Plant Extracts Inducing Enzyme Activity in Grains Against Loose Smut Disease

This study investigated the role of endogenous Palestinian plant extracts in inducing wheat and barley resistance systems against loose smut disease with the aim to alternate the chemical pest control with natural fungicides. Twenty indigenous herbal plant extracts and essential oils were assessed for their biological and antifungal properties against Ustilago tritici and Ustilago nuda. Their potential role in inducing resistance pathways was studied on four different cultivars of wheat and barley. Two common enzyme indicators – guaiacol peroxidase (POX) and polyphenol oxidase (PPO) – are expressed in plants only after physical or chemical induction. The antifungal activity of the plant extracts was investigated in vitro. Totally 70 % of the plant extracts showed antifungal activity against Ustilago tritici and Ustilago nuda. Coridothyme extracts ranked first (61 %) in the fungal growth inhibition, followed by varthemia, salvia, ambrosia, artemisia, and lemon thyme. Some plant extracts significantly increased the POX and PPO effect compared to control for all the wheat and barley cultivars tested. The study revealed that oregano, clove or lavender and pomegranate, common yarrow or chamomile oil effectively induced the resistance indicator enzymes in wheat and barley.

Screening of winter barley varieties (Hordeum vulgare) for resistance against loose smut (Ustilago nuda) and covered smut (Ustilago hordei) in Germany

see the full text

Inheritance of Carboxin Resistance in a European Field Isolate of Ustilago nuda

Two carboxin-resistant field isolates of Ustilago nuda from Europe were crossed with a carboxin-sensitive field isolate from North America. Meiotic tetrads isolated from germinating F1 teliospores of one of the hybrids were tested for carboxin resistance and mating type. Carboxin resistance was shown to be controlled by a single gene (CBX1R), because a 1:1 segregation of carboxin resistance was observed in all 27 tetrads. Tetrad analysis indicated that the loci for carboxin resistance (Cbx1) and mating type (MAT1) segregate independently but may be located on the same chromosome. Tetrad analysis was not possible with the F1 hybrid of he other field isolate, and its resistance cannot yet be attributed to CBX1R. Carboxin resistance was qualitatively dominant to sensitivity in vitro, as demonstrated by triad analysis of germinating F1 teliospores. Quantitative in planta infection percents supported the conclusion that CBX1R is dominant, although incompletely, in the F1 hybrid of one of the field isolates. Also, fewer than expected carboxin-sensitive F2 individuals were observed in planta. However, inoculations of host plants with U. nuda have resulted in similar, unexpected variation in the past.