Economic and physiological traits of Pima cotton lines in Uzbekistan and their correlation

ABSTRACT

In the article, the morpho-physiological indicators in the thin fibrous lines of cotton belonging to G. barbadense L. type, total water content in plant leaves, water retention properties of leaves, transpiration intensity, specific leaf density, third leaf dry weight and third leaf level indicators and morphological-economic traits have the results of the analysis of plant productivity, productivity up to October 10, cotton weight per boll, fiber yield, fiber index and weight of 1000 seeds. Pima cotton lines and standard Surkhon-14 variety differed from each other by physiological indicators of water exchange of plant – total water content in the leaves, transpiration rate and leaf water retention. Morphological-economic and physiological indicators of fine fiber cotton lines were evaluated comparatively. T-2006, T-10, T-1 and T-5445 - boll weight, T-167 and T-663 fast ripening, T-167, T-2006 and T-5440 - productivity, T- 5440 and T-5445 - fiber yield, T-10, T-167, T-5440 and T-5445 - fiber index, T-10, T-1 and T-2006 are valuable in terms of 1000 seed weight characteristics have been identified as primary selection item and was recommended for use as a primary source.

АННОТАЦИЯ

В статье рассмотрены морфофизиологические показатели тонких волокнистых линий хлопчатника, относящиеся к типу G. barbadense L., общее содержание воды в листьях растений, водоудерживающие свойства листьев, интенсивность транспирации, удельная плотность листьев, сухая масса третьего листа и третьего уровня листа и морфолого-экономические признаки имеют результаты анализа урожайности растений, урожайност до октября, веса  коробочки, урожая волокна, индекса волокна и массы 1000 семян. Линии хлопчатника Pima и стандартный сорт Сурхон-14 отличались друг от друга по физиологическим показателям водообмена растений - общему содержанию воды в листьях, скорости транспирации и влагоудержанию листьев. Проведена сравнительная оценка морфолого-экономических и физиологических показателей линий тонковолокнистого хлопчатник. Т-2006, Т-10, Т-1 и Т-5445 - масса коробочки, Т-167 и Т-663 быстросозревающие, Т-167, Т-2006 и Т-5440 - урожайность, Т-5440 и Т-5445 - выход волокна, Т-10, Т-167, Т-5440 и Т-5445 - индекс волокна, Т-10, Т-1 и Т-2006 ценны с точки зрения весовых характеристик 1000 семян, были определены как первичный элемент выбора и рекомендован к использованию в качестве первоисточника.

Keywords: G. barbadense L., cotton, line, physiology, productivity.

Ключевые слова: G. barbadense L., хлопчатник, линия, физиология, урожайность.

Introduction

Cotton plant is an important technical crop that provides raw materials for the textile, food, chemical, paper and other industries. In the world market, the fiber of G. barbadense L. type cotton varieties is very valuable and is valued at 1.5-2 times and more than the fiber of Upland cotton varieties. From 1 ton of this type of fiber, 1.3-2.0 times more fabric is woven than the fiber of Upland cotton varieties, and its cost is 3-4 times more expensive [5].

In the decree of the President of the Republic of Uzbekistan, Sh.М. Mirziyoyev on February 7, 2017 under number PD-4947 “About strategy of actions on further development of the Republic of Uzbekistan”, the tasks for creation and introduction of new selection of varieties of agricultural crops resistant to diseases and pests, adapted to local soil-climatic and ecological conditions have been set for implementation. Cabinet of Ministers of RUz  on January 30, 2020 adopted a resolution № 47 “About effective organization of cultivation of fine-fiber cotton, stimulation of the mechanism of reproduction and introduction of new varieties”. These decrees and resolutions show that our president and government pay great attention to the further development of cotton growing, in particular, to the further expansion of the area under Pima cotton.

At present, one of the urgent tasks of today is to create new varieties of Pima cotton, suitable for the region of Uzbekistan, which are precocious, high-yielding, high-fiber, resistant to adverse environmental factors. Therefore, it is important to study the relationship of morphological-economic traits to the physiological traits of Pima cotton plants.

