Variation for dry matter yield,seed yield and other agronomic traits in Ladino white clover landraces and natural populations

Summary A set of Ladino white clover ecotypes including the last available landraces and some natural populations collected from old permanent meadows, together with some white clover varieties of various origins, were evaluated as monocultures for dry matter (DM) and seed yield assessed in separate field experiments. Other agronomic traits were also recorded. The best performing variety, Espanso, was significantly outyielded by some ecotypes for DM and seed production. Compared to landraces, natural populations yielded on average far less seed but as much DM and tended towards higher persistence indicating that domestication of the native Ladino at the farm level only improved seed yield of the crop. Natural populations showed, besides lower values of most seed yield components, a distinct canopy architecture characterized by smaller leaves, longer internodes and denser stolons. Seed weight proved the best character discriminating between the two ecotype groups. Significant variation for most traits was found both among landraces, in which it was mostly relatable to differences among provenances, and among natural populations. The relations between the main multivariate patterns of phenotypic variation and a set of environment collecting variables suggested that evolutive adaptation to different agronomic practices was a major determinant of the overall variation found in landraces. Evidence is provided that a relevant part of the variation observed among ecotypes for some important traits could be genetic.Abbreviations DM dry matter - DMY dry matter yield - NRH number of ripe heads - NFH number of florets per head - PL petiole length - LS leaf size - IL internode length - NS number of stolons - PRO protein content - SY seed yield - TSW thousand seed weight - NSF number of seeds per floret - PCA principal components analysis - PC principal component     

Breeding components for mixture performance

Summary The problems posed by breeding components for use in binary mixtures are discussed. Breeding and selection strategies designed to overcome some of these problems are outlined.     

Effects of loci determining photoperiod sensitivity (Ppd-H1) and vernalization response (Sh2) on agronomic traits in the 'Dicktoo'×'Morex' barley mapping population

The objectives of this research were to determine the individual and interaction effects of the Ppd-H1 and Sh2 loci on agronomic traits under short- and long-photoperiod regimes. Nineteen doubled haploid (DH) lines from the ‘Dicktoo’בMorex’ mapping population, which represented the four genotypes at the Ppd-H1 and Sh2 loci, were pheno-typed in controlled environment photoperiods. Both Ppd-H1 and Sh2 had significant effects on several agronomic traits, in addition to their role in determining first node appearance and flowering time. The magnitude of these effects depended on daylight. Under long-day conditions (18 h) Ppd-H1, and under short-day conditions (12 h) Sh2 was a significant determinant of most characters. The interactions between these two loci were significant for several characters, particularly for yield components, under both long- and short-photoperiod regimes. Under the long-day treatment, Ppd-H1 influenced plant height through the determination of node number. There was an epistatic association between the two loci for both 1000-kernel weight and tillering. The combination of photoperiod insensitivity and vernalization requirement caused a significant increase in tillering. This was paralleled by a decrease in 1000-kernel weight. Under the long-day treatment, neither Ppd-H1 nor Sh2 influenced plant yield. Under short-day conditions, the combination of photoperiod insensitivity and vernalization requirement had a pronounced negative effect on plant yield.     

Evaluation of proline analysis and chlorophyll fluorescence quenching measurements as drought tolerance indicators in durum wheat (Triticum turgidum L. var. durum)

Summary The possibility of using proline accumulation and fluorescence inhibition as predictive tests for drought tolerance in durum wheat has been investigated. The drought susceptibility of 25 genotypes was evaluated by comparing yields and yield components in irrigated and non irrigated conditions in the field. A drought susceptibility index (DSI) was calculated based on yields from irrigated and dry treatments and compared with the results obtained using the two physiological criteria. Proline accumulation and chlorophyll fluorescence inhibition were found to be significantly and negatively correlated with DSI of grain yield, biological yield, and thousand kernel weight, and tiller index. The use of both criteria for breeding durum wheat in Mediterranean dryland is discussed.     

The drought response of landraces of wheat from the northern Negev Desert in Israel

Summary Diverse landraces of wheat, collected from the semi-arid (150 to 250 mm of total annual rainfall) Northern Negev desert in Israel were considered as a potential genetic resource of drought resistance for wheat breeding. These materials were therefore evaluated for their reponses to drought stress in agronomical and physiological terms. Up to 68 landraces, comprising of Triticum durum, T. aestivum, and T. compactum were tested in two field drought environments, in one favourable field environment, under post-anthesis chemical plant desiccation which revealed the capacity for grain filling from mobilized stem reserves, under a controlled drought stress in a rainout shelter and in the growth chamber under polyethylene glycol (PEG)-induced water stress. Biomass, grain yield and its components, harvest index, plant phenology, canopy temperatures, kernel weight loss by chemical plant desiccation, growth reduction by PEG-induced drought stress and osmotic adjustment were evaluated in the various experiments.Landraces varied significantly for all parameters of drought response as measured in the different experiments, which was in accordance to their documented large morphological diversity. Variation in grain yield among landraces under an increasing drought stress after tillering was largely affected by spike number per unit area. Kernel weight contributed very little to yield variation among landraces under stress, probably because these tall (average of 131 cm) landraces generally excelled in their capacity to support kernel growth by stem reserve mobilization under stress. Yield under stress was reduced with a longer growth duration of landraces only under early planting but not under late planting. Landraces were generally late flowering but they were still considered well adapted phenologically to their native region where they were always planted late.Landraces differed significantly in canopy temperature under drought stress. Canopy temperature under stress in the rainout shelter was negatively correlated across landraces with grain yield (r=0.67^**) and biomass (r=0.64^**) under stress. Canopy temperature under stress in the rainout shelter was also positively correlated across landraces (r=0.50^**) with canopy temperature in one stress field environment. Osmotic adjustment in PEG-stressed plants was negatively correlated (r=–0.60^**) with percent growth reduction by PEG-induced water stress. It was not correlated with yield under stress in any of the experiments. In terms of yield under stress, canopy temperatures and stem reserve utilization for grain filling, the most drought resistant landrace was the Juljuli population of T.durum.     

