Variations in macadamia varietal susceptibility to Phytophthora multivora and P. cinnamomi

Incidence of diseases caused by various Phytophthora spp. in macadamia is increasing worldwide, often resulting in severe yield loss and death of both juvenile and old macadamia trees. In Australia, P. cinnamomi and P. multivora has been identified to cause severe stem canker in macadamia orchards. Currently, various varietal improvement research programs on macadamia are underway, not only to obtain high-yielding and precocious macadamia germplasm but to develop macadamia genotypes with acceptable levels of tolerance/resistance to pests and diseases. In this study, we selected macadamia genotypes for their acceptable levels of tolerance/resistance to Phytophthora infection, after screening about 360 macadamia genotypes against to P. cinnamomi and P. multivora, using a rapid detached leaf and plant inoculation assays. These macadamia plant materials were collected from a major macadamia arboretum in Queensland. Our results revealed segregation of macadamia genotypes into two spectrum of susceptible and tolerant macadamia genotypes. Hence, strong representatives within the tolerant and susceptible spectrum were further investigated in order to understand if the basis of the differential response is driven by a variation in structural, physiological or genetic markers, following a challenge with Phytophthora spp. Our result revealed a marked variation in structural response during the infection process, between the selected susceptible, ‘HAES816’ and tolerant germplasm and ‘HAES344’. This information will provide evidence to support potential preferential selection of tolerant macadamia genotypes potentially useful for breeding against Phytophthora diseases. Further studies will characterize tolerant macadamia progenies to develop marker-assisted selection protocols for resistance, and explore defense mechanisms response.

Bacterial and Fungal Pathogen Synergetics after Co-infection in the Wheat (Triticum aestivum L.)

Wheat is one of the most important staple grains in the world and the leading source of calories, production is limited by biotic stress. There is a number of pathogen attacks on wheat crops, depending on environmental conditions. In some cases, more than one crop pathogen attack leads to higher damage or decrease susceptibility. There are very few studies in the field of multiple pathogen interactions; in this study, we analyzed the co-infectionof wheat with fungal and bacterial pathogens. Field isolated Xanthomonas translucens and Xanthomonas compestris bacteria have been used against GM-322 and PDKV varieties co-infected with Fusarium fungus spp. In our experiment, we used Fusarium oxysporum, Fusarium graminearum, Fusarium equitus. Compared to the combined effect of the fungus and bacteria, we measured the length and width of the infected leaf part. We have observed that there is more susceptibility to X. compestris and F. graminearium in the GM-322 wheat variety. The second susceptible cvs was PDKV when we co-infected F. oxysporum and then X. translucens fungal and bacterial infected symptom analysis showed yellow stripes on the leaf surface of the wheat crop. We observed head blight in wheat when it was infected with F. graminearum and X. compestris. As a result, we concluded that varietal susceptibility also depends on co-infection pathogen attacks and their synergetic interaction.

Weeds and weed control in forage pea: A Review

A major limitation factor for the low productivity in peas is weeding. A particularly critical moment in the race between the crop and weeds is the early period of growth and development. Given the influence of the varying climatic and soil conditions on the diversity and density of weed species, a differentiated approach is needed to remove them by using chemical and agrotechnical means. Studies on the varietal susceptibility to herbicides in forage pea in Bulgaria are very limited due to the fact that varietal diversity was not available in the recent past. The objective of the paper is to present a short analysis of the studies relating to weeding in peas and the control of the more important weed groups in it as well as to establish an individual approach in applying agrotechnical and chemical methods for weed control in growing different pea varieties of winter and spring forms. The use of pea varieties different in biological type as well as the possibilities to use varieties from the European variety list in modern agriculture determines the need to test the reaction of each individual variety not only to the herbicides recommended for this crop, but also to new herbicidal preparations and doses. Determining the composition of weed associations, applying suitable herbicides and herbicide mixtures in weed control of pea, combined with proper agrotechnics, is a prerequisite for optimizing the biological productive potential of the crop.