Department of Plant Science

Permanent URI for this collectionhttps://repository.chuka.ac.ke/handle/chuka/421

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HORT 421: HORTICULTURAL SEED PRODUCTION
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 421: HORTICULTURAL SEED PRODUCTION
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 421: HORTICULTURAL SEED PRODUCTION
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 421: HORTICULTURAL SEED PRODUCTION
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 421: HORTICULTURAL SEED PRODUCTION
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 361: FLORICULTURE 1 (MAJOR CUT FLOWERS)
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 333: GENERAL VEGETABLE PRODUCTION
(Chuka University, 2024-12-16) Chuka University; ; ;
HORT 212: PLANT IDENTIFICATION
(Chuka University, 2024-12-16) Chuka University; ; ;
Genetic and Phenotypic Diversity of Selected Kenyan Mung Bean (Vigna Radiata L. Wilckzek) Genotypes.
(Springer Open., 2021) Mwangi, J. W.; Piero, N. M.; Kariuki, M. P.; Okoth, O. R.
Background: Mung bean is a pulse crop principally grown in the tropic and subtropic parts of the world for its nutrient-rich seeds. Seven mung beans accessions from Eastern Kenya were evaluated using thirteen phenotypic traits. In addition, 10 SSR markers were used to determine their genetic diversity and population structure. This aimed at enhancing germplasm utilization for subsequent mung bean breeding programs. Results: Analysis of variance for most of the phenology traits showed significant variation, with the yield traits recording the highest. The first three principal components (PC) explained 83.4% of the overall phenotypic variation, with the highest (PC1) being due to variation of majority of the traits studied such as pod length, plant height, and seeds per pod. The dendogram revealed that the improved genotypes had common ancestry with the local landraces. The seven mung beans were also genotyped using 10 microsatellite markers, eight of which showed clear and consistent amplification profiles with scorable polymorphisms in all the studied genotypes. Genetic diversity, allele number, and polymorphic information content (PIC) were determined using powermarker (version 3.25) and phylogenetic tree constructed using DARWIN version 6.0.12. Analysis of molecular variance (AMOVA) was calculated using GenALEx version 6.5. A total of 23 alleles were detected from the seven genotypes on all the chromosomes studied with an average of 2.875 across the loci. The PIC values ranged from 0.1224 (CEDG056) to 0.5918 (CEDG092) with a mean of 0.3724. Among the markers, CEDG092 was highly informative while the rest were reasonably informative except CEDG056, which was less informative. Gene diversity ranged from 0.1836 (CEDG050) to 0.5102 (CDED088) with an average of 0.3534. The Jaccards dissimilarity matrix indicated that genotypes VC614850 and N26 had the highest level of dissimilarity while VC637245 and N26 had lowest dissimilarity index. The phylogenetic tree grouped the genotypes into three clusters as revealed by population structure analysis (K = 3), with cluster III having one unique genotype (VC6137B) only. AMOVA indicated that the highest variation (99%) was between individual genotype. In addition, marker traits association analysis revealed 18 significant associations (P < 0.05). Conclusion: These findings indicate sufficient variation among the studied genotypes that can be considered for germplasm breeding programs.
Stubborn Disease of Citrus Caused by Spiroplasma Citri: A Short Note.
(EScience Press, 2021) Kiptoo, J. J.; Kiptoo, G. J.; Chemoiwa, E.; Pixley, K.; Abbas, A.; Usman, H. M.; Mubeen, M.
Citrus fruit is considered a very nutritious and delicious diet. Citrus consists of lemon, oranges, mandarin, and grapefruit which have economic value in the world. Significant losses occur in citrus due to numerous diseases. Among various diseases, citrus trees are seriously affected by a phytopathogenic mollicute Spiroplasma citri which causes stubborn disease. S. citri is transovarially transmitted by several leafhopper species. Symptoms include smaller and cupped leaves, small size, crook fruits with aborted seeds. Moreover, irregularity on the fruits such as different sizes, shapes, and typically lighter, smaller fruits than its healthy counterpart has also been observed. The affected fruits often drop before maturity. The color inversion is often seen with the stylar end remaining green and the peduncle end showing color. Various molecular and biochemical tests are conducted to identify S. citri. Under in-vitro conditions, S. citri grows on SP4 media where a fried egg-like shaped colony is observed. Keeping the importance of the stubborn citrus disease, the present short note briefly described the symptomology, detection, transmission, and management.
