Compilation (Jenalyn)
Compilation (Jenalyn)
Compilation (Jenalyn)
Rice bacterial blight, also called bacterial blight of rice, deadly bacterial disease that is among
the most destructive afflictions of cultivated rice (Oryza sativa and O. glaberrima). In
severe epidemics, crop loss may be as high as 75 percent, and millions of hectares of rice are
infected annually. The disease was first observed in 1884–85 in Kyushu, Japan, and the causal
agent, the bacterium Xanthomonas oryzae pathovar oryzae (also referred to as Xoo), was
identified in 1911, at that time having been named Bacillus oryzae. Thriving in warm,
humid environments, bacterial blight has been observed in rice-growing regions of Asia, the
western coast of Africa, Australia, Latin America, and the Caribbean. Although not commonly
found in the United States, a bacterial strain related to Xoo has been listed as an agricultural
select agent by the U.S. Department of Agriculture, a designation that places it under strict
regulations.
CONTROL MEASURE
The main control measures are the use of disease-free or treated seeds and crop rotation. Stubble
and straw should be burned after paddy harvesting on unhealthy soil. After seeing the disease, an
additional 20 kg of potash fertilizer per acre should be applied to the water. Spraying chelated
zinc at the rate of 1 gram per liter of water reduces the severity of the disease. Methods of
controlling rice bacterial blight are limited in effectiveness. Chemical control has been largely
ineffective in minimizing bacterial blight because of safety concerns, practicality, and bacterial
resistance. Biological control methods, which rely on the use of bacterial antagonists of
pathogens (disease-causing organisms), can reduce bacterial blight, though their use has been
limited. The most-common method of defending against rice bacterial blight is the cultivation of
rice varieties with genes that confer resistance to Xoo infection. Over 30 resistance genes,
termed Xa1 to Xa33, have been identified in rice plants, and some, such as Xa21, have
been integrated into the genomes of commercial rice strains. These resistant rice varieties have
been largely successful, dramatically reducing yield losses in many rice-producing countries.
FAVOURABLE CONDITIONS
Planting resistant varieties has been proven to be the most efficient, most reliable, and cheapest
way to control bacterial blight.
Banana bunchy top is a viral disease caused by a single-stranded DNA virus called the banana
bunchy top virus (BBTV). It was first identified in Fiji in 1879, and has spread around the world
since then.[1] Like many viruses, BBTV was named after the symptoms seen, where the infected
plants are stunted and have "bunchy" leaves at the top.[2] The disease is transmitted from plant-to-
plant in tropical regions of the world by aphids,[3] banana aphids which can also feed
on Heliconia and flowering ginger (from the family Zingiberaceae), which is an important factor
in control of the disease. There are no resistant varieties, so controlling the spread by vectors and
plant materials are the only management methods.[1] Symptoms include spotting any deformed
plant appearance.
TRANSMISSION
All babuviruses are aphid transmitted including BBTV. Information is lacking regarding vector-
virus interactions. The virus is transmitted through vegetative planting material and tissue
cultured plants derived from infected sources. There are no reports on vector transmission.
However, since the virus is a member of the genus Babuvirus, it is conceivable that the banana
aphid, P. nigronervosa, may able to transmit ABTV in a persistent and circulative manner similar
to BBTV. PCR assays have been established for ABTV detection (Sharman et al., 2008).
NANOVIRIDAE
BOTANICAL DESCRIPTION
Abaca (Musa textilis nee) is a member of the Musaceae family to which the banana also belongs.
Although the resemblance of the abaca to banana is close, there are basic differences. Abaca
stalks are more slender, the leaves are smaller, narrower and more pointed than those of the
banana. A distinguishing dark line on the right hand side of the upper surface of the leaf blade is
pronounced in abaca. The fruit of abaca is smaller, non-edible and contains ,many seeds.
CULTURAL MANAGEMENT
Soil Requirement
Abaca grows in clay loam and sandy clay loam types of soil, rich in organic, matter,
loose, friable and well-drained. The water table is preferably 80 cm with 60%-80% saturation.
The Soil has pH level of 6.0-7.0 and elevation of less than 1,000 m above sea leave.
Climatic Requirements
The optimum temperatures requirements for abaca has not been fully determined, but it grows in
areas with temperatures of 20’C during cool months and 25’C during warm months. A relative
humidity of 78% to 85% and evenly distributed rainfall throughout the year are conditions
conductive to good growth.
METHODS OF PROPAGATION
Seed pieces (corms)
Suckers
Tissue
Culture Seeds
Abaca Mosaic
- is caused by abaca mosaic petiole, pseudostem, flower bracts and fruits. This disease
causes leaf mottling found in the petiole, pseudostem , flower bracts and fruits. Formation
of irregular, pale green or yellowish streaks on the leaves can be seen extending from
midrib to the leaf margin. Spray insecticides to to vectors and infected plants including
the surrounding weeds before rouging and burning the infested plants.