Crop physiological analysis of seed quality variation in common bean (Phaseolus vulgaris L.)

Keywords : Physiological maturity, harvest maturity, earliness, common bean, Phaseolus vulgaris L., morphological markers, variation, moisture content, dry weight, viability, vigour, electrical conductivity, tetrazolium, seed lot, seed filling, maturation drying, temperature, rainfall.Common bean yield is low in Kenya and use of poor quality seed by small-scale farmers has been identified as a major yield constraint. This research project aimed at increasing insight into development of common bean seed quality and its variation during crop production and into how conditions during production affect these. In experiments involving bean cultivars Rosecoco and Mwezi Moja, physiological maturity (PM), i.e. the moment of maximum seed dry weight, was achieved at 58% seed moisture content. Harvest maturity (HM) was defined to occur at 20% moisture content. At PM, the percentage viable seeds as measured by tetrazolium test was still increasing. It became maximum closer to HM implying that seed development does not stop at PM. Seed vigour as measured by electrical conductivity (EC) was maximum at PM and remained constant until HM. Seeds in pods of different earliness and seeds of the whole crop all achieved maximum viability at the same moment beyond PM. The maximum viability achieved also was the same in all seed classes. Maximum seed vigour was achieved at PM in individual seed classes and was achieved earlier in seeds from earlier pods than from later pods. The vigour of seeds from the individual earliness classes at their optimum moment of harvesting was higher than the vigour of seeds from all pods combined. Individual seed variation in dry weight, moisture content and EC over time was lower in seeds from earlier pods than from all pods combined. Seed lots produced under different weather conditions and at two sites differed in quality within and between seed lots. Within seed lots, variation in individual seed quality as quantified by mean - median, range 0 - 100%, variance and standard deviation (SD) in individual seed EC was high when there were seeds with extremely high values deviating from the bulk of the seeds. Seed lots with deviating values did not necessarily have large variation in the bulk of the seeds, as quantified by the ranges 0 - 75% and 25 - 75%. Low variation in individual seed EC as quantified by mean - median, SD and the range 0 - 75%, was associated with good quality as measured by low bulk EC and/or high percentage viable seeds. Associations were clearer at PM than at HM. Relationships between individual seed variation and bulk quality were different at the two sites implying both the degree of variation and the level of individual seed quality can determine bulk quality. No relationship was found between CV% in individual seed EC and bulk quality. High temperature and less rainfall both could reduce seed quality. Over the ranges studied, high temperature was more detrimental than limited rainfall. Weather conditions seemed to reduce seed quality mainly through reducing the maximum quality attainable during crop development. Quality deterioration "in planta" was less important. Variations in weather conditions during production did not lead to lower quality seed lots through increasing variation within the crop, as measured by duration of flowering or pod set or plant-to-plant variation in number of flowers. Production conditions conducive to low seed yield or low individual seed weights were also conducive to low percentage of viable seeds. However, high seed yield does not guarantee high percentage viable seeds. Although the moment all seeds within a crop or crop fraction achieve the final red purple colour pattern was identified as a good indicator of PM, practically the use of pod and seed colour changes was an unreliable method for determining when to harvest. Results imply that processes determining the changes in colour and those determining changes in seed moisture content are differentially affected by external conditions. Based on the results of this research, picking pods from individual pod classes based on 20% seed moisture content could improve the uniformity within the harvested seeds and subsequently the final quality of the seeds harvested. This was shown for seeds from early pods.</p

How weather during development of common bean (Phaseolus vulgaris L.) affects the crop’s maximum attainable seed quality

Weather conditions affect the seed quality of major crops including common bean. This study aimed to evaluate whether seed quality is affected through weather effects on the quality achievable at the end of seed filling (PM) or through changes in quality during maturation drying in the period between PM and harvest maturity (HM). The research also aimed to establish relationships between seed yield and seed quality. Twenty-four common bean (Phaseolus vulgaris L.) crops from two cultivars were sown on different dates in Eldoret and Kitui, Kenya. Seed quality was quantified as the percentage of viable seeds determined with a tetrazolium test, and as vigour measured by electrical conductivity (EC). Over the range  of weather conditions during our study, high temperatures were more detrimental to seed quality than little rainfall. The two cultivars differed in susceptibility to high temperatures. High temperatures and little rainfall seemed to reduce seed quality mainly through reducing maximum quality attainable during the course of crop development. The quality in general did not change significantly between PM and HM, but in some cases the proportion of viable seeds increased between PM and HM, especially when ambient temperatures were relatively low. For seed samples free from mechanical damage, EC appeared to be an unsuitable criterion to detect quality differences at HM, because in almost all seed lots quality was indiscriminately classified as ‘good’, whereas viability varied between 69 and 100%. Production conditions leading to low seed yields or seeds of low weight resulted in a low percentage of viable seeds but conditions resulting in fairly high yields or heavy seeds did not guarantee a high percentage of viable seeds

