Combining ability of yield and yield components among Fusarium oxysporum f.sp. strigae-compatible and Striga-resistant sorghum genotypes

ABSTRACT

Use of sorghum [Sorghum bicolor (L.) Moench] cultivars with partial resistance to Striga spp. and Fusarium oxysporum f.sp. strigae (FOS) represents a novel strategy to control Striga. This study aimed to identify the nature of gene action controlling grain yield and yield components and to select promising sorghum crosses possessing both FOS compatibility and Striga resistance, along with good combining ability effects. One-hundred hybrids, developed from pairwise matings among 10 FOS compatible, high-yielding female lines and 10 Striga-resistant male lines, were evaluated with and without FOS inoculation. The F₁s were field evaluated at three locations in Tanzania known for their severe Striga infestation, using an alpha lattice design with two replications. General (GCA) and specific combining ability (SCA) variances were significant for grain yield per plant, hundred-seed weight, plant height, flowering time and the number of Striga plants. The study demonstrated FOS inoculation to be an effective means of controlling Striga. Families 675?×?672, AS435?×?3993 and 4643?×?AS436 displaying large SCA effects for grain yield, and 4567?×?AS429, 3424?×?AS430 and 3424?×?AS436 with small SCA effects for Striga counts should be useful genetic resources for breeding and integrated Striga management.     

Mulching offers protection from Striga asiatica L. Kutnze parasitism in Sorghum genotypes

The production of sorghum is hampered by the parasitic weed Striga asiatica L. Mulching is promoted as a component of the conservation agriculture systems in sub Saharan Africa. The objective of the study was to assess the effects of mulching and Striga infestation on sorghum chlorophyll content, Striga attachments, sorghum height, and yield. The 2?×?2?×?10 factorial experiment was replicated three times for two seasons. The pot experiment was laid out as a completely randomised design. The first factor was mulching at 0 and 3?tons/ha. The second factor was infestation at two levels: infested and uninfested while the third factor was sorghum varieties at 10 levels. Data collected was plant height, chlorophyll content, Striga counts and sorghum yield. Results indicated that mulching increased chlorophyll content in the second season and not first. Infestation reduced chlorophyll content in both seasons. For the second season, mulching increased chlorophyll content in all genotypes except Ruzangwaya, Mukadziusaende and SC Sila. The genotypes Mukadziusaende, Chiredhi and Hlubi were able to maintain height despite infestation by Striga. Generally yield was higher in uninfested pots across all varieties except Mukadziusaende for the first season. Sorghum arundinaceum was highly susceptible to Striga and hence cannot be a source of resistant traits for Sorghum bicolour breeding. Mulching in Striga infested plants increased plant height and chlorophyll content. Mulching tended to diminish the pathological effects of the Striga parasite in some varieties. Therefore, mulching negated the effect of Striga parasitism and resulted in yield maintenance in some genotypes and hence can be taken up by farmers in Striga infested areas as a beneficial cultural practice.     

Evaluation and Importance of Genetic Resistance to Leaf Stripe in Western European Barleys

Abstract

Several varieties of spring barley were tested in the greenhouse for resistance to leaf stripe (Drechslera graminea) following exposure to high levels of inoculum in the field, or by using the sandwich inoculation method. Pedigree analyses confirmed that most highly resistant varieties have obtained their resistance from a gene in the landrace Hordeum laevigatum via the variety ‘Vada’, while the remaining few may have it from the donor ‘Ricardo’, or from the cumulative effect of partial resistance. Experiments with fungicide seed treatment of ‘Golf’ and ‘Triumph’, which represent highly resistant, and susceptible genotypes, respectively, showed that the former always remained healthy, and does not benefit from seed treatment, whereas the latter requires treatment every year to avoid any seed loss.     

