Boll Retention Research Articles

The trade-off between root growth redundancy and premature senescence under different straw returning modes affects boll formation and seedcotton yield

The indeterminate growth habit of cotton (Gossypium hirsutum L.) makes a coordinated rootshoot relationship critical for increasing yield, which requires comprehensive consideration of root growth redundancy and premature senescence. Although recent evidence suggests that straw management affects root growth and thus seedcotton yield, there is limited documentation on the dynamics of root physiological activity and the rootshoot relationship of cotton under different straw returning modes. The present study compared four treatments: straw removal (CK), straw mulching (SM), straw incorporation (SI), and strawderived biochar incorporation (SBI) in an 8year field experiment. The growth dynamics of roots, shoots and reproductive organs, root physiological activity and seedcotton yield were investigated. The results showed that longterm straw application significantly enhanced seedcotton yield, but the effect varied significantly with straw returning modes. The seedcotton yield increased by 30.5%, 17.8% and 1.8% under SBI, SI and SM respectively in the 8th year of straw management, compared to CK. SBI and SI significantly enhanced the biomass of cotton roots and shoots while had higher growth rate of shoots relative to roots from peak squaring stage to peak bollsetting stage. This reduced root growth redundancy and increased the boll loading and boll capacity of root system. Besides, SBI increased the root activity, soluble protein content and antioxidant enzyme activities, and reduced the root malondialdehyde content from peak bollsetting stage to boll opening stage. These resulted in the greatest increase in boll number (53.862.1%) and boll biomass (39.480.4%) at the boll opening stage under SBI compared to CK. Overall, strawderived biochar improved the boll retention capacity of cotton roots by balancing the growth redundancy and premature senescence of the root system, and was a more suitable straw returning strategy to promote boll formation and increase cotton yield.

Improving the soil K+/Na+ ratio under moderate salt stress synergistically increases the yield and quality of cotton fiber and cottonseed

Cotton production areas have been shifted to saline-alkaline soils with high Na+ content, resulting in low soil K+/Na+ ratios, leading to K+ deficiency in cotton, which is detrimental to the yield and quality of the fiber and cottonseed. It was hypothesized that improving the soil K+/Na+ ratio by applying potassium under moderate salt stress could affect the contents of K+ and Na+ in various organs of cotton bolls. This could affect the growth and biomass distribution of the cotton bolls, ultimately impacting the yield and quality of both the fiber and the cottonseed. To test this hypothesis, a pot experiment using the cotton cultivar CCRI-79 was conducted in 2021 and 2022, and the results showed that improving the soil K+/Na+ ratio under moderate salt stress (1) increased the cotton boll K+/Na+ ratio, accelerated boll growth, and increased the proportion of boll biomass distributed to the fiber and the cottonseed kernel. (2) increased fiber and cottonseed yield. Specifically, the boll retention rate and the number of fruit nodes increased, thereby increasing the boll number. The increase in boll weight can be explained by an increase in the components of fiber and cottonseed yield per boll. Compared with those in the control soil without added salts (C), the fiber and cottonseed yield at a K+/Na+ ratio of 1:9 (SK2) were only 7.1%–21.0% and 4.9%–17.0% lower, respectively. (3) increased fiber and cottonseed quality. SK2 can completely alleviate the effects of moderate salt stress on fiber uniformity, length, and micronaire. And the fiber strength of SK2 is only 5.0%–7.2% lower than C. The oil content and yield of cottonseed kernels increased, and the total unsaturated fatty acid (UFA) and unsaturated index (UI) increased. Although the protein content decreased, the protein yield increased, and the total amino acid (TAA) content increased. SK2 and C did not differ significantly in oil and protein contents. Taken together, these findings indicate that the optimal alleviation of moderate salt stress on the yield and quality of fiber and cottonseed was achieved at a K+/Na+ ratio of 1:9. These results will help to synergistically increase the yield and quality of cotton fiber and cottonseed in saline-alkaline soil and provide new clues for elucidating the mechanism through which the K+/Na+ ratio regulates salt tolerance in cotton.

