This fungus has two form of reproduction. In asexual reproduction, bulbous black sporangia are produced at the tips of upright hyphae which contain numerous haploid sporangiospore.
This is heterothallic species (Schipper 1984) which mean it needs the hyphae of opposite mating type for the sex to occur. During sexual reproduction,when haploid hyphae of different mating types are in close proximity to each other it gives rise to the formation of the diploid zygospore. It involves the two process plasmogamy ( fusion of cytoplasm) and karyogamy (fusion of nuclei)respectively.
Zygospores are dormant overwintering structure in unfavorable environmental condition with the thick cell wall. They germinate producing a sporangium or vegetative hyphae on the commencement of favorable environment. Meiosis during the germination of zygosporangium makes the spores or hyphae haploid.
Generally sporangiospore either produced by the germination of zygospore or asexually produced by sporangia attack on the host surface. Then it starts growing on it penetrating its mycelia. This invasion of pathogen causes the maceration of healthy tissue and symptoms of watery rot start appearing
Haphazardly handled fruit/vegetable during harvesting, transportation and storage are susceptible to this fungus. Thus proper handling becomes imperative.
Peppermint and sweet basil volatile oils extracted from leaves are some of the potential natural biocide against the post harvest decay of the peach. (Ziedan and Farrag)
“Host eradication (rouging) and crop rotation are some effective cultural practices against this pathogen. Spacing plants properly in the field or greenhouse prevents the creation of high humidity conditions on plant surfaces and inhibits infection” (Agrios, 1997).
Tridax procumbens, Venonia amygdalina, chromolaena odorata and Azadirachta indica are some the biocontrol agents who’s aqueous and ethanolic extract has the profound inhibitory action on the mycelial growth of this kind of rot fungus.
Benomyl, Thiabendazole, Dichloron, and Imazalil are some examples of postharvest chemical treatments that are presently used to control this fungus.
Fruits treated with hot water dip at 50°C for 3 min + bioagent Debaryomyces hansenii has been beneficial for the minimum incidence and infected area of Rhizopus stolonifer. (Dinesh singh and Gautam Mandal, 2006)
Bacillus subtilis, Micrococcus spp., Corynebacterium spp are some of the bacteria that have the profound effect on the on the inhibition of Rhizopus stolonifer associated with barley grains. Pantoea agglomerans CPA-2 is found effective for pear soft rot. Fumigation of with acetic acid and Combined hot water and radiation treatments are found efficient for the decay control in stone fruit and tomato respectively.
This versatile phytopathogen excretes the fungal peptic enzymes that degrade and dissolve the pectin contained in the middle lamella of the plant cells. (Miguel Gerardo Velázquez–del Valle, 2007)
This eventually leads to the colonization of agricultural products like vegetable and fruits which is recognized as the soft rot. This pathogen can survive in wide range of temperature and relative humidity
Initially affected part of fruit/vegetable gives the mild pleasant smell but as the yeast and bacteria move inside it the sour odor develops. Initial pleasant fleshy rot may attract fruit flies as well. After some days that vegetable/fruit becomes wet as the fungus start exuding whitish yellow liquid and whole fruit/vegetable is covered by the fungal mycelia with the black sporangia at the tip.
This pathogen has been identified as a Pre-emergence Seedling Disease Pathogen of Beta vulgaris causing damping off on it.
In cherry tomato, the fungus causes cracking on fruits following making wounds on it.Then infected parts on cracks become water soaked and disintegrate in watery rot.
Head rot caused due to this fungus have caused the reduction in the seed yield and quality of sunflower seed.
This fungus has caused the initial flower and flower bud rot which lead to the premature death of the fruits and other infected parts in Rauvolfia serpentine in India.
“When warm, humid, wet weather coincide with the flowering and fruiting season, rhizopus rot cause the total loss of fruit in jackfruit trees.”(Scot Nelson, 2005).It is the most important post harvest disease in sweet potato as well.
This fungus has the branched and filamentous hyphae generally without the cross wall (i.e. coenocytes).The presence of root like rhizoid and stolon is the characteristic feature of this genus.
Presense of recurved sporangiophore is the diagnostic morphological characteristics of genus Rhizopus.Rhizoids and stolons are hyaline to dark brown in color.
The sporangiophores contain the dark, round sporangium that contains an apophsate columella and several oval, colorless or brown spores. Columella is the sterile portion in the sporangium which helps in exchanging nutrient between the active protoplasm below and the developing spores inside the upper portion of the sporangial head. Collarette is the remnant of sporangial wall when it dissolves. The columella is apophysate i.e. swollen.
