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Published in Crop Sci. 44:2032-2037 (2004).
© 2004 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA

CROP BREEDING, GENETICS & CYTOLOGY

Phenology Measurements and Fiber Associations of Near-Long Staple Upland Cotton

Chris A. Braden* and C. W. Smith

Dep. of Soil and Crop Science, Texas A&M Univ., College Station, TX 77843-2474

* Corresponding author (cbraden{at}tamu.edu)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Breeding for long staple, early maturing upland cotton (Gossypium hirsutum L.) genotypes is a criterion for many breeding programs. Vertical flowering interval, horizontal flowering interval, and boll maturation period of long staple cotton was studied in four field-grown experimental strains and three cultivars in 1998 and 1999 at College Station, TX. Phenological traits of earliness, fiber length development period (FLDP), and fiber quality characteristics, especially fiber length measurements, were evaluated. TAM 94L-25 and TAM 94M-14, near long staple breeding lines, exhibited agronomically acceptable vertical (VFI) and horizontal (HFI) fruiting intervals and a slightly longer boll maturation period (BMP) when compared with current and obsolete cultivars. Fruiting interval measurements, BMP, and FLDP were all positively associated. No associations among fiber length measurements and earliness components were noted. Positive correlations were detected between FLDP and advanced fiber information system (AFIS) upper quartile length of fibers by weight (UQLw) and high volume instrument (HVI) upper half mean fiber length (UHM) across these seven genotypes. Negative relationships were noted between BMP and fiber quality parameters, while FLDP was negatively associated with fiber maturity parameters. Breeding for long staple genotypes has been successful, resulting in lines that possess improved yield and fiber quality but without unduly delaying crop maturity.

Abbreviations: AFIS, advanced fiber information system • BMP, boll maturation period • FLDP, fiber length development period • HFI, horizontal flowering interval • HVI, high volume instrument • Ln, mean fiber length by number (AFIS) • Lw, mean fiber length by weight (AFIS) • Mic., micronaire (HVI) • MR, maturity ratio (AFIS) • SFCn, short fiber content as percentage by number of fibers less than 12.7 mm (AFIS) • SFCw, short fiber content as percentage by weight of fibers less than 12.7 mm (AFIS) • Str., fiber bundle strength (HVI) • UHM, upper half mean fiber length (HVI) • UI, fiber uniformity index (HVI) • UQLw, upper quartile length of fibers by weight (AFIS) • VFIA, first position vertical flowering interval • VFIB, second position vertical flowering interval


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
CROP MATURITY of cotton is a complex character. Most breeders have their own concept of how early maturity can be achieved and this creates ambiguity around the use and meaning of these terms in both literature and practice (Munro, 1971; Ray and Richmond, 1966; Richmond and Radwan, 1962, Walker, 1979). Over the years, breeders have selected earlier maturing cultivars so growers could maximize early season moisture, avoid late season buildup of insects, optimize their opportunity to recover from in-season stresses, and avoid crop damage due to inclement weather during the harvest season. Development of early-maturing cultivars is based, in part, on an understanding of the interaction of developmental traits that affect maturity. Two measures of repeated flowering events, VFI and HFI, have been used to characterize the rate at which reproductive structures occur during development. These two measures have been used widely to characterize differences in flowering rate and to predict the extent of the flowering period in cultivars (McClelland, 1931; Munro, 1971; Namken et al., 1975; Phipps, 1981). Namken et al. (1975) stated that differences in flowering rate may be more important than date of first bloom in predicting maturity and concluded that a shift to a shorter vertical flowering interval contributed to earlier maturity. Temperature plays an important role in determining the flowering rates of cotton. Hesketh et al. (1972) observed a VFI of 2.0 d and HFI of 6.0 d at 30°C, which was three times faster than at 18°C.

A third factor in the fruiting process, BMP, is the length of time from anthesis until the boll opens, defined as when the sutures dehisce, exposing the seed cotton and resulting in the drying of lint and seeds. Unfortunately, there are conflicting reports concerning boll maturation and its contribution to earliness. Hintz and Green (1954) found no difference in rate of boll growth or period of boll maturation between an extremely early-maturing cultivar and a late-maturing cultivar. Godoy (1984) did not detect significant differences in BMP among seven early entries and a standard full-season commercial cultivar. Hood (1984) reported some variation in the boll maturation period. Others (Gipson and Joham, 1969; Phipps, 1981; Thangsupanich, 1981) have reported differences in the rate of boll development. Morris (1962) reported that BMP varied among inbred lines, seasons, flowering dates within a given inbred line, and among bolls set at one flowering date within a given inbred line and trial. The majority of data appear to indicate that breeding for either shorter or longer BMP is possible. Several reports note that temperature and maturation have an inverse relationship (Gipson and Joham, 1968a, 1968b, 1969; McMichael and Powell, 1971; Powell, 1969; Reddy et al., 1999).

