Susceptibility Of Grain Amaranth Lines To Hemipteran Bug Infestation In Relation To Stem And Inflorescence Colours, And Seed Coat Type

Abstract

In trials conducted during the first rainy season of two conscutive years (1999 and 2000) to evaluate the relative susceptibility of 28 grain Amaranth lines to shield bug (Hemiptera) attack, three species namely Aspervia armigera F., Nezara viridula L. and Cletus ochraceus Herich-Schaffer were identified to be most important. These species were most abundant and attacked the inflorescence. The occurred of other identified hemiperous bugs was low and sporadic. Observations during the two cropping seasons showed that grain amaranth lines NH84/457-IL (Opaque), NH84215-2 and NH84/463 were outstanding as having low susceptibility to the bugs. Lines highly attacked were NH84/494, ED82/1019A and NH84/445-2. Lines having intermediate susceptibility levels were also observed.
A relationship was established between bug attack and stem pigmentation, inflorescence and seed coat colours. Aspervia armigera, N. viridulla and C. ochraceus attack on the various lines significantly (P<0.01) decreased with the paleness of the plant characteristics (R2 = 0.53, 0.36 and 0.65 respectively).
Keywords: Aspervia armigera, Cletus ochraceus, Grain amaranth, Nezara viridula, Stem pigmentation, Inflorescence colour, Seed coat.