Morphological identification of the ryegrass hybrid<i>Lolium multiflorum</i>×<i>Lolium perenne</i>and isolation of the pathogen<i>Fusarium pseudograminearum</i>in the Western Cape

Abstract

Weed resistance to herbicides present one of the greatest current economic challenges to agriculture. Herbicide&#13;\nresistant ryegrass (Lolium spp.) is a serious problem in Western Cape grain-producing areas. Morphological and&#13;\npathogenic analyses were performed on ryegrass samples. Morphologically, 50% of specimens were classified&#13;\nas rigid ryegrass, 48% as a hybrid, namely L. multiflorum  L. perenne and 2% as perennial ryegrass. Fusarium&#13;\npseudograminearum (cause of Fusarium crown rot) was isolated from six localities. Pathogencity tests confirmed&#13;\nthat F. pseudograminearum isolates obtained from ryegrass and wheat are pathogenic on both crops, indicating&#13;\nthat ryegrass can act as an alternative host and a source of inoculum of this important soilborne pathogen. Grass&#13;\nweed infestation can favour the disease, and grass weed control is therefore recommended as part of an integrated&#13;\nstrategy to manage crown rot. Knowledge on morphological differences among ryegrass may be important to guide&#13;\ndifferential weed management of ryegrass. Smother cropping, as part of conservation farming, should receive more&#13;\nprominence to suppress herbicide-resistant ryegrass and simultaneously reduce the occurrence of crown rot.