THE RELATIONSHIP BETWEEN MORPHOLOGIC CHARACTERS AND RUST RESISTANCE IN A CROSS BETWEEN EMMER, (TRITICUM DICOCCUM) AND COMMON WHEAT, (TRITICUM VULGARE)

Abstract

A study of morphologic character in relation to field resistance to black stem rust of wheat (Puccinia graminis tritici, Erikss. & Henn) was made on the cross Vernal (Triticum dicoccum, Schubl.) × Marquis (T. vulgare, Host.). Fifteen morphologic characters were used including spike form, spike compactness, stem hollowness, rachis articulation, rachis width, spikelet adherence, glume adherence, keel sharpness and seed character, all of which are of species differentiating importance. A random group of 276 F2plants showed no strong or moderately strong correlations between rust reaction and other characters: the most significant correlation coefficients ranged from.13 to.27. Between any two morphologic characters no strong relationships were found, the highest correlation coefficient obtained being.37. In the entire F2population of 21,480 plants there were 232 vulgare-like hybrids showing the high rust resistance of Vernal, although Marquis had a fairly uniform infection of moderate severity. All of these hybrids proved, upon laboratory examination, to be of vulgare or near-vulgare type in nearly all characters especially the economically important characters spike form, rachis articulation, spikelet adherence and glume adherence. This study, therefore, demonstrates that high rust resistance can be transferred from dicoccum to a vulgare-type wheat without great difficulty. It is concluded that the attainment of desirable combinations of emmer rust resistance with important morphologic characters of vulgare depends primarily upon having a population of many thousands of individuals from which to select.