It is known that the quantitative characteristics of cotton mainly include valuable economic characteristics – precocity, productivity, fiber length, yield, tensile strength and fineness, boll weight and other characteristics. The main product of cotton is fiber, which is evaluated according to its quality. G.barbadense L. cotton is the youngest and most plastic species, its first homeland is South America[1,13].

Worldwide, G.barbadense L. type accounts for 9% of the total cotton area. Mainly grown on the islands and plains of the United States, it became known as Sea Island. Later, Sea Island cotton varieties entered the Nile valleys of Egypt and were grown in large areas as long staple Egyptian cotton varieties [4,15].

The countries with the highest yields of cotton fiber in the world are the United States, Egypt, Israel, Australia and Uzbekistan, and the countries with the lowest yields are Asia, Africa, Oceania, Europe and South America [14]. Today, Uzbekistan produces more than 1 million tons of cotton fiber, and ranks the fifth place in the world and is the second largest seller after the United States [16].

The Republic of Uzbekistan is one of the countries in the world that has mastered the cultivation of Pima cotton. The main reason for this is the heat in the wide areas of southern regions of the country, particularly the heat in Sherabad are higher than in Cairo (Egypt), and in Termez higher than in Alexandria (Egypt) and Bayram Ali (Turkmenistan) and also allows for the effective work of advanced breeders and seed scientists of the country [8]. To date, in cotton-growing countries, including our country, the area under cotton has been reduced, taking into account changes in market demand and other conditions. In 1987, Pima cotton varieties were planted on 204,000 hectares of land in the country, and the total yield was 587,000 tons. Our country is the second largest producer of these cotton varieties in the world after Egypt [8]. Given the high value of the products of Pima cotton varieties on the world market, it is necessary to create and introduce such varieties in our country.

Due to the shortage of fine fiber in the world, the United States has increased the area under the finest fiber Pima cotton varieties (G.barbadense L.) from 80,000 to 110,000 hectares. In addition to its own fine-fiber varieties, India purchases an additional 150,000 tons of Pima fiber [8].

Although Pima cotton varieties account for 3% of world cotton production, they are commercial varieties that provide high quality fiber [4,6]. Pima varieties are mainly grown in the fields of Egypt, the western, northwestern United States, and some provinces of China[7]. In 2012, 94% of Pima varieties grown in the USA were grown in the San Joaquin Valley, California, and the remainder in Arizona, New Mexico, and Texas [4,7]

During the years of independence of Uzbekistan, the number of textile enterprises processing fiber of long-staple varieties, the production of high-quality finished fabrics and durable yarns for domestic and foreign markets has increased [3].

The main goal of world cotton selection programs is to increase cotton yields and improve fiber quality[2,3]. Pima cotton varieties are highly demanding to high heat temperatures in terms of biological characteristics and are grown in small areas in the southern regions of the country [5].

In Uzbekistan, Pima cotton varieties have been planted in small areas due to their late maturity, low yields and small sized bolls. The creation of Pima cotton varieties that fully meet the needs of domestic and foreign markets and provide good quality fiber with world requirements and the expansion of the area of Pima cotton in our country will greatly benefit the economy of our country. This raises the issue of improving the productivity and early ripening of G. barbadense L. type cotton varieties [5]. Pima cotton varieties are very resistant to verticillium wilt disease, which is the main disease of Upland cotton varieties [1].

According to Sh. Akmuradov, there is no correlation between plant height and the main valuable economic characteristics, including the weight, fiber yield and length of cotton in a single boll[1].

Nabiev (2019) et al., noted that the lower and compact the height of the cotton plant is, the greater the number of seedlings, the better the level of flowering and ripening, and the weak and moderate correlation of cotton ripening with the plant height trait [11].

As Uzbekistan is the northernmost cotton-growing country, one of the main tasks is here to study the precocity of cotton. Also, early-maturing cotton varieties are essential not only for the northern regions, but also in hot regions for early and high-quality harvesting in a short period of time without the onset of adverse weather conditions.

