Plant-pathogenic fungi produce an array of extracellular hydrolytic enzymes that enable them to penetrate and infect the host tissue; these enzymes are collectively called cell wall-degrading enzymes (CWDE). They may contribute to pathogenesis by degrading wax, cuticle and cell walls, thus aiding tissue invasion and pathogen dissemination. Furthermore, they can act as elicitors of host defense reaction.Fusarium head blight (FHB) is a disease caused principally by Fusarium graminearum on crops, occurring all over the world. Important economic losses on wheat-growing areas have been registered by altering quality parameters of grains. Significant progress has been made in understanding the infection process from F. graminearum on wheat, based on genomic technologies. The virulence degree of this phytopathogen on crops could arise from differences in the production of extracellular enzymes, factors controlling the establishment of infection.Fusarium graminearum isolates from different geographical areas have been examined, and a combination of morphological and molecular data allowed the division of fungi in diverse groups, which have been related to the variation in pathogenicity. In most studied cases there is a correlation between the presence of pectic enzymes, disease symptom and virulence, being also their production decisive in the infection process.

Chitin, the most abundant aminopolysaccharide in nature, is a rigid and resistant structural component that contributes to the mechanical strength of chitin-containing organisms. Chemically, it is a linear cationic heteropolysaccharide composed of N-acetyl-D-glucosamine and Dglucosamine units. The enzymatic degradation of chitin is performed by a chitinolytic system with synergistic and consecutive action. Diverse organisms (containing chitin or not) produce a great variety of chitinolytic enzymes with different specificities and catalytic properties. Their physiological roles involve nutrition, parasitism, chitin recycling, morphogenesis, and/or defense. Microorganisms, as the main environmental chitin degraders, constitute a very important natural source of chitinolytic enzymes. Nowadays, the most used method for pest and plant diseases control is the utilization of chemical agents, causative of significant environmental pollution. Social concern has generated the search for alternative control systems (i.e., biological control), which contribute to the generation of sustainable agricultural development. Interactions among the different organisms are the natural bases of biological control. Interest in chitinolytic enzymes in the field of biological control has arisen due to their possible involvement in antagonistic activity against pathogenic chitin-containing organisms. The absence of chitin in plants and vertebrate animals allows the consideration of safe and selective "target" molecules for control of chitin-containing pathogenic organisms. Fungi show appropriate characteristics as potential biological control agents of insects, fungi, and nematodes due to the production of fungal enzymes with antagonistic action. The antagonistic interactions between fungi and plant nematode parasites are among the most studied experimental models because of the high economic relevance. Fungi which target nematodes are known as nematophagous fungi. The nematode egg is the only structural element where the presence of chitin has been demonstrated. In spite of being one of the most resistant biological structures, eggs are susceptible to being attacked by egg-parasitic fungi. A combination of physical and chemical phenomena result in their complete destruction. The contribution of fungal chitinases to the in vitro rupture of the eggshell confirms their role as a pathogenic factor. Chitinases have been produced by traditional fermentation methods, which have been improved by optimizing the culture conditions for industrial processes. Although wild-type microorganisms constitute an alternative source of chitinolytic enzymes, the advances in molecular biology are allowing the genetic transformation of fungi to obtain strains with high capability as biocontrol agents. Simultaneously, a better understanding of rhizosphere interactions, additional to the discovery of new molecular biology tools, will allow the choosing of better alternatives for the biological control of nematodes in order to achieve an integrated management of t...