Production of Mineral Nutrient-Rich Multipurpose Pumpkin Leafy Vegetables Using Integrated Nitrogen, Mulch, and GA3
(Chuka University, 2022) Mwaura, M. M.; Isutsa, D. K.; Munyiri, S. W.
Understanding the effect of nitrogen, mulch and gibberellic acid on minerals and metabolites in multipurpose pumpkin (Cucurbita moschata Duch) is important since it is a dependable source of food, providing families producing it with various diets that contribute to household food and nutrition security. However, production of the pumpkin using optimal or integrated inputs has not yet been embraced in most African countries, resulting in under-realization of its maximum potential. To respond to this challenge, a split-split plot experiment arranged in randomized complete block design and replicated three times was conducted for two seasons from January 2019 to July 2020. The nitrogen (0, 50, 100 and 150 kg N/ha) was assigned to main plots, mulch (no mulch, black-painted and unpainted rice straws) to sub-plots, and gibberellic acid (GA3) (0 mg/L, 40 mg/L and 80 mg/L) to split-plots. Nitrogen was applied as calcium ammonium nitrate (CAN) in two equal doses for each rate at three weeks post- emergence and at the beginning of flowering. The black-painted and unpainted rice straws were placed on plots after land preparation. The GA3 solution was sprayed to plants using a 1-L sprayer, starting with 40 mg/L, followed by 80 mg/L, once during the fourth week post-emergence. Data collection was done fortnightly from the fourth week after emergence up to fruit harvest stage. Data values were subjected to analysis of variance using SAS software version 9.3 and means separated using the least significant difference test at α=0.05. All the measured parameters were significantly (P<0.05) different. Highest levels of K and Mg were obtained for 100 kg N/ha. On the other hand, P and beta-carotene were highest where unpainted rice straws were used, while application of 80 mg/L GA3 yielded high amounts of P and K. Results further showed that combined N fertilizer, mulch and GA3 consistently had significant (P<0.05) effects on N, P, K, Mg and beta-carotene (highest 23 ppm was for N1M1GA1). Therefore, sole nitrogen fertilizer, mulch, GA3, and combined rates that promote the desired mineral nutrient and beta-carotene contents in multi-purpose pumpkin leaves should be adopted and applied, depending on the kind.
Earthing up and Pruning Systems on Post-Harvest Quality of Tomato (Solanum lycopersicon).
(International Journal of Plant & Soil Science, 2022) Keter, I. K.; Oloo-Abucheli, G. O.; Muraya, M.; Kiplangat, C. T.
Tomato is a popular and extensively cultivated vegetable among the economically promising commodities in the horticulture sector in Kenya. It provides a wide variety of nutrients with many health-related benefits. This study investigated the effect of integration of pruning and earthing up on postharvest. The experiments were carried out in a split-plot arranged in a randomized complete block design (RCBD) and in CRD for both field and laboratory work respectively. Fruit yield data was taken after each harvest. The results from the analysis of variance for the effect of factors (earthing up and pruning system) and their combined effect showed that there was a significant effect on the average weight loss percentage and total soluble solids in both cultivations. The treatments had a significant effect on the average weight loss percentage, total soluble solids, and fruit firmness in both cultivations. The highest fruit weight loss percentages were recorded from all stem pruning system with no earthing up. The highest fruit firmness (3.41 N mm-1 in cultivation 1 and 3.24 N mm-1 in cultivation 2) was recorded from a single stem pruning system and earthing up to 30 cm. The highest total soluble solids (TSS) percentage 6.09 % was recorded in both cultivations under a single stem pruning system and earthing up to 30 cm. To improve tomato postharvest, farmers are encouraged to consider triple stem pruning system in combination with earthing up to level 30 cm.
Effects of Agricultural Nutrients Influx on Water Quality in Thiba River basin, a sub-catchment of Tana River Basin in Kirinyaga County, Kenya.
(EAST AFRICAN NATURE & SCIENCE ORGANIZATION, 2022) Njue, J. M.; Githae, E. W.; Magana, A. M.