Assessment of farmers’ perceptions of production constraints,and their trait preferences of sorghum in western Ethiopia: implications for anthracnose resistance breeding

Sorghum, Sorghum bicolor (L.) Moench is an important food security crop widely grown by smallholder farmers in sub-Saharan Africa (SSA), including Ethiopia. In SSA, the potential of sorghum production and productivity has not been realised due to an array of constraints. Colletotrichum sublineolum disease is one of the main biotic constraints causing significant yield losses. The objectives of this study were to assess farmers’ perception, preferences and constraints to sorghum production and productivity in western Ethiopia, and to identify key drivers for anthracnose resistance breeding. A participatory rural appraisal study was undertaken in six selected districts in the East Wellega and West Shewa Administrative Zones in Ethiopia. Data were collected through structured questionnaires involving 165 respondent farmers. Further focus group discussions were held with 180 farmers and development agents. Sorghum is the third most preferred cereal crop after Eragrostis tef and Zea mays in western Ethiopia. About 79% of interviewed farmers cultivated sorghum during the study season. Farmers perceived that sorghum production is constrained by anthracnose disease, bird attack, loose smut and covered smut diseases. The most important farmer-preferred traits in sorghum varieties in the study areas were anthracnose resistance and tolerance to bird attack. Breeding sorghum varieties with the farmer-preferred traits is an important consideration to enhance productivity and adoption of improved sorghum cultivars in western Ethiopia.     

Agronomic evaluation and identification of potential cowpea (Vigna unguiculata L. Walp) genotypes in South Africa

Cultivar development of cowpea with increased grain yield depends on evaluation and selection of genetically unique and complementary breeding lines. The objective of this study was to evaluate cowpea collections using agronomic traits to select promising parents to develop breeding population. Twenty-two cowpea genotypes were field evaluated using a randomised complete block design with three replications in two locations in South Africa. Analysis of variance revealed significant genotypic (G) and locations (L) differences for all agronomic traits evaluated. Significant differences were also observed for most of the traits due to G X L, G X Year (Y), L X Y and G X L X Y interactions effects. The genotypes tested at two locations showed considerable genetic variation for the following agronomic traits that varied for number of leaves (NL) (20.08–179.78), leaf length (LL) (12.36–67.72 cm), leaf width (LW) (4.78–22.02 cm), number of branches (NB) (6.81–13.85), number of pods per plant (NPPP) (14.33–54.04), number of seeds per pod (NSPP) (11.7286.28), pod diameter (PD) (5.75–22.73 mm), plant height (PH) (6.57–233.71 cm), pod length (PL) (3.94–100.92 mm), hundred seed weight (HSWt) (8.11–49.52 g) and grain yield (GY) (0.10-1.48 t ha^?1). Grain yield was significant and positively correlated with all of the traits except leaf length. The principal component analysis (PCA) identified four principal components (PCs) contributing to 73.62% of the total explained variation amongst the tested genotypes. The selected cowpea genotypes for most of agronomic characteristics are useful and candidate genetic resources for the development of breeding population in cowpea breeding and enhanced production and productivity for food and nutrition in the country.     

Resistance breeding and biocontrol of Striga asiatica (L.) Kuntze in maize: a review

Purpose: The aims of this article are to highlight pre-breeding procedures for identifying primary sources of Striga-resistance genes and to summarize complimentary breeding techniques that enhance partial resistance of maize varieties against Striga species.

Materials and methods: The paper presented a comprehensive account of Striga screening and controlling techniques and highlighted the potential of integrating partial resistance with FOS to boost maize production and productivity in SSA.

Results: Striga infestation is a major constraint to maize production and productivity in Sub-Saharan Africa (SSA). A lack of Striga-resistant maize varieties and the limited adoption of other control methods hinder effective and integrated control of the parasitic weed in maize and related cereal crops globally. Genetic resistance of maize should be complemented with the use of Fusarium oxysporum f.sp. strigea (FOS), a biocontrol agent known to suppress Striga.

Conclusions: A combined use of genetic resistance and FOS has remained largely unutilized in controlling Striga in Africa. A combination of conventional and molecular Striga-resistance breeding tools as well as the use of FOS are promising methods to effectively control Striga in SSA.     

