Erick K. Cheruiyot

Polyphenols as Potential Indicators for Drought Tolerance in Tea (Camellia sinensis L.)

Plant polyphenols have gained prominence in quality of plant products and in human health. An experiment was conducted to determine the association of tea polyphenols with water stress and their suitability as indicators for drought tolerance. The experiment was conducted in a ‘rain-out’ shelter, and consisted of six tea clones (BBK 35, TRFK 6/8, TRFK 76/1, TRFK 395/2, TRFK 31/30, and TRFK 311/287) and four levels of soil water contents (38, 30, 22, and 14% v/v), which were maintained for a period of 12 weeks. The treatments were arranged in a completely randomized design and replicated three times. Plant growth was monitored over 6 weeks, and a water stress index was calculated to determine water-stress tolerant clones. Total polyphenols in tea shoots was analyzed and a regression analysis done. The results indicate that declining soil water content (SWC) reduced both growth and content of polyphenols in tea. Tolerant clones maintained a high polyphenol content at low SWC, and also showed less fluctuation in phenolics when subjected to changes in SWC. There was significant (P<0.001) correlation of total polyphenol content with shoot growth and WSI of tea, and a linear relationship (r2=0.97) between SWC for tea and both, water stress index and shoot polyphenol content. We report that there is a potential to use polyphenols as indicators for selection of drought-tolerant tea cultivars.

High fertilizer rates increase Susceptibility of tea to water Stress

A study to determine the association of fertilizer with soil water deficit in tea [Camellia sinensis (L.) O. Kuntze] was conducted in a rain-out shelter using potted plants, in which five rates of fertilizer (0, 75, 150, 225 and 300 kg Nitrogen ha−1) and six levels of soil water content (38, 34, 30, 26, 22 and 18% v/v) were applied in a complete randomized design and replicated three times. The soil water treatment was maintained for a period of 12 weeks during which shoot growth, plant water relations, and dry matter partitioning in tea were determined. A parallel field experiment with the above fertilizer rates was conducted at three sites in which shoot density and shoot weight were determined during the dry season. Fertilizer improved leaf-to-root and leaf-to-total mass ratios (P < 0.001), reduced shoot growth, shoot water potential and specific leaf area (P < 0.001). The fertilizer exacerbated drought effect on tea through disproportionate assimilate partitioning which consequently weakened the ability of tea to tolerate water stress. Results suggest an indirect contribution of fertilizer supply to drought susceptibility in tea.

Physiological and biochemical response of tea [ Camellia sinensis (L.) O. Kuntze] to water-deficit stress

Summary A study to determine the physiological and biochemical responses of eight tea [Camellia sinensis (L.) O. Kuntze] cultivars to water-deficit stress was conducted in a ‘rain-out shelter’ using potted plants. Three levels of soil moisture content [34, 26, or 18% (v/v) water] were applied to three plants of each cultivar in a complete randomised design, and the whole experiment was replicated three-times. The treatments were applied for 12 weeks, during which time plant water status, shoot extension rates, changes in gas exchange parameters, and leaf proline and glycinebetaine concentrations were determined. The imposition of severe water-deficit conditions [18% (v/v) soil water content] caused a significant (P 0.05) decline in the relative water content of leaves, shoot water potentials, and shoot extension rates from mean values of 84.8% to 50.6%, -0.80 to -1.15MPa, and 1.87 to 0.29 mm d-1, respectively, compared to plants grown in a well-watered soil [34% (v/v) soil water content]. The three gas exchange parameters measured (stomatal conductance, evapotranspiration rate, and rate of net photosynthesis) also declined significantly (P 0.05) with decreasing soil moisture content. In contrast, water-deficit stress increased the accumulation of leaf proline and glycinebetaine from mean values of 0.104 to 0.244 ?mol g-1 FW, and from 1.567 to 2.025 ?mol g-1 DW, respectively. The eight tea cultivars differed significantly (P 0.05) in their responses to water-deficit stress. Proline accumulation was significantly (P 0.05) higher in the drought-tolerant cultivars, ‘TRFK 306’, ‘TRFCA SFS150’, and ‘EPK TN14/3’, suggesting that proline concentration could be used as a marker for drought-tolerance in tea.