Grafted Mangoes Enhances Smallholder Farmers Livelihoods in Matinyani Division, Kitui County

Mango (Mangifera indica L.) fruit is produced and consumed globally, regionally, and locally. The fruit is a potential source of essential nutrients including potassium, phosphorous, magnesium and is an excellent source of vitamin A and C. Mangoes can also be sold to earn income. Kitui County is among the leading Counties in mango production with smallholder farmers concentrating on local varieties which are fibrous and of little market value. This study was conducted at Matinyani Division of Kitui County to investigate mango varieties grown and income generated by smallholder mango farmers in Matinyani Division. A sample of 120 mango farmers was studied and simple random sampling technique was used to select respondents. Primary data was obtained by use of questionnaires while secondary data was obtained by review of relevant literature. Data collected was analyzed using Statistical Package for Social Scientists (SPSS) version 20.0 of year 2009.The results revealed that in Matinyani Division both local and grafted mangoes were grown. The local mangoes grown included: Ngowe, Dodo and Boribo with majority of the farmers growing Ngowe mango. Varieties of grafted mangoes grown included: Apple, Kent, and Tommy with majority of the farmers growing Apple mangoes. On income generation, the study revealed that, farmers earned KES 1,000 to KES 15,000 per annum from sale of local mangoes with majority earning KES 1,000 to KES 5,000. On the other hand, farmers earned KES 1,000 to KES 20,000 per annum from sale of grafted mangoes with majority earning KES 6,000 to KES 9,000.The study concludes that, grafted mango farming is essential in enhancing livelihoods of smallholder mango farmers and recommends farmers to be sensitized to increase growth of grafted mango varieties.

Baseline Survey On Factors Affecting Sorghum Production And Use In Eastern Kenya

Sorghum ( Sorghum bicolor (L.) Moench) is an under-utilized crop and one of the most important cereal crops in semi-arid tropics. In Kenya, sorghum is grown in the often drought-prone marginal agricultural areas of Eastern, Nyanza and Coast Provinces. Due to its C4 photosynthetic nature, extensive root system, waxy leaves and ability to stop growth in periods of drought the crop is well adapted to low lands that have higher temperatures, prone to drought and flooding. Sorghum, which is closely related to maize in utilization, therefore, could be an alternative staple food crop in arid areas prone to drought. As an indigenous Kenyan crop, sorghum could provide food security and become a suitable alternative in eastern Kenya. Despite its suitability in the semiarid areas, the area under sorghum production is still low and farmers attain low yields in eastern Kenya. Most farmers still opt to grow maize which is frequented by crop failures. The purpose of this study was to gather information on socio-economic factors affecting sorghum production and the sorghum farming system used by the farmers in the region, landraces grown by farmers, source of seed, traits preference, maturity period, cultural practices, pre and post harvest handling, utilization and constraints in sorghum production in lower eastern Kenya region. The study was conducted in Mbeere, Kitui, Makueni and Mutomo districts of eastern Kenya. Parameters studied were expressed as percentages and bar graphs constructed. Analysis of Variance was performed, and Least Significant Differences were used for separation of means at 0.05 level of confidence. Sorghum is grown widely as source of food and seed for planting is obtained from informal systems. Farmers hardly use inputs due to low income. Eastern region is a high agricultural area and productivity could be improved by use of locally available germplasm. The study found out that farmers in eastern Kenya maintain a diversity of sorghum landraces unique in their adaptation, food quality, grain yield, quality of harvested products and biotic stress resistance. Sorghum grain has high levels of iron and zinc, hence may be used to reduce micronutrient malnutrition. However, the production is low due to constraints such as lack of income to purchase fertilizer and chemicals, inadequate quality seed, susceptibility to pests and diseases resulting to low yields

Evaluation of Seed Quality Attributes of Sorghum Germplasm Accessions from Eastern, Coastal and Nyanza Regions, Kenya

