Abbes Zouhaier, Kharrat Mohamed, Delavault Philippe, Chaïbi Wided, Simier Philippe
Institut National de la Recherche Agronomique de Tunisie (INRAT), Laboratoire des Grandes Cultures, Rue Hédi Karray, 2080 Ariana, Tunisia.
Plant Physiol Biochem. 2009 Feb;47(2):153-9. doi: 10.1016/j.plaphy.2008.10.004. Epub 2008 Nov 1.
The parasitic weed Orobanche foetida (Poiret) is an emergent agronomical problem on faba bean in Tunisia. The Tunisian breeding programs for faba bean resistance to O. foetida have produced several tolerant lines including the line XBJ90.03-16-1-1-1, which limits both parasite attachments to the host roots and growth of the attached parasites. The present study aims to provide a better understanding of the nutritional relationships between the parasite and this tolerant line in comparison with the susceptible Bachaar genotype. Phloem saps of faba bean were harvested using phloem exudation experiments. The major organic compounds potentially transferred from both faba bean genotypes to the parasite were identified as sucrose, raffinose, stachyose, citrate, malate, asparagine (ASN), aspartate (ASP), glutamine, glutamate, serine, alanine and GABA. However, the phloem exudates of the tolerant line were highly deficient in nitrogen when compared to that of the susceptible line. When attached to roots of the tolerant line, the parasite displayed limited activities of soluble invertases in tubercles, and especially in shoots, suggesting that the low performance of the broomrapes attached to the tolerant line resulted from a reduced capacity to utilize the host-derived carbohydrates. On the other hand, the mechanisms involved in the osmotic adjustment and primary metabolism of the parasite did not differ significantly according to the host genotype: mineral cations, especially potassium and calcium, predominated as the major osmotically-active compounds in both tubercles and shoots; shoots accumulated preferentially hexoses as organic solutes although tubercles accumulated preferentially starch and soluble amino acids, especially ASP and ASN. This suggests an important role for a glutamine-dependent asparagine synthetase (EC 6.3.5.4) in the N metabolism of the parasite.
寄生杂草列当（Orobanche foetida (Poiret)）是突尼斯蚕豆种植中出现的一个农业问题。突尼斯针对蚕豆抗列当的育种项目培育出了多个耐性品系，包括XBJ90.03 - 16 - 1 - 1 - 1品系，该品系既能限制寄生虫附着于寄主根部，又能抑制附着寄生虫的生长。本研究旨在与感病的Bachaar基因型相比，更好地了解寄生虫与该耐性品系之间的营养关系。通过韧皮部渗出实验采集蚕豆韧皮部汁液。两种蚕豆基因型中可能转移至寄生虫的主要有机化合物被鉴定为蔗糖、棉子糖、水苏糖、柠檬酸盐、苹果酸盐、天冬酰胺（ASN）、天冬氨酸（ASP）、谷氨酰胺、谷氨酸、丝氨酸、丙氨酸和γ-氨基丁酸。然而，与感病品系相比，耐性品系的韧皮部渗出物中氮含量极低。当附着于耐性品系根部时，寄生虫在瘤状物中，尤其是在地上部分，可溶性转化酶的活性有限，这表明附着于耐性品系的列当生长不良是由于利用寄主来源碳水化合物的能力降低所致。另一方面，根据寄主基因型，寄生虫渗透调节和初级代谢所涉及的机制并无显著差异：矿质阳离子，尤其是钾离子和钙离子，是瘤状物和地上部分主要的渗透活性化合物；地上部分优先积累己糖作为有机溶质，而瘤状物则优先积累淀粉和可溶性氨基酸，尤其是ASP和ASN。这表明谷氨酰胺依赖性天冬酰胺合成酶（EC 6.3.5.4）在寄生虫氮代谢中发挥着重要作用。