ABSTRACT Excessive enrichment of waters with nutrients and the associated adverse biological effects leads to eutrophication, which is one of the major environmental problems across the world. Various studies have revealed the overuse of inorganic fertilizers to increase agricultural productivity in Kenya contributes to pollution of water bodies. In order to meet increasing demand for clean water, sustainable use and conservation of available water resources is therefore paramount. This study was done to find out effects of agricultural nutrient pollution in Thiba River, a sub-catchment of Tana River Basin, located in Kirinyaga County, Kenya. The study area was divided into four distinct agro- ecological zones based on different anthropogenic activities. Ecological survey design was used in the study. Sampling was done during the wet and dry season. Water samples were analysed for temperature, transparency, pH, electrical conductivity (EC), salinity, total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD), phosphates, nitrates, nitrites, ammonia, and toxic microalgae. All parameters showed both spatial and temporal variations with statistically significant differences (p˂0.01). Temperature of the river ranged from 14.57 0C to 28.08 0C due to climatic changes along the agro- ecological zones. The pH ranged from 7.02 to 8.51. The DO values decreased from the highlands to lowland within the range of 9.00 mg/l at the reference site to 5.43 mg/l at the most polluted site. EC ranged from 20.54 µScm-1 at the reference site during the wet season to 251.2 µScm-1 at the rice irrigation scheme site during dry season. The TDS ranged from 16.9 ppm at the reference site to 167.05 ppm at the most polluted site. Salinity also had a high variation with a range of 0.01 ppt at the reference site to 0.07 ppt at the most polluted site. The highest values of BOD (3.49 mg/l) were recorded at the rice irrigation scheme during the wet season and the lowest (0.22 mg/l) at the forest edge reference site.The lowest levels of NH4, P, NO2 and NO3 were recorded at the forest edge reference site at 1.088 µg/l, 1.177 µg/l, 0.217 µg/l and 0.148 µg/l respectively during the dry season while the highest values for the same nutrients were recorded at the rice irrigation site at 11.439 µg/l, 4.933 µg/l, 1.518 µg/l and 2.721 µg/l in the same order. There was a high peak of all nutrient levels at the rice irrigation scheme zone which was attributed to the extensive use of inorganic fertilizers. Dam water samples were analysed for members of Cyanobacteria group of microalgae which are bio-indicators of eutrophic waters. Out of the seven members of this group that were identified four were toxic genera. These were Nostoc, Oscillatoria, Anabaena and Microcystis. During the wet season Nostoc had the highest population followed by Oscillatoria and Anabaena. No Microcystis was observed during the wet season. There was a steady increase of all the genera during the dry season with Microcystis making appearance. Microcystis and Oscillatoria had a very high correlation. This study concludes that various anthropogenic activities especially agriculture along the study site are the main factors of Thiba River pollution hence a major threat to human, livestock and aquatic organisms. Environmental protection laws should be enforced by the government.
Genome-Wide Identification of the B-Box Gene Family and Expression Analysis Suggests Their Potential Role in Photoperiod-Mediated β-Carotene Accumulation in the Endocarp of Cucumber (Cucumis sativus L.) Fruit
(MDPI, 2022) Obel, H. O.; Chen, J.; Li, J.; Njogu, M. K.; Tian, Z.; Li, Y.; Cheng, C.
Carotenoids are indispensable to plants and essential for human nutrition and health. Carotenoid contents are strongly influenced by light through light-responsive genes such as B-Box (BBX) genes. BBX proteins, a class of zinc-finger transcription factors, mediate many light-signaling pathways, leading to the biosynthesis of important metabolites in plants. However, the identification of the BBX gene family and expression analysis in response to photoperiod-mediated carotenoid accumulation in cucumber remains unexplored. We performed a genome-wide study and determined the expression of cucumber BBX genes (hereafter referred to as CsaBBXs genes) in the endocarp of Xishuangbanna cucumber fruit (a special type of cucumber accumulating a high level of β-carotene in the endocarp) using an RNA-seq analysis of plants previously subjected to two photoperiodic conditions. Here, 26 BBX family genes were identified in the cucumber genome and named serially CsaBBX1 through CsaBBX26. We characterized CsaBBX genes in terms of their phylogenetic relationships, exon-intron structures, cis-acting elements, and syntenic relationships with Arabidopsis thaliana (L.) Heynh. RNA-seq analysis revealed a varied expression of CsaBBX genes under photoperiod treatment. The analysis of CsaBBXs genes revealed a strong positive correlation between CsaBBX17 and carotenoid biosynthetic pathway genes (phytoene synthase, ζ-carotene desaturase, lycopene ε-cyclase, β-carotene hydroxylase-1), thus suggesting its involvement in β-carotene biosynthesis. Additionally, nine CsaBBX genes (CsaBBX 4, 5, 7, 9, 11, 13, 15, 17 and 22) showed a significant positive correlation with β-carotene content. The selected CsaBBX genes were verified by qRT-PCR and confirmed the validity of RNA-seq data. The results of this study established the genome-wide analysis of the cucumber BBX family and provide a framework for understanding their biological role in carotenoid accumulation and photoperiodic responses. Further investigations of CsaBBX genes are vital since they are promising candidate genes for the functional analysis of carotenoid biosynthesis and can provide genetic tools for the molecular breeding of carotenoids in plants.