Foliar application of silicon and boron improves boll retention, lint yield and fiber quality traits of transgenic cotton

BackgroundCotton (Gossypium hirsutum L.) is an important fiber crop that has a widespread cultivation in tropical and subtropical regions globally. The decline in cotton production over the last two decades may be attributed to the effects of climate change and imbalances in mineral nutrition. However, mineral nutrition, particularly micronutrients has been less focused in cotton production. Silicon (Si) and boron (B) are considered crucial micronutrients that play diverse functions in the physiological and biochemical development of plants, as well as in enhancing their resistance to abiotic stress. MethodsThe present study investigated the impact of individual and combined foliar application of Si and B on the development of transgenic (Bt) cotton, as well as their impacts on boll retention, seed cotton production, and fiber quality indicators. Treatments included individual application of 2.0- and 4.0-mM Si and 0.5- and 1.0-mM B, and combined application 2.0 mM Si + 0.5 mM B, 2.0 mM Si + 1.0 mM B, 4 mM Si + 0.5 mM B and 4.0 mM Si + 1.0 mM B. Water spray and no foliar application were regarded as controls for comparison. ResultsCombined application of 4 mM Si + 1.0 mM B resulted in the highest ginning out turn (39%), fiber uniformity (83%) and fiber length (28 mm). The longest plant height and the highest number of closed bolls per plant were recorded with sole application of 0.5 mM B, while sole application of 1 mM B produced the highest number of monopodial branches (20.26), sympodial branches (33.53) and total number of bolls (37.03) per plant. The highest boll weight (18.39 g), boll retention (64.38%) and seed cotton yield (1253.7 kg ha−1) were recorded for sole application of 1.0 mM B. ConclusionThe results revealed that combined foliar application of 4.0 mM Si + 0.5 or 1.0 0.5 mM fiber quality traits, whereas sole application of 1.0 mM B improved growth and yield related traits. Therefore, B and Si can be applied in combination to improve the fiber quality, whereas sole application of B could increase yield-related traits.

Influence of Heliothinae (Lepidoptera: Noctuidae) pests on cotton yield components across a range of planting dates in the southeastern USA

Because of H. zea resistance to Bt toxins, there is renewed interest in cotton IPM, including adjusting planting date. Later planted crops often receive more damage or support larger populations of Heliothinae pests, but this has not been well-documented in cotton. We explored the effects of planting date relative to Heliothinae pests in cotton across various planting windows in the southeastern USA during 2020 and 2021. In-season injury, plant mapping, box mapping, and yield were assessed. In 2021, these planting dates were split with a protective insecticide. Peak boll injury by Heliothinae larvae was not different by planting date and insecticide sprays were usually effective to minimize injury. In general, there were more bolls in position one. Boll retention was usually similar across positions, but was sometimes higher in the lower positions. Bolls that contributed the most to yield tended to be in position one or monopodia bolls, and the yield contribution tended to decrease as boll position increased. As planting date progressed, the highest percent contribution to yield tended to be on lower nodes in the plant. Yields tended to be higher in the early and middle planting dates and were higher in insecticide sprayed plots when the economic threshold was exceeded. We found clear evidence for plant compensation from H. zea feeding in one trial. Planting date relative to Heliothinae pressure level was negligible, given the plant's ability to compensate and the extended window reproductive tissue was available in earlier planting dates relative to later planting dates.

PLANTING DATES AFFECTS ON SEED COTTON YIELD AND CONTRIBUTED CHARACTERS OF COTTON ADVANCE LINES UNDER CHANGING CLIMATIC CONDITIONS OF TANDOJAM, SINDH PAKISTAN

Cotton crop is an imperative role in Pakistan’s economy. It faces several environmental situations which check its growth and production. Climate changes bring a head new pressure for cotton cultivation in the Pakistan especially in Sindh province. The present study was carried out at Nuclear Institute of Agriculture (NIA), Tandojam in 2021. Four advance lines NIA-88, M-32, NIA-Bt. 89 and NIA-Bt.90 along with two local check varieties IUB-2013 and CRIS-121 were evaluated under two planting dates viz. 1st April and 1st May having three replicates under randomized complete block design with factorial arrangements. The data depicted that crop sown on 1st April produced more seed cotton yield (2855.5 kg ha-1) than sown on 1st May with (1674.4 kg ha-1). Comparing the average varietal performance in both sowing dates, NIA-88 produced maximum seed cotton yield (2339.2 kg ha-1) while minimum seed cotton yield (2137.2 kg ha-1) was exhibited by check variety CRIS-121. Boll retention % was maximum (44%) in advance line NIA-88. The maximum number of bolls plant-1 (42.0), sympodial branches plant-1 (26.0), ginning out turn percentage (42.0), seed index (8.1g) and staple length (29.0mm) respectively was obtained in 1st April sowing date while minimum number of bolls plant-1, sympodial branches plant-1, ginning out turn percentage, seed index and staple length (33.0), (15.0), (36.3), (6.0g) and (27.0mm) took in 1st May sown crop. Associating the average varietal performance in both sowing dates NIA-88 produced maximum number of bolls plant-1(44.0), sympodial branches plant-1 (23.0), ginning out turn percentage (40.4), seed index (9.0g) and staple length (29.0mm) respectively. The results indicated that the planting dates and genotypes influenced on seed cotton yield and associated traits in current changing climate scenario for cotton crop.

