No abstract

Streptomyces scabies (Thaxter) causes destructive and serious damages to many vegetable field crops, including potato. Fourteen pure isolates were obtained from naturally diseased potato tubers showing symptoms of common scab disease, collected from different localities of Sohag governorate, Egypt. All tested isolates were identified as S. scabies (Stc) according to morphological and biochemical tests. Isolate Stc 10 exhibited the highest activity of polyphenoloxidase enzyme, followed by isolate Stc 11, while isolate Stc 2 produced the lowest activity of this enzyme. Concerning the peroxidase activity, the isolates varied in their production; Stc 11 exhibited the highest activity enzyme, followed by isolate Stc 2, whereas isolate Stc 10 produced the lowest activity of enzyme. In regard with Tyrosine Amonnia Lyase (TAL) activity, isolate Stc 2 exhibited the highest activity, followed by isolate Stc 10, whereas isolate Stc 11 exhibited the lowest activity. Agarose gel electrophoresis of the PCR amplification products revealed a band representing the expected 279 bp DNA fragment in each DNA extracted from the highly pathogenic isolates Stc 10 and 11. The results demonstrated that PCR amplification of the nec1 gene could be used as a reliable marker for detecting pathogenic Streptomyces isolates on potato tubers.

Ralstonia solanacearum is one of the most critical and widespread pathogenic bacteria that causes wilt disease in vegetable crops, including potatoes. In vitro study was conducted to screen potential actinobacterial isolates for their antibacterial activity against two isolates (Rs3 and Rs11) of bacterial wilt pathogen, R. solanacearum. Soil samples were collected from different localities. From collected soil samples, 45 morphologically distinct actinomycetes isolates were isolated. In the screening test, 7 isolates were selected, showing inhibitory activity against the pathogen. These seven efficient isolates were subjected to the cell-free suspension test. From the cell-free suspension test, only three cell-free suspensions of 3 isolates exhibited inhibitory activity against both pathogenic isolates. Isolate ACT27 exhibited the highest effect on both tested Rs3 and Rs11 pathogenic isolates, followed by ACT7 and ACT9. Whereas isolates ACT20, ACT33, and ACT13 showed the intermediate effect on both tested pathogenic isolates Rs3 and Rs11. Data also indicated that isolate ACT22 exhibited a minor effect on both tested Rs3 and Rs11 pathogenic isolates. Data also indicated that only three cell-free supernatants of isolates (ACT7, ACT9, and ACT27) give an inhibitory effect against both tested R. solanacearum pathogenic isolates. They are not varied so much in the degree of their activity. In this study, it can be concluded that actinomycetes isolates have antibacterial activity against this target pathogen. Also, the investigated isolates can be used through detailed further in vivo tests.

Streptomyces common scab is one of the most bacterial diseases that costs economic loses to potato plants. Streptomyces scabiei (Thaxter 1891) Lambert and Loria (syn. Streptomyces scabies) is the main causal agent of common scab in potato in the field. Eight potato cultivars namely, Diamont, Lady Rossete, Burna, Lady Bellford, Skenta, Flora, Brofent and Everest were tested for their susceptibility to common scab disease under greenhouse conditions. They varied to some extent in the degree of their susceptibility. Lady Rosette appeared to be the highest susceptible one followed by Burna, Everest, and Skenta. Lady Bellford, Diamont respectively, and Brofent showed intermediate disease severity. Flora cultivar exhibited the least degree of scab symptoms. The role of certain potato tubers constituents in the physiology of disease susceptibility was investigated (sugar contents, pectin substances and calcium contents), Lady Bellford cultivar contained the highest concentration of total sugar followed by Flora, Burna, and Everest but Skenta, Lady Rosette respectively and Diamont were approximately had equal in total sugar contents, while, Brofent cultivar contained the lowest content of total sugar. Skenta cultivar contained the highest concentration of pectin substances and calcium contents followed by Flora and Lady Bellford finally Burna cultivars respectively.

Cactus pear is a dominant crop to arid lands with high nutritional value. The cactus pear fruits are used in food processing as add value to food products. In this study, cactus pears were grown under three irrigation regimes (T1, T2, and T3) where two of them (T2 and T3) implicated severe deficit irrigation conditions on the crop. The relationship between applied irrigation water regimes and fruit physical and chemical properties including antioxidants, pigment and vitamin C content was studied. Also, the aim from this study utilizes cactus pear"s pulp (CPP), as additive value, in the processing of wheat flour cupcake. Samples of cupcake were made by adding 20%, 40%, 60% and 80% CPP based on wheat flour weight. Fruits obtained under T2 and T3 treatments had higher color concentration than T1. T2 irrigation regime yielded higher contents of total phenolic and flavonoid (TPC and TFC) than those produced under T3 and T1. Antioxidant activity was the highest in T2. Thus, fruits pulp obtained from T2 was selected for cupcake making. The content of soluble solids was 18 Brix in all treatments. Vit C. was significantly higher (P≤0.05) in T3 (56.04 g AA/kg) than T1 (55.42 g AA/kg) and T2 (51.01 AA/kg). The content of betacyanin"s in T1 was higher (0.47 mg \100mg dry weight) in fruits pulp than T2 and T3 (0.44 and 0.54 mg\100mg dry weight). Sensory evaluation showed that fortification with 60% cactus pear pulp had the best sensory characteristics meanwhile cupcakes fortified with 80% cactus pear pulp was not acceptable.