According to Kimsanbaev (2009), the precocity of cotton, like in all seed plants, is determined by the time it takes for the seed to awaken from viability to formation of mature seed and the opening of the first boll in the bush under sequenced phases and development stages. In this case, it is necessary to take into account the intensity of successive opening of the bolls in the bush, as well as the total yield before the onset of frost.

The number of fully ripened bolls and the weight of cotton in the bolls play an important role in the formation of high productivity in Pima cotton varieties [7,9,12].

Breeding scientists working with fine-fiber cotton have a task to create precocious cotton varieties that can produce the first-second type fiber of good quality, high yield, with large bolls, a fiber yield of 34% and more in the main cotton growing areas, resistant to fusarium wilt, root rot and macrosporiosis. It should be noted that the creation of such varieties will allow to grow not only in the southern regions of the country, but also in the middle regions, and will bring great economic benefits to cotton farms.

The aim of the study was to investigate the physiological and morphological-economic characteristics of the local cotton lines of the fine-fiber G. barbadense L. species and to determine their correlation level.

Research objects and methods

As an object of the study, new lines Т-167,Т-663,Т-2006,Т-5440,Т-5445,Т-450 belonging to fine-fiber G. barbadense L.species created by the scientists of Research Institute of Genetics and Plant Experimental Biology of AS of RUz, and also Т-1ва Т-10 lines obtained from fine-fiber ruderal subspecies ssp. vitifolium through crossbreeding, standard Surkhon-14 variety were used.

Our research was conducted in 2019-2020 in the field of the experimental base Zangiota, located in Zangiota district of Tashkent region, belonging to the Institute of Genetics and Experimental Biology of the Academy of Sciences of the Republic of Uzbekistan. This area is located 1 km from Tashkent, in the upper reaches of the Chirchik River, at an altitude of 398 meters above sea level. The climate is characterized by strong heat in summer (June, July, August) and a sharp drop in temperature in winter (especially in December and January). Sunny days are 175-185 days, the period without frost makes 200-210 days. Precipitation is observed in autumn, winter and spring, and in summer the air is dry, which requires watering the cotton. The soil of the experimental field is a typical gray soil with low humus and moderate sandy by mechanical content. The slope of the land is weak, unsalted, weakly damaged by wilt. Groundwater is deep (8.0 meters and more). Soil moisture capacity is 22%, bulk density - 1.32-1.33 g / cm³. During the experiment of dissertation work irrigation was carried out in the scheme 1-2-1 in the growing season and the total volume of water was 4800 -5000 m³ / ha in the experimental field. This allowed the soil moisture to be kept at an acceptable level, i.e. 70% -72% relative to the limited field moisture capacity (LFMC). The farming technical measures applied in the year of the experiment allowed to ensure good growth and development of plants.

In our experiment, a 90x20x1 sowing scheme was used. Seeds were planted at a depth of 4 cm. Mineral fertilizers were applied by feeding three times during the growing season at the generally accepted norm, i.e. the total annual norm was N-250 kg / ha, Р₂О₅-180 kg / ha, К₂О -115 kg / ha. The first feeding with fertilizers was carried out at the beginning of budding, the second at mass budding, the third one was at flowering stages. Inter-row processing/softening and weed control were carried out in conjunction with irrigation. Chemicals against thrips and aphids were used during the growing season of the plants.

To determine the physiological parameters of water exchange of plants of fine-fiber cotton lines, the 3rd leaf at the main stem from the growth point of 10 typical plants on each line was used. The total water content in the leaves was determined by the method of N.N. Tretyakov et al. (1990), the water retention property of the leaves by Kushnirenko M.D. et al (1970) method, transpiration intensity by Ivanov A. A. (1950) method.

