Effects of motes on lint quality of interspecific cotton hybrids.
The technological quality of lint is negatively affected by an excessive number of motes in three major respects: (i) increased numbers of tangled and seed coat neps, (ii) increased short-fiber content, and (iii) decreased fiber maturity (Pearson, 1949; Bargeron and Garner, 1988).
Neither roller ginning nor saw ginning eliminates most motes from the lint. Motes that are small, relative to mature seeds, may pass through the gin device with the fibers and be transferred to the cleaning machines. During the cleaning processes, the relatively thin-walled, brittle motes fracture and may form seed coat neps. Generally, only about 50% of the impurities are removed during the cleaning processes (Bargeron and Garner, 1988).
The neps and seed-coat fragments eventually end up in the yarn and cloth where they are responsible for approximately 27% of the yarn's imperfections (Herbert and Thibodeax, 1993). Raw cloth may show bright white or black spots, which may be eliminated by the chemical processes of mercerization, bleaching, and dyeing. However, cloth that has passed through these processes may still show lighter spots containing high numbers of immature fibers that lack the secondary wall thickening responsible for dye absorption. These defects are assumed to be derived partially from mote fragments (Hughs et al., 1988).
Lint of interspecific hybrids of cotton (G. hirsutum X G. barbadense) tend to have a high proportion of impurities and neps, which reduce the quality of the yarn and fabric (Hughs and Lalor, 1986). Much of these fiber impurities are related to the presence of a large number of motes in the seed cotton produced by these hybrids. This study was aimed at determining the effects of motes of various sizes and certain fiber properties on the number of tangled and seed coat neps in the lint of cotton ISHs.
MATERIALS AND METHODS
Samples of seed cotton of various genotypes were grown in the field at Mivchor farm, located in the Lachish district in the southern internal plane of Israel. The soil at the experimental location was grumosol, typical for the region. Management practices, irrigation scheduling, fertilization, and weed and pest control were as recommended for commercial cotton cultivation.
A factorial (two irrigation treatments x 13 genotypes) experimental design in a split-plot arrangement (irrigation in main plots) was employed. Each plot consisted of four 8-m long rows, the two central rows of which were used for sampling. Irrigation treatments consisted of (i) dryland treatment (not irrigated, apart from 20 mm for seed germination) and (ii) irrigated treatment (watered with 240 mm). Irrigation was applied twice a week during 70-d period starting at flowering onset, via a drip system consisting of 4 L/h emitters spaced at 1.92 m by 1 m (between lines and along the line, respectively). The genotypes evaluated included 13 experimental or semi-commercial ISHs (G.h. x G.b.) produced by Hazera (1939) Ltd. (Mivchor Farm, Israel): 149-86, 149-31, 175-86, 175-31, 195-86, 195-1, 175-1, 116-132, 116-2, 83-132, 83-2, 195-14, and 151-14, as well as a control commercial cultivar, Pima S-5 (G.b.). Treatments were replicated four times with the exception of the ISHs 195-14 and 151-14, which were only replicated twice. All the examined ISHs were fuzzless ("naked" seed), enabling uniform roller-ginning, comparable with the Pima control.
Seed-cotton samples from each experimental plot were manually harvested. Each seed cotton sample was gently blended manually and a 40-g subsample (found to give a fairly low variation within a specific sample) was taken for mote sorting. Motes were manually separated from the seed cotton and sorted by size into three groups and counted. The three mote size groups were as follow: (i) small motes--1 to 2 mm in width and up to 3 mm in length, either fiberless or attached to very short ([is less than] 1 mm) fibers; (ii) medium motes--1 to 3 mm in width and 3 to 5 min in length, usually attached to short ([is less than] 10 mm) fibers; and (iii) large motes--3 to 5 mm in width and 5 to 8 mm in length, attached to fibers of almost maximal length (25-30 mm) with a silky appearance. These were distinguished from normal seeds by their lighter color and somewhat shrunken and easily fractured seed coats.
After mote removal, the rest of the 40-g seed cotton subsample was ginned by a miniature laboratory saw gin, the lint was weighed, and the number of mature seeds were counted. Two types of mote indices were used to characterize motes of each category: (i) mote percentage of total seed potential (number of seeds + motes of all sizes), and (ii) number of motes per gram of lint obtained from the entire 40-g subsample.
