Effects of soil temperature, seeding depth and seeding date on rhizoctonia seedling blight and root rot of chickpea

Effects of soil temperature, seeding depth, and seeding date on rhizoctonia seedling blight and root rot of chickpea. Rhizoctonia solani Kühn, a prevalent fungal pathogen in cultivated prairie soils, can be an important factor affecting seedling establishment of chickpea (Cicer arietinum L.). Studies were undertaken to determine the impact of different soil conditions on seedling establishment, development of root rot, and productivity of desi (Tyson) and kabuli (Sanford) chickpea plants sown in the presence of R. solani AG-4. The impact of soil and air temperatures and seeding depth was studied under controlled conditions, and the influence of seeding date was investigated at three field sites. The host responded to warm soils by increasing its growth rate, and the pathogen by increasing its virulence. The kabuli cultivar, Sanford, showed greater susceptibility to root rot caused by R. solani than the desi cultivar, Tyson. Root rot and shoot infection levels increased with soil temperature for both cultivars, but reached maximum values at substantially lower temperatures for Sanford. Shoot biomass of infected treatments for this cultivar was substantially lower than the controls, while the biomass of Tyson was affected to a lesser degree. Air temperatures of 17/3 °Cday/night allowed relatively unhindered plant growth, even of the more susceptible cultivar, Sanford, in the presence of R. solani, while warmer and cooler temperatures resulted in high mortality and diminished plant growth in surviving plants. Seedling emergence and seedling dry weight were greater at a seeding depth of 2 cm than at 5 cm for seedlings grown in infested soil. In inoculated field plots, seedling emergence was greatest in treatments seeded in late May to early June compared those seeded in early or mid-May; in noninoculated treatments, both emergence and yield were lower in treatments seeded in late May than at the earlier seeding dates. Seeding date did not affect the occurrence of root rot. Incidence de la temperature du sol, de la profondeur des semis et de la date d’ensemencement sur la fonte des semis par Rhizoctonia et sur le pourridié du pois chiche. Can. J. Plant Sci. 84: 901–907. Rhizoctonia solani Kühn, champignon pathogène courant dans les sols cultivés des prairies, peut nuire considérablement à l’implantation du pois chiche (Cicer arietinum L.). On a donc entrepris des études pour déterminer l’incidence de divers états du sol sur l’enracinement des plantules, ’apparition du pourridié et la productivité des pois chiches desi (Tyson) et kabuli (Sanford) semés en présence de R. solani AG-4. On a vérifié les effets de la température du sol et de l’air et de la profondeur des semis en milieu contrôlé, tandis que l’incidence de la date d’ensemencement a été évaluée sur le terrain à trois endroits. Quand le sol est chaud, la plante pousse plus rapidement , mais l’agent pathogène est plus virulent. Sanford (le cultivar kabuli) est plus sensible au pourridié causé par R. solani que le cultivar desi Tyson. La gravité du pourridié et le degré d’infection des pousses augmentent avec la température du sol chez les deux cultivars, mais atteint le maximum à une température nettement plus basse chez Sanford. La biomasse des pousses infectées de ce cultivar était passablement plus faible que celle des témoins, Tyson étant moins affecté sur ce plan. Une température diurne/nocturne de 17/3 °C permet à la plante de croître relativement sans difficulté en présence de R. solani , meme pour Sanford, qui est plus sensible. Une température plus élevée ou plus basse se traduit par un taux de mortalité accru et une croissance plus lente chez les plants survivants. Le pourcentage de levée et le poids sec des plantules sont plus élevés quand on sème les graines à 2 cm plutôt qu’à 5 cm de profondeur dans les sols contaminés. Dans les parcelles inoculées, le pourcentage de levée est plus élevé quand on sème les graines entre la fin de mai et le début de juin que lorsque les semis ont lieu au début de mai ou au milieu du mois; dans les parcelles non inoculées, le pourcentage de levée et le rendement sont plus faibles quand on sème à la fin de mai plutôt qu’à une date antérieure. La date d’ensemencement n’a aucune incidence sur la manifestation du pourridié