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Nippon Eiyo Shokuryo Gakkaishi (J. Jpn. Soc. Nutr. Food Sci.) 36, 219~224 (1983) Relationship between maceration and pectic-substance release of vegetable tissues when they were boiled in different pH solutions was studied. The results obtained were as follows : 1. Vegetable tissues were kept firm when cooked at pH 4. They were rapidly softened by cooking either above pH 5 or below pH 3. By prolonged cooking carrot, potato and Japanese radish were considerably macerated even at pH 4. Maceration of lotus and burdock, however, was very slow under the same conditions. 2. Pectic substances released from vegetables during cooking were the least at pH 4 and they increased above pH 5 and below pH 3. 3. Pectic substances released from vegetables during cooking above pH 6 gave positive results by the thiobarbituric acid tests. These results suggest that the enhanced softening at neutral and alkaline pH is ascribed to the degradation of pectin by a transelimination mechanism but at low pH it is caused by hydrolytic cleavage of pectin and removal of divalent cation from the cell walls of vegetables. 4. The rate of softening of vegetables by cooking depends on their kinds. It is likely that the obstruction to softening of vegetables such as lotus and burdock is caused by heat-resistant and insoluble substances other than pectin of middle lamella, covalent connections between pectin and other insoluble cell wall materials, or rigid structures of the tissues.-ì •Ø ‚ðŽÏ ‚½ ‚AE ‚«‚Ì ŽÏ •` ‚ÌpH‚AE •d ‚³‚É ‚ ‚¢ ‚Ä ‚ÌOE¤ ‹ † ‚Í Hughes‚ç1)‚Ì ‚ ¶ ‚Ⴊ ‚¢ ‚à‚É‚Â ‚¢ ‚Ä ‚AE,Sterling2)‚Ì ‚É ‚ñ ‚ ¶‚ñ‚É ‚ ‚¢ ‚Ä ‚Ì•ñ ••‚ª ‚ ‚邪,‚¢ ‚¸‚ꂸ‚ê ‚àƒy ƒN ƒ` ƒ"Ž¿ ‚AE ‚Ì ŠÖ OEW‚ð '² ‚× ‚Ä ‚¢ ‚È ‚¢•B OEã "¡ ‚ç3)‚Í ‚ê ‚ñ ‚±‚ñ ‚ðpH4.1•` 6.5‚Å ‰Á "M ‚µ‚½ ‚AE ‚« ƒy ƒNƒ`ƒNƒ`ƒ" ‚ª-n •o ‚· ‚épH‚AE,ƒy ƒN ƒ` ƒ"‚ª "M-n ‰t ' † ‚Å•ª ‰ð ‚· ‚épH‚ª ‚¾ ‚¢ ‚½ ‚¢ˆê 'v ‚· ‚é ‚± ‚AE ‚© ‚ç,-ì •Ø ‚ð ŽÏ ‚Ä•_ ‚ç‚© ‚É ‚È ‚é ‚Ì ‚Í •×-E •Ç ‚É ŠÜ ‚Ü‚ê ‚Ä ‚¢ ‚éƒy ƒNƒ`ƒNƒ`ƒ"Ž¿ ‚Ì' †,‚¨‚à‚É‚¨‚à‚É ƒy ƒNƒ`ƒNƒ`ƒ"‚ª ƒgƒ‰ƒ" ƒX ƒG ƒŠ ƒ~ƒl •[ ƒV ƒ ‡ƒ"‚É ‚ae ‚Á‚Ä •ª ‰ð ‚· ‚邽 ‚ß ‚Å ‚ ‚é ‚AE•ñ •• ‚µ‚Ä ‚¢ ‚é•B-{ •ñ ‚Å ‚Í,Ž_ •« •ó 'Ô ‚Å-ì•Ø ‚ð ŽÏ ‚½•ê • ‡ ‚Ì-ì •Ø ‚Ì"î ‰» ‚AE ƒy ƒNƒ`ƒ" Ž¿ ‚Ì ŠÖOEW ‚ð-¾Šm ‚É ‚· ‚é-Ú"I ‚Å,Še Ží-ì •Ø ‚ðpH 1•`8‚Ì ŠÉ •Õ ‰t ‚¨‚ae‚Ñ‚¨‚ae‚Ñ •… ' † ‚Å ‰Á "M ‚µ‚½ ‚AE‚«‚Ì-ì •Ø ‚Ì •d ‚³ ‚AEƒy ƒNƒ`ƒ" Ž¿ ‚Ì-n •o-¦ ‚Ì ŠÖ OEW‚ð OEŸ "¢ ‚µ‚½ •B "¯Žž ‚É-ì •Ø ‚Ì Ží-Þ ‚É ‚ae ‚é"î ‰» ‚Ì"ï ˆÕ ‚Ì OE´ˆöOE´ˆö ‚É‚Â ‚¢ ‚Ä'² ‚× ‚½ ‚Ì‚Å ‚±‚ê ‚ç ‚ÌOE‹ ‰Ê ‚ð •ñ ••‚· ‚é•B ŽÀ OE± •û-@