THE INHERITANCE OF RUST RESISTANCE: V. THE INHERITANCE OF RESISTANCE TO RACE 15B OF STEM RUST IN TEN VARIETIES OF DURUM WHEAT

Abstract

The inheritance of resistance to race 15B of stem rust was studied in the varieties St. 464, C.I. 7805, Amarai bianco tipo 142 (P.I. 192179), Arabian, Camadi Abdu tipo 103, Rojal de Almeria (P.I. 191194), C.I. 7870, C.I. 7875, C.I. 8133 and Golden Ball. Rust tests were conducted on F2 plants from diallel crosses and on F2 families from back-crosses to the susceptible varieties, Stewart and Nugget. The following genes are present in the varieties:1. Srd2 conditioning a type 1-X reaction and present in St. 464, C.I. 7805, P.I. 192179, C.I. 7870, C.I. 7875 and C.I. 8133.2. Srd4 conditioning a type 2–2+ reaction and present in Arabian, P.I. 191194 and Golden Ball.3. Srd5 conditioning a type 2 reaction and present in the same varieties as Srd2, plus Arabian.4. Srd6 conditioning a type 1−–1 reaction in Camadi.Two of the genes, Srd2 and Srd5, are additive in effect and together condition a type O; to 1− reaction.