Genetic variability predicting breeding potential of upland cotton (Gossypium hirsutum L.) for high temperature tolerance

BackgroundHigh temperature stress at peak flowering stage of cotton is a major hindrance for crop potential. This study aimed to increase genetic divergence regarding heat tolerance in newly developed cultivars and hybrids. Fifty cotton genotypes and 40 F1 (hybrids) were tested under field conditions following the treatments, viz., high temperature stress and control at peak flowering stage in August and October under April and June sowing, respectively.ResultsThe mean squares revealed significant differences among genotypes, treatments, genotype × treatment for relative cell injury, chlorophyll contents, canopy temperature, boll retention and seed cotton yield per plant. The genetic diversity among 50 genotypes was analyzed through cluster analysis and heat susceptibility index (HSI). The heat tolerant genotypes including FH-Noor, NIAB-545, FH-466, FH-Lalazar, FH-458, NIAB-878, IR-NIBGE-8, Weal-AG-Shahkar, and heat sensitive, i.e., CIM-602, Silky-3, FH-326, SLH-12 and FH-442 were hybridized in line × tester fashion to produce F1 populations. The breeding materials’ populations (40 F1) revealed higher specific combining ability variances along with dominance variances, decided the non-additive type gene action for all the traits. The best general combining ability effects for most of the traits were displayed by the lines, i.e., FH-Lalazar, NIAB-878 along with testers FH-326 and Silky-3. Specific combining ability effects and better-parent heterosis were showed by the crosses, viz., FH-Lalazar × Silky-3, FH-Lalazar × FH-326, NIAB-878 × Silky-3, and NIAB-878 × FH-326 for seed cotton yield and yield contributing traits under high temperature stress.ConclusionHeterosis breeding should be carried out in the presence of non-additive type gene action for all the studied traits. The best combiner parents with better-parent heterosis may be used in crossing program to develop high yielding cultivars, and hybrids for high temperature stress tolerance.

Cotton leafroll dwarf disease: An enigmatic viral disease in cotton.

Cotton leafroll dwarf virus (CLRDV) is a member of the genus Polerovirus, family Solemoviridae. Geographical Distribution: CLRDV is present in most cotton-producing regions worldwide, prominently in North and South America. The virion is a nonenveloped icosahedron with T = 3 icosahedral lattice symmetry that has a diameter of 26-34 nm and comprises 180 molecules of the capsid protein. The CsCl buoyant density of the virion is 1.39-1.42 g/cm3 and S20w is 115-127S. Genome: CLRDV shares genomic features with other poleroviruses; its genome consists of monopartite, single-stranded, positive-sense RNA, is approximately 5.7-5.8 kb in length, and is composed of seven open reading frames (ORFs) with an intergenic region between ORF2 and ORF3a. CLRDV is transmitted efficiently by the cotton aphid (Aphis gossypii Glover) in a circulative and nonpropagative manner. Host: CLRDV has a limited host range. Cotton is the primary host, and it has also been detected in different weeds in and around commercial cotton fields in Georgia, USA. Cotton plants infected early in the growth stage exhibit reddening or bronzing of foliage, maroon stems and petioles, and drooping. Plants infected in later growth stages exhibit intense green foliage with leaf rugosity, moderate to severe stunting, shortened internodes, and increased boll shedding/abortion, resulting in poor boll retention. These symptoms are variable and are probably influenced by the time of infection, plant growth stage, varieties, soil health, and geographical location. CLRDV is also often detected in symptomless plants. Vector management with the application of chemical insecticides is ineffective. Some host plant varieties grown in South America are resistant, but all varieties grown in the United States are susceptible. Integrated disease management strategies, including weed management and removal of volunteer stalks, could reduce the abundance of virus inoculum in the field.

Impact of foliar fertilization of nutrients and biofertilizer on the growth and yield of hybrid cotton (Gossypium hirsutum L.)