Efficiency of spatial analyses of field pea variety trials

Several spatial analyses of neighboring plots are now available for improving the precision of variety trials. The objective of this study was to evaluate the efficiency of three commonly used spatial analyses, a nearest neighbor adjustment (NNA), a least squares smoothing (LSS), and a first-order autoregressive model (AR1), in removing field trends from 157 field pea (Pisum sativum L.) variety trials tested in different growing zones across Alberta, Canada, during 1997 to 2001. All trials were conducted with a randomized complete block (RCB) design with three or four replications. A complete replication (block) was planted in a single field tier. Yield data from each of the 157 trials were subject to the conventional RCB analysis and the three spatial analyses. The LSS, NNA, and AR1 analyses removed an average of 22, 16, and 7% residual variation compared with the RCB analysis, respectively, but the amount of removal by the three analyses varied considerably among the trials. Each spatial analysis achieved more error reduction in 1997 and 1998, where trials contained larger block sizes than in 1999 to 2001, where trials contained smaller block sizes. The efficiency in spatial variation removal was great with large block sizes that involved large numbers of varieties. Furthermore, the LSS and NNA analyses were more effective in such removal than the AR1 analysis

Proteomelevel change in the roots of Pisum sativum L. in response to salinity

We initiated a proteomics-based approach to identify root proteins affected by salinity in pea (Pisum sativum cv. Cutlass). Salinity stress was imposed either on 2-wk old pea plants by watering with salt water over 6 wk or by germinating and growing pea seeds for 7 days in Petri dishes. Concentrations of NaCl above 75 mM had significant negative effects on growth and development of peas in both systems. Salinity-induced root proteome-level changes in pea were investigated by 2-D electrophoresis of proteins from control, 75 and 150 mM NaCl-treated plants and seedlings. The majority of the protein spots visualised showed reproducible abundance in root protein extracts from whole plants and seedlings. Of these proteins, 35 spots that exhibited significant changes in abundance due to NaCl treatment were selected for identification using ESI-Q-TOF MS/MS. The identities of these proteins, which include pathogenesis-related (PR) 10 proteins, antioxidant enzymes such as superoxide dismutase (SOD) as well as nucleoside diphosphate kinase (NDPK) are presented, and the roles of some of them in mediating responses of pea to salinity are discussed. This is the first report of salinity-induced changes in the root proteome of pea that suggests a potential role for PR10 proteins in salinity stress responses. Our findings also suggest the possible existence of a novel signal transduction pathway involving SOD, H2O2, NDPK and PR10 proteins with a potentially crucial role in abiotic stress responses

Differences in the growth stages of Erysiphe pisi on cultivars of field pea (Pisum sativum L.)

