2. Manifestation of pokkah boeng

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

140 Fusarium - Plant Diseases, Pathogen Diversity, Genetic Diversity, Resistance and Molecular Markers

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 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

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,

Fusarium species complex, a destructive fungal disease in sugarcane-growing regions.

and physiological disorders and nutritional deficiencies.

roots of plants.

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 damaged top, and stalk may occur in highly susceptible varieties. The base of affected leaves is often narrower than that of normal leaves. Ladder-like lesion on the spindle leaves pronounced yellowing, wrinkling of the spindle, twisting or tangling appearance of the spindle, marketing red stripes, and shortening of the leaves accompanied the malformation or distortion of the young leaves. The most advanced and serious stage of pokkah boeng is a top rot phase. Leaf infection sometimes continued to downward and penetrates in the stalk by way of a growing point. The young spindles are killed and the entire top dies. Leaf sheaths may also become chlorotic and develop asymmetrical necrotic areas of reddish color.

physiological responses in plants and animals. It also produces a variety of other compounds

*Fusarium* Species Complex Causing Pokkah Boeng in China

http://dx.doi.org/10.5772/intechopen.73133

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Fusarium species are commonly identified based on their micro- and macroscopic features. But these features are mostly unstable and render the taxonomy of the group problematic. The presence of different taxonomic systems for the genus also contributes to this problem. A number of molecular tools have been used to circumvent these limitations and also to characterize Fusarium isolates in terms of their genetic diversity, population biology, and phylogeny. In the studies presented here, Fusarium strains isolated from agricultural soils and plant tissues

Fusarium fujikuroi (formerly Gibberella fujikuroi) species complex (FFSC) members cause important diseases in gramineous crops. The FFSC becomes compatible with the species concept of F. moniliforme as described by Snyder and Hansen or section Liseola as defined by Wollenweber and Reinking. Fusarium fujikuroi is known to produce a broad spectrum of secondary metabolites. To recognize and define species in the FFSC, various operational species concepts have been applied. However, a variety of genetic, ecological, and biological traits and properties may be used for this purpose. Only morphological species recognition (MSR), biological species recognition (BSR), and phylogenetic species recognition (PSR) have contributed significantly to the classification of Fusarium species in the FFSC. Of these, the MSR was the most widely used and has dominated Fusarium taxonomy since its establishment in 1809. The MSR also takes into account physiological characters such as growth rates at different temperatures, host associations, and secondary metabolite production. The majority of the current GFC species definitions and descriptions are based on such polyphasic or integrative taxonomic approaches that incorporate various types of data. Till now, two species of FFSC have been identified to cause

Fusarium verticilloides is the most commonly reported fungal species infecting sugarcane. F. verticillioides is the accepted species, which was also known as Fusarium moniliforme. It can able to produce the chemical agent fusaric. Among the Fusarium species, F. verticillioides is the most prominent Fusarium species in China. It is regulated by the fumonisin biosynthetic gene cluster (FUM), responsible for transport proteins. In our previous study, a total of 101 isolates were recovered from the sugarcane plants affected by pokkah boeng, which were collected from the major sugarcane-producing areas (Guangxi, Yunnan, Guangdong, Fujian, Hainan) in China throughout 2012 and 2013. More than 90% of the isolates (94 isolates) belonged to F. verticillioides, which was closely related to F. sacchari, using the morphological observation and the phylogenetic tree of rDNA-ITS region sequence amplified using fungus-conserved ITS1 and ITS4 primers.

Fusarium verticillioides causes seedling decay, stalk rot, and mycotoxin contamination in sugarcane. This destructive disease occurs virtually everywhere that sugarcane is grown worldwide. Airborne spores (conidia) arising from fungal growth on plant debris or current growth on silks or leaves may cause infection. F. verticillioides (teleomorph Gibberella moniliformis) is a filamentous fungus that produces two types of conidia—macroconidia and microconidia. The fungal colony of the F. verticillioides isolate (CNO-1) appeared to be pale in color but became

such as other mycotoxins, pigments, antibiotics, and phytotoxins.

were characterized using different DNA-based tools.

sugarcane pokkah boeng disease in China.

3.1.1. Fusarium verticillioides

The reddish tissue form ladder-like lesions, often with dark edges. These lesions sometimes break through the surface of the rind. Occasionally, the pathogen also attacks the spindle, and from there it moves down the terminal portion of the stalk causing top rot. The pathogen makes its entry into the host tissues through any sort of injury made by insects or borers or natural growth cracks, etc. The severity of symptoms varies with the susceptibility of a variety and with the congenial environmental conditions and governs the development of the causal organism. During fungal penetration and growth inside the plant, Fusarium proteases and mycotoxins act in a kind of strategic cooperation during spike and core colonization by featuring complementary roles during the host defense suppression and the intracellular colonization of spikelet.
