Ascertaining of Ug99-race specific genes in wheat genotypes assigned to stem rust resistance based on phenotypic and genotypic reaction

Five wheat genotypes including two commercial cultivars (Mist1 and Misr2) and three Ug99-race specific genes (Sr24, Sr25, and Sr31) were screened for stem rust resistance based on phenotypic and genotypic reaction. Based on phenotypic reaction, Sr24 (LcSr24Ag) and Sr31 (Seri-82) exhibited seeding and adult plant resistance while the wheat cultivars, Misr1 and Misr2 were susceptible. Sr25 Agatha (CI 14048)/9*LMPG-6 DK16 exhibited seedling resistance while showed susceptibility at adult plant stage. Based on genotypic reaction, DNA markers showed that gene Sr25 was only found to be present in Misr1 and Misr2 while Sr24 and Sr31 were absent in both cultivars. Although, virulence to Sr25 was detected. However, avirulence to Sr24 remains this gene as a suitable resistance gene to be incorporated into wheat genotypes for disease resistance to local Pgt population

An active role of systemic fungicides to curb wheat powdery mildew caused by Blumeria graminis f. sp. tritici

Efficacy of five systemic fungicides (flusilazole, propiconazole, diniconazole, cyproconazole and tetraconazol) in curbing powdery mildew disease of wheat (Sakha93) and its impact on yield components were evaluated under field condition during two successive season. Both fungicides, propiconazole and diniconazole exhibited the highest value of efficacy (88.80% each) recording the lowest rate of disease infection (1 each). The contrast was noticed with tetraconazol (55.50% efficacy, 4 disease infection) with significant differences to untreated control during both seasons. The results of fungicide application reflected on yield components where 1000-kernel and 1000-ml weights recorded the highest values with propiconazole (49.03 g and 742.65 g) followed by diniconazole (47.69 g and 737.62 g), respectively. Tetraconazol come in the last order in this respect (44.39 g and 672.07 g). An active role of fungicide (propiconazole) on Blumeria graminis f. sp. tritici was examined on infected wheat leaves (8-day old seedlings) by scanning electron microscopy (SEM). To investigate the effect on early develop of conidia, fungicide was applied at 24 h post inoculation (hpi), and collapsed conidia along with blocked development beyond the primary appressoria were observed. Where conidia germinated, appressoria formed two or three lobes. To investigate the effect on fungal morphogenesis, applying of fungicide at 2 day post inoculation (dpi) greatly reduced the mycelium formation associated with a rapid collapse of hyphae compared with untreated control. Fungicide treatment at 10 dpi inhibited and delayed sporulation alongside formation of aberrant and collapsed conidiophores. The conidiophores formed elongated tubes with no regular or sepatated chain of conidiospores. Results concluded that fungicide is an efficient curative fungicide at very low concentrations if it is applied early enough after infection. Also, fungicide has a significant impact on fungal survival.

Allelism and resistance loci of powdery mildew and leaf rust in Egyptian hexaploid bread wheat

To incorporate resistance genes of powdery mildew (Pm) and leaf rust (Lr) effectively in breeding programs allelic interaction should be explored. The response and molecular patterns of three Pm genes, Pm3, Pm8, Pm17, and three Lr genes, Lr10, Lr24, and Lr26 were investigated in 15 Egyptian wheat cultivars. Postulation of different Pm and Lr resistance genes in Egyptian wheat cultivars was carried out according to seedling phenotyping data that resulted from inoculation with a set of five pathotypes of Blumeria graminis f. sp. tritici and twelve pathotypes of Puccinia triticina. Responses and molecular patterns revealed the presence of resistance genes Pm3 and Lr10 in the cultivar Misr-1, Pm17, and Lr24 in the cultivar Giza-171, and Pm8 and Lr26 in a further ten cultivars. Molecular markers confirmed the presence of Pm8 and Lr26 in six wheat cultivars, Sakha-94, Sakha-95, Gemmeiza-10, Gemmeiza-11, Sids-13, and Shandweel-1. The presence of Pm17 in Giza-171 was confirmed by the STS marker iag95. A comparison of phenotypic and genotypic data between cultivars Giza-171 and Amigo demonstrated that Pm17 in cv Giza-171 is allelic to Pm8. The existence of Lr24 in Giza-171 was confirmed by using STS marker J09. Based on these results, Pm17 and Lr24 in Giza-171 may be located on translocated chromosomes. In cv Misr-1, the presence of Pm3 and Lr10 on the same region of 1AS chromosome could represent a rare recombination event. Field responses revealed specific resistance of Misr-1 and Giza-171, which may be attributed to the presence of Pm3 and Lr10 in Misr-1 and Pm17 and Lr24+ additional genes in Giza-171

Application of plant extracts as inducers to challenge leaf rust of wheat

Abstract Five plant extracts, i.e., henna, Lawsonia inermis; acalypha, Acalypha wilkesiana; chinaberry, Melia azedarach; pomegranate, Punica granatum; and lantana, Lantana camara, were tested as inducers to protect wheat against leaf rust infection caused by Puccinia triticina Eriks. The plant extracts were applied pre-infection on susceptible wheat cultivar "Gemmiza-7" under field conditions during two growing seasons (2016/2017 and 2017/2018). All the tested plant extracts were found to be effective against the leaf rust infection. They significantly reduced the coefficient of infection (ACI) to be ranging 7.50 to 20.00, compared to the non-treated control (ACI = 75.00). Lantana extract was the most effective one (efficiency = 88.88%), which was very close to the fungicide “diniconazole” (efficiency = 89.92%). Henna extract ranked second (80.00%), followed by chinaberry (76.00%), acalypha (72.00%), and pomegranate (68.00%). However, wheat yield components were significantly increased by all the tested treatments, especially lantana extract and the fungicide. Similarly, biochemical analyses revealed a significant increase in the plant contents of chlorophyll a and b, total phenolics, and oxidative enzymes activities (POX and PPO) at all the tested treatments. Results indicated that the tested plant extracts could induce wheat resistance to leaf rust