Static and Varied Magnetic Fields Effects on Shrinkage and Sprouting Characteristics of Stored Potatoes
(Taylor & Francis Group, 2022) Irungu, F. G.; Mahungu, S. M.; Mathenge, S. G.; Mutungi, C. M.; Ndiritu, F. G.
The effects of static and varying magnetic fields (MF) on shrinkage and sprouting characteristics of stored potatoes were studied. Static MF was produced by the use of direct current (DC), while alternating current (AC) produced varying MF. Intensities of DC MF were set at 0.5, 1.0, 1.5, and 2.0 mT and those of AC MF set at 0.2, 0.4, 0.6 and 0.8 mT. The exposure time of DC MF on potatoes was held at 10, 20, 40, 60, and 120 s, while the exposure time of AC MF was 10, 20, 40, 80, and 160s. Potatoes were then stored in a dark room, with light intensity and temperature of 0 lm/m2 and 14 ± 2 °C, respectively, for 8 weeks after which they were examined. Weight reduction was significantly (P < 0.05) lower in potatoes that were subjected to both DC and AC MF than in the untreated tubers. However, it is the DC MF of 2.0 mT that resulted in low acceptable weight loss of less than 10%. Fewer numbers of sprouts per tuber were observed in potatoes that were exposed to DC MF of 0.5, 1.0, and 2.0 mT for 60 s or AC MF of 0.4, 0.6, and 0.8 mT for 80 s, respectively. Our results provide important insights on the applicability of static and varying magnetic fields on reduction of postharvest losses in potatoes.
Production of Mineral Nutrient-Rich Multipurpose Pumpkin Fruits using Combined Nitrogen, Mulch and Gibberellic Acid
(2022) Mwaura, M. M.; Munyiri, S. W.; Isutsa, D. K.
The present study assessed effectsof nitrogen, mulch and gibberellic acid(GA3) onminerals and metabolites in pumpkin fruits. Nitrogen(0, 50, 100 and 150 kg N/ha), three mulches (none,unpainted,black-painted rice straws) and GA3(0, 40 and 80 mg/L) were used in randomized complete block design, replicated three times in two seasons,and each plant occupied2mx2m space. Post-harvest data values were subjected to analysis of variance using SAS and means were separated using the least significant difference test (α=0.05).Nitrogen positively and significantly affected N, P and Mg. It negatively and significantly affected K, beta-carotene and TSS. Mulch positively and significantly influenced P, Mg and beta-carotene, but not TSS. GA3 positively and significantly affected Mg and beta-carotene, while it negatively and significantly affected N, P, and K. There was consistent significant effect of combined N, mulch and GA3on N, P, K, Mg and beta- carotene (highest 29 ppm was for N3M0GA0).Thus nitrogen, mulch, GA3, alone or combined consistently enhance mineral nutrients and metabolites in pumpkin fruits.
Integrated Nitrogen, Mulch and Gibberellic Acid Significantly Enhance Photosynthates in Multipurpose Pumpkin Leaves
(2022) Khasungu, I.; Mwaura, M. M.
Pumpkin (Cucurbita moschata Duch.) edible leaves, fruits and seeds contribute to household food and nutrition enhancement. However, cultivation using limitedinputslead to poor growth. This study assessed effectsof nitrogen, mulch and gibberellic acid (GA3) on photo synthates in pumpkin leaves. Nitrogen at 0, 50, 100 and 150 kgN/ha, mulchas none, unpainted and black-painted rice straws, and three GA3at 0, 40 and 80mg/L were appliedin randomized complete block design, replicated three times in two seasons,with2mx2mplant-spacing. Data values were subjected to analysis of variance using SAS and means separated using the least significant difference test (α=0.05).Nitrogen significantly (P<0.05) increased moisture and proteins, while it negatively reduced fat, ash and carbohydrates. Mulch significantly reduced moisture, fat, ash and proteins, but increased total carbohydrates. GA3significantly reduced moisture,fat and proteins only. Combined N, mulch and GA3effect consistently increased moisture and proteins (highest 21% for N3M1GA1), but reduced fat, ash and carbohydrates (lowest 46% for N3M1GA0). This study recommends use of N, mulch and GA3 that elicitthe desired response.
