1. Introduction

Sugarcane is a major crop in Southern China, and it is the third biggest sugarcane producer in the world. Sugarcane is one of the most important crops grown commercially in the tropical and subtropical region. Sugarcane belongs to the genus Saccharum L. composed of hybrids [1, 2]

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

derived from Saccharum officinarum (noble clones), S. sinense (Chinese clones), S. barberi (North Indian clones), and S. spontaneum. This species has C4 photosynthesis, resulting in a vigorous biomass accumulation under tropical conditions, but it also implies a less growth in temperate regions. It grows well in deep, well-drained soils of medium fertility of sandy loam soil textures with a pH range from 6.0 to 7.7. It plays a major role in the economy of sugarcane-growing areas. Sugarcane can be affected from different organisms with various factors such as environmental and physiological disorders and nutritional deficiencies.

India, and China [10–14]. Pokka boeng disease of sugarcane has associated with several diseases of sugarcane such as sett rot, root rot, and wilt [15]. The pathogen is transmitted by air currents, and airborne spores will colonize the leaves, flowers, and stems of the plant [16]. Pokkah boeng causes serious yield losses in commercial plantings. Reported outbreaks of the disease, while looking spectacular, have caused economic losses. The fungus was reported to

*Fusarium* Species Complex Causing Pokkah Boeng in China

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Pokka boeng diseases are dependent upon the environmental conditions, quality of setts, and handling of the plants, e.g., exposing sugarcane plants to stress either from water stress, temperature, pH, or soil nutrition. Hail damage can cause cane plants to be easily susceptible to diseases due to the bruised stalks and broken leaves, giving the diseases access to the damaged setts. Some of the favorable conditions for disease development included drenched conditions of the soil, lack of cultural practices that result in the growth of weeds, constant cultivation of same variety in the field, and existence of susceptible varieties in the surroundings. It is very important for a farmer to prevent and control such pests and diseases to avoid losses. Fusarium species complex can produce many kinds of toxic secondary metabolites known as mycotoxins, which can easily enter humans and animals through food and feed

The taxonomy of Fusarium species complex (FSC) is based on phylogenetic, biological, and morphological species concepts [18, 19]. Species in the FSC produce a wide range of mycotoxins that contaminate food and are harmful to human and animal health. Fusarium species are common and can survive for long periods in soil. The nature of Fusarium disease is that they often become a problem after plant stress occurs. It is now well known that Fusarium causes two different diseases, one in stalk and the other in leaves/spindle, and two different species, namely, F. sacchari and F. verticillioides, respectively, were associated with these diseases. Conventional field-based screening for resistance to pests and diseases is a key compo-

Several control measures may be implemented to minimize potential sugarcane yield loss caused by pests and diseases, but an integrated approach is often recommended. Good farming practices are essential but do not guarantee eradication of infections. The planting of resistant cultivars is recommended as the best and most economical approach for controlling pests and diseases, having the least impact on the environment and increasing productivity without the need for other inputs, such as costly chemical applications or labor. Breeding sugarcane that is resistant to multiple pests and diseases is difficult due to the complex genome of sugarcane [21]. Additional genome-scale comparative and functional studies are needed to elucidate the evolution and diversity of pathogenicity mechanisms, which may help inform

The initial symptoms were easy to recognize the disease since they attack the top parts and are chlorotic areas at the base of young leaves. Heavily infected plants showed a malformed or

occur systemically in all plant parts of sugarcane.

because of their resistance to milling, processing, and heating [17].

nent of the breeding program prior to release of a commercial cultivar [20].

novel disease management strategies against Fusarium pathogens.

2. Manifestation of pokkah boeng

Many biotic and abiotic stresses affected the sugarcane production and are known to be one of the oldest cultivated plants in the world. Improving sugarcane production will greatly help in economic prosperity of the farmers and others associated with sugarcane cultivation. Large numbers of sugarcane pathogens have been recorded all over the world. One of the current major diseases affecting sugarcane and sugar production is pokkah boeng. It is caused by Fusarium species complex, a destructive fungal disease in sugarcane-growing regions.