They have the network of filament (hyphae) which penetrate inside the bread surface and extract the nutrient from it. They are multicellular with the cell wall made up of chitin
Structure
Size
Shape
Color
Sprangia
82.7×196.7 mm
Globose/sub globose and flattened at base
First white then black
Sporangiophore
2.6~5.8×12.3~24.2 mm
Simple/long/smooth walled/non septate
Light brown
Sporangiospore
8.2~18.8 mm in diameter
irregular,irregular oval, elongate, angular
Brownish black
streaked
Columella
64.1×136.3 mm
Umbrella shape
Brownish gray
Kingdom:
Fungi
Phylum:
Zygomycota
Class:
Zygomycetes
Order:
Mucorales
Family:
Mucoraceae
Genus:
Rhizopus
Species:
Rhizopus stolonifer
Molecular phylogeny of this fungus has been studied through the rDNA sequencing which was found useful for the molecular identification of the species. Phylogenetic analysis
inferred from the D1/D2 region of LSU rDNA sequences gives us the idea that the genus Rhizopus contain four clades, the R. lyococcus group, the R. stolonifer group, the R. oryzae group, and the R. microsporus group.
This pathogen causes the huge loss in the agriculture commodity there by creating the problem for human being and is the cause of zygomycosis in human being. In the flip side, it fungus has some good quality that can be utilized for benefit of human kind. It can produce transform the steroid hormone (e.g. progesterone) so it is used to make the birth control pill which is used by women to prevent the pregnancy.
Prinsen Geerligs in 1985 found that this mold can be used to ferment the tempeh. Furthermore, it can be used for the commercial production of alcohol, organic acid, fumaric acid and cortisone.
This versatile phytopathogen excretes the fungal peptic enzymes that degrade and dissolve the pectin contained in the middle lamella of the plant cells. (Miguel Gerardo Velázquez–del Valle, 2007)
This eventually leads to the colonization of agricultural products like vegetable and fruits which is recognized as the soft rot. This pathogen can survive in wide range of temperature and relative humidity
Initially affected part of fruit/vegetable gives the mild pleasant smell but as the yeast and bacteria move inside it the sour odor develops. Initial pleasant fleshy rot may attract fruit flies as well. After some days that vegetable/fruit becomes wet as the fungus start exuding whitish yellow liquid and whole fruit/vegetable is covered by the fungal mycelia with the black sporangia at the tip.
This pathogen has been identified as a Pre-emergence Seedling Disease Pathogen of Beta vulgaris causing damping off on it.
In cherry tomato, the fungus causes cracking on fruits following making wounds on it.Then infected parts on cracks become water soaked and disintegrate in watery rot.
Head rot caused due to this fungus have caused the reduction in the seed yield and quality of sunflower seed.
This fungus has caused the initial flower and flower bud rot which lead to the premature death of the fruits and other infected parts in Rauvolfia serpentine in India.
“When warm, humid, wet weather coincide with the flowering and fruiting season, rhizopus rot cause the total loss of fruit in jackfruit trees.”(Scot Nelson, 2005).It is the most important post harvest disease in sweet potato as well.
This is one of the important species in genus Rhizopus. It is recognized as black bread mold also because it generally attacks the bread and produces the black colored sporangium and spore. In fact it has the whole mycelium of black color.
Rhizopus stolonifer was first established in 1818 by the (Ehthrenberg) Vuillemin. Even he was the first person to discover the genus Rhizopus.
This fungus is worldwide in distribution. They are mostly saprophyte growing on various things like bread, jams, pickles, cheese, moist food stuffs, leather goods, soft fruits and vegetables.
This fungus is regarded as opportunist pathogen of human being as it causes the parlous disease called zygomycosis in which fungal infection are seen in face and oropharyngeal cavity.
This plant pathogen is responsible for causing disease in many vegetables and fruits and recognized as pathogen with wide host range
Rhizopus stolonifer is commonly known as black bread mold.[1] It is a member of Zygomycota and considered the most important species in the genus Rhizopus.[2] It is one of the most common fungi in the world and has a global distribution although it is most commonly found in tropical and subtropical regions.[3] It is a common agent of decomposition of stored foods.[4] Like other members of the genus Rhizopus, R. stolonifer grows rapidly, mostly in indoor environments.[5]
This fungus was first discovered by the German scientist Christian Gottfried Ehrenberg in 1818 as Rhizopus nigricans. The name was changed in 1902 to Rhizopus stolonifer by the French mycologist J. P. Vuillemin.[6]
Rhizopus stolonifer is a worldwide distributed species. It is found on all types of mouldy materials. It is often one of the first molds to appear on stale bread.[6] It can exist in the soil as well as in the air. A variety of natural substrata are colonized by this species because R. stolonifer can tolerate broad variations in the concentration of essential nutrients and can use carbon and nitrogen combined in diverse forms.[6]
In the laboratory, this fungus grows well on different media, including those that contain ammonium salts or amino compounds.[6] However, R. stolonifer will not grow on Czapek's agar because it cannot utilize nitrogen in the form of nitrate.[6] Rhizopus lives in hyphae and matured spores.