Transfer of leaf rust and stripe rust resistance from <Emphasis Type="Italic">Aegilops umbellulata</Emphasis> Zhuk. to bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Aegilops umbellulata acc. 3732, an excellent source of resistance to major wheat diseases, was used for transferring leaf rust and stripe rust resistance to cultivated wheat. An amphiploid between Ae. umbellulata acc. 3732 and Triticum durum cv. WH890 was crossed with cv. Chinese Spring Ph ^I to induce homoeologous pairing between Ae. umbellulata and wheat chromosomes. The F₁ was crossed to the susceptible Triticum aestivum cv. ‘WL711’ and leaf rust and stripe rust resistant plants were selected among the backcross progenies. Homozygous lines were selected and screened against six Puccinia triticina and four Puccinia striiformis f. sp. tritici pathotypes at the seedling stage and a mixture of prevalent pathotypes of both rust pathogens at the adult plant stage. Genomic in situ hybridization in some of the selected introgression lines detected two lines with complete Ae. umbellulata chromosomes. Depending on the rust reactions and allelism tests, the introgression lines could be classified into two groups, comprising of lines with seedling leaf rust resistance gene Lr9 and with new seedling leaf rust and stripe rust resistance genes. Inheritance studies detected an additional adult plant leaf rust resistance gene in one of the introgression lines. A minimum of three putatively new genes—two for leaf rust resistance (LrU1 and LrU2) and one for stripe rust resistance (YrU1) have been introgressed into wheat from Ae. umbellulata. Two lines with no apparent linkage drag have been identified. These lines could serve as sources of resistance to leaf rust and stripe rust in breeding programs.     

Changes in soil fertility and Striga hermonthica prevalence associated with legume and cereal cultivation in the Sudan savannah zone of Ghana

In the Sudano–Sahelian zones of West Africa, cultivated land is degraded due to reduced fallow periods and Striga hermonthica (Del.) Benth. infestation, and poses a serious threat to sustainable food production. To provide options for addressing these problems, we investigated the possibility of replacing the short fallow periods with food legume cultivation. We tested this in two farming communities within the Sudan savannah zone of Ghana. In the 1997 and 1998 cropping seasons, selected farmers within each community planted soybean [Glycine max. (L.) Merr.] or bambara groundnuts [Vigna subterranea (L.) Verdc.] on continuously cropped, Striga‐infested farmlands, whereas lands that were maintained under two or three years of bush fallowing were planted to millet [Pennisetum glaucum (L.) R. Br.] or sorghum [Sorghum bicolor (L.) Moench]. Analysis of soil sampled from 0–15 cm (plough layer) revealed that contents of major plant nutrients were inadequate to support long‐term crop production. Within each farming community, total nitrogen content at initial sampling showed significant negative correlation with the number of Striga seeds in the plough layer. Under legume cultivation, soil organic carbon content increased and the number of Striga seeds per square metre decreased in both communities from a mean value of 28 183 seeds m⁻² to 8185 seeds m⁻². Under cereal cultivation Striga seed density increased from 9383 seeds m⁻² to 16 696 seeds m⁻². The study provides evidence that introduction of food legume cultivation on farmlands with high S. hermonthica infestation as an alternative to bush fallow system could help achieve sustainable crop production in the Sudan savannah zones of sub‐Saharan Africa. Copyright © 2003 John Wiley & Sons, Ltd.     

Maize genotype effects on the response to Azospirillum inoculation

Two field experiments were carried out in Northern Argentina, during the 1989–1990 and 1990–1991 growing seasons, on Argentinian and Brazilian maize genotypes. The inoculant consisted of a mixture of four Azospirillum brasilense strain isolated from surface-sterilized maize roots in Argentina and three A. lipoferum strains isolated from surface-sterilized maize or sorghum roots in Brazil. Establishment of the inoculated strains was confirmed by the antibiotic resistance of the strains in the highest dilution vials. In all treatments, numbers of Azospirillum spp. were increased and the inoculated strains were found in the highest dilutions. While grain yields of the different genotypes varied between 1700 and 7300 kg ha^-1, total N accumulation was much less variable. Significant inoculation effects on total N accumulation and on grain yields were consistently negative with one Argentinian genotype and positive with four Argentinian and two Brazilian genotypes. Significant inoculation effects on leaf nitrate reductase activity at the flowering stage, observed in the range-55% to +176%, indicated the presence of various interactions between the plant NO _inf3 ^sup- metabolism and Azospirillum spp. Three Brazilian and one Argentinian maize genotype showed significant decreases in leaf nitrate reductase due to inoculation while four Argentinian genotypes showed significant increases in leaf nitrate reductase activity. The results of the present study, were consistent over the two field experiments and strongly indicate that more detailed plant genotype-Azospirillum spp. strain interaction studies, taking the entire N metabolism in the plant into account, are needed to allow better inoculation results of cereal crops.     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

