Question

Explain the mechanisms that striga (witchweed) uses to parasitize its host plants.

Answer 1

Explain the mechanisms that striga (witchweed) uses to parasitize its host plants.

ANSWER:

Striga commonly known as witchweed, recognized as cereal pests in Africa,austrelia,asia.Striga sp are predominantly found on open grassland and savannahs in semiarid tropical regions.It is an orobanchaceae family parasite.some sp are serious pathogen to cereal crops.

                      Crops that are commonly affected are sorghum,rice,sugarcane,and a large range of weedy grasses.it reducing yields of crop and wiping out the entire crop in some cases.Host plant symptom such as stunting,choloresis.An increase in monoculture in some part of Africa has led to reduce soil fertility thus further worsening the situation with regard to striga infestation.presence of host derived germination and also temperature is an important factor that affecting the distribution of striga.To break seeds dormancy in striga prolonged wxposure to high temp and humid condition is required.

                     Witchweed seeds minute and produced in large number ,it germinate when it contact with a host root and develop hausteria.which penetrate host root cells .host root contain strigolactones,that is a signaling molecule that promote seed germination in striga.A belt like swelling forms where parasite root attach to root of host.The first 4 or 6 weeks of life cycle are under ground where young plant dependent upon on its host.After emerging plant can photo synthesis it’s own food but takes water and mineral from the host.Witchweed seed spread rapidly by wind , water and soil via animal.

                     After stimulation of germination ,striga seeds sends initial root to probe the soil for host root.The initial root surface,release quinone .A haustorium will develop from initial root ,if it get the proper concentration of quinines.Hausterium is a specialized organ penetrates the host and forms a vascular union between the plants .After recognizing host root,the hausterium begin to rapid cell division and elongation within 48-72 hours.The haustorium penetrate the host root cortex.Oscula a finger like structure in haustorium ,penetrate host xylem through pit of membrane.Striga sieve tube develop in host phloem with 8 cells,this allow nutrition from host to striga.Then the secure their position by swelling process within xyleme.striga cotyledons emerge after trapping the host cells.