Development of high-throughput methods to screen disease caused by Rhizoctonia solani AG 2-1 in oilseed rape

Background: Rhizoctonia solani (Kühn) is a soil-borne, necrotrophic fungus causing damping off, root rot and stem canker in many cultivated plants worldwide. Oilseed rape (OSR, Brassica napus) is the primary host for anastomosis group (AG) 2-1 of R. solani causing pre- and post-emergence damping-off resulting in death of seedlings and impaired crop establishment. Presently, there are no known resistant OSR genotypes and the main methods for disease control are fungicide seed treatments and cultural practices. The identification of sources of resistance for crop breeding is essential for sustainable management of the disease. However, a high-throughput, reliable screening method for resistance traits is required. The aim of this work was to develop a low cost, rapid screening method for disease phenotyping and identification of resistance traits. Results: Four growth systems were developed and tested: (1) nutrient media plates, (2) compost trays, (3) light expanded clay aggregate (LECA) trays, and (4) a hydroponic pouch and wick system. Seedlings were inoculated with virulent AG 2-1 to cause damping-off disease and grown for a period of 4–10 days. Visual disease assessments were carried out or disease was estimated through image analysis using ImageJ. Conclusion: Inoculation of LECA was the most suitable method for phenotyping disease caused by R. solani AG 2-1 as it enabled the detection of differences in disease severity among OSR genotypes within a short time period whilst allowing measurements to be conducted on whole plants. This system is expected to facilitate identification of resistant germplasm

Evaluation of substrate productivity and market quality of oyster mushroom (Pleurotus ostreatus) grown on different substrates

Substrate is one type of the major factors affecting the yield and quality of oyster mushroom (Pleurotus ostreatus). Six substrates, cotton lint waste, maize stover, jatropha cake, corncobs, wood shavings and wheat straw were evaluated for their productivity and impact on mushroom market quality of P. ostreatus. Wheat straw was used as a control because it is commonly used for mushroom production in Zimbabwe. The experiment was carried out in a low cost mushroom growing house and laid out in a randomized complete block design with each treatment replicated four times. Bags containing the pasteurized substrates were spawned at a rate of 8%. Three flushes were harvested from which substrate productivity was evaluated by determining mean number of basidiocarps (MNB), mean basidiocarp weight (MBW) and biological efficiency (BE) while mushroom market quality was evaluated on the basis of basidiocarp percentage number within pileus diameter groups; >7, 5-7, 3-5, 7 and 5-7 cm size groups and highest in the deformed group. There were, however, no significant differences in the 3-5 and 0.05). Cotton lint waste and maize stover are competent alternatives to wheat straw as they are equally productive and produce high market quality mushrooms

Germination performance of tobacco varieties in response to different water potentials, priming and post - priming storage durations

Sub optimal seed germination and seedling establishment are major problems in tbacco (Nicotiana tabacum L) transplant production maybe due to dormancy, low soil moisture and poor seed to media contact in the float tray system . Seed priming in which seeds imbibe water or osmotic solutions followed by drying offers rapid germination and uniform seedling establishment