Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)Each phase has unique characteristics with respect to the epidemiology and management of seeddisease.(b). Management of seed borne diseases in seed production fieldi. Elimination of Inoculum Sourcesii. Disease management during anthesisiii. Disease management during seed developmentiv. Disease management during seed maturationi. Elimination of inoculum, sourcesThe first opportunity for management of seed diseases is to eradicate or reduce pathogeninoculum in the seed production field for e.g. Removal of crop residue (Phomopsis seed decay ofsoybean). Removal of Infected weeds as perennial source of contamination (Brassica seed fieldsby X. campestris pv. Campestris in Brassica ) . Destruction of infested seeds, the primary sourceof inoculum, by burning or by vacuuming fields (for ergot in perennial grass seed productionfields).ii. Disease management during anthesisThe optimal time for Fusarium moliniforme infection of maize kernels by silk inoculationoccurs when silk begin to senesce. The infection process also may be influenced by environment.rain and warm temperature following anthesis resulted in increased grain mold contamination ofcaryopses of sorghum.Knowledge of the mechanism and enviornmental influences on infection atthis growth stage has been used to advantage in disease management. Several group ofpathogens including smuts, ergots, viruses, and nematodes infect seeds during anthesis.a uniquefeature of infection at this growth stage is the facility for infection of embryos and other internalseed tissues. Embryo invasion by viruses from the mother plant is dependent on short-livedcytoplasmic connections to the male or female gametophytes. The potential for biological controlduring antesis was demonstrated by inoculation of wheat florets with a stain of C. purpurea that didnot biosynthesize ergot alkaloids, but had sufficient parasitic vigor to displace alkaloid- producingstrains.iii. Disease management during seed DevelopmentSeed infection during seed development can occur by invasion through natural openingsincluding the funiculus and micropyle, by direct penetration of the seed or caryopsis, or from podsor freshy fruits. Infection also can be strongly influenced by environment. Osorio & McGee showedthat exposure of soybean pods to frost at --4.5 or -25 0 c immediately before physiological maturitypredisposed seed to infection by Fusarium graminearum and Alternaria alternata but reduced seedinfection by Phomopsis longicolla .More over there are numerous reports of fungicide applicationsin seed production field to control seed borne pathogens. But more strategically these studies arerarely considered in disease epidemiology.The pod infection occurs at any time from floweringonwards for number of seed borne pathogens e.g. in Phomopsis seed decay of soybeam ,X.campestrisis pv. Vignicola but the fungus will not infect seeds until seed maturation begins. Thisdisease epidemiological aspect may be used as predictive methods of fungicidal application.- 38 -