The growth and development of cotton fibers can be classified into four distinct, yet overlapping phases: (i) initiation, (ii) elongation, (iii) secondary cell wall synthesis, and (iv) maturation (Ramsey and Berlin, 1976; Meinert and Delmer, 1977; DeLanghe, 1986). Cumulatively, these phases constitute the BMP. Gipson and Ray (1969) stated that there was a positive correlation of the elongation phase with fiber length as measured by hand (the seed were floated out on the convex side of a watch glass and the fiber made to stream out with a jet of water and length measured with a centimeter rule) at the highest temperature in their study. Ironically, the cultivar with the shortest fiber length had the longest elongation period at the two lower temperatures and shortest elongation period at the highest temperature. Studying the regression coefficients between accumulated heat units and the elongation phase, Quisenberry and Kohel (1975) suggested that those cultivars that produced longer fibers were more responsive to available heat units than were those cultivars that produced shorter fibers.

Common knowledge of early-maturing cultivars assumes reduced yield and fiber quality, unfavorable traits in today's marketplace. Namken and Heilman (1973) reported that the fiber quality of agronomically determinate cultivars tended to be slightly lower than that of a then standard cultivar. Correlation analysis among earliness components and fiber properties concluded that there was a significant and positive association of VFI, HFI, and BMP with UHM fiber length. Thus, longer-fibered genotypes tend to be associated with full season maturity and conversely, shorter fibers with early-maturity. This suggests either genetic linkage or physiological associations between earliness and some fiber quality parameters (Godoy, 1984). Comprehension of these intervals and their interrelationships with other morphogenic characters in near-long staple genotypes is important in both measuring and utilizing information on the development rate of parameters which affect earliness. The objectives of this study were (i) to compare VFI, HFI, and BMP of TAM 94L-25 and TAM 94M-14, near-long staple Texas Agriculture Experiment Station breeding lines, with a number of mid to early-maturing genotypes varying in fiber length and (ii) to determine correlations among phenological measurements of maturity, FLDP, and fiber length measurements as determined by HVI and AFIS.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Four upland cotton strains [TAM 94L-25 (Smith, 2003), TAM 94M-14, TAM 94WD-17, and TAM 91C-95Ls (Smith, 2001)] and three cultivars [‘Suregrow 125’ (PVP 9400063), ‘Tamcot CAMD-E’ (Bird, 1979a), and ‘Acala Maxxa’ (PVP 9000168)] were planted in a randomized complete block design with four replications in 1998 and eight replications in 1999 at the Texas A&M Research Farm near College Station, TX. Soil type for both years was a Westwood silt loam, a fine-silty, mixed thermic Fluventic Ustochrept, intergraded with Ships clay, a very fine, mixed, thermic Udic Chromustert. Plots were two rows, 12 by 1 m, with a blank row on each side. In 1998, approximately 63 ha-cm of irrigation were applied pre plant. Genotypes were planted on 20 April 1998 with skips replanted on 30 April. Early in the growing season, plots were thinned to single plant culture (approximately 40 cm between plants). Cultural practices, including furrow irrigation were designed to maximize boll retention. Because of high demand and limited supplemental water resources, plots were furrow irrigated only twice, on 3 June and 1 July 1998, receiving approximately 31 ha-cm of water at each application. Because of timely and beneficial rainfall in 1999, no supplemental irrigation was needed. Plots were planted on 12 April 1999.

Genotypes
The strains and cultivars were chosen on the basis of their HVI fiber length performance before 1998. The general genetic background of each genotype is as follows.

Phenological Measurements
Tagging of flowers was not initiated until all genotypes exhibited blooms. Flowers were then tagged on the day of anthesis with dated tags. Untagged flowers or developing bolls were not detached to maintain normal boll load and consistency from plant to plant. Tagging of white flowers started on 22 June and continued until 17 July in 1998. In 1999, tagging of white flowers was initiated on 20 June and continued through July 16.