The impact of drought on sorghum production,and farmer's varietal and trait preferences,in the north eastern Ethiopia: implications for breeding

Purpose: Sorghum [Sorghum bicolor (L.) Moench] has been cultivated for centuries as a staple food crop for millions of people in sub-Saharan Africa and Asia. In Ethiopia a total of 4.34 million tons of sorghum is being produced per annum, predominantly in the arid and semi-arid areas. However, the yield and quality of sorghum is affected by a wide array of production constraints, notably severe and recurrent drought stress. The aim of this study were to determine the impact of drought on sorghum production and productivity over time and space, and to identify farmers’ trait preferences, production constraints and coping strategies when dealing with drought in north eastern Ethiopia.

Materials and methods: Participatory rural appraisal (PRA) was employed in three administrative zones of north eastern Ethiopia. One Woreda from each Zone and two Kebeles from each Woreda were selected on the basis of sorghum area coverage, production, consumption and prior information on the intensity, duration and spatial coverage of drought. In each kebele, 30 respondents were selected for interview and 12 key informants were selected for group discussions and transect walk personal observations. Data collected from 180 respondents was subjected to statistical analysis and the information gathered from 72 key informants through focus group discussions and transect walk observations were used in discussing the results.

Results and discussion: The present study found that productivity of sorghum was challenged by recurrent droughts, Striga infestation, insects, birds, diseases, a lack of varieties with farmers-preferred traits and high yield potential, limited policy support, a lack of improved seed system, poor sorghum production practices and application of crop input and poor soil fertility, in a decreasing order of importance. Among the listed sorghum production constraints, severe drought in the post-flowering stage was identified by most interviewed farmers as the leading constraint across the three study zones. Focus group discussions and transect walk observations held in each Kebele revealed that farmers’ had lost numerous valuable local landrace varieties due to extreme drought conditions over the years. A significant number of interviewed farmers preferred to grow high grain and biomass yielder medium-maturing sorghum varieties which can be sown at the normal planting time but which would escape post-flowering drought.

Conclusion: Overall, sorghum breeding programme should be directed at developing farmers’ ideal sorghum varieties with high grain and biomass yield, adequate level of drought and Striga tolerance. In addition, development of farmer preferred medium-maturing sorghum varieties suitable for April planting should be strengthen to boost its productivity and to increase varietal adoption rate in the area.     

植物防御酶与桉树对焦枯病抗性的关系

为筛选鉴定桉树对焦枯病(CylindrocladiumqulnqueSeptatumMorgan)抗性的生化指标,对福建省11个桉树主栽种系接种焦枯病菌前后关键防御酶系中的过氧化物酶(POD)和超氧岐化酶(SOD)活性及其同工酶变化进行了研究.结果表明:无论是桉树健叶还是接种后的病叶,体内POD、SOD活性均表现为抗病种系>中抗种系>中感种系>感病种系,呈规律性变化;接种前后POD同工酶谱带数与桉树对焦枯病的抗性间不呈规律性变化,而SOD谱带数与抗病性成正比.从抗病育种角度出发可将接种前后桉树POD、SOD活性和接种后SOD同工酶谱带作为桉树对焦枯病抗性早期鉴定的生化指标.     

