International Journal of Agricultural Sciences

International Journal of Agricultural Sciences ISSN: 2167-0447 Vol. 5 (3), pp. 587-594, May, 2015. © International Scholars Journals

Full Length Research Paper

Analysis of the resistance to Phytophthora pod rot within local selections of cacao (Theobroma cacao L.) for breeding purpose in Cameroon

Lious chanel Baudelaire

Department of Agronomy, Faculty of Agriculture, University of Montpellier, Montpellier, France.

E-mail: [email protected]

Abstract

The level of resistance against Phytophthora pod rot (PPR) was assessed among locally-selected accessions of cacao, the so-called selection of Nkoemvone (SNK), in Cameroon. The evaluation approaches have included four tests: Leaf disc inoculation (LDT); detached pod inoculation (DPT); artificial inoculation of pods and counting of successful infections (%SI); and field observations of the disease incidence (FI). The studied accessions were classified into four groups according to their genetic origin: SNK; SNK600-Tr (SNK*ICS); SNK600-Tr*UA (UPA*ICS); SNK600-Tr*UA (UPA*SNK). In all four testing methods, the groups UPA*ICS and SNK appeared respectively as the least and the most susceptible accession groups. Four resistance classes were defined for each testing method. A great part of the accessions were found in the intermediary resistance classes, based on DPT, LDT and %SI. Few accessions have displayed a significant level of PPR resistance in all testing methods. Rank correlation of the different accessions groups based on their performance in the four tests have shown that all correlation coefficients were positive (r = 0.37 – 0.87) and significant (p ≤ 0.06). The best correlation was registered between %SI and FI with r = 0.87 (p = 0.01). Subsequently, a unique classification of all accessions was done according to the scores recorded in all the testing methods. The use of locally-selected accessions (SNK) in the varietal development as well as in the cacao seed production is discussed.

Key words: Cacao plant pathology, oomycetes, screening methods, resistant cultivars, selection.

International Journal of Agricultural Sciences ISSN: 2167-0447 Vol. 5 (3), pp. 541-550, May, 2015. © International Scholars Journals

Full Length Research Paper

Evaluating the correlation between yield and yield components in sunflower under different planting dates

Mohammed Mahfouz Henedi

Department of Agronomy, Faculty of Agriculture, German University in Cairo, New Cairo

Email: [email protected]

Abstract

The relationships between planting dates and yield and it's components in sunflower was evaluated through orthogonal polynomial regression analysis. Five field experiments were conducted during the summer season of 2011 to study the effect of five planting dates and three oilseed sunflower genotypes and their interactions on yield and yield components of sunflower. The highest seed yield, oil yield, plant height, head diameter, 1000-seed weight, seed yield plant^-1 and oil content were obtained at the earliest planting date (1st May). The evaluated genotypes differed significantly for all the studied traits. Sakha 53 cultivar was the best cultivar in seed yield, oil yield, plant height, head diameter, thousand seed weight and seed yield plant plant^-1 followed by Giza 102 and Pioneer hybrid 63M02, respectively. Orthogonal polynomial regression analysis revealed that, yield and yield components were significantly affected by planting date in linear responses. Multiple linear regression analysis indicated that seed yield plant^-1, head diameter and thousand seed weight were the most important variables contributing toward higher seed yield (kg ha^-1). Finally, it can be concluded that planting sunflower cultivar Sakha 53 on 1st May was recommended for maximizing seed and oil yields per unit area under the environmental conditions of this study.

Key words: Sunflower, planting date, genotype, regression analysis, yield, yield components.

International Journal of Agricultural Sciences ISSN: 2167-0447 Vol. 5 (3), pp. 521-532, May, 2015. © International Scholars Journals

Review

Selection of host behavior of aphid parasitoids (Aphidiidae: Hymenoptera)

*Imram V. Akram, Shoaib B. B, Abdul H. Kkan and Mohammed L. Malik

Department of Crop Science, Faculty of Agriculture and Environmental Sciences, University of Karachi, Karachi, Pakistan.

