ABSTRACT-Populus deltoides is the exotic species of poplar introduced in India in late 50s and has been grown significantly in North-western states. It is one of the most important commercial tree planted in agrosilvicutural system adopted by farmers of the region. Meanwhile, it is prone to number of biotic and abiotic agents, which affects the plantations and thus depreciates its quality. Hence, to prevent the loss and manage the diseases, apart from fungicidal use biocontrol strategy has been adopted. In the present study fifteen isolates of Alternaria alternata has been tested against Trichoderma harzianum and Trichoderma viride. Both the antagonists were at par in suppressing the fungal growth and did not achieve the significant level of inhibition. T. harzianum could be shown as better biocontrol agent than the latter owing to the percent growth inhibition shown by the isolates.

Poplar, an important tree in the agri-silvicultural system, is propagated mainly through cuttings to maintain genetic purity. Monocultures of poplar clones are amenable to many diseases as they have a narrow genetic base. Pathogenic populations have variability in terms of pathogenicity and virulence which are governed by its genetic makeup. Mapping the variability and selection of potential pathogenic isolates for breeding disease resistance remains a challenge. During the survey conducted in poplar nurseries located at different geographical sites, altogether 72 isolates of Alternaria alternata, were collected from four commercial clones of P. deltoides. Three selection methods were attempted to select fifteen potent A. alternata isolates based on growth rate, sporulation and spore size (maximum length and maximum breadth). Initially, Rough Gauging Method which is simply based upon index of sum of the character's values and Equal Class Interval Method which depends upon the index of class interval scores were applied. To overcome the limitations of the above two methods, Unequal Class Interval Method was proposed based on Coefficient of Variation for each character assessed. The index was constructed using the geometric rather than arithmetic mean as the former normalizes the range, so that, no range dominates the scores assigned to the characters. The proposed method is recommended for the situations when the criterion variable depends upon various growth characters having inherent significant variation among each other.

Poplar is the one of the domesticated forest trees in India and has better synergy with agriculture system than forestry operations. Populus deltoides have shown great promise in north-western part of India. Many a times, single clone of poplars have been propagated extensively. Ninety per cent of the total planted poplar comprises of clones G-48, WSL-22, WSL-39, Udai, WSL-32, Wimco81 and S7C15 in the states of Punjab, Haryana, Uttarakhand and Uttar Pradesh. High incidence of Alternaria leaf spot was noticed on different commercial clones of P. deltoides (G-48, Udai, WSL-22 and WSL-39) during surveys in poplar nurseries (2009-11). The most common method of managing plant diseases is use of fungicides. In vitro efficacy of two fungicides, namely, propiconazole (systemic) and chlorothalonil (non-systemic) was tested against Alternaria alternata isolates using poisoned food technique. It was observed that propiconazole was more effective in suppressing the growth of the fungus than chlorothalonil as cent per cent inhibition was achieved for all the isolates at 40ppm. On the other hand, cent per cent inhibition of growth was achieved for only four isolates, no. A15, A24, A41 and A47 at highest concentration of 400ppm of chlorothalonil. The study indicated that propiconazole proved to be effective at a very low concentration of 40ppm against A. alternata under in vitro conditions.

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Background: Secondary metabolites of the plant have shown antimicrobial activity. Saponins, from pericarp of S. mukorossi have been reported to possess antimicrobial efficacy against a variety of bacteria and fungi. The present study entails to asses this efficacy against different forest fungi. Methods: Seeds of S. mukorossi, a medicinal plant of family Sapindaceae, collected from different sources viz. Dehradun and Gyarahdevi (Uttarakhand) and Nainatikker (Himachal Pradesh) were tested for their antifungal properties on the basis of IC50. Chloroform and methanol extract of fruit pericarp from three sources of soap nut were assayed against eight forest fungi using poisoned food technique. Both the extracts were screened at four concentrations of 0.5%, 1.0%, 1.5%, and 2%. Results: In our screening, we have found that chloroform extract of all sources registered IC50 at all concentrations against Phoma sp. and P. dalbergiae whereas, methanol extract of all the three sources attained IC50 at all concentrations against Phoma sp., P. dalbergiae, R. solani and T. piluliferum. IC50 was not achieved against A. alternata and F. oxysporum at any concentration of the sources in both the extracts. Conclusion: It can be concluded from the present study that though saponins of soap nut tree have many useful biological activities but chloroform and methanol extracts do not contain comparable biological activity against common forest fungi.