Shoot Epicatechin and Epigallocatechin Contents Respond to Water Stress in Tea [Camellia sinensis (L.) O. Kuntze]

An experiment was conducted to determine the association of tea catechins to water stress in tea, with the objective of determining their suitability as indicators for predicting drought tolerance in tea (Camellia sinensis). The study consisted of six tea clones (BBK 35, TRFK 6/8, TRFK 76/1, TRFK 395/2, TRFK 31/30, and TRFK 311/287) and four levels of soil water content (38, 30, 22, and 14% v/v), which were arranged in a complete randomized design and replicated 3 times. The treatments were maintained for a period of 12 weeks. Tea shoots were sampled for catechin analysis during the 6th week of water treatment, in which fresh shoots with two leaves and a bud were plucked and steamed for 2 min, and dried at 70 °C to constant weight. Subsequently, the samples were ground and analyzed for catechins using an HPLC system. The total catechins showed significant correlation with shoot growth (r=0.65, P=0.006), soil water content (r=0.54, P=0.0066), and water stress index (r=0.67, P=0.0004). The epicatechin (EC) correlated with shoot growth (r=0.58, P=0.0032), soil water content (r=0.62, P=0.0014), and water stress index (r=0.63, P=0.0010). Similarly, epigallocatechin (EGC) correlated with shoot growth (r=0.65, P=0.0006), soil water content (r=0.50, P=0.0133), and water stress index (r=0.60, P=0.0021). However, epigallocatechin gallate (EGCg) and epicatechin gallate (ECG) showed no significant response to changes in soil water content. The shoot contents of EC and EGC in the six clones showed varied responses, with a distinct pattern in the water-stress tolerant clones (TRFK 6/8 and TRFK 31/30). The results suggest a potential use for EC and EGC as indicators in predicting drought tolerance in tea.

Rapid decay of dolichos [Lablab purpureus (L.) Sweet] residue leads to loss of nitrogen benefit to succeeding maize (Zea mays L.)

The traditional natural fallows are no longer practicable in sub-Saharan Africa and technologies to replace them are being popularised through management of short fallow systems. Dolichos [Lablab purpureus (L.) Sweet] is among the legumes used to improve such fallows and its residues are incorporated to improve yield of succeeding cereal. Two field studies were conducted to determine dolichos residue mineralisation schedule and response of maize to timing of the residue incorporation, to establish if the current residue incorporation practice maximises nutrient benefit to succeeding cereal. Dolichos residue was applied at 2 t/ha in litterbags, buried in the field at 15-cm depth and retrieved after 1, 2, 4, 8 and 16 weeks, and the remaining debris analysed for loss of weight, N, P and K. A parallel split-plot experiment was set up to determine response of maize to time of residue incorporation, with or without fertiliser nitrogen supplementation. The main plot treatments were nitrogen fertiliser applied at 0, 30 and 60 kg/ha at sixth fully opened leaf in maize. The subplot treatments were residue management regimes, which included four residue incorporation times of 2, 4, 6, and 8 weeks before sowing maize, residue removal off the field, residue mulched on surface and traditional weedy fallow. Results show rapid loss of N, with 50% being released within the first 2–4 weeks after burying. Residue incorporated at 2 and 4 weeks before sowing improved maize yield, while residue removal off-field reduced yield comparably with the traditional weedy fallow. However, there were no statistical differences among the timing of the dolichos residue incorporation. These results reflect poor synchrony of mineralised N and uptake by succeeding maize as currently practiced and suggest residue incorporation closer to sowing maize to benefit the cereal.

Effect of Harvesting Stage on Sweet Sorghum (Sorghum bicolor L.) Genotypes in Western Kenya

Harvesting stage of sweet sorghum (Sorghum bicolor L. Moench) cane is an important aspect in the content of sugar for production of industrial alcohol. Four sweet sorghum genotypes were evaluated for harvesting stage in a randomized complete block design. In order to determine sorghum harvest growth stage for bioethanol production, sorghum canes were harvested at intervals of seven days after anthesis. The genotypes were evaluated at different stages of development for maximum production of bioethanol from flowering to physiological maturity. The canes were crushed and juice fermented to produce ethanol. Measurements of chlorophyll were taken at various stages as well as panicles from the harvested canes. Dried kernels at 14% moisture content were also weighed at various stages. Chlorophyll, grain weight, absolute ethanol volume, juice volume, cane yield, and brix showed significant (p = 0.05) differences for genotypes as well as the stages of harvesting. Results from this study showed that harvesting sweet sorghum at stages IV and V (104 to 117 days after planting) would be appropriate for production of kernels and ethanol. EUSS10 has the highest ethanol potential (1062.78 l ha−1) due to excellent juice volume (22976.9 l ha−1) and EUSS11 (985.26 l ha−1) due to its high brix (16.21).

