Field scale functional agrobiodiversity in organic wheat: Effects on weed reduction,disease susceptibility and yield

Deployment of diversity at the species and at the genetic levels can improve the ability of crops to withstand a wide range of biotic and abiotic stressors in organic and low-input cropping systems, where the response to stresses through external input is limited or restricted in comparison with conventional systems. Although there are several strategies to use agrobiodiversity in wheat-based systems, their implementation is limited by the lack of a clear relationship between agrobiodiversity and provision of key agroecosystem services. In a three-year field trial in Central Italy we compared common wheat Italian and Hungarian pure lines, Italian old cultivars and Hungarian and British Composite Cross Populations (CCPs), grown with or without a contemporarily sown Subterranean clover living mulch. We aimed at linking crop performance, in terms of yield, weed reduction and disease susceptibility, to three categories of functional diversity: (1) functional identity, represented by the identifying traits of cultivars, (2) functional diversity, represented by the genetic heterogeneity of wheat crop population, and (3) functional composition, represented by the co-presence of wheat and the living mulch.Concerning cultivars, effects of functional identity were predominant for weed reduction and grain yield. Old cultivars tended to better suppress weeds but to be less yielding. Italian cultivars were more advantaged than cultivars of foreign origin, thanks to a better matching of their growth cycle into local climate. Functional diversity effects on yield and weed reduction were confounded with identity effects, given that all the CCPs were of foreign origin. In fact, the performance of CCPs was generally aligned with a central-European pure line. However, differences in yield components suggest that CCPs can evolve peculiar yield formation strategies. Moreover, CCPs were less susceptible than pure lines to foliar diseases. For functional composition, the living mulch was able to reduce dicotyledonous weed abundance and weed biomass without reducing wheat yield unless wheat was poorly established. Despite the strong morphological and phenological differences among the tested cultivars, no interactions were found between cultivar and living mulch presence, suggesting that, in conditions similar to our experiments, there is room to freely combine elements of crop diversity. Crop diversification strategies in wheat should be further explored and optimized, especially by constituting CCPs from locally adapted germplasms and by improving the feasibility and efficacy of legume living mulches.     

Effects of row spacing and liquid manure on directly drilled winter wheat in organic farming

In the optimisation of grain yield and quality of wheat, plant distribution is a key factor. In contrast to high yield levels, at moderate levels, widening the row space did not decrease grain yield. To gain information about changes in the quality and yield with changing in row spacings in organic farming systems, experiments were conducted at two locations in the Swiss midlands in 2001/2002. Winter wheat (Triticum aestivum L., cv. Titlis) was directly drilled in rows 0.1875 and 0.3750 m apart at the same seeding rate per area. An unfertilised treatment and the usual application of 60 m³ ha⁻¹ liquid farmyard manure were compared. While the grain yield was not decreased by the wider row spacing, the thousand kernel weight (TKW), and grain protein content were increased from 42.6 to 43.5 g and from 11.7 to 12.7%, respectively, compared to the narrow row spacing. Liquid manure, on average of both experimental sites, increased the yield (from 3.725 to 4.765 Mg ha⁻¹) and the grain protein content (from 12.0 to 12.5%). Doubling the space between the rows from 0.1875 to 0.3750 m seemed to be a suitable strategy for managing directly drilled winter wheat in organic farming systems.     

Breeding for organic agriculture: the example of winter wheat in Austria

Breeding for organic agriculture (BFOA) is a strategy for a commercial breeding company based on the exploitation of the frequently observed high correlation for many traits between conventional, low input (LI) and organic agriculture (ORG). Indirect selection under LI can be useful to roughly divide the germplasm into the genotypes better adapted to high input and those better adapted to LI or ORG conditions. BFOA is an evolving process, in which two methods are currently applied: early generations are either selected following the pedigree system under LI, or grown as bulk populations on ORG fields. In the latter case the system switches to LI after individual ear selection under ORG conditions. In both methods, the first replicated yield trial is grown parallel under ORG and LI. Subsequently, the genotypes are grouped into conventional or ORG advanced trial series. The BFOA strategy allows that the larger genetic variability of both the organic and conventional gene pool can be exploited in the selection for ORG. Hitherto, seven winter wheat varieties were released in Austria after exclusive organic VCU testing.     

棉花抗黄萎病品种选育的轮回选择研究——基础群体的构建

利用我国发现并鉴定的陆地棉核雄性不育系—洞Ａ为工具,将国内外现有的十多个抗（耐）棉花黄萎病的品种（系）和种质系导入到二个轮回群体中,拓建了棉花抗黄萎病轮回选择基础群体。从而为同步提高棉花的产量、品质和抗病性打下基础。     

Selection response for carbon isotope discrimination in a Triticum polonicum×T. durum cross: Potential interest for improvement of water efficiency in durum wheat

