Leafspot of Peanut Associated With Magnesium Deficiency

Abstract

It is generally recognized that the susceptibility and prevalence of manv plant diseases are associated with plant nutrition. The peanut plant is susceptible to leafspot infection which becomes economicallv important during the last half of its growth period when the crop is planted in the spring. The severity and rapid spread of infection in the field may not be due to the mere presence of the organism, which is ubiquitous, but to the susceptibility of plants suffering from improper niutrition in certain stages of their growth. Results herein reported of a nutritionial study with the Dixie Runner variety of peanut support this assumption.The experimental peanut plants were grown in sand culture with the roots of each plant in a single gallon glass jug which completely isolated the roots from the fruiting or pegring zone of the plant ( fig. 1). The nutrients were applied to the rooting medium by the continuous flow miiethod of SHIVE and STAHL (6), while the nutrients on the pegging zone were applied on the surface and by feedingo through the base of the box. For 75 days after germination the rootino and fruiting zones of all cultuires were supplied HOAGLAND'S (4) no. 1 complete nutrient solution modified by reducing the concentration of the macronutrienits by half and the microniutrients to onetenth. Ferrous iron was added as needed. At the enid of that period the following nutrient treatments were begun on the rootinog medium: complete, ininus phosphorus, minus potassiumii, minus calciumii, inus magnesium, minus sulphur, and minus Inieronutrient elements. The complete nutrient solution was applied to the fruiting medium throuohout the experiment.There were three replicates of single plants to each treatment and the roots of each culture received 1.5 liters of nutrielnt solution daily; the pegging region received 3.5 liters of solution weekly. Plants were grown 21 days in the greenhouse after germination alnd then because of high temperature were moved outside under a framiie cov-ered with one thickness of cheesecloth. This report will deal only with the results obtained with the magnesium-deficient cultures, sinee these plants were the only ones that developed the leafspot disease to any appreciable extent uinder the conditions of this experiment.The leaves of the minus-magnesium plants showed interveinal chlorotic centers with green margins 24 days after magnesiumi was withheld from the roots. However, the effect appeared initially on the first leaf below the growing tip of the oldest branches. This is in eontrast to the typical magnesium deficieney on other plants which usually ocecurs first on the basal 237 www.plantphysiol.org on May 9, 2018 -Published by Downloaded from

The Influence of Mineral Deficiency on Vegetative Growth, Flower and Fruit Production, and Mineral Composition of the Peanut Plant

“…Magnesium deficiency as previously reported by BLEDSOE, et al, (2) (19) indicate the importance of magnesium in nut production. Within two weeks after treatments were started, symptoms of calcium deficiency became apparent by restricted growth and the appearance of small interveinal brown pitted areas accompanied by marginal chlorosis on the upper surface of fully developed leaflets proximal to the growing tips.…”

“…The middle leaves of lateral branches and the following stages of fruit development were selected from each plant for mineral analysis: (1) gynophores prior to entering the sanid of the fruiting medium, (2) The necessity of aii externial suiplyp of nuiitrienits in both the rooting and fruiting media of the peanuit plant for optimum growth and fruit production is shown in tables 1, II, and IIT. Without exception it was found that plants supplied with the complete solution in the rooting medium, irrespective of the nature of the fruiting medium, notably surpassed the plants of all other cultures not only in the total amount of vegetative growth, flower and gynophore production, but also in the character of growth and general appearance of the plants.…”

“…high, selected containers with the more uniform individuals were placed in boxes of sand. The method of isolating the rooting and fruiting media, the basic and supplementary nutrient solutions used, and their method of application -have already been described (2). The pH of all solutions was adjusted to approximately 5.5.…”

The Effects of Three Levels of Magnesium on the Nutrient-Element Composition of two Inbred Lines of Corn and on their Susceptibility to Helminthosporium Maydis

“…Bledsoe et al (3) reported a relationship between the magnesium content of leaf tissue and the incidence of peanut leafspot. They found that plants grown at low magnesium levels had less magnesium in the leaf tissue and developed about fifty times more leaf spots than did plants grown at high magnesium levels.…”

“…The influence of nutrition on the severity of plant diseases has received considerable attention (3,7,15,16,17,18,20,21,22,23). Wingard (25) gives a general review of the literature pertaining to this subject.…”