Intergenerational assessment of biofumigation on fitness and phenology of Ambrosia artemisiifolia and Abutilon theophrasti

The lethal and sublethal effects of Indian mustard (Brassica juncea L. cv. ‘Caliente 199’) biofumigation on common ragweed (Ambrosia artemisiifolia L.) and velvetleaf (Abutilon theophrasti Medik.) fitness and phenology across generations were studied. First generation (G1) weed seeds were exposed in Petri dish germination test to allelochemicals produced after rehydrating the dried Indian mustard tissues at rates of 0 (control), 3.5 and 7.0 mg cm-2 of dried tissues for A. artemisiifolia and 0 (control), 2.33 and, 3.5 mg cm-2 for A. theophrasti. Surviving germinated G1 seeds were sown in greenhouse for phenological surveys and reproduction component measurements. The same treatments were applied to G2 and G3 seeds. For each generation, seed parameters were measured. Biofumigation reduced the weed fitness by decreasing the seed germination and survival, increasing seedling mortality, delaying emergence and flowering for both species and decreasing the number of seeds produced of A. artemisiifolia. However, second and third generations may improve their tolerance to biofumigation by increased number of dormant seeds for A. artemisiifolia, seedling survival for both species, increased seed production for A. theophrasti, relative weight of embryo and testa thickness for A. artemisiifolia. Quantification of target weed fitness from biofumigation enables us to understand the weed population performance in the field.