Characterisation of sweet stem sorghum genotypes for bio-ethanol production

In an effort to characterise and select promising sweet stem sorghum genotypes with enhanced biofuel productivity, the present study investigated phenotypic variability present among diverse sweet stem sorghum genotypes based on ethanol production and related agronomic traits. One hundred and ninety genotypes were evaluated. Data were subjected to variance, cluster, correlation, path coefficient and principal component analyses. Significant differences (P?<?0.01) were detected among tested genotypes for all measured traits. Days to flowering varied from 62 to 152 with a mean of 93. Plant height varied from 90 to 420?cm with a mean of 236?cm. Stem diameter ranged from 7 to 31?mm with a mean of 16?mm. Biomass yield varied from 6.668 to 111.2?t?ha^?1 with a mean of 30?t?ha^?1. Stalk dry matter content ranged from 17.2% to 44.2% with a mean of 29.8%, while fibre content varied from 8.92% to 34.8% with a mean of 17.2%. The stalk brix yield varied from 3.3% to 18.9% with a mean of 12.1%. Ethanol productivity ranged from 240.9 to 5500?l?ha^?1 with a mean of 1886?l?ha^?1. The best ethanol producing genotypes were AS203, AS391, AS205, AS251 and AS448. Days to flowering, plant height, stalk brix and stem diameter exerted the greatest indirect effects on ethanol production through higher biomass production. Biomass yield had the greatest direct effect on ethanol production. Therefore, the above traits should be considered during breeding sorghum for bio-ethanol production. Also, the traits had high heritability values, hence selection should provide for good genetic gains. Overall, the above sweet stem sorghum genotypes are useful genetic resources for breeding of sorghum with enhanced bio-ethanol production.     

Noodle Quality as Related to Sorghum Starch Properties

Starch was extracted from 10 sorghum genotypes and physicochemical properties (amylose content and pasting, textural, and thermal properties) were evaluated. The amylose content was 24–30%. DC‐75 starch had the highest peak viscosity (380 Rapid Visco Analyser units). Gelatinization peak temperature occurred over a narrow range (67–69°C). Genotypes Kasvikisire and SV2 produced white starches. Starches from other genotypes were different shades of pink. The starch noodles prepared were, accordingly, either white or pink. Cooking enhanced the pink coloration of noodles. Cooking loss, noodle rehydration, and elasticity were evaluated. Cooking loss was low (mean 2.4%). Noodle elasticity was highly correlated with starch pasting properties of hot paste viscosity (HPV) (r = 0.81, P < 0.01) and cold paste viscosity (CPV) (r = 0.75, P < 0.01). Noodle rehydration was significantly correlated to the initial swelling temperature of starch (T_i) (r = ‐0.91, P < 0.001) and gelatinization peak temperature (T_p) (r = 0.69, P < 0.05). The findings suggest a potential area of food application for sorghum genotypes of different grain colors. Evaluation of starch properties could be a good starting point for selecting sorghum genotypes with superior noodle‐making properties.     

Interactions between a vesicular-arbuscular mycorrhizal fungus (Glomus intraradices) and Streptomyces coelicolor and their effects on sorghum plants grown in soil amended with chitin of brawn scales

 The effect of the interaction between a vesicular-arbuscular (VA)-mycorrhiza (Glomus intraradices no. LAP8) and Streptomyces coelicolor strain no. 2389 on the growth response, nutrition and metabolic activities of sorghum (Sorghum bicolor) plants grown in non-sterilized soil amended with chitin waste was studied in a greenhouse over 8 weeks. Chitin amendment resulted in an increase in the microbial population and chitinase activity in soils. Growth of mycorrhizal G. intraradices no. LAP8 and non-mycorrhizal sorghum plants increased as compared with other treatments either in the presence or absence of S. coelicolor strain 2389. VA-mycorrhizal inoculation significantly increased the growth, photosynthetic pigments, total soluble protein and nutrient contents of sorghum compared to non-mycorrhizal sorghum. Such increases were related to increased mycorrhizal colonization. Inoculation with S. coelicolor 2389 significantly increased the intensity of mycorrhizal root colonization and arbuscular formation, but the levels of mycorrhizal infection and their beneficial effects were significantly reduced with the addition of chitin waste to the soil. Analysis of the content of total amino acids and ammonia in leaves on the basis of dry matter production showed that, in most instances, total amino acids of mycorrhizal plants were significantly higher than those of non-inoculated plants. The microflora of the rhizosphere was highly affected by mycorrhizal inoculation. Quantitative changes in acid and alkaline phosphatase activities of the roots in response to the mycorrhizal inoculation are discussed. Received: 11 August 1999     