The remaining seed cotton from all. replicates of each specific genotype under each irrigation regime was pooled to obtain an adequate sample size for ginning. A pilot-plant roller gin that is comparable to a commercial unit was used to obtain lint for further quality tests. This pilot plant consists of commercial seed cotton cleaner and gin (Lummus, Columbus, GA) adapted for experimental purposes by reduced machinery width.
Fiber span length, length uniformity, fineness (Micronaire value), strength, elongation, and short-fiber content were determined with an HVI tester (Zellwerger Uster Ag, Uster, Switzerland). Maturity index and percentage of mature fibers were measured with a 11C Finenness/ Maturity Tester (Shirley Ltd., Manchester, UK) (ASTM, 1979). A lint sliver was prepared by a miniature spinning plant (Shirley Ltd., UK) and the neps in each sliver were counted by a Nepometer (Textest Ltd., Zurich). Neps were sorted into tangled neps, containing only fibers, and seed coat neps, containing also an extraneous plant material (Herbert et al., 1988).
SAS statistical software (Cary, NQ was used for all statistical analyses (Joyner, 1985). The CORR procedure was used for correlation analyses and the Stepwise procedure with the MAXR option was used for multivariate correlation analyses.
Correlation between Mote Indices and Neps
High and significant correlation coefficients (r [is greater than] 0.81; P [is less than] 0.001) were found between the two types of indices (mote percentage of total seed potential and motes per gram of lint) for each of the mote sizes. However, correlating motes on a weight basis with nep counts gave higher coefficients than correlations between neps and mote percent of total seed potential (Table 1) because neps were calculated on the basis of weight. The index which characterizes motes as a percentage of seed potential is most frequently used in the literature (Pearson, 1949; Bhardwaj and Weaver, 1984) and is probably more relevant when aspects of pollination and seed set are being examined. Expressing motes on a weight basis is more relevant when aspects of lint quality are involved. Among the three mote sizes, medium motes were correlated with number of neps (tangled, seed coat, and total) more often than the small and large motes.
Table 1. Correlation coefficients between nep numbers and two types of mote indices in ISHs of cotton under dryland and irrigated treatments. Correlations were calculated between means of genotypes (n = 14 and n = 28 for each treatment and for both treatments, respectively).
Tangled neps, per 1 g lint Dryland + Dryland Irrigated irrigated Small motes, 0.48 0.51 0.37 % of seed potential n.s. n.s. n.s. Medium motes, 0.44 0.18 0.17 % of seed potential n.s. n.s. n.s. Large motes, -0.24 0.29 0.02 % of seed potential n.s. n.s. n.s. Small motes, 0.58 0.57 0.39 no. per 1 g lint (*) (*) (*) Medium motes, 0.60 0.28 0.39 no. per 1 g lint (*) n.s. (*) Large motes, 0.18 0.49 0.21 no. per 1 g lint n.s. n.s. n.s. Seed coat neps, per 1 g lint Dryland + Dryland Irrigated irrigated Small motes, 0.47 0.06 0.02 % of seed potential n.s. n.s. n.s. Medium motes, 0.41 0.62 0.55 % of seed potential n.s. (*) (**) Large motes, -0.01 0.19 -0.02 % of seed potential n.s. n.s. n.s. Small motes, 0.51 0.13 0.06 no. per 1 g lint n.s. n.s. n.s. Medium motes, 0.69 0.61 0.69 no. per 1 g lint (*) (***) (**) Large motes, 0.37 0.04 0.29 no. per 1 g lint n.s. n.s. n.s. Total neps, per 1 glint Dryland + Dryland Irrigated irrigated Small motes, 0.58 0.31 0.22 % of seed potential (*) n.s. n.s. Medium motes, 0.52 0.62 0.53 % of seed potential n.s. (*) (**) Large motes, -0.17 0.31 0.00 % of seed potential n.s. n.s. n.s. Small motes, 0.67 0.40 0.27 no. per 1 g lint (**) n.s. n.s. Medium motes, 0.69 0.73 0.70 no. per 1 g lint (**) (**) (***) Large motes, 0.29 0.57 0.15 no. per 1 g lint n.s. n.s. n.s.
(*), (**), (***), and n.s. indicate significant correlation coefficients at the 0.05, 0.01, and 0.001 levels, and non-significant correlation, respectively.
Correlation between Lint Properties and Neps
Fiber span length was positively correlated and micronaire value negatively correlated with tangled neps, but neither of them correlated with seed coat neps (Table 2). Mature-fiber percentage and maturity index (two independently measured parameters representing the same fiber characteristic) and fiber elongation were the only lint quality parameters correlated with seed coat neps. In most cases, the same quality traits were also correlated with total number of neps and usually exhibited lower coefficients than those obtained with a specific type of neps.
