Uma T. Palni

Compost: Its role, mechanism and impact on reducing soil-borne plant diseases

Soil-borne plant pathogens are responsible for causing many crop plant diseases, resulting in significant economic losses. Compost application to agricultural fields is an excellent natural approach, which can be taken to fight against plant pathogens. The application of organic waste products is also an environmentally friendly alternative to chemical use, which unfortunately is the most common approach in agriculture today. This review analyses pioneering and recent compost research, and also the mechanisms and mode of action of compost microbial communities for reducing the activity of plant pathogens in agricultural crops. In addition, an approach for improving the quality of composts through the microbial communities already present in the compost is presented. Future agricultural practices will almost definitely require integrated research strategies to help combat plant diseases.

Microbiological studies of ethnic meat products of the Eastern Himalayas.

Native microorganisms from some ethnic meat products of the Eastern Himalayas such as lang kargyong, yak kargyong, faak kargyong, lang satchu, yak satchu and suka ko masu were isolated and characterized. The bacterial isolates included Lactobacillus sake, Lactobacillus curvatus, Lactobacillus divergens, Lactobacillus carnis, Lactobacillus sanfrancisco, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus brevis, Enterococcus faecium, Leuconostoc mesenteroides, Pediococcus pentosaceous, Bacillus subtilis, Bacillus mycoides, Bacillus thuringiensis, Bacillus lentus and Bacillus licheniformis, Micrococcus and Staphylococcus. Yeast isolates included Debaryomyces hansenii, Debaryomyces polymorphus, Debaryomyces pseudopolymorphus, Pichia burtonii, Pichia anomala, Candida famata and the mould Rhizopus was also identified. Many of the LAB isolates demonstrated some antimicrobial activity, enzymatic activity and a few showed a high degree of hydrophobicity. None of the strains produced biogenic amines.

Micropropagation of Rosa damascena Mill. from mature bushes using thidiazuron

Summary An efficient protocol for micropropagation of Rosa damascena Mill. has been established using single node segments from mature bushes. The effect of thidiazuron has been compared with that of N6-benzyladenine (BA) on in vitro shoot proliferation. The cultures initiated on medium supplemented with thidiazuron (TDZ) and/or cultured continuously on TDZ containing medium for 32–48 weeks exhibited considerably more shoot proliferation and growth during subsequent culture on a medium containing BA. Shoots induced on TDZ containing medium and then sub-cultured (8–12 times) on medium containing BA, attained the capacity to grow and proliferate on a medium free from plant growth regulators (PGR). Microshoots from TDZ induced cultures could be rooted easily on indole-3-butyric acid (IBA) supplemented medium. A short treatment with IBA (100 mM; 12 h) was found to be very effective for root induction. The rooted plants were successfully transferred to pots after 15 d of hardening in a mist chamber with about 70% survival.

Heat-shock induced somatic embryogenesis in callus cultures of gladiolus in the presence of high sucrose

Summary Heat-shock (HS, 50°C 1.h) induced somatic embryogenesis (SE) or shoot bud differentiation (SB) in one year old cytokinin dependent and auxin independent callus cultures of Gladiolus hybridus Hort. grown on high (>174.mM) or low (<116.mM) sucrose medium, respectively. The effect of high sucrose on SE could not be attributed to its role as an osmotic agent alone, because additional sucrose (over and above the normal concentration of 58.mM sucrose) when replaced with mannitol resulted in SB. As in the case of HS, incorporation of putrescine into high sucrose medium also induced SE (and inhibited SB), whereas addition of putrescine to low sucrose medium induced SB. SE was not observed in cultures grown on low sucrose medium. There was more somatic embyro formation in cultures grown on medium gelled with agar than with phytagel. Histological studies revealed that embryo differentiation occurred from the surface layers of callus with no vascular connection with the parent tissue. The somatic embryos could be converted easily into plantlets (ca. 100%) upon transfer to a medium containing less sucrose (58.mM); the plantlets were subsequently transferred to the field, after hardening, with more than 70% survival.

Application of Chenopodium ambrosioides Linn. essential oil as botanical fungicide for the management of fungal deterioration in pulses

Essential oils isolated from 35 aromatic plants of Gorakhpur Division, India, were screened at 0.36 μl ml− 1 against four dominant fungi Aspergillus flavus Link, A. niger van Tieghem, A. ochraceus Wilhelm and A. terreus Thom found on stored pigeon pea (Cajanus cajan Linn.) seeds. Chenopodium ambrosioides Linn. and Citrus aurantium Linn. oils exhibited strong antimycotic activity (100% mycelial inhibition). The minimum inhibitory concentration of C. ambrosioides oil was less (0.07 μl ml− 1) than that of C. aurantium oil, against all the test fungi. Both the oils were fungicidal at higher doses (1.71–2.78 μl ml− 1). C. ambrosioides oil exhibited broad fungitoxic spectrum against 16 other storage fungi of pigeon pea seeds. The oil remained effective with increased inoculum load, and physical factors had no adverse effect on its toxicity. C. ambrosioides oil proved superior to aluminium phosphide and ethylene dibromide, synthetic fumigants, at 0.29 μl ml− 1 and significantly protected 1 kg of pigeon pea seeds from microbial attack for up to 6 months. Chenopodium oil can be recommended as an effective substitute of synthetic fumigants for storage of pigeon pea seeds.

