Consecutive Crop Seasons Research Articles

Variation and inheritance of leaf angle, and its association with spot blotch (Bipolaris sorokiniana) severity in wheat (Triticum aestivum)

One thousand four hundred and seven spring wheat germplasm lines belonging to Indian and CIMMYT wheat programs were evaluated for their leaf angle and resistance to spot blotch caused by Bipolaris sorokiniana during three consecutive crop seasons, 1994–95, 1995–96 and 1996–97.Disease severity was recorded at six different growth stages beginning from tillering to late milk stage. Three crosses (M 3109 × Sonalika, HP 1808 × K 9006 and HD 2662 × K 9006) were made between genotypes with erect and drooping leaves. M 3109 was resistant, Sonalika susceptible while the other three lines possessed moderate resistance to spot blotch. Individually threshed F2 plants were used to advance the generations. Leaf angle and spot blotch resistance were recorded in parents, F1, F3, F4and F5 generations. Leaf erectness in F1 generation showed partial dominance. Evaluation of F3, F4 and F5 progenies(120–150) revealed that leaf angle was under the control of few genes that appeared to be close to three. Germplasm lines with erect and semi-erect leaves displayed lower spot blotch severity than those having drooping and semi-drooping leaves. Lines homozygous for erect leaf posture in F3,F4 and F5 generations showed significantly lower mean AUDPC than those with drooping leaves. A positive correlation (0.58) between leaf angle and AUDPC further indicated a positive influence of leaf erectness on severity to spot blotch disease.

Forecasting growth and yield of groundnut (Arachis hypogaea) with a dynamic simulation model ‘PNUTGRO’ under Punjab conditions

The dynamic simulation model ‘PNUTGRO’ was used to predict groundnut growth and yield from 1989 to 1993 at Ludhiana, India. The simulated flowering, pegging and physiological maturity dates, leaf area index (LAI), pod and seed yields and shelling percentage of groundnut were compared with actual observations for the commonly grown cultivar, M-335. The simulated phenologic events showed deviations of only −3 to +3 days for flowering, −3 to +2 days for pegging and −4 to +2 days for physiological maturity of the crop. The model estimated the LAI to be within 95–108% (mean 101·5%) and shelling percentage to be within 93–108% (mean 100·5%) of the actual values. The model predicted the pod yields from 89 to 111% (mean 100%) and seed yield from 90 to 110% (mean 100%) of the observed yields. The results obtained with the model for the five consecutive crop seasons revealed satisfactory predictions of phenology, growth and yield of groundnut and hence the model ‘PNUTGRO’ can be used for prediction of groundnut production in the central plains of the Indian Punjab.

Pathogenic and non-pathogenic mycoflora in the air and phylloplane ofTriticum aestivum L.

Aerobiological investigations were carried out over wheat (Triticum aestivum L.) fields near Barrackpore, West Bengal, India for two consecutive crop seasons. In 1990–91, except for the very seedling stage there was a more or less uniform spore count up to the maximum vegetative growth state and from flowering onwards, a gradual increase in total cfus was observed with the peak (331 CFUs) during the harvesting stage. In the second season, similar results were recorded where peak spore load (2064 CFUs) in the air was during harvesting operation followed by a sudden decline in the empty field.Cladosporium spp. dominated both the seasons mainly up to February.Penicillium, Curvularia, Aspergillus andCephalosporium were the most frequent non-pathogenic fungal types. Among the pathogenic fungi,Alternaria andDrechslera were recorded to be the most virulent to wheat crop, after inflorescence to later stages in both the seasons causing heavy leaf damage producing necrotic spots during which peak cfus were found.Fusarium was frequently found showing the peak during vegetative growth period.Sclerotium was more common in the second season than in the first season. High occurrence ofnigrospora was recorded in the earlier stages. Sterile forms' were found regularly. The phylloplane studies revealed thatCladosporium was the most dominant flora contributing 40–66% up to February in winter; gradually disappeared from the leaf surface with the onset of summer.Aspergillus andPenicillium showed the reverse picture. WhileCurvularia was isolated in high amount during later stages;Nigrospora mainly during the vegetative growth stages.Alternaria (caused Alternaria blight) andDrechslera were significantly isolated during harvesting (28.08%)and at late ‘grain maturation’ stage (80.10%), respectively.Sclerotium and ‘Sterile forms’ were recorded regularly unlikeFusarium andHelminthosporium.

Effect of nitrogen rates on rice growth and biological nitrogen fixation

SUMMARYThe effect of different rates (0–140 kg/ha) of nitrogen fertilizers on soil cyanobacteria and rice crop performance were studied in a rice-cropping system on an alkaline Fluvent soil at Valencia, Spain, during three consecutive crop seasons (1990–92). The results showed that the rice fields of Valencia favour the development of N2-fixing cyanobacteria. Nitrogen fixation varied during the cultivation cycle, reaching its highest values at the maximum tillering stage, 5–6 weeks after sowing, and showed a positive correlation with the abundance of cyanobacteria and a negative correlation with the amount of N fertilizers used. Grain yield increased with increasing amounts of N fertilizers up to 70 kg N/ha. N rates appeared to affect grain yield by causing variations in the number of panicles/m2. Leaf chlorophyll readings at the end of the tillering stage were positively correlated with the number of panicles/m2, suggesting that it could be a useful parameter for predicting productivity. There was a significant increase in the N uptake of the rice but a decrease in the apparent N recovery and Nuse efficiency of applied fertilizer N, with the application of increasing rates of N fertilizer. In all instances, except in plots fertilized with 140 kg N/ha, the amount of N removed by plants was significantly higher than that applied as N fertilizer. The differences were positively correlated with the values for N fixation, suggesting a significant contribution by N fixation to rice production. These results show that a rational use of biological N fixation, in combination with inorganic N fertilization, would permit the input of N fertilizers to be reduced by c. 50% without any significant loss of productivity and with an ecological benefit for the whole ecosystem.