Table 2. Correlation coefficients between nep numbers and lint-quality characteristics in ISHs of cotton under dryland and irrigated treatments. Correlations were calculated between means of genotypes (n = 14 and n = 28 for each treatment and for both treatments, respectively).
Tangled neps, per 1 g lint Dryland + Dryland Irrigated irrigated Short-fiber content, % -0.51 -0.40 -0.32 n.s. n.s. n.s. Span length 2.5%, mm 0.54 0.72 0.55 (*) (**) (**) Length uniformity, % 0.53 0.37 0.38 n.s. n.s. (*) Breaking strength, 0.68 -0.15 0.30 g per tex (**) n.s. n.s. Elongation, % -0.11 -0.15 -0.11 n.s. n.s. n.s. Mature fibers, % -0.51 -0.35 -0.42 n.s. n.s. (*) Maturity index -0.53 0.04 -0.17 (*) n.s. n.s. Micronaire value -0.55 -0.82 -0.66 (*) (***) (***) Seed coat neps, per 1 g lint Dryland + Dryland Irrigated irrigated Short-fiber content, % -0.08 -0.06 -0.09 n.s. n.s. n.s. Span length 2.5%, mm 0.18 0.24 0.24 n.s. n.s. n.s. Length uniformity, % 0.14 0.25 0.21 n.s. n.s. n.s. Breaking strength, 0.30 0.12 0.14 g per tex n.s. n.s. n.s. Elongation, % -0.54 -0.06 -0.20 (*) n.s. n.s. Mature fibers, % 0.00 -0.67 -0.48 n.s. (**) (**) Maturity index -0.04 -0.62 -0.46 n.s. (*) (*) Micronaire value 0.99 -0.17 -0.04 n.s. n.s. n.s. Total neps, per 1 g lint Dryland + Dryland Irrigated irrigated Short-fiber content, % -0.41 -0.26 -0.25 n.s. n.s. n.s. Span length 2.5%, mm 0.49 0.58 0.50 n.s. (*) (**) Length uniformity, % 0.44 0.40 0.38 n.s. n.s. n.s. Breaking strength, 0.63 0.02 0.28 g per tex (*) n.s. n.s. Elongation, % -0.36 -0.13 -0.22 n.s. n.s. n.s. Mature fibers, % -0.36 -0.75 -0.62 n.s. (**) (***) Maturity index -0.40 -0.51 -0.46 n.s. n.s. (*) Micronaire value -0.34 -0.57 -0.40 n.s. (*) (*)
(*), (**), (***), and n.s. indicate significant correlation coefficients at the 0.05, 0.01, and 0.001 levels, and non-significant correlation, respectively.
Influence of Fiber Properties and Motes on Cotton Technological Quality
Multivariate regression analysis was used to determine the effects of both mote number and quality traits on the occurrence of neps in ginned lint. Ranges, means, and standard deviations of the variables used in the multiple regression analysis are presented in Table 3. Nine regression analyses were performed using either tangled neps, seed coat neps, or total neps as dependent variables, each analyzed under individual irrigation regimes as well as under both regimes combined. It is important to emphasize here that the statistical procedure allowed the introduction of any of the variables, with no limitation, into the multivariate equation, and that the final equation was the one with the highest [R.sup.2], where all variable coefficients were significant (with the exception of two equations containing a coefficient with P [approximate] 0.06). Medium motes were introduced into seven of the nine multivariate equations, while small motes were introduced into three equations and large motes into one equation (Table 4). Medium motes revealed the closest association with seed coat neps and total neps, and thus this trait was introduced into each of the multivariate equations. Among the eight lint-quality traits considered, the percentage of mature fibers was introduced into six of the equations, micronaire into two equations, and fiber span length and elongation into one equation, respectively. [R.sup.2] values of the resulting equations were between 0.51 and 0.79.
Table 3. Ranges, means, and standard deviation of the data used in the multivariate regression analyses, as well as values of the control cultivar GA cv. Pima S-5, under dryland and irrigated treatments (n = 14 for each treatment, except for the control cultivar).
