Marigold: A Diagnostic Tool for BGMForecasting and Management inChickp - PDF document

Marigold: A Diagnostic Tool for BGMForecasting and Management inChickpeaContributed by Suresh Pande, G Krishna Kishoreand J Narayana RaoCrop Improvement ThemeICRISAT, Patancheru, IndiaBotrytis gray mould (BGM) is a disease that mainlyattacks the reproductive structures of a chickpea plant.Flower abortion is a common symptom of the disease(Fig. 1) which remains undiscovered until the damage isvisible on the canopy. As a result, timely application offungicides is hampered in the integrated diseasemanagement. The predictive models (Shtienberg andElad 1997) to estimate disease severity and timing arebased on complex mathematical calculations, and they donot account for inoculum pressure. To identify analternative indicator for a reliable diagnosis, forecastingand management of BGM, several ornamental plantscommonly grown during the chickpea season as acollateral host of Botrytis cinerea were evaluated.The controlled environment investigations on hostpathogen interaction were carried out with marigoldTagetus erecta L.). Flowering plants of marigold whenspray-inoculated with B. cinerea (3 x 10 conidia mL-1from chickpea and incubated in an environment (15°Cand 100% RH) needed for BGM development, producedFigure 1. BGM infection on chickpea flowers.Figure 2. Progressive symptoms of Botrytis cinerea infectionon marigold: (A) Initial lesion development and sporulation onbloomed flowers and (B) rotted young buds; (C) sporulation onflowers; (D) sporulation on flower buds and lesion developmenton leaves; (E) sporulation on all the aerial plant parts.symptoms on the leaves, flowers, flower buds and stems.Six days after inoculation (DAI), dark lesions wereobserved on a fully bloomed flower (Fig. 2A).Concurrently, all the young buds appeared completelyrotted, but did not support sporulation (Fig. 2B). By 12DAI, masses of wind blown grey sporulation on flowersand flower buds were clearly visible (Fig. 2C and 2D).Between 15 and 20 DAI, profuse grey sporulation wasobserved on all the aerial plant parts (Fig. 2E).The early infection of B. cinerea causing moldyinfection on marigold clearly identified its usefulness tofarmers as a diagnostic tool to predict BGM epidemicsand its management in chickpea. Marigold as an indicatorplant to apply prophylactic fungicidal protection tochickpea crop in Nepal has been successfully validated.Infection of B. cinerea on the flowers of marigold andDahlia, grown at Ishurdi and Jessore in Bangladesh,indicates the possible integration of this farmer friendly,low-cost BGM forecasting system. 1 An Open Access Journal published by ICRISAT________________________________________________________________________________________________________ SAT eJournal | ejournal.icrisat.org December 2005 | Volume 1 | Issue 1 ReferenceShtienberg D and Elad Y. 1997. Incorporation of weatherforecasting in integrated, biological-chemical management ofBotrytis cinerea. Phytopathology 87:332!340. An Open Access Journal published by ICRISAT________________________________________________________________________________________________________ SAT eJournal | ejournal.icrisat.org December 2005 | Volume 1 | Issue 1