Morpho-Argro-Physio-Karyotypic Characterization of Wild Cotton (Gossypium spp.) Germplasm from Selected Counties in Kenya
Njagi, Anthony Kiranga
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Cotton (Gossypium species) occupies a prime position as a fibre crop of the world. Today cotton is used as a natural fibre, while seeds are used for making cooking oil, soup and seed cake for animal feed industry. Wild cotton germplasm performance in Kenya has not been studied. While current cultivated variety (HART 89M) has a narrow genetic base, the wild cotton germplasm provides a gene pool that is required for its improvement. Understanding the correlation of traits influencing seed cotton yield is pre-requisite for effective improvement of HART 89M. The study helps in the identification of yield components, significant correlation of boll weight with plant height, number of fruiting branches and number of nodes per plant. The study was aimed at assessing the differences and relationship between domesticated cotton HART 89M with wild cotton and karyotypic analysis. Data on agronomic traits collected from a sample of forty-five plants, selected at random per studied genotypes were analysed using t-test, ANOVA and Pearson correlation coefficiency. Data on germination were collected on weekly basis from emergent of the first seedling. The data on the rate of flowering was also collected on weekly basis from emergent of the first flower. At maturity, data was collected on height, number of fruiting branches, length of the longest fruiting branch, internodal length, number of nodes on longest fruiting branch and yield per plant. Data on boll traits involved random collections of thirty three bolls per genotype. Each boll was weighed, ginned, seed and lint weighed separately. On karyotypic analysis, young shoot apex were treated and observed under leica microscope. The study revealed a significant difference in agronomic performance in all traits among the studied genotypes, height (F = 98.842, df = 4, p ≤ 0.05), number of fruiting branches (F = 25.973, df = 4, p ≤ 0.05), length of fruiting branches (F = 58.726, df = 4, p ≤ 0.05), number of nodes on the fruiting branches (F = 27.726, df = 4, p ≤ 0.05) and yield (F = 178.85, df = 4, p ≤ 0.05) per bush. On boll result displayed a significant difference among the studied genotypes, boll weight (F = 25.938, df = 4, p ≤ 0.05), seeds weight (F = 21.181, df = 4, p ≤ 0.05), lint weight (F = 26.593, df = 4, p ≤ 0.05) and lint- seed weight ratio (F=2.264, df = 4, p ≤ 0.05). It also revealed a significant difference between the standard genotype (HART 89M) and studied wild genotypes. G. barbadense was significant differently higher in height (102.42 cm), (t = 20.24, P ≤0.05), number of fruiting branches, 30.47 (t = 9.18, P ≤0.05), length of the longest fruiting branch 34.34 (t = 8.14, P ≤0.05), number of nodes on the longest fruiting branch, 2.49 (t = 7.46, P ≤0.05) and yield 133.73 (t=17.73, P ≤0.05) compared with others genotypes. On boll traits the highest significant difference with HART 89M was found with G. kirkii on boll weight, 0.73g (t = 7.72 P ≤0.05), seed weight 0.52g, (t = 8.67 P ≤ 0.05), and lint weight 0.20g (t =3.21, P ≤ 0.05). The results revealed a significant and positive correlation between height, number of fruiting branches, number of nodes on fruiting branch and number of seeds per boll with seed cotton yield. Within the studied genotype, there was a significant positive correlation between yield and other boll traits. The ploidy study revealed that the three cotton species had tetraploid chromosomes of complement 2n = 52 and two species had diploid chromosome of complement 2n = 26. All the five cotton species revealed the presence of metacentric, acrocentric and telocentrics chromosomes. G. kirkii nuclei revealed both parallel and ant-parallel chromosome location. During future breeding program, the yield related traits might be kept in mind during selecting, as they were the major attributes of the seed cotton yield. Cotton development agency, need to develop the farming of G. harbaceum and G. kirkii for seed cotton production for Cooking oil extraction and animal feed industries to avoid competition between lint and oil production.