Breeding spring wheat for improved allelopathic potential

Abstract

It is becoming apparent that allelopathy plays a significant role in the competitive ability of cereals against weeds; barley, wheat and rice cultivars with high allelopathic activity have been identified. However, direct breeding efforts to improve allelopathy have to date only been reported in rice. In this study, a breeding programme in spring wheat (Triticum aestivum) was evaluated to determine the efficiency of selection of allelopathy and the ability of breeding lines to suppress weeds in the field. The material used originated from a cross between a Swedish cultivar with low allelopathic activity and a Tunisian cultivar with high allelopathic activity. Allelopathic activity was measured as growth inhibition of perennial ryegrass (Lolium perenne) roots when grown together with the wheat cultivars on agar. For screening of F 2 populations, a single plant bioassay was used for the first time. In the F 6 and F 7 generations, three breeding lines with an average improved allelop-athy of 20% and one line with an unimproved allelopathy activity, but with the same phenotype as the high allelopathic lines, were tested together with the low allelopathic Swedish parent. The main result from the field study was a 19% average reduction of weed biomass for the high allelopathic lines, but no significant reduction of the low allelopathic breeding line. Early shoot length and early crop biomass (stages 37-39, Zadoks scale) and straw length of the high allelopathic lines were not significantly different from the Swedish parent. A negative effect was that grain yield was reduced by 9% in the high allelopathic lines. It is suggested that the reduced biomass of weeds in plots planted with the highly allelopathic wheat lines is related to differences in allelopathic activity and not differences in plant growth.

Research on the allelopathic potential of wheat

“…If early vigour is also improved to the level of triticale, weed biomass could be reduced by 40% -60%. In spring wheat, an improvement of PAAr by 20% resulted in an average reduction in weed biomass of four near isogenic breeding lines by 19% [41]. Some of the wheat-rye substitution lines showed a PAA value as high as 63%.…”

Breeding of commercially acceptable allelopathic rice cultivars in China

“…However, any increase in weed suppression by breeding is likely to impair grain yield and subsequently rice productivity. Although a certain yield reduction may be accepted if weed competitive ability is improved sufficiently to reduce other weed management options,29 the relationship between grain yield and weed suppression needs to be identified under field conditions. This study reports on crosses between allelopathic rice PI312777 and commercial Chinese cultivars (N2S, N9S, Huahui354, Peiai64S and Tehuazhan35) to develop commercially acceptable allelopathic rice cultivars using traditional breeding methods.…”

Plant breeding for organic agriculture: something new?

“…Weed competitiveness and the ability to establish symbiont relations with micro-organisms in the soil are relevant for OF because they can enhance the uptake of resources and its use efficiency [27,29]. Research has shown that there exists genetic variation for weed competitiveness in cereals [30][31][32][33], and that early vigor and allelopathy can be useful traits to enhance weed suppression [30,34].…”