Sorghum (Sorghum bicolor L.) is an important cereal crop in Kenya. Despite the crops importance, the yields attained by farmers in Eastern, Coastal and Nyanza regions of Kenya remain low. Access to good quality seeds of sorghum is one of the constraints facing the subsistence farmers. Good quality seed is important for increasing yield to attain food security. The aim of this study was to evaluate quality attributes of the seed used by farmers. A total of 108 germplasm accessions were obtained from 76 farmers. The seeds were tested for time and percentage of germination, seed vigour index, shoot and root dry weight. Data collected was subjected to analysis of variance. Means were separated using Fisher’s Least Significance Difference test at p ≤ 0.05. Seed samples of 26 accessions attained germination percentage below stipulated standards by Seeds and Plant Varieties Act CAP 326. Majority of seeds showed longer mean germination time with only nine accessions germinating in less than ten days. Seed vigour index was relatively high in most of the accessions, while biomass accumulation varied from high to very low among accessions. Though most of the seeds attained a high germination percentage, about 92% of seeds showed longer mean germination time. The environmental conditions in the fields, pre and post harvest handling practices impact on the seed quality hence the wide variability in germination percentage, germination time, seed vigour index and dry matter accumulation. Therefore the need to improve quality of seeds used by subsistence farmers by providing extension services on best pre and post harvest handling practices. Increasing production of sorghum in these regions will contribute significantly towards realizing food security. Further analysis could be carried out on genetic and sanitary quality aspects of the seeds planted by farmers in Eastern, Nyanza and Coastal regions

Pollen Longevity in Ecologically Different Zones of Western Kenya

Maize ( Zea mays L.) is the most important staple crop in Kenya with the small holder farming systems accounting for about 75-80% of the total production. Most of the small-scale farmers plant locally adapted landraces and there are concerns about the possible contamination of these through geneflow from novel varieties, including the transgenics. The survival of pollen after dehiscence is an important factor affecting the geneflow. Studies were conducted to investigate the duration of pollen viability in two locations in western Kenya - Eldoret and Kakamega, representing the highland tropical and moist mid-altitude/transitional zones, respectively. Pollen was collected at dehiscence and exposed as a thin layer in the open air for 0 (control), 15, 30, 60, 120 and 240 minutes. Pollen viability was assessed by measuring the seed set after pollination, scoring percentage pollen color change and percentage pollen germination. Pollen maintained viability for 120 minutes after dehiscence in Eldoret (T=23-24°C; RH=45-55%; ∅=-109 to -82 MPa) and for 240 minutes in Kakamega (T=25-27°C; RH=68-83%; ∅=-53 to -26 MPa). The differences in pollen longevity were attributed to the differences in atmospheric water potential between the two locations. The results suggest that the likelihood of genetic contamination of the landraces through geneflow from novel varieties is higher in the moist mid-altitude zones than in the highland tropical zones of Kenya.Le maïs ( Zea mays L.) est une culture de grande importance au Kenya où, selon les systèmes agricoles du pays, la production par des petits exploitants compte environ 75 à 80% de la production globale. Principalement, la plupart des agriculteurs plantent des variétés locales et il y a lieu de s&apos;inquiéter de la possibilité de contamination lors de la circulation des gènes à travers les nouvelles variétés, y compris la trans-génétique parce que la survie du pollen, en tant que facteur important, stimule la circulation des gènes après son ouverture. Ces études étaient menés pour examiner la durée de la viabilité du pollen dans deux endroits, à l&apos;Ouest du Kenya: Eldoret et Kakamega, représentant respectivement la région tropicale montagneuse et la région humide d&apos;altitude moyenne/ zones transitionnelles. En tant pondeur de mince taille, le pollen était récolté en plein air, à l&apos;ouverture et exposé pour 0 (contrôle), 15, 30, 120, et 240 minutes. La viabilité du pollen était évaluée en mesurant la position de la graine après le transport du pollen, le pourcentage du changement de la couleur du pollen et le pourcentage de la germination du pollen. A Eldoret, le pollen avait maintenu une viabilité pendant 120 minutes après l&apos;ouverture (T=23-24 °C); RH=45-55%; ∅=-109-82 MPa) et 240 minutes à Kakamega (T=25-27 °C; RH=68-83%; ∅=-5326 MPa). Les différences de la longévité du pollen étaient imputables aux différences potentielles de l&apos;eau atmosphérique entre les deux endroits. Les résultats ont suggéré que la probabilité de la contamination génétique des variétés locales pour la circulation des nouvelles variétés est plus élevée dans les zones humides d&apos;altitude moyenne que dans les régions tropicales montagneuses du Kenya