During the experiment, the morphological traits of lines and the standard variety were determined by generally accepted methods. Valuable economic traits of cotton were identified by conducting phenological observations an recording on cotton yield per plant, number of bolls, weight of cotton in a single boll, biological precocity (time of opening of the first boll in the plant up to 50%), plant height, fiber yield, index, length, weight of 1000 seeds and using the generally accepted methods in the laboratory (UzCGRI, 2007).

The figures obtained for each trait were statistically processed by the variance analysis method to prove whether the difference between the lines and varieties was reliable or unreliable using the ANOVA method by the Fisher criterion, and the smallest difference (P <0.05 and P <0.01) was determined at 95% reliability. Correlation coefficients between the traits were also determined using the Statview program (SAS Institute Inc., Cory. NC. USA).

Research results and their analysis

Analysis of morphological-physiological traits of Pima cotton. Physiological indicators of water exchange were determined during the flowering- harvesting of plants in a special experimental area in the Zangi area of the Institute.

According to the results obtained, the total water content in the plant leaves ranged from 77.8% (T-2006) to 79.43% (T-5440) in fine-fiber varieties and lines (Table 1). The indicators total water content of fine-fiber lines and Surkhan-14 variety were close to each other. The leaf water retention (LWR) of the plants is the lowest in the T-10 line which spent 21.10% of the total water content in the leaves on evaporation in 2 hours, while the highest rate was noted in the T-450 line and Surkhan-14 variety, their 28.56. % and 29.30% water content relatively were found to have been spent on evaporation. Transpiration intensity was highest in the Surkhan-14 variety at optimal water regime in which fresh leaf made 263.3 mg Н₂О/1 gram in 1 hour, while the lowest indication was in the T-10 and T-2006 lines with 149.04 mg and 156.56 mg Н₂О/1 gram in 1 hour, respectively (Table 1).

Table 1.

Indicators of total water content, water retention properties and transpiration intensity in the leaves of Pima cotton lines and varieties

The specific leaf area density (SLAD), i.e., leaf thickness was highest in T-663 and Surkhan-14 variety, 61.15 mg and 60.72 mg / 10 cm2, respectively, and lowest in the T-5445 line, 49.68 mg. The above-mentioned physiological parameters of water exchange were determined, the dry mass of the 3rd leaf from the growth point of the plant was the highest in the T-10 and T-2006 lines, which made 937.3 mg and 909.0 mg, respectively, the lowest rate was noted in the T-5445 line, at 573.5 mg, respectively. The 3^rd leaf area index was the highest in the T-1, T-2006, and T-10 lines (162.6 cm²; 158.3 cm² and 157.9 cm², respectively), while in the T-5440 line it was the smallest, at 108.8 cm² ( Table 2).

Table 2.

Leaf area density, dry mass of the 3^rd leaf and surface parameters of the 3^rd leaf in Pima cotton varieties and lines

Analysis of morphological-economic traits of Pima cotton

When the trait of the weight of cotton in a single boll of fine-fiber cotton lines was studied, it was found that the highest value was in the T-1 line (Table 3).

The weight of cotton in one boll in the standard variety Surkhon-14 was 4.0 grams. The lines T-1, T-663, T-450, T-5440, T-10 were statistically differentiated by bigger size of the bolls relative to this variety, and their index of the trait of cotton weight per boll was 4.9; 4.8; 4.7; 4.4 g and 4.4 g, respectively. Hence, these lines can be used as a primary material in selection work aimed at increasing the boll size of fine-fiber cotton. The remaining lines did not differ statistically from Surkhon-14 variety by this trait.

In the Pima cotton lines, the yield as of October 10, i.e., the cotton yield per plant per period, was determined. The results obtained are presented in Table 7. According to the results, the cotton yield until October 10, i.e the weight of cotton per plant in the standard variety Surkhon-14 was 44.2 g, while in the lines the highest rate of this trait were recorded in the lines T-2006 and T-5440, 41.9 g and 40.5 g respectively (Table 7).

