Seed Dormancy and Seed Morphology Related to Weed Susceptibility to Biofumigation

Abstract

Biofumigation is practiced to control soilborne pests and weeds in agronomic fields. The objectives of this research were to assess the dose response of weed seeds to Indian mustard biofumigation and associate responses to seed dormancy state, initial dormancy, and seed parameters. A petri dish biofumigation methodology was developed to expose seeds of common lambsquarters, bird vetch, wild carrot, common ragweed, green foxtail, velvetleaf, hairy galinsoga, and red clover to allelochemicals produced after rehydrating 0 (control), 1.94, 2.90, 5.81, 11.61, and 17.41 mg cm−2of dried mustard powder. Weed species expressed specific dose responses, estimated ED50, LD50, and maximal mortality. Hairy galinsoga and wild carrot were consistently the most affected by biofumigation, with maximal mortality reaching 97% and 95%, ED50values for germination were 1.91 and 2.68 mg cm−2, and LD50values were 3.31 and 3.69 mg cm−2of dried mustard tissue, respectively. Initial dormancy was assessed by germination and tetrazolium tests. Seed parameters such as testa thickness, relative weight of the testa, and seed size were measured directly by manual dissection, weighing seed structures, and stereomicroscopic imaging software measurements. Linear regression analyses revealed initial dormancy to be positively related to ED50and LD50values with a significant interaction with seed surface and seed width, respectively. Exposure to 5.81 mg cm−2of dried mustard powder increased common ragweed seed mortality for after-ripened seeds by 293% and by 58% for primary dormant seeds compared with untreated seeds. Mortality of common lambsquarters secondary and primary dormant seeds increased by 730% and 106%, respectively, and for wild carrot by 1,193 and 156%, respectively. Results underline the potential to incorporate biofumigation into weed management programs for repression of susceptible weed species.

Impact of Indian mustard growth and incorporation on annual weed population dynamics and communities

“…Different responses observed between years and sites may be explained by the variability of the biofumigant potential and biofumigation conditions, but also by the intra-and interspecific vulnerability of weeds to the allelochemicals released during biofumigation. Previous work showed that weed seed susceptibility to biofumigation allelochemicals differed according to seed dormancy, seed size and testa thickness (Lefebvre et al, 2018). Furthermore, as PCoAs considered individual weed species responses to treatments, species composition of the weed community in each site may partly explain the difference between sites.…”

“…Samples were prepared for HS GC‐MS as described in Lefebvre et al . (). Volatile organic probes were also analysed via thermal desorption–gas chromatography.…”

“…Analyses by headspace (HS) (TurboMatrix TM HS 40 Trap; PerkinElmer, Waltham, MA, USA) and gas chromatography-mass spectrometry (GC-MS) [Clarus Ò 680 (GC) and Clarus Ò SQ8 (MS); PerkinElmer, USA] were performed on Indian mustard material to identify and quantify ITCs and other allelopathic compounds that were released during biofumigation. Samples were prepared for HS GC-MS as described in Lefebvre et al (2018). Volatile organic probes were also analysed via thermal desorption-gas chromatography.…”

“…A promising aspect of biofumigation for weed control in agroecosystems is the potential to reduce seedbank persistence. Indeed, high concentration of ITCs and increased exposure time may cause a lethal effect on weed seeds (Lefebvre et al, 2018). It is unknown from the literature whether weed community susceptibility to biofumigation is related to emergence periodicity.…”

“…It is unknown from the literature whether weed community susceptibility to biofumigation is related to emergence periodicity. The number of dormant seeds in a seed lot affects weed seed response to biofumigation (Lefebvre et al, 2018). Therefore, it is pertinent to assess in field conditions the repressive effect of biofumigation on weeds when the technique is applied at different times of the year.…”