differences in their seed coat surface structure and thickness,
suggesting that morphological structure and seed coat color concomitantly contribute to the fly resistance
in some safflower genotypes. Based on the results obtained, genotype A82 may be suggested as a
preferable and superior genotype for cultivation in areas under infestation by the safflower fly.

Key words: Carthamus spp
Safflower fly
Seed coat color
Seed hardness
Resistance
Scanning electron microscopy