Mass selection for kernel depth in early maize

Summary Effectiveness of mass selection for kernel depth in an early maize (Zea mays L.) synthetic, i.e. NDSAB, was evaluated in eight North Dakato environments. Four cycles of selection for deeper kernels were evaluated for grain yield and associated traits by using corresponding randomly selected subpopulations of NDSAB to adjust out inbreeding effects on selected subpopulations. General combining ability (GCA) effects of selected subpopulations also were evaluated for these traits.Subpopulations selected from one to four cycles for deep kernels were reciprocally crossed to corresponding randomly selected subpopulations in a factorial mating design. Subpopulations, selfed subpopulations, and subpopulation crosses were evaluated for yield and associated traits. Subpopulations selected for deep kernels generally had deeper kernels, higher yields, heavier kernels, more kernel rows per ear, and lower test weights than corresponding randomly selected subpopulations. Differences in GCA effects among selected and unselected subpopulations generally corresponded to differences between selected and unselected parental subpopulations. Inbreeding effects from selfing were observed for all traits, but no average heterosis was detected when subpopulation crosses were compared to parental subpopulations. Reciprocal differences were observed for all traits except kernel depth, but these differences were inconsistent relative to whether deep kerneled females made superior hybrids to unselected females.Results supported the use of mass selection for kernel depth as a means of grain yield improvement in the short term for NDSAB. However, negative associations of kernel depth with test weight may restrict long term use of this procedure.Journal Article No. 1505 of the North Dakota Agric. Exp. Stn., Fargo     

The effect of major dwarfing genes on yield potential in spring wheats

Summary A composite convergent cross of 16 spring wheat parents produced a set of unselected progeny lines among which the major dwarfing genes, Rht1, Rht2 and Rht3, were distributed against a common random genetic background. Random subsets of these lines were grown under irrigation and optimal conditions in 4 experiments with replicated bordered plots in southern New South Wales in order to measure the dwarfing gene effect on yield potential. The dwarfing gene composition of each line was determined by test crossing and seedling responsiveness to gibberellic acid.Lodging was negligible in the two experiments in 1982. While present in the two in 1983, it was not strongly associated with yield. Grain yield levels were appropriately high (mean 5.9 t/ha). In all but 1 experiment the Rht1+Rht2 dwarf genotypes gave highest yields while the Rht3 group yielded on average 3% lower, Rht2 9% lower, Rht1 11% lower, and the non-dwarf or tall group yielded 24% lower. These yield differences were positively associated with harvest index, kernels per m² and kernels per spike, but negatively associated with mature plant height. Even within major dwarfing gene classes, grain yield was significantly and negatively associated with height.     

Stability of 1000-grain weight and its relation with other traits of barley in dry areas

Summary The effects of 1000-grain weight, its stability and the correlation coefficients with other traits of 50 barley varieties were studied at 18–20 environments. Additional material was used to study genotypic correlations among traits. Significant differences in stability of 1000-grain weight were found among varieties. Two-row varieties were on average more stable than 6-row varieties. The 1000-grain weight was among the most stable and grain yield the most variable traits. This was discussed in connection with stem reserves translocation to the grain. Consistently high yielding varieties had around average stability of 1000-grain weight. Regression coefficient, b, for 1000-grain weight was positively correlated with variance of log transformed data, both valid estimates for stability of 1000-grain weight. The correlation coefficient of 1000-grain weight with grain yield was positive or non-significant, with number of grains per tiller mainly negative and with volume weight it was positive. In 6-row barley, 1000-grain weight was positively correlated with grain yield, straw yield, total biological yield, and plant height, and negatively with number of tillers per m² and number of grains per tiller.     

Partial resistance to neck blast influenced by stage of panicle development and rice genotype

Summary Neck nodes of eight rice genotypes were inoculated with a virulent isolate of the blast pathogen at four slightly different, increasingly older stages of panicle development shortly after flowering. Resistance to infection as well as resistance to growth of the pathogen after infection was assessed. Significant differences between genotypes were found for both components of resistance. Resistance to growth of the pathogen sharply increased with aging of the neck node as was indicated by a large reduction of the length of the lesions on the culm, but resistance to infection did not change much. The lesion length was closely related to yield loss. A small delay in time of infection can lead to a large decrease in yield reduction. Meaningful comparison of partial resistance to neck blast between genotypes therefore requires infection at an identical stage of panicle development. In the field, where panicles are in different stages of development, selection of genotypes that do show the symptoms of neck blast together with relatively little yield loss in infected panicles is recommended.     

婴幼儿配方奶粉研究进展

婴幼儿配方奶粉是非母乳喂养婴儿最重要的营养来源,我国婴幼儿配方奶粉市场需求巨大,但基础营养与加工技术研究起步较晚。本文从母乳营养需求、配方奶粉标准和奶粉基料研发等方面,详细介绍了婴幼儿配方奶粉的营养学研究进展;从干法与湿法等生产工艺对配方奶粉特性的影响方面论述了婴幼儿配方奶粉加工技术的研究进展;同时也讨论了婴幼儿奶粉中存在的危害风险,为我国婴幼儿配方奶粉在基料选择、生产技术和产业发展方面提供参考。