Features Selection in Statistical Classification of High Dimensional Image Derived Maize (Zea Mays L.) Phenomic Data.
(Science and Education Publishing, 2022) Gachoki, P.; Muraya, M.; Njoroge, G.
Phenotyping has advanced with the application of high throughput phenotyping techniques such automated imaging. This has led to derivation of large quantities of high dimensional phenotypic data that could not have been achieved using manual phenotyping in a single run. Hence, the need for parallel development of statistical techniques that can appropriately handle such large and/or high dimensional data set. Moreover, there is need to come up with a statistical criteria for selecting the best image derived phenotypic features that can be used as best predictors in modelling plant growth. Information on such criteria is limited. The objective of this study is to apply feature importance, feature selection with Shapley values and LASSO regression techniques to find the subset of features with the highest predictive power for subsequent use in modelling maize plant growth using high- dimensional image derived phenotypic data. The study compared the statistical power of these features extraction methods by fitting an XGBoost model using the best features from each selection method. The image derived phenomic data was obtained from Leibniz Institute of Plant Genetics and Crop Plant Research, -Gatersleben, Germany. Data analysis was performed using R-statistical software. The data was subjected to data imputation using 𝑘 Nearest Neighbours technique. Features extraction was performed using feature importance, Shapley values and LASSO regression. The Shapley values extracted 25 phenotypic features, feature importance extracted 31 features and LASSO regression extracted 12 features. Of the three techniques, the feature importance criterion emerged the best feature selection technique, followed by Shapley values and LASSO regression, respectively. The study demonstrated the potential of using feature importance as a selection technique in reduction of input variables in of high dimensional growth data set.
Rhizoctonia Solani of Potato and its Management: A Review
(EScience Press, 2021) Kiptoo, J.; Iqbal, S.; Umer, M.; Shad, M. A.; Usman, H. M.; Bhatti, A. M.; Abbas, A.
Potatoes are an annual and the most cultivated tuberous crop worldwide. Potatoes play an important role to fulfil the world’s basic food requirements because of enriched nutrients and delicious taste. Rhizoctonia solani is the most virulent and widely distributed soil-borne fungus that causes severe yield losses of potatoes globally. Several management practices have been adopted to overcome the yield losses inflicted by this fungus. Biocontrol agents play a significant role as mycoparasites and activate defense mechanisms through disease resistance genes to suppress pathogens. Compost is also applied as a soil amendment that increases soil fertility through the addition of organic matter in soil and nutrients uptake in organic form. Besides, it is a rich source of carbon and nitrogen which can address soil erosion, nutrients and organic matter depletion issues and restores soil fertility by adding organic matter and reducing the incidence of soil-borne pathogens in the soil. Biochar utilization in the agriculture sector is increasing day by day because of its great potential for disease suppression. Both biochar and compost are used commercially to improve plant growth and suppress potato diseases caused by R. solani. Therefore, in this review, we discussed the symptoms on potatoes, epidemiology and biological characteristics of R. solani and summarized to date control strategies mainly focusing on biological, chemical, biochar and compost approaches.
Use of Cost-Effective Biofertilizers Interventions for Enhanced food Security and Soil Management Amidst Covid-19 Crisis. Review
(2022) Mbaka, F. K.; Oloo-Abucheli, G. O.; Ndukhu, H. O.
Current soil management strategies are mainly dependent on inorganic chemical-based fertilizers, which are expensive and have led to a serious threat to human health and environment. Moreover, COVID-19 pandemic caused economic recession coupling with the effects of climate change. The effect of the pandemic has led to increased prices of inputs particularly chemical fertilizers, resulting in a reduction in crop production. Soil fertility which is a function of agricultural production has declined overtime due to nutrient depletion. The exploitation of cost effective and beneficial microbes as a biofertilizer has become paramount importance in agriculture sector for their potential role in food safety, sustainable crop production and soil fertility improvement. The eco-friendly approaches inspire a wide range of application of plant growth promoting rhizobacteria (PGPRs), endo- and ectomycorrhizal fungi, cyanobacteria and many other useful microscopic organisms that have led to improved nutrient uptake, plant growth and plant tolerance to abiotic and biotic stress. The present review highlights; biofertilizers relevance and plant tolerance to environmental stress, biofertilizer exploitation and nutrient profile of crops, potential significance of beneficial microbes in sustainable agriculture. The knowledge gained from the literature appraised herein will help in understand the benefits of biofertilizers towards sustainable agriculture in reducing problems associated with the use of chemicals fertilizers.

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