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Culm anatomy revealed association of vascular bundle number and silicon content with lodging behaviour in Kodo millet (Paspalum scrobiculatum L.)

2019-12-01T00:00:00Z

Title: Culm anatomy revealed association of vascular bundle number and silicon content with lodging behaviour in Kodo millet (Paspalum scrobiculatum L.) Authors: Sreeja, R; Arul, L; Bapu, Kannan JR; Kumari, Nirmala A; Subramanian, A Abstract: In dry lands, small millets such as kodo millet contribute to regional food security to some extent. It is normally harvested using paddy combine harvester due to labour scarcity. However, the current varieties are not amenable for mechanized harvesting as they lodge at grain filling and maturity stages, thus resulting in heavy grain loss in terms of quality and quantity. In this context, we studied the anatomical features of culm and elemental composition in relation to lodging behaviour in kodo millet (Paspalum scrobiculatum L.), which is one of the important yield limiting factors in this crop. The strong culm genotype, Adari had higher culm thickness, thicker mechanical tissue, more lignin deposition and more number of vascular bundles per cross section when compared to the weaker counterpart, Aamo10. However, not all the genotypes with thicker culm were lodging resistant. Sel21 which recorded the highest culm thickness (1283.4 μm) among the genotypes lodged heavily as higher culm thickness in Sel21 was not supported by an increased number of vascular bundles. Interestingly, TNPsc183 which had a moderate culm thickness of 782.82 μm exhibited a low degree of lodging and had more number of vascular bundles per cross section than Sel21. Hence, ‘number of vascular bundles per unit area’ appears to be an important trait in contributing lodging resistance in kodo millet. SEM-EDX studies for silicon and potassium contents in culm implicated the role of silicon, but not potassium in imparting culm strength in kodo millet. However, more potassium content in parenchymatous cell wall suggests its role in imparting strength to the non-lignified cells of the culm. Page(s): 893-898

Understanding the role of uncharacterized and hypothetical pathogenicity genes of Colletotrichum orbiculare to oxidative stress and phenolics of cucumber plant in anthracnose development

2019-12-01T00:00:00Z

Title: Understanding the role of uncharacterized and hypothetical pathogenicity genes of Colletotrichum orbiculare to oxidative stress and phenolics of cucumber plant in anthracnose development Authors: Shanmugam, V; Veena, KH; Jain, Shekhar; Aggarwal, Rashmi; Ilakkiyaselvan, G Abstract: Uncharacterized and hypothetical pathogenicity genes of Colletotrichum orbiculare inciting anthracnose of cucumber are poorly annotated but could be potential antifungal targets in anthracnose control. Hence, to associate them with specific functions in fungal–host interactions for exploitation in anthracnose control, their responses to reactive oxygen species produced due to oxidative burst and constitutive or induced phenolics, the earliest known defence mechanisms of host plants were assessed. Among commercially available related phenolic compounds, at the lowest concentration of 1 mM, ferulic and chlorogenic acids were less toxic to the pathogen. Among the phenolics, a less significant expression of superoxide dismutase coupled with a strong expression of catalase in ferulic acid greater than that in menadione and hydrogen peroxide, respectively indicated its oxidative effect through generation of radicles similar to that of hydrogen peroxide. However, lack of expression of beta-ketoadipate pathway genes in response to the phenolic acids indicated the role of other phenol metabolizing genes of the pathogen. In planta expression followed by constitutive expression of uncharacterized and hypothetical pathogenicity genes of C. orbiculare in a minimal medium indicated that 6 of the genes are not redundant and may function under stress conditions. Among the genes, significant expression of ENH87556 in menadione (1.3-fold) together with a weak expression in hydrogen peroxide in relation to untreated control indicated its role in oxidative stress generated due to the superoxide radical of menadione. Additionally, a strong expression (3.8-fold) of the gene in ferulic acid greater than that of either control, minimal medium or minimal medium with leaf extract indicated its role in phenol metabolism. Thus, the gene could be a potential molecular target for anthracnose control upon validation by functional analysis. Page(s): 899-907

Volatile, nonvolatile composition and biological activities of Ageratum houstonianum Mill. against diamondback moth, Plutella xylostella (L.) and aphid, Aphis craccivora Koch

2019-12-01T00:00:00Z

Title: Volatile, nonvolatile composition and biological activities of Ageratum houstonianum Mill. against diamondback moth, Plutella xylostella (L.) and aphid, Aphis craccivora Koch Authors: Adebisi, Olonisakin; Dolma, Shudh Kirti; Verma, Praveen Kumar; Singh, Bikram; Reddy, SG Eswara Abstract: Ageratum houstonianum, commonly called as bluemink or flossflower, is a predominant weed growing widely in the western Himalaya region. Here, we studied its chemical composition of essential oil (EO), characterization of pure compounds, screening of EO, fractions and pure compounds for their insecticidal activities against larvae of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) and aphid, Aphis craccivora Koch (Hemiptera :Aphididae).The volatile composition of the EO from above ground parts of A. houstonianum was extracted by steam distillation and characterized by GC and GC–MS analysis. Precocene II (42.16%), precocene I (18.65%) and beta–caryophyllene (15.56%) were the main constituents. Fatty acid composition of the plant was determined using GC–MS after derivatization. The compounds ageratochrome and 1–heptadecene were isolated and characterized using Mass, ¹H and ¹³C NMR spectroscopy. EO, hexane/methanol fractions and isolated compounds were tested against P. xylostella and A. craccivora. Results indicated that EO, hexane fraction, ageratochrome and 1–heptadecene showed more toxicity to larvae of P. xylostella (LC₅₀=2.82, 4.91, 2.15, 4.86 mg/mL, respectively); whereas methanol fraction was more effective against A. craccivora (LC₅₀=1.11 mg/mL) in the residual toxicity assay. The EO also showed repellent activity to P. xylostella (RC₅₀ =2.25 mg/mL). Page(s): 908-915

Shelf life of bioagents and longevity of biologically coated pigeonpea seed

2019-12-01T00:00:00Z

Title: Shelf life of bioagents and longevity of biologically coated pigeonpea seed Authors: Jagadeesh, V; Patta, Sujatha; Triveni, S; Keshavulu, K; Rani, K Jhansi; Raghavendra, K Abstract: Biological seed coating is a new technique of seed treatment through which biological agents are coated over the seed surface for effective control of seed and soil-borne pathogens. In this study, pigeonpea seed was biologically coated with Pseudomonas fluorescens, Rhizobium spp. and Phosphorus solubilizing bacteria (PSB) using biofriendly polymer and sugar syrup as adjuvants. The shelf life of bioagents and seed quality parameters was studied during six months of storage period. The colony units of Pseudomonas increased with biofriendly polymer either as individual or in consortia with biofertilizers. Six months after treatment, more colony units of Pseudomonas fluorescens were recorded on the surface of biologically coated seed of pigeonpea with biofriendly polymer as an adjuvant compared to sugar syrup. Seeds coated with Pseudomonas and PSB using biofriendly polymer recorded high seed germination and seedling vigour compared to sugar syrup. The observations reveal that there is a possibility of coating seed with biological agents using biofriendly polymer immediately after processing or before packaging without affecting the shelf life of bioagents and seed quality. Thus, the biologically coated pigeonpea seed in advance of cropping season can go a long way in minimizing risk associated with on farm seed treatment. Page(s): 916-922