Adaptability and Stability Study of Selected Sweet Sorghum Genotypes for Ethanol Production under Different Environments Using AMMI Analysis and GGE Biplots

The genotype and environment interaction influences the selection criteria of sorghum (Sorghum bicolor) genotypes. Eight sweet sorghum genotypes were evaluated at five different locations in two growing seasons of 2014. The aim was to determine the interaction between genotype and environment on cane, juice, and ethanol yield and to identify best genotypes for bioethanol production in Kenya. The experiments were conducted in a randomized complete block design replicated three times. Sorghum canes were harvested at hard dough stage of grain development and passed through rollers to obtain juice that was then fermented to obtain ethanol. Cane, juice, and ethanol yield was analyzed using the additive main effect and multiplication interaction model (AMMI) and genotype plus genotype by environment (GGE) biplot. The combined analysis of variance of cane and juice yield of sorghum genotypes showed that sweet sorghum genotypes were significantly (P < 0.05) affected by environments (E), genotypes (G) and genotype by environment interaction (GEI). GGE biplot showed high yielding genotypes EUSS10, ACFC003/12, SS14, and EUSS11 for cane yield; EUSS10, EUSS11, and SS14 for juice yield; and EUSS10, SS04, SS14, and ACFC003/12 for ethanol yield. Genotype SS14 showed high general adaptability for cane, juice, and ethanol yield.

Genetic Diversity of Farmers’Preferred Sorghum Accessions and Improved Lines from ICRISAT Reveal a Disconnect Between Innovation and Technology Transfer

The genetic diversity of 65 accessions of sorghum [Sorghum bicolor (L.) Moench] collected from various farmers and germplasm lines from ICRISAT-Kenya were analyzed. Simple sequence repeats (SSR) markers were used in order to determine the extent and distribution of its genetic diversity. Twenty-nine (29) SSRs markers were polymorphic and a total of 192 alleles were detected which showed diversity. The number of alleles per primer ranged from 2 to 17, with an average of 6.62. The range of polymorphism information content (PIC) ranged from 0.03 to 0.86, with total average of 0.82. According to the results analyzed, estimates of the mean allelic pattern across the two populations was generated; expected heterozygosity (He; 0.45, 0.54), average observed alleles (Na; 3.40, 6.20), number of private allele (0.23, 3.03), and Shannon information index (I; 0.85, 1.13) for farmer and ICRISAT-Kenya germplasm, respectively. The expected heterozygosity (He) varied from 0 to 0.26 with an average of 0.05. The Neighbor-joining phenogram based on Nei’s genetic distance grouped the 65 accessions into three main groups. The analysis of molecular variance (AMOVA) revealed that 99% of the total genetic variation was within accessions in a population whereas the genetic variation among populations in accessions accounted for 1% of the total genetic variation. Genetic diversity in ICRISAT sorghum material compared to the farmer’s collection suggested little infiltration of improved germplasm to the farmers.

Biochemical quality indices of sorghum genotypes from east Africa for malting and brewing

There is a gradual shift to substitute barley with sorghum in brewing industry to reduce the cost of doing business and make beer products more competitive. This study evaluates the sorghum genotypes for desirable malting and brewing characteristics. Biochemical characteristics assayed for 131 sorghum [ Sorghum bicolor (L) Moench] accessions included total starch, amylopectin, amylose, proteins, tannins contents, germination energy and germination capacity. Results indicate that starch contents ranged from 22.8 - 81.2%, amylose from 11.5 - 30.2% while the amylopectin content ranged from 6.6 - 59.8%. Generally, amylose contents of sorghum genotypes were lower than their amylopectin contents, with a ratio of 1:2. The mean protein content for the sorghum accessions was 9.4% with a range of 3 - 18%, while that of barley was from 7.7 - 9.8%. Germination energy and germination capacity for sorghum ranged from 82.9 - 99.8% and 74.0 to 99.5%, respectively. Barley varieties showed germination energy and capacity greater than 98%. Sorghum tannin contents ranged from 2.55 mg/100 ml to as high as 100 mg/100 ml while barley varieties had tannin contents of 8.9 to 10.3 mg/100 ml. Two genotypes, SDSA 1x ICSR 43 and SP 993520-1 were the most favorable for brewing. Keywords: Sorghum, starch, protein, tannin, germination energy, malting and brewing African Journal of Biotechnology , Vol. 13(2), pp. 313-321, 8 January, 2014