Alternative Hosts of Cercospora beticola in Field Surveys and Inoculation Trials

Cercospora beticola, the cause of Cercospora leaf spot (CLS) of sugar beet and table beet, has a broad range of potential alternative hosts. The role of these hosts as inoculum sources in the field is unclear and has had limited investigation since the advent of DNA-based pathogen identification. The presence of C. beticola on alternative hosts associated with table beet fields of New York was assessed in field surveys during 2016. Lesions were collected, and 71 cercosporoid conidia were isolated for phylogenetic comparison. C. beticola was identified from Solanum ptycanthum (n = 4), Chenopodium album (n = 2), and Spinacia oleracea (n = 1), whereas C. chenopodii was identified on Chenopodium album (n = 51). Artificial inoculation of 21 plants species demonstrated that C. beticola was pathogenic to Brassica kaber, Chenopodium album, Carthamus tinctorius, Rumex obtusifolius, and Spinacia oleracea. These results indicate that although C. beticola may be pathogenic to a range of plant species, the role of symptomatic tissue for inoculum production on alternative hosts in the field appears limited. Observations of C. beticola on necrotic and naturally senescent tissue suggest saprophytic survival on plant debris of a range of species, which has implications for CLS epidemics and disease management.

Allelopathic effect of Brassica on weed control and yield of wheat

The experiment was conducted at the Agronomy farm of Sher-e-Bangla Agricultural University to identify the allelopathic effect of Brassica species along with their incorporation methods to control weeds in wheat field. The experiment was assigned in a split-plot design where three cultivated Brassica spp. were in the main plot and five different ways of green Brassica biomass inclusion were in the sub-plot. Brassica crops were uprooted at 30 days after sowing (DAS) and incorporated to the soil @ 0.5 kg m-2 as per treatment. Wheat seeds were sown on December 04, 2007 using 20 cm line to line distance. Weeds e.g., Amaranthus spinosus, A. viridis, Lindernia procumbens, Heliotropium indicum, Polygonum hydropiper, Celosis argentina, Ageratum conyzoides, Brassica kaber and Digitaria ischaemum were not found in the wheat field. Significantly the highest weed dry matter (1.72 g m-2) was found in Brassica juncea plots at 30 DAS but in Brassica napus field (1.44 g m-2) at 50 DAS. The lowest weed dry matter at 30 DAS (0.89 g m-2) was recorded with total incorporation of Brassica biomass to the soil but 50% incorporation and 50% spreading at 50 DAS. The Brassica biomass spreading above ground, mixed with soil and 50% spreading + 50% mixed with soil resulted positively compared to other ways of biomass incorporation. The highest grain yield (3.83 t ha-1) of wheat was given by Brassica juncea when spreaded on the above ground soil.Bangladesh Agron. J. 2014, 17(1): 73-80

Seasonal cycles in germination and seedling emergence of summer and winter populations of catchweed bedstraw (Galium aparine) and wild mustard (Brassica kaber)

Catchweed bedstraw and wild mustard each produce two populations per year: a winter population (WP) in June, and a summer population (SP) in September. Experiments were conducted to determine whether the WP and SP differ in seed mass and seasonal germination. Seeds of both weeds were buried at 0, 5, 10, and 20 cm in cultivated fields, and retrieved at monthly intervals for 24 mo for germination tests in the laboratory. Additionally, seedling emergence from seeds buried at 0, 5, and 10 cm in the field was evaluated for 1 yr. Seeds from the WP were heavier than those from the SP for both species. Germination of exhumed seeds was affected by burial depth and by seed population. It was highest for seeds that remained on the soil surface and declined with increasing depth of burial. The WP of catchweed bedstraw produced two germination peaks per year, whereas the SP and all populations of wild mustard had only one peak. The WP of both weeds germinated earlier than the SP. Seedling emergence for both species in the field was greater for the WP than for the SP. Increasing soil depth reduced seedling emergence of both the WP and SP of wild mustard and affected only the WP of catchweed bedstraw. We conclude that the WP and SP of catchweed bedstraw and wild mustard seeds used in this study differed in seed mass, seasonal germination, and seedling emergence. The ability of a WP to produce large seeds that germinate early and have two germination peaks per year could make these populations a serious problem in cropping systems.

Inheritance of picloram and 2,4-D resistance in wild mustard (Brassica kaber)

The primary goal of this research was to determine the inheritance of cross-resistance to several groups of auxinic herbicides through classical genetic approaches using auxinic herbicide–resistant (R) and –susceptible (S) wild mustard biotypes obtained from western Canada. F1 progeny were raised from crosses between homozygous auxinic herbicide–R and –S wild mustard parental lines. The F1 and F2 populations were assessed for picloram (pyridine group) and 2,4-D (phenoxyalkanoic group) resistance or susceptibility. Analyses of the F1 as well as the F2 progeny indicate that a single dominant gene confers the resistance to picloram and 2,4-D similar to an earlier report of dicamba-based (benzoic acid group) resistance in this wild mustard biotype. Furthermore, analyses of backcross progeny in this species indicate that resistance to all three auxinic herbicides, i.e., picloram, dicamba, and 2,4-D, is determined by closely linked genetic loci. With this information on inheritance of resistance to several auxinic herbicide families, the R biotype of wild mustard offers an excellent system to isolate and characterize the auxinic herbicide–resistance gene.

Pseudocercosporella capsellae. [Descriptions of Fungi and Bacteria].

A description is provided for Pseudocercosporella capsellae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: White leaf spot and Grey stem of Cruciferae. HOSTS: Brassica campestris (rape), B. chinensis, B. juncea (Indian mustard), B. napus (swede), B. nigra (black mustard), B. oleracea (cabbage and cultivars), B. pekinensis, B. rapa (turnip), Capsella bursa-pastoris, Conringia persica, Goldbachia torulosa, Lepidium sp., Litvinovia tenuissima, Malcolmia africana, Neslia paniculata, Raphanus raphinastrum (white charlock), R. sativa (radish), Rapistrum perenne, Sinapis alba (white mustard), S. arvensis (= Brassica kaber; charlock), Sisymbrium sp. (Brassicaceae). GEOGRAPHICAL DISTRIBUTION: AFRICA: Algeria, Ethiopia, Kenya, South Africa. NORTH AMERICA: Canada (New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec), USA (Alabama, Alaska, California, Connecticut, Florida, Indiana, Louisiana, Maryland, Massachusetts, Minnesota, Missouri, North Carolina, Oregon, Pennsylvania, Texas, Virginia, West Virginia, Wisconsin). CENTRAL AMERICA: Antigua. SOUTH AMERICA: Chile. ASIA: Bhutan, China, India, Israel, Japan, Peninsular Malaysia, Nepal, Sri Lanka, Taiwan, Turkey. AUSTRALASIA: Australia (New South Wales, Queensland, South Australia, Tasmania, Victoria, Western Australia), New Zealand. EUROPE: Belgium, Denmark, Estonia, France, Germany, Great Britain, Ireland, Latvia, Norway, Romania, Sweden. TRANSMISSION: By air-borne and splash dispersed conidia and by seeds, crop debris and volunteer plants or perennial weeds.