Difference in response to aluminum stress among Tibetan wild barley genotypes

Wild barley (Hordeum sp.) germplasm is rich in genetic diversity and provides a treasure trove of useful genes for crop improvement. We carried out a comprehensive program combining short‐term hydroponic screening via hematoxylin‐staining of root‐regrowth procedure and filter paper–based evaluation of diverse germplasm in response to Al/acid stress using 105 annual Tibetan wild barley and 45 cultivated barley genotypes. Root elongation among the 105 Tibetan wild barley genotypes varied significantly after Al exposure, ranging from 62.9% to 80.0% in variation coefficients and 4.35 to 4.45 in diversity index. These genotypic differences in Al resistance were fairly consistent in both the hydroponic and filter paper–based evaluations: XZ16, XZ166, and XZ113 were selected as Al‐resistant genotypes, and XZ61, XZ45, and XZ98 as Al‐sensitive wild genotypes. Furthermore, significantly lower Al concentrations in roots and shoots were detected in the three selected Al‐resistant genotypes than in the three sensitive genotypes in the filter paper–based experiment. Meanwhile, XZ16 was the least affected by Al toxicity in regard to reduced SPAD value (chlorophyll meter readings), plant height, root length, dry biomass, tillers per plant, and chlorophyll fluorescence (Fv/Fm) in the long‐term hydroponic experiment compared with the Al‐resistant cultivated barley cv. Dayton, while XZ61 had the severest stress symptoms.     

Leaf mineral element concentrations and growth of sweet sorghum subjected to acid soil stress

Abstract

The nutritional profile of sweet sorghum [Sorghum bicolor (L.) Moench] cultivars grown under acid soil field stress conditions is a critical consideration when developing plants which are adapted to these infertile soils. Uptake and accumulation of macro‐ and micronutrients vary among genotypes and ultimately Influence plant growth and development. This study compared fourteen sweet sorghum germplasm lines and varieties for their Individual patterns of leaf nutrient concentrations and productivity when grown under acid soil field conditions (pH 4.45 to pH 4.85) at three locations over a two‐year period. Significant year x location interactions were found for Fe, K, and Ca concentrations at both Blairsville and Calhoun and for Mn and P levels at Blairsville and Calhoun, respectively. Data from Calhoun on plant height, dry weight, visual stress ratings, and rainfall indicate a possible association between drought tolerance and acid soil tolerance in sorghum. No significant differences in A1 concentrations were found among these sweet sorghum lines and varieties, which indicate that their acid soil tolerance mechanisms are probably not related to A1. MN 1054 accumulated the highest levels of Mn in the three acid soils. The highest concentrations of Mg and P were found in Brandes. MN 960 had the highest visual stress ratings (highest susceptibility) while Brandes, Ramada, Roma, and Wray were the most tolerant. All fourteen cultivars apparently have some tolerance to acid soil stress conditions.     

Challenges to the exploitation of host plant resistance for Striga management in cereals and legumes by farmers in sub-Saharan Africa: a review

Striga hermonthica, Striga asiatica and Striga gesneroides are obligate root parasites that cause severe yield losses in cereals and legumes in sub-Saharan Africa. Genetic control of Striga through resistance is widely considered to be the most practical and economically feasible method for long term control. The paper presents a comprehensive account of the Striga resistance mechanisms and environmental limitations to their usage in sub-Saharan Africa. Components of Striga resistance in cereals and legumes include low germination stimulant production, low haustorial initiation factor, mechanical barriers, incompatibility, antibiosis and Striga avoidance due to root growth habits. The successful exploitation of resistance has been limited by existence of specificity towards hosts, parasites that have evolved races specific host cultivars, Striga genetic variance which enables parasite to adapt to new resistance alleles and diverse hosts which support the parasite even in the absence of cereals together with low fertility due to nutrient mining in the smallholder sector. The results imply that different resistance mechanism may need to be present in genetically heterogeneous varieties or cereals with different resistance mechanisms may be rotated in the same field. Comprehensive Striga management systems should also address soil fertility in the small holder farmers of sub-Saharan Africa.     