This study has been conducted to evaluate the usefulness of carbon isotope discrimination (δ) in mature kernels as a criterion for the improvement of water-use efficiency and yield under drought in durum wheat. For this purpose, Triticum durum‘Om Rabi 5’ was crossed with T. polonicum pseudochrysospermum 9 (Tp9) which has been found to be more drought tolerant and to have a lower carbon isotope discrimination value of the grain. The F₂ population showed a wide segregation for carbon isotope discrimination. Further, divergent selections (selection of plants most different in carbon isotope discrimination) were made among individual F₂ plants, and for carbon isotope discrimination in F₃ progenies under field conditions. Selected F₃ and F₄ progenies were evaluated under field conditions for morphological and agronomical traits. Broad-sense heritability (h²_b), response to selection and realized heritability (h²_r) were high. The narrow-sense heritability (h²_n= 0.37 ± 0.047) indicated that additive and dominance effects were involved in the genetic control of carbon isotope discrimination. Negative correlations were noted between carbon isotope discrimination and grain yield and between carbon isotope discrimination and biomass yield within years and generations. An explanation of this result is attempted by analysing the relationships between carbon isotope discrimination and several phenological and morphological traits influencing the water-use efficiency. The divergent groups selected for low and high carbon isotope discrimination exhibited significant differences for days to heading, plant height, shape of the spike and number of spikelets per spike. Correlations were also found between carbon isotope discrimination and plant height, harvest index, shape of the spike, spike length, and number of spikes per plant. The potential use of carbon isotope discrimination as a criterion for the improvement of water-use efficiency in durum wheat is discussed by considering the genetics of this trait (variability, heritability, response to selection) and also the associations with phenological and morphological traits.     

Possibilities of family selection in a cultivar of lucerne,Medicago sativa L., for resistance to the stem nematode,Ditylenchus dipsaci (Kühn) Filipjev

Summary Half-sib families representing the lucerne cultivar Resis were tested for resistance to a stem nematode population, recovered from lucerne. The percentage resistance of the HS-families varied from 13 to 88%. The mean resistance for the cultivar was approximately 50%. Half-sib family selection would be more efficient than recurrent mass selection. The observed data suggest the action of a few genes with relatively large effects.     

A specific PCR assay for resistance to biotypes 1 and 2 of the rosy leaf curling aphid in apple based on an RFLP marker closely linked to the Sd1 gene

This report describes the conversion of a restriction fragment length polymorphism (RFLP) marker (the 2B12a locus). linked to the Sd₁ aphid resistance gene, to a polymerase chain reaction (PCR) based marker. A section of the 2BI2 probe was sequenced and two primers were designed lo amplify this sequence in the cultivars‘Prima’and‘Fiesta’: all the amplification products were the same size. After sequencing. two specific 24-mer oligonueleotides were synthesized (DdARM-5¹ and DdAR.M-3²) to exploit a single base-pair difference. These primers were used to screen 44 plants from the‘Prima’x‘Fiesta’family and generated a single amplification product (196bp). in approximately half of the seedlings, which was linked to the resistance gene Sd₁,. The DdARM primer combination was used to evaluate a range of apple cultivars and selections, including some varieties derived from‘Cox’and alternative sources of resistance reported in the literature. In parallel with this work, the phenotypic response of the same genotypes was either confirmed or determined in replicated glasshouse tests. The sequence characterized amplified regions (.SCAR) marker was amplified in all the resistant plants, with the exception of‘Northern Spy’and 3760 (the sources of Sd₂ and Sd₃ resistance, respectively), but never in the susceptible plants. The possible role of this marker in a marker-assisted breeding strategy, and its compatibility with a SCAR marker linked to the I, gene for resistance to apple scab. is discussed.     

A new method for evaluation of the resistance to rice kernel cracking based on moisture absorption in brown rice under controlled conditions

We developed and evaluated the effectiveness of a new method to detect differences among rice cultivars in their resistance to kernel cracking. The method induces kernel cracking under laboratory controlled condition by moisture absorption to brown rice. The optimal moisture absorption conditions were determined using two japonica cultivars, ‘Nipponbare’ as a cracking-resistant cultivar and ‘Yamahikari’ as a cracking-susceptible cultivar: 12% initial moisture content of the brown rice, a temperature of 25°C, a duration of 5 h, and only a single absorption treatment. We then evaluated the effectiveness of these conditions using 12 japonica cultivars. The proportion of cracked kernels was significantly correlated with the mean 10-day maximum temperature after heading. In addition, the correlation between the proportions of cracked kernels in the 2 years of the study was higher than that for values obtained using the traditional late harvest method. The new moisture absorption method could stably evaluate the resistance to kernel cracking, and will help breeders to develop future cultivars with less cracking of the kernels.     

Resistance in Cucumis sativus L. to Tetranychus urticae Koch. 2. Designing a reliable laboratory test for resistance based on aspects of the host-parasite relationship

Summary The relationship between the twospotted spider mite and cucumber has been studied on plants and on leaf disks of a number of varieties with different levels of resistance. Existing laboratory tests are critically discussed and it appears that they are only reliable if many factors are taken into account. A new, more efficient laboratory test for resistance, measuring acceptance and reproduction is described.