Fungicidal activity of fluopicolide for suppression of Phytophthora capsici on squash

The efficacy of a new fungicide fluopicolide in suppression of Phytophthora blight caused by Phytophthora capsici was evaluated under laboratory and field conditions. Studies with 51 P. capsici isolates from vegetable crops in Georgia, USA, indicated that 5.9% of the isolates were resistant, 19.6% were intermediately sensitive, and 74.5% were sensitive to 100 μg ml⁻¹ of mefenoxam based on in vitro mycelial growth. EC₅₀ values of fluopicolide in inhibiting mycelial growth of 25 isolates, representing resistant, intermediately sensitive, and sensitive to mefenoxam, ranged from 0.05 to 0.35 μg ml⁻¹ with an average of 0.2 μg ml⁻¹ EC₅₀ values of fluopicolide in suppressing zoospore germination and sporangium production of the 25 isolates ranged from 1.1 to 4.5 μg ml⁻¹ and 0.3–9.0 μg ml⁻¹, respectively. Evaluation of a collection of 150 P. capsici isolates from vegetables and irrigation ponds found none of the isolates were resistant to 10 μg ml⁻¹ of fluopicolide. Field experiments were conducted to determine the efficacy and application methods of fluopicolide for control of P. capsici on squash in spring 2007 and 2009. Fluopicolide applied through drip irrigation or as a foliar spray at 86.6 or 115.4 g ha⁻¹ consistently provided significant disease reduction and increased squash yield. Results with fluopicolide were similar or slightly superior to mefenoxam applied at recommended rate. Fluopicolide applied at 57.7 g ha⁻¹ did not provide consistent satisfactory disease suppression. The results indicated that fluopicolide was effective in suppression of different stages of the life cycle of P. capsici and could be a viable alternative to mefenoxam for managing Phytophthora blight in squash production.     

Comparative analysis of essential oil components of two Cryptomeria species from China

The essential oils obtained by hydrodistillation from leaves of Chinese native Cryptomeria japonica and Cryptomeria fortunei were analyzed by GC and GC-MS. Fifty-seven compounds were identified in the essential oils of C. japonica with α-elemol (20.12%), kaur-16-ene (14.84%), β-phellandrene (5.97%), β-elemene (5.87%), α-eudesmol (5.62%) and β-eudesmol (5.03%) as main constituents. Forty components were identified in the oil of C. fortunei with kaurene (34.04%), α-elemol (13.34%), γ-eudesmol (10.80%), β-eudesmol (10.16%), α-pinene (2.75%) and γ-cadinene (1.92%) as the most abundant components. This study demonstrated the occurrence of α-elemol chemotype in C. japonica and kaurene chemotype in C. fortunei from China. The essential oil compositions of two Cryptomeria samples were shown that they can be used for green plant protection, pharmaceutical, perfume and food industries.     

Genotypic variation for root traits of maize (Zea mays L.) from the Purhepecha Plateau under contrasting phosphorus availability

Phosphorus (P) deficiency is a major constraint for maize production in many low-input agroecosystems. This study was conducted to evaluate genotypic variation in both root (root architecture and morphology, including root hairs) and plant growth traits associated with the adaptation of maize landraces to a P-deficient Andisol in two locations in the Central Mexican highlands. Two hundred and forty-two accessions from the Purhepecha Plateau, Michoacan were grown in Ponzomaran with low (23 kg P₂O₅ ha⁻¹) and high (97 kg P₂O₅ ha⁻¹) P fertilization under rain-fed field conditions, and subsequently a subset of 50 contrasting accessions were planted in the succeeding crop cycle in Bonilla. Accessions differed greatly in plant growth, root morphology and P efficiency defined as growth with suboptimal P availability. The accessions were divided into 3 categories of P efficiency using principal component and cluster analyses, and 4 categories according to the retained principal component and their relative weight for each genotype in combination with growth or yield potential. The distribution of accessions among three phosphorus efficiency classes was stable across locations. Phosphorus-efficient accessions had greater biomass, root to shoot ratio, nodal rooting, nodal root laterals, and nodal root hair density and length of nodal root main axis, and first-order laterals under P deficiency. Biomass allocation to roots, as quantified by the allometric partitioning coefficient (K) was not altered by P availability in the efficient accessions, but inefficient accessions had a lower K under low P conditions. Accessions with enhanced nodal rooting and laterals had greater growth under low P. Dense root hairs on nodal root main axes and first-order laterals conferred a marked benefit under low P, as evidenced by increased plant biomass. Late maturity improved growth and yield under low P. These results indicate that landraces of the Central Mexican highlands exhibit variation for several root traits that may be useful for genetic improvement of P efficiency in maize.     

Low variability of flower volatiles of Rosa damascena Mill. plants from rose plantations along the Rose Valley, Bulgaria

The composition of volatile compounds in the rose essential oils obtained from the rose flowers has been known to be affected by a number of factors including the region of rose growing. The variations of the flower volatile composition of Rosa damascena plants growing in 11 different rose plantations along the famous Rose Valley in Bulgaria were studied following GC/MS metabolite profiling. ANOVA statistical test revealed that only 14 of a total of 90 identified compounds were significantly influenced by the geographic location of the sampled rose plantation. The hierarchical clustering analysis based on the subset of these 14 compounds revealed no clear correlation between the levels of rose flower volatiles and geographic location of the studied rose plantations. The results from the study suggest low variability of rose flower volatiles accumulation and elevated plasticity of the common R. damascena genotype industrially cultivated in the Rose Valley.