The newly released high yielding cotton cultivars are higher boll retention rate than conventional cultivars that have higher overall nutrient demand during the flowering and boll development stages. Therefore, this field experiment was conducted at during summer, 2020 at Annamalai University experimental farm, Department of Agronomy, Faculty of Agriculture, Annamalai Nagar, Tamil Nadu, India, 608 002 to ascertain the impact of foliar application of essential nutrients and biofertilizers on growth and yield of cotton. The experiment was laid out in randomized block design with twelve treatments of foliar application macro and micro-nutrients with and without Pink pigmented facultative methylotrophic bacteria (PPFM) and replicated thrice. Foliar application of macro, micronutrients and PPFM registered the increased values of growth characters, yield attributes and yield of hybrid cotton. Among the foliar application practice tested, foliar application of 2% urea + 1% PPFM at flowering and boll development stages significantly resulted in the enhances values of growth characters viz., plant height (157.40 cm), Dry matter production (6003 kg/ha), number of monopodial branches (3.28/plant), growth analysis like Leaf area index (4.30), Crop growth rate (7.01 g/m2/day) and Relative growth rate (0.0144 g/g/day), yield attributes viz., number of sympodial branches (21.77/plant), number of squares (83.77/plant), number of bolls (45.04/plant), boll weight (5.58 g) and seed cotton yield (3185 kg/ha). This was statistically on par with the foliar application of 2% MgSO4 + 1% PPFM at flowering and boll development stages. The lower values of growth characters, yield attributes and yield were recorded under water spray treatment. Based on the results of field investigation it can be concluded that foliar application of 2% urea + 1% PPFM at flowering and boll development stages can possibly enhance the growth and yield of hybrid cotton grown under dryland condition.

Foliar application of mepiquat chloride and nitrogen improves yield and fiber quality traits of cotton (Gossypium hirsutum L.).

Cotton (Gossypium hirsutum L.) is one of the most important cash crops primarily grown for fiber. It is a perennial crop with indeterminate growth pattern. Nitrogen (N) is extremely important for vegetative growth as balanced N-nutrition improves photosynthesis, resulting in better vegetative growth. Excessive N-supply results in more vegetative growth, which increases the incidence of insect pest and diseases’ infestation, pollute surface and ground water, delays maturity and produces low crop yield with poor quality. The use of plant growth regulators (PGRs) is an emerging option to control excessive vegetative growth. The PGRs help in improving plant architecture, boll retention, boll opening, yield and quality by altering growth and physiological processes such as photosynthesis, assimilate partitioning and nutrients dynamic inside the plant body. Mepiquat chloride (1,1-dimethylpiperidinum chloride) is globally used PGR for canopy development and control of excessive vegetative growth in cotton. This study investigated the effect of mepiquat chloride (MC) and N application on yield and yield components of transgenic cotton variety ‘BT-FSH-326’. Two N rates (0, 198 kg ha-1) and five MC rates (0, 30,60, 90 and 120 g ha-1) were included in the study. Results revealed that MC and N application improved boll weight, number of bolls per plant, and seed cotton and lint yields. The highest seed cotton and lint yields (3595 kg ha-1 and 1701 kg ha-1, respectively) were observed under foliar application of 198 kg ha-1 N and 120 g ha-1 MC. Fiber length, fiber strength, micronaire and uniformity were significantly improved with foliar application of MC and N. In conclusion, foliar application of MC and N could be helpful in improving yield and fiber quality of cotton.

The relationship between boll retention and defoliation of cotton at the fruiting site level

AbstractDefoliation is used to ease mechanical harvest and reduce lint staining of cotton (Gossypium hirsutum L.). Crop conditions are important determinants of its efficiency, but their effects have not been fully examined. We performed a multiple‐site field study during 2018–2020 (under 17 environmental conditions, covering three cotton regions in China) to explore the relationship between boll retention and defoliation at the fruiting site level. The hormonal defoliant, thidiazuron and boll opener, ethephon, were tank‐mixed or their combination product was used in this study. There was a positive Spearman ranking correlation between boll retention and defoliation in most experimental sites, with correlation coefficients (r) ranging from .275 to .725 at 7 d after application of harvest aids, suggesting that the leaves at fruiting sites bearing bolls dropped more easily than those at fruiting sites where abscission occurred. The positive correlation declined with the fruiting sites up the plant and away the mainstem. The differences in defoliation between fruiting sites with or without bolls were high (around 60–70%) at lower and/or inner positions, but low or negligible at upper and/or outer positions. It appears that the higher light intensity at upper and outer portions of plant may enhance leaf drop and thus reduce the dependence of defoliation on boll retention. In conclusion, a high boll retention would accelerate leaf removal, and may enhance leaf abscission on cloudy days or within more closed canopy.