This species is known as a saprotroph and plays an important role in the early colonization of substrata in soil. Nonetheless, it can also behave as a parasite of plant tissues causing a rot of vegetables and fruits.[2] Like other species of Rhizopus, R. stolonifer grows rapidly and spreads by means of the stolons.[2] The stolons provide an aerial structure for the growth of the mycelium and the occupation of large areas. They can climb vertically as well as horizontally.[7] Rhizopus species periodically produce rhizoids, which anchor it to the substrate and unbranched aerial sporangiophores.[8] Sporangiophores of R. stolonifer can be up to 2.5 mm long and about 20 μm in diameter.[6] The spores are shaped differently depending on the available nutrients. They can be ovate, polygonal or angular.[6] The optimal temperature for growth varies between 25 and 30 °C.[7] The thermal death point, which is defined as the lowest temperature that can kill all cells in ten minutes, is 60 °C.[7] Rhizopus stolonifer can grow in acidic environments with a pH of as low as 2.2. The pH range can vary from 2.2 to 9.6.[9] Ultraviolet irradiation can delay spore germination.[10]
Rhizopus stolonifer can reproduce asexually and sexually. It is a heterothallic species.[3] Sexual reproduction occurs when compatible mating strains are paired, ultimately giving rise to zygospores. The sporangiophore contains both '+' and '−' mating type strains.[11] Meiosis is delayed until the germination of the zygospores. The gametogenia often differ in size, regardless of mating type. This difference in size is not due to sex but presumably due to nutrition.[12]
The disease caused by this fungus occurs mainly on ripe fruits, such as strawberries, melon and peach, which are more susceptible to wounds and have a higher sugar content.[13] R. stolonifer can also cause soft rot of many vegetables, flowers, bulbs, corms, and seeds.[14] After a couple of days, the infected fruits become soft and release juices with an acidic odour.[13] When the humidity and temperature are favourable, the mycelial growth occurs rapidly at the surface of the infected fruit and the disease causes the development of long mycelial stolons with black sporangia and spores.[13] When the fungus germinates, it produces different kinds of esterases, including cutinase, which help the fungus to penetrate the plant cell wall.[13] The disease can also affect other adjacent healthy fruits when distributed by wind or insect activity.[4]
Some species of Syncephalis can reduce the asexual reproduction of R. stolonifer and therefore may delay or even prevent the post-harvest disease caused by this fungus.[15] Fengycin, which is an anti-fungal complex, also induces the fungal cell death via necrosis and apoptosis.[16] The treatment of sweet potatoes with sodium orthophenyl phenol (Stopmold B) and dichloran (Botran W) have effectively reduced storage rot.[17]
Rhizopus stolonifer is an opportunistic agent of disease and hence will only cause infection in people with a weakened immunity. Zygomycosis is the main disease that might be caused by this fungus in humans and while it is not entirely understood yet, this disease is very dangerous and can be fatal.[11] More commonly, Rhizopus stolonifer may cause respiratory infections, sinusitis, and otomycosis.[18] The action of smelling spoiled food may be a source of inhalation exposure to the mold.[11]
Rhizopus stolonifer is important economically as an agent of post-harvest storage decay.
While Saccharomyces cerevisiae is the most important source of industrial alcohol, R. stolonifer and other species of Rhizopus also produce ethyl alcohol which is the most important fermentation product.[4] Rhizopus stolonifer is also used commercially to manufacture fumaric acid and lactic acid of high purity.[19] The presence of zinc reduces the amount of fumaric acid produced by the fungus.[10]
Rhizopus stolonifer is commonly known as black bread mold. It is a member of Zygomycota and considered the most important species in the genus Rhizopus. It is one of the most common fungi in the world and has a global distribution although it is most commonly found in tropical and subtropical regions. It is a common agent of decomposition of stored foods. Like other members of the genus Rhizopus, R. stolonifer grows rapidly, mostly in indoor environments.
