Grain mold histopathology, damage assessment, and resistance screening within Sorghum bicolor (L.) Moench lines
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Date
1981
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Abstract
Sorghum grain molds are defined as prematurity diseases resulting from infection of spikelets or developing kernels as early as anthesis by parasitic field fungi. Curvularia spp and Fusarium spp are the predominant grain molding fungi in Texas and India. The principal species of these two genera are Curvularia lunata and Fusarium moniliforme. Grain molding fungi reduce germination, weight, and size of kernels and increase discoloration compared with controls, when they are inoculated onto panicles at anthesis F. moniliforme increases preharvest sprouting. Spikelet tissues are infected initially and the developing kernel (ovary) is colonized a few days later. Damage to the developing kernels is related to the earliness and severity of infection. Curvularia lunata infects sterile lemma, lemma, palea, lodicules, anthers, and filaments within the first few days after inoculation at anthesis. Symptoms of infection, reddening of glume and pericarp surfaces, are evident 5 days after anthesis. Colonization of tissues at the floret-rachis branch junction and pedicel cause abortion of kernels or reduce kernel filling. Concurrently, a false black layer forms at the placenta 10 to 16 days earlier than normal. Little or no colonization of the kernel occurs when the false black layer forms. Colonization of the ovary wall (mesocarp) occurs between 5 and 10 days. Penetration into the endosperm from the ovary wall is restricted by the peripheral endosperm. C. lunata gains access to the germ and endosperm tissues via the placental sac and endosperm transfer cells. Colonization of the tissues is intercellular initially, but soon develops intracellularly. Fusarium moniliforme infects sterile lemma, lemma, palea, lodicules, and filaments within the first few days after inoculation at anthesis. Symptoms, reddening of spikelet tissues, are evident at 5 days. Colonization of the pedicel and basal ovary tissues occurs, primarily from the lodicules and filaments, between 5 and 10 days. Mycelial mats, progressing acropetally, are produced between the ovary wall and the aleurone layer between 5 and 10 days after anthesis. F. moniliforme mycelium enters the endosperm, germ, and ovary wall tissues directly from the mycelial mats...
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Major plant pathology