To determine the VFI of first (VFIA) and second (VFIB) fruiting positions and the HFI, 10 plants in each of two replications in 1998 and four replications in 1999 of each genotype were selected and marked early in the growing season. To determine the date the tagged bolls matured (defined as when the sutures dehisced naturally or under pressure between the thumb and forefinger), tagged bolls from the 10 plants in each plot were monitored daily beginning about 35 d after the first flowers were tagged. Date of maturity was recorded on the same tag, which also identified the date of anthesis. At crop maturity, plants were defoliated and the 10 plants from each plot were severed near ground level and removed from the field. These plants were then sheltered from the weather and mapped at a later date. Plant mapping involved harvest of all tagged open bolls by fruiting position defined as main-stem node and sympodial site. Bolls from the same fruiting site among the 10 plants per plot were combined. Plant data were recorded and phenological measurements were calculated. The interval, in days, between the appearances of flowers at equivalent positions on successive sympodia is referred to a VFI. Sufficient data points were collected to allow determination of the first and second position VFI. On a per plant basis, the VFI for both first and second sympodial fruiting positions were calculated by dividing the number of days between the latest dated tag available and the earliest dated tag available by the intervening number of sympodial branches. Ultimately, a plot mean value was attained for comparison purposes. The HFI is the average number of days between the appearances of flowers at sequential positions on the same sympodium. On a per sympodium basis, the HFI was calculated by dividing the number of days from the appearance of a flower at the proximal sympodial position and the distal sympodial position and dividing by the number of intervening fruiting positions. The HFI for each plant was then determined by averaging the intervals on all sympodia from which a mean plot value was determined. The BMP was simply the average number of days from anthesis to boll maturity as defined above, which was first determined on a per plant basis and then on a per plot basis. Because of missing fruiting sites caused by environmental conditions or loss of tags in cutting, transport, and storage, a few plants did not yield any phenological data.

All fiber measurements were determined from an allotment of 30 mature bolls, majority from first positions within the lower fruiting zone, taken from or near the same anthesis date within each plot before removal of 10 plants from the field. These bolls were allowed to dry in a greenhouse, after which the seedcotton was hand removed from the bur and ginned on a roller gin. AFIS and HVI data were determined by Cotton Incorporated (Cary, NC). Fiber length development period (FLDP) is the biological time interval from anthesis to the day that the lint fibers ceased growing in length. Analysis and data of these genotypes is reported by Braden and Smith (2004). For each year and genotype, the FLDP was determined as the number of days from anthesis to fiber length not different (P = 0.05) than the longest fiber length attained.

Statistical Analysis
Analyses of variance for phenological measurements and BMP were calculated on the basis of plot means. The General Linear Models (GLM) procedure of SAS (SAS, 1999) was used to perform the analyses. Waller–Duncan K-ratio LSD was used to separate treatment means when significant differences existed at P < 0.05. Correlation coefficients were determined by using Pearson's correlation procedure in SAS (Cary, NC).


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Thirty-five days with temperatures at or above 37.8°C, with 25 of those consecutive and only 1.29 cm of rain characterized the 1998 growing season at College Station, TX. The high heat probably led to excessive fruit abscission. On the basis of the amount of rainfall received during the growing season, 1999 was the inverse of 1998. Timely and beneficial rainfall enabled the cotton plants to retain fruit at most positions and to develop cotton fibers under limited moisture stress.

Smith (2003) had previously confirmed the HVI UHM fiber length differences among the selected parents. TAM 94L-25 and TAM 94M-14 averages approximately 31 mm UHM length while TAM 91C-95Ls averages about 30 mm (Smith, 2001). Suregrow 125 averaged 28.8 mm at College Station during 1993 to 2001 (Smith et al., 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002), and Acala Maxxa averaged 29.2 mm at College Station under irrigated conditions during 1996 to 2001 (Smith et al., 1996, 1997, 1998, 1999, 2000, 2001, 2002).

All phenological measures of maturity varied across environments (Table 1). However, no significant genotype x year interactions was detected for VFIA, VFIB, and HFI. Only for BMP did genotypes respond differently to the 2 yr of this study. This suggests that the reproductive growth and development of these seven genotypes is predictable and while modified by the environment are primarily under genetic control. This significant genotypic VFIA in the ANOVA disagrees with the results of Hood (1984) and Villareal et al. (1993); however, the HFI among genotypes agrees with both. The variation for BMP agrees or disagrees with many (Gipson and Joham, 1969; Godoy, 1984; Hintz and Green, 1954; Hood, 1984; Morris, 1962; Phipps, 1981; Thangsupanich, 1981; Villareal et al., 1993).