Fusarium is a devastating phytopathogenic fungi belonging to Division: Ascomycota, Class: Sordariomycetes, Order: Hypocreales and Family: Nectriaceae. The fungal genus Fusarium is composed of a large number of species that can be pathogenic on plants. Within the genus the following 16 sections have been recognized: Eupionnotes, Macroconia, Spirarioides, Submicrocera, Pseudomicrocera, Arachnites, Sporotrichiella, Roseum, Arthrosporiella, Gibbosum, Discolor, Lateritium, Liseola, Elegans, Martiella, and Ventricosum. However, many Fusarium species are abundant in fertile cultivated and rangeland soils rather than in forest soils [3]. Fusarium species are causal agents of various diseases affecting many economically important cereals, crops, etc. Airborne Fusarium species are rarely found in the cultures obtained from soil or the roots of plants.

Fusarium species can grow on a variety of substrates and have efficient dispersal mechanisms owing to their worldwide distribution. Plant debris in soils plays a very important role as nutrient reservoir for Fusarium species to continue living in soils as saprotrophs [4]. Fusarium spp. also produce gibberellic acid [5], fusaproliferin, and beauvericin [6]. Fusaproliferin and beauvericin have been found to be toxic to insects [7, 8]. The pathogens are difficult to control by conventional strategies such as the use of resistant host cultivars and synthetic fungicides.

Pokkah boeng disease on sugarcane has been recorded in almost all countries where sugarcane is grown commercially. It normally appears during periods of hot humid conditions when the cane is growing rapidly. This disease was originally described in Java in 1896, denoting a malformed or distorted top. The temperature, light, and fertilizer regimes are optimized for maximal plant growth, but these conditions may also be favorable for pathogens. Walker and Went (1896) were the first ones who describe the pokkah boeng disease on sugarcane. Generally, it appears that slowly growing fungi, which are less efficient than quickly growing fungi at escaping competition by entering specific niches, have a higher prevalence of enmity against competing fungi. Geh [9] first reported the presence of the disease in Malaysia. It may cause substantial damage to the crop and not severe except in very susceptible varieties.

Pokkah boeng is a reemerging disease of sugarcane—which has been found recently to cause major yield losses—in most sugarcane-producing regions, including South Africa, Malaysia, India, and China [10–14]. Pokka boeng disease of sugarcane has associated with several diseases of sugarcane such as sett rot, root rot, and wilt [15]. The pathogen is transmitted by air currents, and airborne spores will colonize the leaves, flowers, and stems of the plant [16]. Pokkah boeng causes serious yield losses in commercial plantings. Reported outbreaks of the disease, while looking spectacular, have caused economic losses. The fungus was reported to occur systemically in all plant parts of sugarcane.

Pokka boeng diseases are dependent upon the environmental conditions, quality of setts, and handling of the plants, e.g., exposing sugarcane plants to stress either from water stress, temperature, pH, or soil nutrition. Hail damage can cause cane plants to be easily susceptible to diseases due to the bruised stalks and broken leaves, giving the diseases access to the damaged setts. Some of the favorable conditions for disease development included drenched conditions of the soil, lack of cultural practices that result in the growth of weeds, constant cultivation of same variety in the field, and existence of susceptible varieties in the surroundings. It is very important for a farmer to prevent and control such pests and diseases to avoid losses. Fusarium species complex can produce many kinds of toxic secondary metabolites known as mycotoxins, which can easily enter humans and animals through food and feed because of their resistance to milling, processing, and heating [17].

The taxonomy of Fusarium species complex (FSC) is based on phylogenetic, biological, and morphological species concepts [18, 19]. Species in the FSC produce a wide range of mycotoxins that contaminate food and are harmful to human and animal health. Fusarium species are common and can survive for long periods in soil. The nature of Fusarium disease is that they often become a problem after plant stress occurs. It is now well known that Fusarium causes two different diseases, one in stalk and the other in leaves/spindle, and two different species, namely, F. sacchari and F. verticillioides, respectively, were associated with these diseases. Conventional field-based screening for resistance to pests and diseases is a key component of the breeding program prior to release of a commercial cultivar [20].

Several control measures may be implemented to minimize potential sugarcane yield loss caused by pests and diseases, but an integrated approach is often recommended. Good farming practices are essential but do not guarantee eradication of infections. The planting of resistant cultivars is recommended as the best and most economical approach for controlling pests and diseases, having the least impact on the environment and increasing productivity without the need for other inputs, such as costly chemical applications or labor. Breeding sugarcane that is resistant to multiple pests and diseases is difficult due to the complex genome of sugarcane [21]. Additional genome-scale comparative and functional studies are needed to elucidate the evolution and diversity of pathogenicity mechanisms, which may help inform novel disease management strategies against Fusarium pathogens.
