Rate of re-infection of tissue culture-derived Latin American and East and Southern African cassava genotypes by mosaic disease

The rate of reinfection by cassava mosaic disease (CMD) in initially virus-free cassava plants of two Latin American and twelve East and Southern African cassava genotypes grown was studied under high disease pressure conditions. An improved clone, TMS 4(2)1425, from the International Institute of Tropical Agriculture was used as check. The virus-free plants had been produced through meristem-tip culture and multiplied in a pest-proof screen house. The genotypes were planted in single row plots of 5 plants each, arranged in a randomized complete block design with 4 replications and spacing of 1 × 1 m2. Incidence and severity of CMD on the genotypes were assessed weekly, from 4 to 16 weeks after planting (WAP). Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) tests for the cassava mosaic virus were carried out using young leaves collected randomly at 15, 16 and 17 WAP from plants both with and without symptoms. Six genotypes had > 60% CMD incidence at 4 WAP; by 7 WAP, 12 genotypes had > 60% incidence. Only Kigoma red, Kiroba, and UKG-41-6 were notinfected at 4 WAP while Mbudumali had 90% incidence at this time. At 16 WAP, ten genotypes had 100% CMD incidence; Kigoma Red was 39.6% infected. ELISA detected a mean CMD reinfection rate of 66.6%; PCR detected 69%. A high negative and significant (P< 0.01) correlation (r = - 0.70) was established between CMD severity and storage root yield.Keywords: Virus-free cassava genotypes, tissue culture, rate of reinfection, cassava mosaic diseas

Shoot and plantlet regeneration from meristems of Dioscorea rotundata Poir and Dioscorea alata L.

In vitro culture media capable of regenerating moderate to high shoots and/or plantlets from meristems of two yam species – Dioscorea rotundata and Dioscorea alata within comparable duration of 10 weeksas commonly obtained in other monocots and root and tuber crops were investigated. The study comprised 125 phytohormone combinations investigated in three factorial experiments each consistingof an auxin (NAA) and a cytokinin (BAP or kinetin), or two cytokinins only. The frequency of direct plantlet regeneration, though significantly (P < 0.05) higher for D. alata than for D. rotundata, was lowand ranged from 0 to 10% at 3 weeks after culture (WAC) and 0 to 35% at 8 WAC. At 8 WAC, shoot regeneration of 42-75% was obtained in D. rotundata in MS medium supplemented with 0.1 M NAA +0.20 M BAP, and shoot + plantlet regeneration of 60-82% obtained in media containing 0.05 M + 0.20 M BAP or 0.46 M BAP + 0.50 M kinetin in D. alata. Both shoot induction and plantlet regeneration were species-dependent. Induced shoots were successfully rooted in MS medium within 3 to 4 weeks, bringing time taken for plantlet regeneration to 11 to 12 weeks. Regenerants were morphologically similar to the mother plants. Results of the present study will facilitate regeneration of plantlets via meristem in D. rotundata and D. alata

Applications of Probiotic-Based Multi-Components to Human, Animal and Ecosystem Health: Concepts, Methodologies, and Action Mechanisms

Probiotics and related preparations, including synbiotics and postbiotics, are living and non-living microbial-based multi-components, which are now among the most popular bioactive agents. Such interests mainly arise from the wide range and numerous beneficial effects of their use for various hosts. The current minireview article attempts to provide an overview and discuss in a holistic way the concepts, methodologies, action mechanisms, and applications of probiotic-based multi-components in human, animal, plant, soil, and environment health. Probiotic-based multi-component preparations refer to a mixture of bioactive agents, containing probiotics or postbiotics as main functional ingredients, and prebiotics, protectants, stabilizers, encapsulating agents, and other compounds as additional constituents. Analyzing, characterizing, and monitoring over time the traceability, performance, and stability of such multi-component ingredients require relevant and sensitive analytical tools and methodologies. Two innovative profiling and monitoring methods, the thermophysical fingerprinting thermogravimetry–differential scanning calorimetry technique (TGA-DSC) of the whole multi-component powder preparations, and the Advanced Testing for Genetic Composition (ATGC) strain analysis up to the subspecies level, are presented, illustrated, and discussed in this review to respond to those requirements. Finally, the paper deals with some selected applications of probiotic-based multi-components to human, animal, plant, soil and environment health, while mentioning their possible action mechanisms