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  		Table 1. Mean squares for first position vertical flowering interval (VFIA), second position vertical flowering interval (VFIB), horizontal flowering interval (HFI), and boll maturation period (BMP) of seven genotypes grown at College Station, TX, in 1998 and 1999.

 
Suregrow 125 averaged 2.8 d between flowers at the first sympodial position, which was longer (P = 0.05) than that required for the four TAM lines (Table 2). TAM 94M-14 had the shortest VFIA at 2.5 d but was not different than Tamcot CAMD-E. TAM 94L-25 was not different than TAM 91C-95Ls, Acala Maxxa, TAM 94WD-17, or Tamcot CAMD-E. Suregrow 125 averaged 2.9 d between flowers at the second sympodial position, which was longer (P = 0.05) than that required for three of the seven genotypes. Each genotype exhibited similar vertical flowering intervals of both first and second position reproductive structures and across all genotypes, first and second position vertical flowering interval was 2.66. Acala Maxxa had the longest HFI, 6.3 d, while the early-maturing Tamcot CAMD-E had the shortest interval of 5.2 d. TAM 94L-25 and TAM 94M-14, the near extra long staple genotypes of interest, had HFI equal to or slightly shorter than the average of all genotypes, 5.7 d, and were not different (P = 0.05) in this measurement of earliness than three other genotypes, including Suregrow 125. Overall, TAM 94L-25 has a fruiting pattern slower than the agronomically determinate cultivar, Tamcot CAMD-E, but faster than the other cultivars, Suregrow 125 and Acala Maxxa. Thus, TAM 94L-25 and TAM 94M-14 do not derive their long fiber length at the agronomically detrimental cost of a slower rate of reproductive development of floral structures.


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  		Table 2. Average phenological measurements and boll maturation period of seven genotypes at College Station, TX, in 1998 and 1999.

 
BMP of these genotypes (Table 2) were compared within years due to the significant genotype by year interaction. In 1998, TAM 94WD-17 averaged 39.5 d from anthesis to boll opening, 4.4 d longer (P = 0.05) than Tamcot CAMD-E, which averaged only 35.1 d. Acala Maxxa and Suregrow 125 exhibited a slightly longer BMP than Tamcot CAMD-E, but were not different. All four experimental strains exhibited BMPs longer (P = 0.05) than Tamcot CAMD-E, however the BMP of near long staple genotypes TAM 94L-25 and TAM 94M-14, were not different from Acala Maxxa and Suregrow 125.

Boll maturation period averaged 8.3 d longer in 1999 than in 1998. All four experimental strains, including the near long staple TAM 94L-25 and TAM 94M-14, exhibited BMPs longer (P = 0.05) than all three cultivars in 1999. Two environmental factors may have accounted for this variation. First, 1998 was hotter than 1999, and since heat units are known to drive a number of plant processes, temperature alone could have accounted for the discrepancy. The second environmental factor to consider is the absolute amount and distribution of radiant energy. As noted earlier, 1999 was not only cooler, it also had more rainfall, and concomitantly less sunshine. In 1999, Acala Maxxa exhibited the shortest BMP, 42.1 d, which was slightly shorter (P = 0.05) than Tamcot CAMD-E and Suregrow 125, which were not different at 43.4 and 43.8 d, respectively. While there was a genotype x year interaction for BMP, apparently brought about by a slight change in the rankings of the 7 genotypes, data in Table 2 clearly show that the two longer-fibered TAM strains, TAM 94L-25 and TAM 94M-14, required a longer amount of time from anthesis to open boll. Data reported by Braden and Smith (2004) indicated that TAM 94L-25 and TAM 94M-14 attained their longer average fiber length not only through an extended FLDP for each year, but also from a greater final average daily growth rate when averaged across years. The extended FLDP is consistent with an extended BMP. It would be desirable to develop high quality upland cotton cultivars with faster rate of fiber length development without sacrificing boll and crop developmental time. However, a longer BMP only extends the crop season by the number of days required for the latest set boll to mature, unlike flowering interval where the effects are cumulative. Thus, producing a crop of long or extra-long staple appears to extend the growing season by an average of 3.5 d on the basis of data in Table 2.