Legume Hosts of Macrophomina phaseolina in Kenya and Effect of Crop Species on Soil Inoculum Levels

AbstractStudies were conducted in eastern Kenya to determine the common legume crop and weed hosts of Macrophomina phaseolina (Tassi) Goid., the inciter of charcoal rot disease. The effect of maize, sorghum, bean, and cowpea on the soil inoculum level was also investigated after field inoculation. All the legume crops and weeds tested were found to be infected by the pathogen after artificial inoculation. Common bean, soybean, cowpea were the most susceptible while pigeonpea, green gram, and hyacinth bean were moderately susceptible. Groundnut, chickpea. Cassia spp. and Crotalaria spp. were least susceptible after artificial inoculation, Monocropping of sorghum, maize, cowpea and common bean for three consecutive crop seasons increased M. Phaseolina soil inoculum in ascending order.

Evaluating an insect pest management system in an irrigated rice environment

AbstractThe efficiency and profitability of an integrated pest management system consisting of a phytosanitary survey and threshold interventions (based on levels of insect damage) was tested at the Vallée du Kou irrigated rice scheme in Burkina Faso, for two consecutive crop seasons in 1987. There was a considerable advantage in cost, number of insecticidal applications and yield of a threshold intervention-based system over arbitrary or routine insecticidal application methods. The proposed method is considered to be environmentally friendly.

Pyrethroids and organochlorines resistance in cotton aphidAphis gossypii(Glov.) (Homoptera: Aphididae) in the Sudan Gezira

Abstract The resistance to insecticides of six Sudanese strains of Aphis gossypii (Glov.) collected from cotton fields in Sudan Gezira over four consecutive crop seasons (1988, 1989, 1990, 1991) and that of two French strains, was studied in the laboratory. When compared with a known English susceptible strain, Sudanese aphids were found to be resistant to the four insecticides tested (fenvalerate, deltamethrin, endosulfan and γ‐HCH) while the French strains were relatively susceptible. Evolution of insecticide resistance in Sudanese strains over the four crop seasons was observed. The high synergist ratios and the decrease in resistance factor for the resistant strain, Sudan V, in experiments with piperonyl‐butoxide (PB), an inhibitor of mixed function oxidase, and pyrethroids (deltamethrin and fenvalerate) and also PB with organochlorines (endosulfan and γ‐HCH), suggested that enhancement of the activity of this class of enzyme was a cause of resistance in the Sudanese strain of A. gossypii.

Influence of Chlormequat on the Growth and Yield of Irrigated and Rainfed Indian Mustard (Brassica juncea) in the Field

SUMMARYThe effect of the field application of chlormequat on the growth, yield and seed oil content of Brassica juncea grown under irrigated and rainfed conditions was evaluated for three consecutive crop seasons. Foliar application at the flower initiation stage increased the number of primary branches, number and length of siliquae, weight of seeds and seed oil content. Chlormequat (50 AS) applied at 80 ml ha−1 increased seed yield by more than 50%. The increase was greater in unirrigated crops.

A quantitative evaluation of the comparative value of six fertilizer–nitrogen sources for potatoes

SUMMARYSix fertilizer–nitrogen sources, each at three levels, together with a control of no fertilizer–nitrogen were compared in field trials in two consecutive crop seasons on a sandy soil comparatively deficient in nitrogen at Patna, Bihar. Four mathematical models were fitted to the potato yield data in order to evaluate the relative availability indices of the individual fertilizers. Data collected on final stand and ‘emergence rate’ index (Bartlett) showed that while urea applications gave rise to a comparatively low speed of emergence, with observed shoot injuries, nitrate of soda caused poor final stands. The other fertilizers had no effect on either the final stand or the speed of emergence.Sulphate of ammonia was chosen as the standard fertilizer for the present study. Ammonium sulphate nitrate was as good as or even slightly better, while ammonium chloride and calcium ammonium nitrate were of intermediate efficiency, in that order. Urea and nitrate of soda were decidedly poor as nitrogen sources for potatoes under the conditions of the study. The concurrent Mitscherlich curves model was found to represent the behaviour of these fertilizers with a good measure of fit.The performance of the six fertilizers is discussed in the light of the availability of NH4+ and NO3-, the phytotoxicity of urea and nitrate of soda, and the harmful effects of Cl-. It is concluded that ammonium sulphate nitrate is the best carrier of nitrogen among those studied for potatoes under the conditions set forth.