Intra-Plant Variability for Heat Tolerance Related Attributes in Upland Cotton

Abiotic stress, particularly heat stress, affects various parts of the cotton plant and ultimately impacts the seed cotton yield. Different portions of a single cotton plant of a cultivar exhibit variable responses to stress during reproductive and vegetative phases. To test this hypothesis, physiological and morphological traits related to heat stress were observed for two flowering positions in 13 genotypes of upland cotton. These genotypes were sown in field conditions in triplicate following a randomized complete block design. Data were collected for pollen germination, pollen viability, cell membrane thermostability, chlorophyll content, boll weight, and boll retention for both the top and bottom branches of each genotype. The collected data were analyzed for the identification of variability within and between genotypes for these two flowering positions. Tukey’s test was applied to estimate the significance of differences between genotypes and positions within each genotype. Results showed that the two positions within the same plant statistically varied from each other. The bottom branches of the genotypes performed significantly better for all traits measured except boll weight. The genotype AA-933 performed best for pollen germination and boll retention, while CYTO-608 exhibited maximum pollen viability in both the bottom and top flower positions compared with other genotypes. Overall, MNH-1016 and CIM-602 showed better cell membrane thermostability and chlorophyll content, respectively. This intra-plant variability can be further exploited in breeding programs to enhance the stress tolerance capabilities of the resulting varieties.

Effect of Spatial-Temporal Light Competition on Cotton Yield and Yield Distribution

The photosynthetically active radiation (PAR) of crop canopy is highly related to yield formation, but how it relates to yield and yield distribution is not well understood. The focus of this study was to explore the relationship between light competition under different densities and yield distributions of cotton. The experiment was conducted in 2019 and 2020 at the Cotton Research Institute of the Chinese Academy of Agricultural Sciences in Anyang city, Henan Province, China. A randomized block design was employed, with a total of three repeats. Each repeat had six density treatments: D1: 15,000; D2: 33,000; D3: 51,000; D4: 69,000; D5: 87,000; and D6: 105,000 plants·ha−1. As predicted, the results showed that the canopy light interception, leaf area index, plant height, and biomass of high-density cotton were higher than those of low-density cotton. The aboveground biomass produced by D6 was the highest, and was 12.9, 19.5, 25.4, 46.3, and 69.2% higher in 2019 and 14.3, 19.9, 32.5, 53.7, and 109.9% higher in 2020 than D5, D4, D3, D2, and D1, respectively. Leaf area, plant height, biomass, boll number, and boll weight were significantly correlated with the light interception rate. D5 (87,000 plants·ha−1) had a higher light interception rate and the highest yield. The highest lint yields produced by D5 were 1673.5 and 1375.4 kg·ha−1 in two years, and was 3.2, 4.3, 5.6, 9.7, and 24.7% higher in 2019, and 6.8, 10.6, 13.5, 21.5, and 34.4% higher in 2020 than D6, D4, D3, D2, and D1, respectively. The boll retention of the lower fruit branch under D5 reached 0.51 and 0.57 in two years, respectively. The shedding rate of the upper fruit branch decreased with the increase in cotton density in two years. The boll retention rate and shedding rate in the lower part of cotton plants were most closely related to light interception, with R2 values of 0.91 and 0.96, respectively. Our study shows cotton yield could be improved through higher light interception by optimizing planting density and canopy structure.

Morphological, physiological and molecular assessment of cotton for drought tolerance under field conditions.

Climate change could be an existential threat to many crops. Drought and heat stress are becoming harder for cultivated crops. Cotton in Pakistan is grown under natural high temperature and low moisture, could be used as a source of heat and drought tolerance. Therefore, the study was conducted to morphological, physiological and molecular characterization of cotton genotypes under field conditions. A total of 25 cotton genotypes were selected from the gene pool of Pakistan based on tolerance to heat and drought stress. In field trail, the stress related traits like boll retention percentage, plant height, number of nodes and inter-nodal distance were recorded. In physiological assessment, traits such as photosynthesis rate, stomatal conductance, transpiration rate, leaf temperature, relative water content and excised leaf water loss were observed. At molecular level, a set of 19 important transcription factors, controlling drought/heat stress tolerance (HSPCB, GHSP26, HSFA2, HSP101, HSP3, DREB1A, DREB2A, TPS, GhNAC2, GbMYB5, GhWRKY41, GhMKK3, GhMPK17, GhMKK1, GhMPK2, APX1, HSC70, ANNAT8, and GhPP2A1) were analyzed from all genotypes. Data analyses depicted that boll retention percentage, photosynthesis, stomatal conductance, relative water content under the stress conditions were associated with the presence of important drought & heat TF/genes which depicts high genetic potential of Pakistani cotton varieties against abiotic stress. The variety MNH-886 appeared in medium plant height, high boll retention percentage, high relative water content, photosynthesis rate, stomatal conductance, transpiration rate and with maximum number transcription factors under study. The variety may be used as source material for heat and drought tolerant cotton breeding. The results of this study may be useful for the cotton breeders to develop genotype adoptable to environmental stresses under climate change scenario.

