Boldo (Peumus boldus) cultivated under different light conditions, soil humidity and plantation density

Boldo (Peumus boldus Mol.) is a medicinal plant native to the central zone of Chile and part of the sclerophyll forest. More than 2000 tons of dried leaves exported annually are wild collected. To develop a cultivation system that supports sustainable production of boldo leaves, we have studied growth and harvest of boldo under different light and soil water conditions. The leaf yield per plant as well as the alkaloid and essential oil content were the same for plants grown under shade and for plants exposed to full sun. The only difference between the shaded and the full sun plants was a higher percentage of stem in the harvested product of shade grown plants. This result would permit the intercropping of boldo in forest plantations without affecting the leaf yield and medicinal quality. The excellent adaptation to dry conditions was confirmed, as the different treatments of soil water led to similar leaf yields and plant heights. Plants submitted to water stress produced fewer but longer shoots and contained less essential oil. None of the treatments except water stress affected the medicinal quality requirements of alkaloid or essential oil concentration in the leaves. Wild collected leaves are inexpensive because of low production costs. To be able to compete with wild supplied leaves in the international market, we have evaluated high density plantings as a way to lower costs of a cultivated product by mechanizing harvest. High planting densities led to loweryielding individuals, but leaf yield per area increased. Plant height and the percentage of leaves in the harvested product was the same for densities of 8- and 16 plants m⁻². The leaves produced by cultivated boldo generally fulfill the requirements described in the European Pharmacopoeia. We conclude that boldo can be successfully cultivated under the described cultivation conditions.     

Characterization of phenotypic diversity,yield and response to drought stress in a collection of Rhodes grass (Chloris gayana Kunth) accessions

Information on available diversity and drought resistance among Chloris gayana accessions would offer considerable potential to select genotypes to alleviate the feed inadequacy that constrains livestock production in dry tropical areas. A collection of 62 C. gayana accessions from the genebank of the International Livestock Research Institute in Ethiopia was characterized using a set of 30 morphological, 4 phenological and 8 agronomic traits to assess diversity within the collection and to select promising accessions for use as livestock feed. In parallel, an experiment was conducted to assess the ability of these C. gayana accessions to maintain productivity under drought stress.     

Influence of plant leaf surface on the development,reproduction and life table parameters of the predacious mite, Agistemus exsertus Gonzalez (Acari: Stigmaeidae)

The influence of leaf surfaces of different host plants on the biology and life table parameters of the predacious mite, Agistemus exsertus Gonzalez was studied in the laboratory. A. exsertus successfully developed and reproduced on all tested plant leaves. Smooth, glabrous pear leaves accelerated the development of A. exsertus and showed the shortest mean generation time. Slightly rough, slightly hairy leaves of mulberry and acalypha were the most suitable surface for oviposition of the predator. These leaves exhibited the highest fecundity and net reproductive rate. On the other hand, leaves of rough, pubescent apple and scabrous, bristly lantana were the least suitable surface for oviposition of A. exsertus. They showed the lowest fecundity and net reproductive rate. Acalypha leaves exhibited the highest intrinsic rate of increase for the predator, whereas lantana leaves showed the lowest value. This difference in the predator response to leaf surfaces of host plants should be considered to enhance the role of the predator in biological control programs.     

Efficacy of composting infected plant residues in reducing the viability of Pepper mild mottle virus, Melon necrotic spot virus and its vector,the soil-borne fungus Olpidium bornovanus

Survival of Pepper mild mottle virus (PMMV) and Melon necrotic spot virus (MNSV) in diseased plant residues of pepper and melon, respectively, was studied in several experiments investigating drying and composting conducted in experimental heaps. The viability of the soil-borne fungus Olpidium bornovanus, the vector of MNSV, in infected melon root residues was also evaluated. Maximum temperatures in the heap reached 61.9–73.8 °C during composting processes. Drying of plant residues reduced the infectivity of MNSV whereas the infectivity of PMMV and O. bornovanus was unaffected by drying. Neither the virus nor the fungus was viable after composting. PMMV antigens where detected by serology after 30 and 60 days composting in the four experiments, but virus infectivity was detected only in one process after 30 days. Our results show that the use of composts using plant residues from PMMV and MNSV-infected crops as organic amendments in SE Spain do not appear to pose a risk of re-introducing pathogens to soil. Environmental conditions in that area are suitable for the adequate elimination of these pathogens from infected vegetable residues through composting even during winter.     

Canopy reflectance in two castor bean varieties (Ricinus communis L.) for growth assessment and yield prediction on coastal saline land of Yancheng District, China

A field experiment was conducted in 2007-2009 in coastal saline regions of Yancheng city in Jiangsu province of China (120°13′E, 33°38′N). The experiment was to investigate relationships among canopy spectral reflectance, canopy chlorophyll density (CCD), leaf area index (LAI), and yield of two Chinese castor varieties (Zi Bi var. and Yun Bi var.) across four N fertilizer rates of 0, 90, 180, and 360 kg N ha⁻¹. These N rates were used to generate a wide range of difference in canopy structure and seed yield. Measurements of canopy reflectance were made throughout the growing season using a hand-held spectroradiometer. Samples for CCD and LAI were obtained on days that reflectance measurements were made. Fifteen hyperspectral reflectance indices were calculated. Canopy spectral characteristics were heavily influenced by saline soil background in the rapid growing period (RGP), thus hyperspectral data obtained in this period were not suited for reflecting castor growth condition or predicting final yield. CCD increased linearly with most reflectance indices in the full coverage period (FCP) and senescent period (SP) for the two castor varieties, whereas LAI did not. Most of reflectance indices were significantly correlated with yield of two varieties in different growing periods. The OSAVI model provided the best yield prediction for Zi Bi var. with predicted values very close to observed ones (R² = 0.799), and the mSRVI705 model was well used for Yun Bi var. yield estimation (R² = 0.759). These results indicate that the hyperspectral data measured at appropriate time could be well used for castor yield estimation.     

Association of Puroindoline b-B2 variants with grain traits,yield components and flag leaf size in bread wheat (Triticum aestivum L.) varieties of the Yellow and Huai Valleys of China

A total of 169 wheat (Triticum aestivum L.) varieties (landraces and cultivars) were used to asses the relationship between Puroindoline D1 alleles and Puroindoline b-B2 variants and grain hardness, other grain traits, yield components, and flag leaf size. Results indicated that the average SKCS hardness of Pinb-B2v3 varieties was significantly greater than that of Pinb-B2v2 varieties within the soft Puroindoline D1 haplotype sub-group. Conversely, no statistically significant difference was obtained for SKCS hardness between varieties with the Pinb-B2v3 vs. Pinb-B2v2 alleles within the two hard Puroindoline D1 haplotypes (Pinb-D1b and Pinb-D1p sub-groups). Therefore, the Puroindoline b-B2 gene may have a bigger impact on soft wheat varieties than hard. Across all varieties, thousand-kernel weight, grain weight per spike, grain diameter, grain number per spike, flag leaf width and area of Pinb-B2v3 varieties were significantly greater than those possessing Pinb-B2v2. These results indicated that the Pinb-B2v3 allele was associated with preferable grain yield traits compared to the Pinb-B2v2 allele in bread wheat. This study provides evocative information for better understanding the molecular and genetic basis of wheat grain yield.