Range Variable Dryland Irrigated Dependent: Tangled neps 33-130 27-147 Seed cost neps 52-113 21-266 Total neps 103-243 61-313 Independent: Small motes, no. per 1 g lint 3.19-25.24 0.93-7.92 Medium motes, no. per 1 g lint 1.31-6.56 0.78-6.93 Large motes, no. per 1 g lint 2.19-5.35 0.52-2.15 Short-fiber content, % 3.50-9.20 3.50-4.80 Span length 2.5%, mm 27.9-34.0 29.2-35.6 Length uniformity, % 81.3-87.4 84.3-88.8 Breaking strength, g per tex 30.2-38.6 33.4-39.0 Elongation, % 3.9-4.7 3.70-4.40 Mature fibers, % 65.7-81.0 65.5-82.6 Maturity index 0.77-0.91 0.74-0.93 Micronaire value 2.7-3.6 2.80-3.70 Mean Variable Dryland Irrigated Dependent: Tangled neps 71.43 67.79 Seed cost neps 85.21 96.07 Total neps 156.64 163.86 Independent: Small motes, no. per 1 g lint 10.61 3.26 Medium motes, no. per 1 g lint 3.16 3.86 Large motes, no. per 1 g lint 3.48 1.48 Short-fiber content, % 4.79 3.66 Span length 2.5%, mm 30.7 32.5 Length uniformity, % 84.69 85.89 Breaking strength, g per tex 34.99 35.19 Elongation, % 4.19 4.11 Mature fibers, % 73.62 74.59 Maturity index 0.83 0.84 Micronaire value 3.14 3.35 s.d. Variable Dryland Irrigated Dependent: Tangled neps 26.28 32.82 Seed cost neps 19.35 55.39 Total neps 37.18 64.83 Independent: Small motes, no. per 1 g lint 5.78 1.73 Medium motes, no. per 1 g lint 1.49 1.68 Large motes, no. per 1 g lint 1.09 0.46 Short-fiber content, % 1.91 0.41 Span length 2.5%, mm 1.78 1.78 Length uniformity, % 1.91 1.34 Breaking strength, g per tex 2.50 1.49 Elongation, % 0.22 0.17 Mature fibers, % 3.92 5.19 Maturity index 0.04 0.06 Micronaire value 0.30 0.27 Value of control cultivar Variable Dryland Irrigated Dependent: Tangled neps 54 40 Seed cost neps 75 21 Total neps 129 61 Independent: Small motes, no. per 1 g lint 3.18 0.93 Medium motes, no. per 1 g lint 1.77 0.78 Large motes, no. per 1 g lint 5.35 0.66 Short-fiber content, % 6.5 3.5 Span length 2.5%, mm 29.2 31.0 Length uniformity, % 83.0 85.2 Breaking strength, g per tex 36.6 39.0 Elongation, % 4.7 4.2 Mature fibers, % 74.5 82.6 Maturity index 0.84 0.93 Micronaire value 2.9 3.4
Table 4. Regression equation associating nep numbers with mote numbers and lint-quality traits in ISHs of cotton under dryland and irrigated treatments (n = 14 and n = 28 for each treatment and for both treatments, respectively). Each column refers to a different equation. Significance levels of the coefficients we indicated in parentheses.
Irrigation regime Dryland Irrigated Dryland + irrigated Independent variables Tangled neps, per 1 g lint Intercept 284.3 398.6 93.1 Small motes, no. per 1 g lint 1.68 7.63 (0.057) (0.031) Medium motes, no. per 1 g lint 8.14 (0.022) Large motes, no. per 1 g lint Span length 2.5%, nun 5.82 (0.012) Elongation, % Mature fibers, % -3.48 (0.007) Micronaire value -112.7 -68.0 (0.002) (0.001) [R.sup.2] 0.76 0.57 0.53 Irrigation regime Dryland Irrigated Dryland + irrigated Independent variables Seed coat neps, per 1 g lint Intercept 215.4 409.0 297.9 Small motes, no. per 1 g lint Medium motes, no. per 1 g lint 6.03 16.45 13.7 (0.044) (0.024) (0.001) Large motes, no. per 1 g lint 7.43 (0.06) Span length 2.5%, nun Elongation, % -41.8 (0.042) Mature fibers, % -5.05 -3.45 (0.031) (0.013) Micronaire value [R.sup.2] 0.62 0.66 0.51 Irrigation regime Dryland Irrigated Dryland + irrigated Independent variables Total neps, per 1 g lint Intercept 343.5 598.9 516.0 Small motes, no. per 1 g lint 2.88 (0.018) Medium motes, no. per 1 g lint 12.84 19.7 19.55 (0.008) (0.006) (0.0001) Large motes, no. per 1 g lint 7.43 (0.06) Span length 2.5%, nun Elongation, % Mature fibers, % -3.5 -6.85 -5.73 (0.027) (0.004) (0.0001) Micronaire value [R.sup.2] 0.79 0.78 0.73
Lint properties of the ISHs were similar or superior to the control cultivar (G. b., Pima S-5) under both irrigation regimes. This concurs with our previous results in which other ISHs were examined under various irrigation regimes (Tal, 1986; Tal et al., 1994, p. 37-43), as well as with results obtained by other researchers (Davis, 1978). However, the occurrence of motes and neps was usually higher in the ISHs than in the control cultivar. This previously reported phenomenon (Bhardwaj and Weaver, 1984; Percy 1986; Hughs and Lalor, 1986) limits the commercialization of cotton ISHs. This study focused on the relationship between motes and the occurrence of neps, and the relative influence of motes of various sizes upon this relationship. A better understanding of this phenomenon could contribute to its reduction and to the improvement of ISHs lint quality.