Potential genotype-based climate change adaptation strategies for sustaining cotton production in the Texas High Plains: A simulation study

• Future seed cotton yield showed mixed response across the Texas High Plains due to differences in baseline temperature. • Yield and growth benefits from CO 2 fertilization were suppressed by increased temperature and water stress. • Future irrigation water use would likely increase due to drier and warmer conditions. • High yielding ideotype showed substantial yield gains under irrigated conditions with marginal increase in water use. • For dryland conditions, the long maturity ideotype simulation resulted in maximum yield gains. The Texas High Plains (THP) is a major cotton-producing region in the United States. Sustaining cotton production under declining groundwater availability in the underlying Ogallala Aquifer and changing climate remains a key challenge for stakeholders in this region. The objectives of this study were to assess climate change impacts on cotton yield and irrigation water use, and evaluate six ideotypes for adaptation. In this study, we used the DSSAT-CSM-CROPGRO-Cotton model for simulating cotton production under 18 projected future climate scenarios and with six potential adaptation ideotypes at Bushland, Halfway and Lamesa in the northern, central, and southern parts of the THP region, respectively. Seed cotton yield and irrigation water use between baseline (1976–2005) and future periods (mid-century:2036–2065 and late-century: 2066–2095) were compared. The irrigated seed cotton yield is expected to increase by 12–21 % at cooler northern sites, and decrease by 2% at the warmer southern site, in the mid-century compared to the baseline. For the same period, seasonal irrigation water use is expected to increase by 6–11 % and dryland seed cotton yield is expected to change by +6 % to −11 % across the locations. The increases in irrigated seed cotton yield were attributed to increased vegetative growth under elevated CO 2 , while the decline in dryland seed cotton yield was due to poor boll retention at high growing season temperatures. Six potential climate change adaptive ideotypes with greater drought and heat tolerances, higher yield potential, and longer maturity were designed and compared to the reference cultivar. For irrigated conditions, increasing area of full leaf and enhancing partitioning of assimilates to reproductive growth (high yield potential) were preferred, because these characteristics increased seed cotton yield substantially (by 3–9 %) with a marginal change in irrigation water use (by −1 to 3 %). For dryland production, a long maturity ideotype with longer boll filling duration was the most effective ideotype with a substantial increase in seed cotton yield by 11–45 %. The results from this study will be useful to THP cotton producers and water managers in making appropriate decisions for adapting cotton production to projected changes in future climate and groundwater availability.

Impact of heat stress responsive factors on growth and physiology of cotton (Gossypium hirsutum L.).

Pakistan ranked highest with reference to average temperatures in cotton growing areas of the world. The heat waves are becoming more intense and unpredictable due to climate change. Identification of heat tolerant genotypes requires comprehensive screening using molecular, physiological and morphological analysis. Heat shock proteins play an important role in tolerance against heat stress. In the current study, eight heat stress responsive factors, proteins and genes (HSFA2, GHSP26, GHPP2A, HSP101, HSC70-1, HSP3, APX1 and ANNAT8) were evaluated morphologically and physiologically for their role in heat stress tolerance. For this purpose, cotton crop was grown at two temperature conditions i.e. normal weather and heat stress at 45°C. For molecular analysis, genotypes were screened for the presence or absence of heat shock protein genes. Physiological analysis of genotypes was conducted to assess net photosynthesis, stomatal conductance, transpiration rate, leaf-air temperature and cell membrane stability under control as well as high temperature. The traits photosynthesis, cell membrane stability, leaf-air temperature and number of heat stress responsive factors in each genotypes showed a strong correlation with boll retention percentage under heat stress. The genotypes with maximum heat shock protein genes such as Cyto-177, MNH-886, VH-305 and Cyto-515 showed increased photosynthesis, stomatal conductance, negative leaf-air temperature and high boll retention percentage under heat stress condition. These varieties may be used as heat tolerant breeding material.

