Response of dry beans to tiafenacil applied preemergence

Tiafenacil is a new non-selective, protoporphyrinogen IX oxidase (PPO) – inhibiting pyrimidinedione herbicide that is under consideration for registration in corn, soybean, wheat, cotton, and other crops to control grass and broadleaf weeds prior to crop emergence. The sensitivity of dry beans to tiafenacil is not known. Four field experiments were completed at Exeter and Ridgetown, ON, Canada during the 2019 and 2020 growing seasons to determine the sensitivity of azuki, kidney, small red, and white beans to tiafenacil applied preemergence (PRE) at 12.5, 25, 50, and 100 g ai ha−1. Tiafenacil at 100 g ai ha−1 caused 5% or less injury to azuki, kidney, small red and white beans, and 0 to 3% injury in azuki bean, 1-5% injury in kidney bean, 1-4% injury in small red bean, and 1 to 4% injury in white bean. Tiafenacil applied PRE at 12.5, 25, 50, and 100 g ai ha−1 caused up to 1, 4, 4, and 5% visible dry bean injury, respectively but caused no negative effect on other growth parameters measured including the final seed yield. Crop injury was generally the greatest with tiafenacil at the 100 g ai ha−1 in dry beans. Generally, kidney, small red, and white bean were more sensitive to tiafenacil than azuki bean. Dry bean injury was persistent and increased with time with the greatest injury observed 8 WAE. Tiafenacil applied PRE can be a useful addition to the current weed control strategies for grass and broadleaf weed control suppression, especially GR horseweed and amaranth species prior to bean emergence.

Enzymatic activity in azuki bean seedlings subjected to salinity and water deficiency

Salinity and water deficiency are factors that limit the initial development of crops, directly interfering with the efficiency of food production. Studies on the behavior of cultivable species under stress are important to determine management actions; therefore, the mechanisms involved in post-stress recovery should be investigated. The objective of this study was to evaluate the effect of water and salt stress on enzymatic activity in azuki bean seedlings. The experimental design was a completely randomized, 4 × 6 factorial arrangement (four reagents: CaCl2, KCl, NaCl, and polyethylene glycol 6000 (PEG 6000) × six osmotic potentials: 0.0, -0.2, -0.4, -0.8, -1.2, and -1.6 MPa). The quantification of protein content and analysis of enzyme (catalase, peroxidase, and phenylalanine ammonia-lyase) activity in seedlings were performed on the 10th day after sowing. NaCl is toxic and recovery of azuki bean seedlings was less likely under salt stress owing to reduced enzymatic activity. In contrast, seedlings subjected to KCl treatment showed increased production of antioxidant enzymes.

Genetic factor for twisting legume pods identified by fine-mapping of shattering-related traits in azuki bean and yard-long bean

SUMMARYLegumes have evolved a unique manner of seed dispersal in that the seed pods explosively split open with helical tension generated by sclerenchyma on the endocarp. During domestication, azuki bean (Vigna angularis) and yard-long bean (Vigna unguiculata cv-gr. Sesquipedalis) have reduced or lost the sclerenchyma and lost the shattering behavior of seed pods. Here we performed fine-mapping with back-crossed populations and narrowed the candidate genomic region down to 4 kbp in azuki bean and 13 kbp in yard-long bean. Among genes located in these regions, we found MYB26 genes encoded truncated proteins in both the domesticated species. We also found in azuki bean and other legumes that MYB26 is duplicated and only the duplicated copy is expressed in seed pods. Interestingly, in Arabidopsis MYB26 is single copy and is specifically expressed in anther to initiate secondary wall thickening that is required for anther dehiscence. These facts indicated that, in legumes, MYB26 has been duplicated and acquired a new role in development of pod sclerenchyma. However, pod shattering is unfavorable phenotype for harvesting and thus has been selected against by human.