Evaluation of Wild Lens Taxa for Agro-Morphological Traits, Fungal Diseases and Moisture Stress in North Western Indian Hills

Exploitation of wild gene pool for breeding is a common practice in an increasing number of cultivated plants. The cultivated lentil could not attain the substantial improvement in the yield potential due to loss of genes for higher productivity and lack of resistance against biotic and abiotic stresses. The absence of evaluation data of wild lentils for characters of economic importance, besides biotic and abiotic stresses, is one of the constraints in their use in lentil breeding programme. In the present study, 70 wild accessions from four wild Lens subsp./sp. (L. culinaris subsp. orientalis, L. odomensis, L. ervoides and L. nigricans) along with 3 checks (Precoz, PL-406 and PL-639) were evaluated for phenological and agro-morphological characters, for their reaction to three fungal diseases (wilt, powdery mildew and rust) and screened for tolerance to moisture stress. The wild accessions showed higher performance for branches/plant as compared to cultivated genotypes. Similarly, a few accessions of L. culinaris subsp. orientalis were earlier to flower and had higher seeds and seed yield/plant as compared to cultivated lentil. However, some were comparable with cultivated genotypes for flowers/peduncle, peduncle length and plant height. The mean performance for flowers per peduncle, leaflets per leaf, plant height, seeds and seed yield per plant increased, while decreased for days to flowering and maturity, and branches per plant during the evolution of cultivated lentil from the wild Lens taxa. Of Lens taxa, L. nigricans had the maximum resistant accessions for biotic and tolerance to abiotic stresses. The valuable variation existing among wild accessions can be exploited following introgression with cultivated lentils. It will help in the flow of useful genes from wild to cultivated lentil for generating wide spectrum of variability and its subsequent use in genetic restructuring of lentil.     

Resource use efficiency of field-grown sunflower, sorghum, wheat and chickpea: I. Radiation use efficiency

Radiation use efficiency () is a crop parameter widely used in crop simulation models, derived here as the slope of the relationship linking crop carbon gain to cumulative intercepted solar radiation. Our objectives were to: (i) determine of field-grown sunflower, sorghum, wheat and chickpea, at three levels of aggregation—day-time net assimilation (A), daily net carbon gain as difference between A and night-time dark respiration (R) and biomass; (ii) assess the robustness of parameter in terms of ability to discriminate between C₃ and C₄ species, pre- and post-anthesis and impact of nitrogen status; (iii) evaluate the opportunity to normalize for climate. Field experiments were conducted in 1998 and 1999 in southern Italy. All crops were well watered. Sunflower and sorghum had two nitrogen application treatments, wheat only one and chickpea had no added nitrogen. Daily intercepted solar radiation was derived from measurements of daily incident solar radiation and the percentage of mid-day light interception. Closed-system canopy chambers monitored canopy gas-exchange rates. , expressed in terms of A, A − R or above-ground biomass, was linear over the entire growth cycle of sorghum and wheat, and up to anthesis in sunflower and chickpea, independent of temperature, vapour pressure deficit and radiation regimes. In sunflower, deviation from linearity was observed after anthesis, due to higher carbon cost in yielding oil seeds. No conclusions could be drawn for post-anthesis chickpea due to the interruption of the experiment caused by a thunderstorm. Overall results showed a great variability in values, independently of classes of species (C₄ and C₃), crops and nitrogen treatments. This indicates that the robustness of to predict biomass productivity in crop simulation models is constrained. Attempts to normalize by vapour pressure deficit (D), for reducing its variability due to climate and overlaps between crops failed.