Genetic variability in cotton germplasm: predicting the agro physiological markers for high-temperature tolerance

AbstractHigh temperature negatively affects cotton production worldwide. In Pakistan, cotton crop faces high temperature at peak flowering during June–July, which is a major reason for yield losses. The present study was conducted to find some agro-physiological markers for high-temperature tolerance. Fifty cotton genotypes were raised under normal sown (high-temperature stress) and late sown (optimum temperature) conditions for 2 years. Data were recorded for relative cell injury percentage (RCI), chlorophyll content (CC), canopy temperature (CT), boll retention percentage (BR), bolls per plant (BP), boll weight (BW), hundred seed weight (HSW), sympodial branches per plant (SBP), plant height (PH) and seed cotton yield (SCY). A large amount of variability was found among cotton genotypes as proved by descriptive statistics. Stable genotypes were selected based on higher SCY and yield components (BP, BW, HSW, SBP, PH and SCY) performance along with less RCI%, high CC and low CT. The results of heatmap analysis showed that the six cotton genotypes viz., FH-Noor, FH-Lalazar, FH-458, FH-466, NIAB-545 and NIAB-878 performed better under high-temperature stress. These selected genotypes can be a source for breeding high-temperature tolerance. Furthermore, the results from correlation analysis confirmed that the traits such as RCI%, CC and CT can be considered as early selection criteria due to their positive association with SCY. Whilst some other parameters such as BP, BW, BR, SBP and PH might be used as direct selection indices for SCY under high-temperature stress.

Foliar feeding of boron improves the productivity of cotton cultivars with enhanced boll retention percentage

Cotton (Gossypium hirsutum L.) is of prime importance because of its quality fiber and edible oil production. Boron (B) is among essential micronutrients for plant growth; it aids in the transfer of sugars and nutrients from leaves to fruit that are involved directly or indirectly in many plant functions. Cotton growth, yield and quality are strongly affected with boron application. A two-year study was conducted to evaluate the impact of foliar applied B (0, 2, 4, 6, 8 and 10 g of B L−1 of water) on the performance of cotton cultivars (FH-113, MNH-786 and CIM-496). The results indicated that growth, yield and quality traits of cotton were significantly influenced by different levels of foliar applied boron as well as cultivars of cotton. Among cotton cultivars, the yield and quality parameters were superior in cultivar “FH-113.” Foliar application of boron at 6 g L−1 of water improved leaf area index and leaf area duration and eventually improved the number of bolls per plant, boll retention percentage, average boll weight, lint yield, ginning out turn, fiber length and uniformity ratio of cotton. Foliar application of B at 6 g per liter of water, showed promising results by improving growth and quality parameters and is recommend to enhance the economical yield production of cotton cultivar “FH-113” with improved quality.

Cotton production during the tropical monsoon season. II – Biomass accumulation, partitioning and RUE in response to boll loss and compensation

Abstract Growth and reproductive structure retention in cotton (Gossypium hirsutum) is dependent on light intensity, which is often irregular in tropical environments due to shading from cloudiness associated with the monsoon. The objective of this study was to evaluate the potential effects that cloudiness-induced reproductive organ abscission and compensatory responses might have on cotton growth, partitioning and conversion of radiation to biomass (radiation use efficiency RUE) as this was unknown for the monsoon tropics. Cotton cultivars representing different morphology were sown in field experiments at closely timed intervals during the early monsoon over 5 seasons to expose crops to varying amounts of cloud-related shading, creating a matrix of crop responses. In paper I, final boll number was strongly linked with lint yield, and boll retention on the early and late flowering sympodia and yield were correlated with the radiation environment during flowering. Grouping sowing time treatments that had a similar intra-canopy distribution of bolls at maturity provided a mechanism to compare yield recovery post boll loss and consider causal factors. Maximum crop biomass ranged from 1232−1933 g m−2. Lint yield was correlated with the fraction of total biomass present as bolls (P Differences in biomass partitioning between cultivars were minor. When cloud cover abated, extended concurrent vegetative and reproductive growth enabled yield recovery. Greater LAI was a consequence of compensatory processes following fruit loss. Faster development of LAI in response to the monsoon during early flowering could further shade lower canopy fruiting sites, exacerbating fruit abscission and impacting yield compensation. RUEg (glucose equivalent) of 2.35 & 2.63 g MJ−1 PAR was comparable with cotton grown in temperate environments but declined when lower canopy fruit abscission followed by extended concurrent growth altered the ratio of vegetative vs reproductive biomass partitioning. Cloudiness poses a dichotomy of challenges for crop management during the tropical monsoon season. After cloudiness-induced fruit loss, extended concurrent growth when the radiation environment improves must be encouraged to enable the initiation of new fruiting sites for yield recovery. However, expansionary canopy growth in response to cloud and fruit loss may exacerbate detrimental shading of the lower canopy and detract from later yield recovery. Therefore management tactics including the use of irrigation, nutrient and growth regulant inputs must achieve an appropriate balance between vegetative and reproductive components during compensatory growth.

