Harmful winter wheat diseases and possibilities for their integrated control in Latvia

Decision support systems based on control thresholds are an important part of integrated disease control systems in winter wheat. Various warning and forecast systems have been developed in different countries (in Latvia – under the framework of Danish-Baltic joint project ‘Development and Implementation of an Internet-based Decision Support System for Integrated Pest Management’), but results were contradictory. The aim of this investigation was to identify the possibilities for integrated disease control under intensive management of winter wheat. Different schemes of fungicide treatment, including a decision support system, were tested in field trials from 2008 to 2012 in two places. Leaf blotches caused by Pyrenophora tritici-repentis and Zymoseptoria tritici are recognised as the most harmful wheat diseases in Latvia. The total impact of diseases, which was calculated as area under disease progress curves, was affected by the year and the scheme of fungicide treatment. Significantly higher yields were obtained in treatments with fungicide application, but differences between control strategies were not significant. The obtained results confirmed that two fungicide applications are not necessary (except certain cases). The results suggest that recommendations should be based on the disease incidence on the third or second leaf of wheat.     

Possibilities for integrated control of winter oilseed rape diseases in Latvia

The sowing area of winter oilseed rape in Latvia has been rapidly increasing during the last 10 years, therefore oilseed rape diseases have become an important risk factor. The present paper reports 4‐year data (2008–2011) on different fungicide application systems (including forecasting systems) tested in field trials in Central Latvia. The development of stem canker (Leptosphaeria spp.) and white stem rot (Sclerotinia sclerotiorum) was evaluated depending on fungicide application schemes. Stem canker was found to be a widespread disease, and coexistence of both L. maculans and L. biglobosa was established in Latvia. There was no epidemic of white stem rot observed during the investigation period (incidence of disease was only 0.7–4.5%). Application of fungicides significantly (P < 0.05) decreased severity of stem canker. However, substantial differences between different treatments were not detected. Yield of oilseed rape fluctuated at about 4.5 tonnes ha^?1, and use of fungicides did not increase the yield. It was found that DaCom Plant Plus program had overestimated the risk of white stem rot in years with low disease pressure, whereas the Swedish model of forecasting, based on the risk‐point system, had produced acceptable forecasts.     

Molecular identification of sex in <Emphasis Type="Italic">Hippophae rhamnoides</Emphasis> L. using isozyme and RAPD markers

In many dioecious plants, gender affects economic value, breeding schemes and opportunities for commercial harvests. Hippophae rhamnoides L. is a dioecious plant species in which female genotypes are commercially preferred over male genotypes. Its berries have rich medicinal, nutritional and pharmaceutical properties because of their large amounts of vitamins, essential oils, proteins, fatty acids, free amino acids and flavanoids. Primary limitation for breeding H. rhamnoides L. is its dioecious nature, since gender cannot be identified by traditional methods. Therefore, some reliable and quick methods need to be developed. This communication deals with the development of isozyme and RAPD markers for early sex identification in this dioecious tree. The isozyme analysis was conducted with four enzyme systems, viz. peroxidase, esterase, malate dehydrogenase and catalase. The peroxidase enzyme system produced a female specific sex marker, which successfully differentiated between the staminate and pistillate genotypes of H. rhamnoides L. Thirty five random decamer primers were used in our study and one male sex linked marker was identified. OPD-20 (5′-ACTTCGCCAC-3′) displayed a band at 911 bp that expressed polymorphism between male and female genotypes. The staminate and pistillate genotypes could be distinguished using RAPD marker OPD-20911. These results revealed the immense potential of peroxidase isozyme patterns and RAPD as genetic markers for sex identification in H. rhamnoides L.