Endophytic Beauveria bassiana (Balsamo-Crivelli) Vuillemin can promote plant growth and health and protect them against herbivores. Two endophytic strains of B. bassiana, BS195 (isolated from soil) and BNE20 (isolated from cucumber), were used by foliar spray and root soaking to evaluate B. bassiana ability to colonize cucumber plants and promote their growth under stressful greenhouse conditions in two separate experiments, as well as its efficacy against Liriomyza sativae Blanchard in a controlled setting. The results showed that the effects significantly depended on the inoculation method and fungal strain. Both B. bassiana strains colonized endophytically the tissues of all cucumber plant parts 30 days post-inoculation, with root soaking being significantly better than foliar spray. The present study showed that the application of B. bassiana BS195, mainly through root soaking, enhanced many growth and health parameters, including plant height, root length, number of leaves, leaf area, fresh and dry weight, the content of dry matter, and the total phenolic content. Cucumber plant treatment with B. bassiana significantly reduced the infestation, severity, number of pupae, and adult emergence of L. sativae after 35 and 51 days of adult release with greater efficiency with the root soaking method. We conclude that introducing B. bassiana through root soaking seems to be effective in stimulating plant growth, and can be a promising technique in controlling L. sativae populations on cucumber plants.
Climate change has a great influence on weed growth and susceptibility of weeds to herbicides. This study determined the effect of six herbicides on three weed species under different CO2 concentrations and temperature levels. The weeds in the study were: (i) wild oat (Avena fatua), (ii) lambsquarter (Chenopodium album), and (iii) wild mustard (Sinapis arvensis). The herbicides used in this study were: (i) 240 g ꞏ l–1 clodinafop-propargyl, (ii) 3% mesosulfuron-methyl + 0.6% iodosulfuron-methyl sodium + 9% mefenpyr-diethyl, (iii) 40 g ꞏ l–1 nicosulfuron, (iv) 480 g ꞏ l–1 glyphosate isopropylamine salt, (v) 75% tribenuron methyl and (vi) 3% mesosulfuron-methyl + 0.6% iodosulfuron-methyl sodium + 9% mefenpyr-diethyl + 300 g ꞏ l–1 bromoxynil + 300 g ꞏ l–1 MCPA. The study was carried out in a fully automated greenhouse which could be adjusted with desired CO2 concentration and temperature. The weeds were exposed to three different temperatures (day/night 26/16 ± 1, 29/19 ± 1 and 32/22 ± 1°C) and CO2 (400 ± 50, 600 ± 50 and 800 ± 50 ppm) levels. A temperature of 26/16 ± 1°C plus a CO2 level of 400 ± 50 ppm was considered as the control. Results showed that 26/16°C × 800 ppm CO2 produced the highest plant length (65.05 cm), plant fresh weight (7.42 g) and plant dry weight (1.31 g) for A. fatua. Similarly, for S. arvensis, the same treatment showed the highest plant length (31.63 cm), plant fresh weight (23.99 g) and plant dry weight (1.82 g) while for C. album, different climatic conditions did not show a significant effect on the growth of this weed. The ED50 values of herbicides for controlling A. fatua, C. album and S. arvensis increased (112.8, 0.6 and 199.4) with an increase in temperature and CO2 levels, respectively. It is predicted that the control of some weeds will be difficult in the climate change that includes an increase in temperature and carbon dioxide in the future.
Phytoplasma subgroups 16SrIV-A and -D are the agents associated with two diseases that significantly threaten palm cultivation in the Americas, namely lethal yellowing (LY) and Texas Phoenix palm decline (TPPD), respectively. Recently, in Puebla State, Mexico, several Phoenix canariensis Chabaud and Syagrus romanzoffiana (Cham.) Glassman palms used as ornamentals began to show symptoms resembling those of TPPD and LY. Therefore, the present study aimed to demonstrate the spread of group 16SrIV phytoplasmas to Puebla, Mexico. Ten symptomatic individuals of both palms were sampled and a nested PCR assay with primer pair P1/P7 followed by LY16Sf/LY16Sr was performed to detect phytoplasma presence. A fragment of about 1.4 kb was amplified in six palms, three (of four) P. canariensis and three (of six) S. romanzoffiana. Sequence analysis of the amplicons revealed that the phytoplasma isolates from Puebla were members of group 16SrIV, subgroups – A (one isolate from P. canariensis) and -D (rest of isolates). This study reports the first occurrence of TPPD and LY on ornamental palm species in the state of Puebla, Mexico.
Root rot of sugar beet (Beta vulgaris L.), caused by Rhizoctonia solani anastomosis group AG 2-2 IIIB is responsible for significant crop losses in North Dakota and Minnesota, USA. Understanding the association between plant age and inoculum density with disease severity of sugar beet cultivars is a prerequisite to properly screen for varietal resistance. Therefore, investigations were conducted to determine the responses of 4-, 6-, and 8-week-old plants in seven commercial sugar beet cultivars to inoculum densities of one, two, and three grains of R. solani-colonized barley in a greenhouse and with three corresponding levels of colonized barley, mycelial plugs, and sclerotia in field experiments. Under greenhouse conditions, disease severity was greatest before plants reached six weeks of age (p = 0.05). There was a positive linear relationship between the density of the inoculum and disease severity. All seven cultivars were equally susceptible (p > 0.05) to R. solani. Interactions between cultivars and plant age and between plant age and intensity of inoculum were not significant (p > 0.05). Field experiments showed that the density of inoculums was significant (p < 0.001), and the disease severity was highest in plants inoculated with three colonized barley seeds per plant compared to doses of other inoculum types.