The infection process of Erysiphe pisi on field pea cvs. ‘Highlight’ and ‘Tara’ carrying resistance gene erl, line ‘JI2480’ carrying resistance gene er2, and susceptible cv. ‘Radley’ (Er) was studied at 20 °C in controlled conditions. The growth stages of E. pisi were observed on these cultivars with an environmental scanning electron microscope and a light microscope. No significant differences in the number of conidia with appressoria within 12 h of incubation and in the shape of the appressoria through the 72-h incubation on all cultivars. The conidia with appressoria on cvs. ‘Highlight’ and ‘Tara’ produced little or no mycelia after 72-h incubation. The conidia on ‘JI2480’ or ‘Radley’ developed primary (Gs5) and secondary mycelia (Gs6) within 24 h of incubation, but significantly fewer conidia with appressoria developed primary or secondary mycelia on ‘JI2480’ compared to ‘Radley’ after 72-h incubation. Significant more lesions were on ‘Radley’ and ‘JI2480’ after 72-h incubation than on ‘Highlight’, but the number of lesions on ‘Tara’ was not significantly different from all these cultivars. These results show that different er genes affected different stages of the infection process of E. pisiDer Infektionsprozess von Erysiphe pisi an den Felderbsensorten ‘Highlight’ und ‘Tara’, die das Resistenzgen er1 tragen, an der Linie ‘JI2480’ mit dem Resistenzgen er2 sowie an der anfälligen Sorte ‘Radley’ (Er) wurde bei 20 °C unter kontrollierten Bedingungen untersucht. Die Beobachtung dieser verschiedenen Wachstumsstadien von E. pisi an den genannten Sorten erfolgte mit dem Raster-elektronen- und Lichtmikroskop. Dabei konnten an allen Sorten nach 12 h Inkubation keine signifikanten Unterschiede in der Zahl der Konidien mit Appressorien und im Aussehen der Appressorien wahrend der 72-stündigen Inkubation festgestellt werden. Die Konidien mit Appressorien produzierten auf den Sorten ‘Highlight’ und ‘Tara’ wenig oder kein Myzel innerhalb von 72 h. Die Konidien auf ‘JI2480’ oder ‘Radeley’ entwickelten primäres (GS5) und sekundäres Myzel (GS6) innerhalb von 24 h Inkubation. Aber signifikant weniger Konidien mit Appressorien bildeten primäres oder sekundares Myzel auf ‘JI2480’ im Vergleich zu ‘Radley’ nach 72 h Inkubation. Signifikant mehr Lasionen erschienen nach 72 h Inkubation auf der Sorte ‘Radley’ und ‘JI2480’ als auf ‘Highlight’, jedoch unterschied sich die Zahl der Läsionen auf ‘Tara’ nicht signifikant von denen auf alien Sorten. Diese Ergebnisse zeigen, dass die unterschiedlichen er-Gene die verschiedenen Stadien des Infektionsprozesses von E. pisi beeinflussten

Competition in a rice - cowpea intercrop as affected by nitrogen fertilizer and plant population Competição em uma cultura consorciada de arroz-guandu em função do fertilizante nitrogenado e da densidade populacional de plantas

The increased productivity or yield advantage provided by intercropping is attributed to a better use of resources by crops grown in mixtures, as compared to the same species grown in sole stands. In an intercropping system with upland rice and cowpea, the intra and inter-competition was quantified, as affected by plant population density and rate of nitrogen. Reductions in number of panicles per rice plant and number of grains per panicle were obtained with high density in both sole and mixture rice populations. Increasing nitrogen rate did not affect yield and yield components in both populations, but number and weight of pods per plant of cowpea in sole stands increased. Land equivalent ratios exceeding unity were obtained, indicating an improved resource use by the crop mixture. Relative crowding coefficient and aggressivity indices showed cowpea to be the dominant crop, with rice being dominated. Nitrogen utilization efficiency was high with intercrops, but was generally poor in stands of high population density.<br>O aumento em produtividade devido a plantios consorciados é atribuído ao melhor uso dos recursos presentes pelas plantas em desenvolvimento conjunto, em comparação às mesmas espécies crescendo em dosséis separados. Em um sistema consorciado de arroz e guandu quantificou-se as inter- e intra competições em relação à densidade populacional e taxa de aplicação de nitrogênio. Reduções significativas do número de panículas por planta de arroz e número de grãos por panícula foram observados para alta densidade, tanto para culturas solteira de arroz como em populações mistas. O aumento das doses de nitrogênio não afetou a produção e os componentes de produção em ambos os sistemas, ao passo que o número e peso de vagens por planta do guandu aumentaram em culturas solteiras. Foram obtidas razões de área equivalente maiores que a unidade, mostrando melhoria no uso da terra nas culturas mistas. O coeficiente relativo de superpopulação e os índices de agressividade mostraram que o guandu é dominante e o arroz dominado. A eficiência do uso de nitrogênio foi alta nas culturas consorciadas, mas em geral baixa para populações de alta densidade