*Corresponding author. E-mail: Akram.imran@ uok.edu.pk

Abstract

Biological control is the central stone of Integrated Pest Management (IPM) paradigm and natural enemies are becoming an increasingly desirable prospect. Parasitoids are a widely used group of invertebrate natural enemies as biological control agents and several species are being used to control various aphid pests. In recent years, an increasing emphasis is being given to the conservation and manipulation of naturally-occurring populations of parasitoids in agricultural ecosystems over traditional approaches to biological control. But these approaches must be underpinned by basic knowledge in host preference behaviour and ecology of the parasitoid species being manipulated. Three aspects of host preference behaviour, namely host recognition, host acceptance and host suitability have been discussed in this paper. Parasitoids’ host selection strategy is based on using long-range and short-range cues. Parasitoids respond to both semiochemical and physical stimuli to locate and recognise their hosts. These responses are either due to aphid sex pheromones acting as kairomones, or due to aphid-induced plant volatiles, acting as synomones. Various interactions like genetic, learning and conditioning factors, which play an important role in host selection behaviour of foraging parasitoids, have been discussed. The learning ability provides the parasitoid with behavioural plasticity to adapt its responses to suit prevailing foraging opportunities and the maintenance of genetic variability within natural populations of parasitoids may promote long-term population stability and help conserving genetic diversity by ensuring flexibility in host selection.

Key words: Aphid parasitoids, host preference, host selection, host recognition, host acceptance, host suitability, conservation of aphid parasitoids, manipulation of parasitoid behaviour, habitat.

International Journal of Agricultural Sciences ISSN: 2167-0447 Vol. 5 (3), pp. 595-600, May, 2015. © International Scholars Journals

Full Length Research Paper

Main component analysis of morphological traits in thirty-nine accessions of rice (Oryza sativa L.) grown in a rainfed lowland ecology of Nigeria

Adeyemi Anthony Kojibola

Department of Crop Production, Faculty of Agricultural Science, University of Benin, Edo, Nigeria.

Email: [email protected]

Abstract

Field experiment was conducted at Edozhigi, National Cereal Research Institute experimental field, to assess the contribution of morphological traits to variability in some accessions of rice. The field was laid out in a randomized complete block design with three replicates. Thirty nine entries collected from farmer’s field and National Cereals Research Institute gene Bank were planted in a plot size of 5 × 1 m. The experiment was conducted in 2009 and 2010 cropping seasons. Data were collected on twelve morpho-physiological traits. The results of the principal component analysis showed that the first 5 principal component axes explained 68.9% (first year) and 61.6% (second year) of the total variations in the rice population. The combined results showed that 65.4% of the variations were accounted for by the first 5 principal components axes. Number of grains per panicle loaded more on the component loading correction plot using the combined results. It accounted for about 17.8% of the variation in the population. High levels of variability were expressed among the varieties and the characters studied which will allow further improvement in the varieties.

Key words: Variation, principal component, rice, variety.

International Journal of Agricultural Sciences ISSN: 2167-0447 Vol. 5 (3), pp. 504-508, May, 2015. © International Scholars Journals

Full Length Research Paper

A study on genetic yield stability in some sunflower (Helianthus annuus L) hybrids under different environmental conditions of Sudan

*Omar Al-Mirghani, Gaafar K. E and Salva Nimeiry

Department of Crop Science, Faculty of Agriculture and Environmental Sciences, Omdurman Islamic University, Omdurman, Sudan.

*Corresponding author. E-mail: [email protected]

Abstract

Nineteen locally developed sunflower (Helianthus annuus L.) hybrids and an introduced one (Hysun 33) were evaluated at two irrigated locations, New Halfa and Rahad for two consecutive seasons (2003/04 and 2004/05) in order to estimate stability of performance for seed yield per ha (t). A randomized complete block design with four replicates was applied at each location. Data on seed yield was collected. The variance of genotype x environment interaction (GxE) was highly significant, suggesting that the yield of the hybrids was inconsistent in different environments. The average ranking of the 20 hybrids, according to stability parameters showed that Salih was the first ranked hybrid followed by Ka99x7, Ka99x29, Ka99x13 and Shambat 6, whereas Hysun33 was the last ranking one. The two released hybrids (Salih and Shambat 6) were adapted favorable environments, whereas Ka99x25-2 adapted unfavourable conditions. However, the graph for scatter points for yield of the locally developed hybrids revealed that Salih and Shambat 6 were stable, whereas that of Hysun 33 was unstable under these environments and its yield was only increased with improving the conditions.

Key words: Sunflower, hybrids, yield, GxE interaction, stability.