Shin-Chuan Hwang

Bio: Shin-Chuan Hwang is an academic researcher. The author has contributed to research in topics: Somaclonal variation & Cavendish banana. The author has an hindex of 1, co-authored 1 publications receiving 199 citations.

Cavendish Banana Cultivars Resistant to Fusarium Wilt Acquired through Somaclonal Variation in Taiwan

Abstract: In vitro propagation produces banana clones that arc very diverse. For 'Giant Cavendish', in addition to resistance to Fusarium wilt, the tissue culture method also generated clones with increased resistance to strong wind, heavier fruit bunches, and sweeter fruit. Therefore, it may be an ideal procedure for horticulturists to select banana clones producing fruit with different taste and might be possible for plant pathologists to select clones resistant to other important diseases. The possibility of applying this technique to the improvement of other crops remains to be exploited. Although 40,000 'Cavendish' plants grown from suckers did not show any visible difference in morphology, about 3 percent of 'Cavendish' plantlets derived from tissue culture were variants. Relatively little is known about the cause of genetic instability induced by the in vitro vegetative propagation. Rapid multiplication and development of cells resulting from mediation of regulators in the tissue culture medium may increase the chance of variation. The mechanism by which the somaclones of 'Giant Cavendish' are resistant to Fusarium wilt is unknown. Since the parental 'Giant Cavendish' is very susceptible to Fusarium wilt, the appearance of resistant somaclones may result from activation of silent resistant genes. However, the creation of resistance genes through mutation as the origin of the resistant phenotype cannot be ruled out. DNA technology will be useful in deciphering the true nature of wilt resistance in the future.

Fusarium Wilt of Banana

Abstract: Banana (Musa spp.) is one of the world's most important fruits. In 2011, 145 million metric tons, worth an estimated $44 billion, were produced in over 130 countries. Fusarium wilt (also known as Panama disease) is one of the most destructive diseases of this crop. It devastated the 'Gros Michel'-based export trades before the mid-1900s, and threatens the Cavendish cultivars that were used to replace it; in total, the latter cultivars are now responsible for approximately 45% of all production. An overview of the disease and its causal agent, Fusarium oxysporum f. sp. cubense, is presented below. Despite a substantial positive literature on biological, chemical, or cultural measures, management is largely restricted to excluding F. oxysporum f. sp. cubense from noninfested areas and using resistant cultivars where the pathogen has established. Resistance to Fusarium wilt is poor in several breeding targets, including important dessert and cooking cultivars. Better resistance to this and other diseases is needed. The history and impact of Fusarium wilt is summarized with an emphasis on tropical race 4 (TR4), a 'Cavendish'-killing variant of the pathogen that has spread dramatically in the Eastern Hemisphere.

Somaclonal variations and their applications in horticultural crops improvement

Abstract: The advancements made in tissue culture techniques has made it possible to regenerate various horticultural species in vitro as micropropagation protocols for commercial scale multiplication are available for a wide range of crops. Clonal propagation and preservation of elite genotypes, selected for their superior characteristics, require high degree of genetic uniformity amongst the regenerated plants. However, plant tissue culture may generate genetic variability, i.e., somaclonal variations as a result of gene mutation or changes in epigenetic marks. The occurrence of subtle somaclonal variation is a drawback for both in vitro cloning as well as germplasm preservation. Therefore, it is of immense significance to assure the genetic uniformity of in vitro raised plants at an early stage. Several strategies have been followed to ascertain the genetic fidelity of the in vitro raised progenies comprising morpho-physiological, biochemical, cytological and DNA-based molecular markers approaches. Somaclonal variation can pose a serious problem in any micropropagation program, where it is highly desirable to produce true-to-type plant material. On the other hand, somaclonal variation has provided a new and alternative tool to the breeders for obtaining genetic variability relatively rapidly and without sophisticated technology in horticultural crops, which are either difficult to breed or have narrow genetic base. In the present paper, sources of variations induced during tissue culture cycle and strategies to ascertain and confirm genetic fidelity in a variety of in vitro raised plantlets and potential application of variants in horticultural crop improvement are reviewed.

Fusarium wilt of banana: Current knowledge on epidemiology and research needs toward sustainable disease management

Abstract: Banana production is seriously threatened by Fusarium wilt (FW), a disease caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc). In the mid-twentieth century FW, also known as "Panama disease", wiped out the Gros Michel banana industry in Central America. The devastation caused by Foc race 1 was mitigated by a shift to resistant Cavendish cultivars, which are currently the source of 99% of banana exports. However, a new strain of Foc, the tropical race 4 (TR4), attacks Cavendish clones and a diverse range of other banana varieties. Foc TR4 has been restricted to East and parts of Southeast Asia for more than 20 years, but since 2010 the disease has spread westward into five additional countries in Southeast and South Asia (Vietnam, Laos, Myanmar, India, and Pakistan) and at the transcontinental level into the Middle East (Oman, Jordan, Lebanon, and Israel) and Africa (Mozambique). The spread of Foc TR4 is of great concern due to the limited knowledge about key aspects of disease epidemiology and the lack of effective management models, including resistant varieties and soil management approaches. In this review we summarize the current knowledge on the epidemiology of FW of banana, highlighting knowledge gaps in pathogen survival and dispersal, factors driving disease intensity, soil and plant microbiome and the dynamics of the disease. Comparisons with FW in other crops were also made to indicate possible differences and commonalities. Our current understanding of the role of main biotic and abiotic factors on disease intensity is reviewed, highlighting research needs and futures directions. Finally, a set of practices and their impact on disease intensity are discussed and proposed as an integrative management approach that could eventually be used by a range of users, including plant protection organizations, researchers, extension workers and growers.