Evaluation of Clausena pentaphylla (Roxb.) DC oil as a fungitoxicant against storage mycoflora of pigeon pea seeds

BACKGROUND The present study aimed to evaluate the antifungal activity of 30 essential oils against four dominant fungi Aspergillus flavus Link., A. niger van Tieghem, A. ochraceus Wilhelm and A. terreus Thom of stored pigeon pea seeds at a concentration of 0.36 µL mL(-1). Various fungitoxic properties, such as minimum inhibitory concentration, minimum fungicidal concentration and fungitoxic spectrum, of the most potent oil were determined. The efficacy of the most potent oil in preservation of pigeon pea seeds for 6 months was also carried out by storing 1 kg of seeds in the oil vapour. RESULTS Clausena pentaphylla and Citrus limon oils were more effective against all the fungi tested, which exhibited 100% per cent mycelial inhibition. The minimum inhibitory concentration of C. pentaphylla oil was determined as 0.07 µL mL(-1) against all the test fungi and was found to be more toxic than Citrus limon oil. C. pentaphylla oil exhibited a broad range of fungitoxicity against 16 other storage fungi of pigeon pea seeds. C. pentaphylla oil significantly protected 1 kg seeds of pigeon pea from fungal deterioration and was superior to synthetic fumigants. The oil did not show any phytotoxicity and the protein content of the seeds was significantly retained for up to 6 months of storage. CONCLUSION Thus, C. pentaphylla oil may be used as an effective fumigant in the ecofriendly management of storage fungi of pigeon pea seeds.

In vitro propagation of Aconitum balfourii Stapf.: an important aconite of the Himalayan alpines

Summary Small leaf segments, obtained from in vitro sprouted axillary buds, have been used to develop an ef®cient micropropagation protocol for Aconitum balfourii Stapf., an important medicinal herb of the Indian Himalayan alpines. Following the induction of callus from cultured leaf segments on Murashige and Skoog (1962; MS) medium containing 4.5.mM 6-benzyladenine (BA) and 26.9.mM a-naphthaleneacetic acid (NAA), the highest values for shoot induction were obtained on the same medium supplemented with the same concentration (4.5.mM) of BA and a lower concentration of NAA (1.4.mM). These individual shoots could be further multiplied easily, with maximum shoot proliferation obtained on MS medium containing 1.1.mM BA only. The shoots obtained either directly from the callus or after multiplication on the above medium, were found to root ef®ciently on MS medium supplemented with 12.3.mM indole-3-butyric acid (IBA). After in vitro hardening in the culture room, the plantlets were transplanted to a greenhouse where the growth of plants was normal. Comparison of mitotic chromosome numbers of root tip cells, protein pro®le and alkaloid content of tubers of in vitro raised and seed grown plants of comparable age showed equal number of chromosomes, identical protein pro®le and similar amounts of diterpenoid alkaloids (aconitine and pseudoaconitine). This paper is the ®rst report describing a complete regeneration protocol, along with quantitative data, for A. balfourii using in vitro methods.

Bioefficacy of plant essential oils against pulse beetles Callosobruchus spp. (Coleoptera: Bruchidae) in pigeon pea seeds with particular reference to Clausena pentaphylla (Roxb.) DC.

Thirty essential oils from higher plants of Gorakhpur Division (India) were evaluated at 0.36 μl/ml against two pulse beetles, Callosobruchus chinensis L. and C. maculatus F., causing infestation of pigeon pea seeds during storage. Clausena pentaphylla oil was more effective and exhibited absolute repellency against both the insects followed by Ocimum canum, Salvia plebeia and Zingiber zerumbet oils. Among these four oils, C. pentaphylla oil was most toxic and showed 100% mortality of both the insects at 10-μl dosage and 24-h exposure (LD50 = 2.7 μl for C. chinensis & 2.4 μl for C. maculatus). Physical factors, viz. temperature, storage and autoclaving, did not cause any adverse effect on the toxicity of Clausena oil. During in vivo investigation, the oil protected 1 kg of pigeon pea seeds completely without reducing weight loss and seed damage up to 6 months when stored in gunny bags and glass containers. The oil was standardised by determining its various physicochemical properties. Thus, C. pentaphylla oil can be judiciously exploited as herbal insecticide against pulse beetles of pigeon pea seeds during storage.

Mycotoxin Menace in Stored Agricultural Commodities and Their Management by Plant Volatiles: An Overview

Mycotoxins are toxic metabolites of fungi when they grow on food commodities. These are potent toxins having severe manifestations in humans and animals, being carcinogenic, mutagenic and teratogenic. Mycotoxin contamination is most widespread in agricultural commodities. These mycotoxins are secondary metabolite products and are produced by several fungi occurring on commercially importance agricultural produce during pre- and post-harvest and incur significant side effects on animalia. Aflatoxins, fumonisins, ochratoxins, deoxynivalenol, zearalenone, patulin are major mycotoxins, produced by Aspergillus, Fusarium, and Penicillium species. Among all, aflatoxins, fumonisins, and ochratoxins are found to have very important role in creating several side effects in human health worldwide. For control of these mycotoxins in agricultural commodities, several physical, chemical and biological management techniques and measures have been developed. However, physical and chemical methods have their own limitations. Plant volatiles isolated from higher plants certainly provide a potential mycotoxin management strategy in stored food commodities. This review describes the mycotoxins contamination in some commercially importance agricultural crops such as rice, wheat, maize, peanut, sorghum, pearl-millets, barley, oat, pulses, oil seeds, fruits and their management through plant volatiles; which may be helpful in developing proper management strategies. Information from meticulous studies of mycotoxins in food commodities throughout the world will help in providing safer food for consumption and in prioritizing future research programs.