Phenology measurements, VFIA, VFIB, HFI, BMP, and FLDP were positively associated (P < 0.01) with each other, indicating harmony among the two fruiting interval measurements and as these fruiting intervals increased, so did the BMP and FLDP (Table 3). The correlation between VFI and HFI is in agreement with the data from Hood (1984) but disagrees with Godoy (1984). The correlation value for BMP and FLDP was 0.87, suggesting longer cotton fiber lengths in these genotypes were associated with a longer fiber elongation phase.


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  		Table 3. Pearson's correlation coefficients among phenological measurements for seven genotypes grown at College Station, TX, in 1998 and 1999.

 
Poor associations between any AFIS fiber length measurement and earliness components were found in this study. Flowering intervals generally were not associated (r = 0.07– 0.83) with most fiber length measurements (Table 4). These relationships also reveal that as the fruiting rate interval decreases, a desirable event, the percentage of short fibers, an undesirable event, increased. The maturity ratio, a desirable event, however, increased with faster fruiting intervals within these seven genotypes. Correlation analysis did not reveal any detrimental relationships among vertical flowering intervals and fiber length parameters suggesting that length and earliness can be improved simultaneously. However, longer fibers may result in higher SFC, which is counterproductive. Micronaire reading was the only HVI fiber property associated with flower interval parameters, being negatively associated (P < 0.01).


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  		Table 4. Pearson's correlation coefficients between phenological measurements and fiber quality measurements for seven genotypes grown at College Station, TX, for the years 1998 and 1999.

 
BMP was negatively correlated (P < 0.05) with micronaire reading, Str., and Uni., indicating that the cultivars requiring fewer days from flowering to open boll had greater secondary wall development, higher fiber bundle strength, and more uniform fiber length. Instrumentation used to measure fiber length had no influence on this relationship. No association among any fiber length measurements, either AFIS or HVI, and BMP were detected, which agrees with Godoy, who similarly reported no correlations among HVI fiber length measurements and BMP. FLDP had significant and positive correlations with UQLw and UHM. This association indicates that long-staple genotypes have a longer fiber length development period than the short-staple genotypes when analyzed on individual years, a conclusion already noted by Braden and Smith (2004). FLDP was negatively associated with MR, Mic., and Uni., once again, as with flowering intervals, indicating that genotypes with a longer fiber elongation period will develop less uniform and less mature fibers. This seems illogical and should be a concern to all. The textile industry demands longer fibers to increase profit and efficiency, and producers request longer fibers to avoid discounts, but these data suggest that cotton breeders attempting to solve this dilemma might also be increasing the variance of fiber lengths found in any population of long staple cultivars.


   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
Significant differences were noted between years for VFIA, VFIB, HFI, and BMP and among seven genotypes for VFIA, HFI, and BMP. Although the temperatures in 1998 accelerated the rate of flowering, both vertical and horizontal, the lack of a genotype x year interaction for VFIA, VFIB, and HFI indicates the strong genetic control of fruiting rates for these genotypes. The rates of flower production of the long-fiber strains, TAM 94L-25 and TAM 94M-14, were agronomically comparable with the commercial genotypes, Suregrow 125, Tamcot CAMD-E, and Acala Maxxa. The BMP of the four experimental strains were longer than those of the commercial genotypes, with TAM 94L-25 and TAM 94M-14 requiring more days from anthesis to open boll than Tamcot CAMD-E, Suregrow 125, and Acala Maxxa. However, since VFI and HFI are not increased, the overall cropping season for long-strains is increased only about 3.5 d.

FLDP for these seven genotypes was associated with all crop maturity indicators and had the highest correlation with BMP. However, only FLDP was associated with fiber length parameters. Although the relationship with FLDP in this paper was counterproductive in identifying long staple, early maturing cultivars, additional germplasm should be investigated.

Received for publication January 12, 2004.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 





This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
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Right arrow Similar articles in ISI Web of Science
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Right arrow Citing Articles via ISI Web of Science (2)
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Google Scholar
Right arrow Articles by Braden, C. A.
Right arrow Articles by Smith, C. W.
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PubMed
Right arrow Articles by Braden, C. A.
Right arrow Articles by Smith, C. W.
Agricola
Right arrow Articles by Braden, C. A.
Right arrow Articles by Smith, C. W.
Related Collections
Right arrow Crop Genetics
Right arrow Cotton

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