There was a positive relationship between the number of motes in seed cotton and the number of neps in the ginned lint. Small and large motes were not as related to nep number (Table 1) and were infrequent in the regression equations (Table 4) relative to medium motes. It is assumed that most small and large motes are successfully removed by the ginning and cleaning processes. Small motes appear to be removed during the technological processes, since they are not fractured due to their small size, and they are less likely to become entangled with the lint because they are fiberless or bear only short fibers. On the other hand, large motes are probably successfully ginned with the mature seeds because of their large size and more fully relatively developed and, therefore, easily removable fibers. Fibers from large motes could decrease cotton maturity, a possibility which is supported by the significant negative correlation coefficient (r = -0.54, P [is less than] 0.05) between number of large motes and percentage of mature fibers under the irrigated treatment.
The most striking result arising from the multivariate regression and correlation analyses under both irrigation treatments relates to the effect of medium motes on neps in the ginned lint. Medium motes are very brittle and possess fibers of medium length. Therefore, these motes are assumed to be fractured and only partially removed during the ginning and cleaning processes. A mote particle with attached fiber will cause a seed coat nep, which explains the close association between medium motes and either seed coat neps or total neps. The assumption regarding fracturing of medium motes is supported by the coefficients of the multivariate equations. Coefficients of small and large motes were between 1.7 and 7.6, whereas the coefficients of the medium motes were between 6.0 and 19.7, indicating that a single medium mote causes three to four times more neps than either a small or a large mote.
The multivariate equations also indicated relationship between the number of neps and fiber properties such as span length, elongation, percentage of mature fibers, and fineness. Among these, percentage of mature fibers was introduced into most of the equations, always with a negative coefficient, indicating t1rat immature fibers are among the major causes of neps in ginned lint. This effect could be attributed, at least partially, to an indirect effect of large motes which were negatively correlated to the percentage of mature fiber, as indicated earlier in this discussion.
The relationship between motes and neps established in this study shows that medium motes play a major role in the formation of neps under both irrigated and dryland conditions. Selection of ISHs with small numbers of medium motes seems to be a possible approach for improving lint quality of these hybrids. The variation in the number of medium motes found in this study could serve as the basis for such a selection. The similar results obtained under both irrigation regimes indicates that the elimination of medium motes is expected to reduce nep numbers under various management practices. It is worth noting, though, that the extent of mote removal or fracturing can be affected by the ginning machinery. Although the pilot-plant gin used in this study closely mimics a commercial gin, the results should be reexamined under commercial ginning before being applied. The development of a method for rapid estimation of medium size mote number would facilitate the application of these findings. Simultaneous selection for a high percentage of mature fibers (which is associated with reduced large mote numbers) could further contribute to the improvement of lint quality of cotton ISHs.
Abbreviation: ISH, interspecific hybrid
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Y. Saranga, The Hebrew Univ. of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Dep. of Field Crops, Vegetables and Genetics, P.O. Box 12, Rehovot 76100, Israel; N. Sass, C. Shimony and R. Yucha, The Israel Fiber Institute, 3 Emek Refaim St., P.O. Box 8001, Jerusalem 91080, Israel; and Y. Tal, Hazera (1939) Ltd., Mivchor Farm, M.P. Sdeh-Gat 79354, Israel. Received 29 July 1996. Yehoshua Saranga, Corresponding author (email@example.com).
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|Author:||Sarunga, Yehoshua; Sass, Navot; Tal, Yechiel; Shimony, Carmela; Yucha, Rivka|
|Date:||Sep 1, 1997|
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