In terms of total productivity, the highest result was noted in the T-2006, T-450 and T-663 lines (64.9 g; 60.5 g and 58.7 g, respectively), and the lowest result was recorded in the T-167 line (48.3 g). The average rate on total productivity in the standard Surkhon-14 variety was 56.6 g per plant (Table 3). By total productivity, the T-2006, T-663 and T-450 lines had higher results than the standard variety. By October 10, the productivity was the lowest in the standard Surkhon-14 variety. The weight of cotton in one boll was higher in the lines than in the standard Surkhon-14 variety.

Table 3.

Parameters of valuable economic traits of Pima cotton lines

Table 8 shows the indicators of traits on fiber yield, index and weight of 1000 seeds in Pima cotton lines and standard Surkhon-14 variety.

Analysis of the results showed that the highest rate of fiber yield was in the standard variety Surkhon-14 (36.7%). In all other lines except T-2006, fiber yield was over 34%. In the lines Т-5445 and Т-5440 the fiber yield was 36,4% and 35,9% respectively, in Т-10 and Т-1 35,6% and 35,1% respectively, in Т-167, Т-450 and Т-663 34,9%, 34,3% and 34,1% respectively. So, the lines of our experiment can correspond today’s requirements. Fiber index rate was the highest in the line Т-10, 7,5 g, while in the remaining genotypes it was 6,3-7,2 g.

The highest results on the weight of 1000 seeds which is one of important valuable economic traits,  were noted in Т-10 and Т-2006 lines (136,8 g and 135,8 g respectively), the lowest rate was in Surkhon-14 variety and Т-167 line (111,4 g and 117,0 g respectively).

Table 4.

Parameters of valuable economic traits of Pima cotton lines

The leaf water retention had a strong positive correlation (0.83) with the transpiration rate, while with the fiber index and the weight of 1000 seeds it had a strong negative correlation (-0.80 and -0.86, respectively). It was found that there was a strong negative correlation (-0.64 and -0.71, respectively) between transpiration intensity and the fiber index, the weight of 1000 seeds. There was a strong positive correlation (0.74) between the specific leaf area density and the fiber yield. Dry mass of  the 3^rd leaf had a strong positive correlation (0.86) with the surface of the 3^rd leaf. It was also found that there was a strong negative correlation (-0.64) between the weight of cotton in one boll and the yield as of October 10. A strong positive correlation (0.74) was noted between the fiber index and the weight of 1000 seeds (Table 5).

Transpiration intensity and water retention from physiological traits had a negative correlation with morphological traits, fiber index and weight of 1000 seeds. Experience has shown that when the transpiration rate and water retention are high, the fiber index and the weight of 1000 seeds are low, or vice versa, when the transpiration rate and water retention are low, the fiber index and the weight of 1000 seeds are high.

When Avtonomov et al studied the correlation between fiber yield and fiber index in fine-fiber cotton, it was found that there was a reliable positive strong and moderate correlation, with a correlation index from 0.40 to 0.85[4]. Vik.A. Avtonomov et al (2009) found that there was no significant correlation between fiber yield and 1000 seed weight, fiber index, yield, and boll weight.

CONCLUSION

Pima cotton lines and standard Surkhon-14 variety differed from each other by physiological indicators of water exchange of plant – total water content in the leaves, transpiration rate and leaf water retention.

Morphological-economic and physiological indicators of fine fiber cotton lines were evaluated comparatively. Tested lines were found to be valuable primary breeding materials by their traits: Т-2006, Т-10, Т-1 and Т-5445 lines by cotton weight in a single boll, Т-167 and Т-663 lines by their prococity, Т-167, Т-2006 and Т-5440 lines by total yield, Т-5440 and Т-5445 lines by fiber yield, Т-10, Т-167, Т-5440 and Т-5445 lines by fiber index, Т-10, Т-1 and Т-2006 lines by the weight of 1000 seeds and they were recommended to use as primary source.

Transpiration intensity and water retention characteristics from physiological traits had a negative correlation with morphological traits, fiber index and weight of 1000 seeds.

ACKNOWLEDGEMENTS

The authors are grateful to the Zangi-Ata Experimental Field Station for providing space and resources to carry out this work.

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