Cotton production during the tropical monsoon season. I – The influence of variable radiation on boll loss, compensation and yield

Growth and reproductive structure development in cotton (Gossypium hirsutum) is dependent on light intensity, which is often irregular in tropical environments due to shading from cloudiness associated with the monsoon. The objective of this study was to evaluate the effects of cloudiness on reproductive organ abscission and how subsequent compensatory organ replacement, with the provision of irrigation, might recover yield in the semi-arid monsoon tropics. Cotton cultivars representing different morphology were sown in field experiments at closely timed intervals during the early monsoon over five seasons to expose crops to varying amounts of cloud-related shading, creating a matrix of crop responses. A wide range for lint yield (1099 to 2900 kg ha−1) was symptomatic of the treatments’ exposure to highly varied environmental conditions. Lint yield was moderately correlated (P < 0.01; Adj R2 = 0.409) with monsoon cloudiness, reducing 235 kg ha−1 per MJ m−2 decrease in the average daily incident radiation during flowering. Final boll number rather than boll size was the key yield component (P < 0.001), with the number of bolls retained and their location within the canopy correlated with the solar radiation pattern spanning flowering. Boll number m−2 decreased linearly in proportion to mean daily incident solar radiation, by 5.02 and 4.39 bolls MJ m−2 during early (P = 0.007) and late flowering (P = 0.02) respectively. Cloudiness-induced boll loss from the early flowering canopy produced a negative correlation with late boll numbers, increasing by 7.2 bolls per MJ m-2 d−1 decrease in mean incident radiation during early flowering (P < 0.001) as lower canopy boll loss enabled surplus assimilates for later set bolls. Fibre quality parameters were not negatively affected by reduced incident solar radiation during flowering and boll filling.The clustering of sowing times into groups according to similarities in the number and final distribution of bolls within the crop canopy provided a mechanism to identify sowing time treatments that shared similar compensation responses. The highest group yields occurred when minimal cloudiness during flowering allowed uninterrupted boll accumulation or alternatively when moderate boll losses from the lower canopy were compensated via additional later set bolls when radiation improved. Yield recovery was restricted for groups where cloudiness was ongoing or increased during late flowering or when canopy factors detracted from efficient use of available radiation. Extrapolation of the linear relationship between boll number and incident radiation showed boll retention was maximised at a mean daily value of 24.2 MJ m−2 (Rmax). Quantification of Rmax was a key finding as it could be applied to calculate a cumulative radiation deficit (RD) = ∑ (if daily radiation is < Rmax then daily RD = Rmax-daily radiation) and provided an alternative independent variable for quantifying the impact of cloudiness during flowering on boll survival. Wider application of this concept requires research in larger solar radiation and temperature regimes than observed here.Yield compensation from cloud induced fruit abscission in the semi-arid tropics will be assisted by management that can extend flowering to create new fruiting sites whilst balancing the partitioning of canopy growth.

Response to deficit irrigation of morphological, yield and fiber quality traits of upland (Gossypium hirsutum L.) and Pima (G. barbadense L.) cotton in the Texas High Plains

Cotton (Gossypium spp.) production around the world often occurs in water limiting environments. Although Upland (G. hirsutum) and Pima (G. barbadense) cottons have been evaluated under conditions of water stress before; these two species are rarely compared to each other. This may be due to differences in irrigation management and environmental constraints (i.e. season length). In 2014 and 2015, two Upland cultivars and two Pima germplasm lines were evaluated at Lubbock, TX, USA. Plant architecture, boll retention, lint yield and fiber quality were assessed under three deficit subsurface drip irrigation levels. Crop water use was evaluated using soil water balance in conjunction with neutron probe soil water content measurements. In 2014 during flowering at the high irrigation rate, Upland cultivars extracted significantly (p<0.01) more water from the soil profile compared with Pima lines resulting in 30 mm greater water use during this period. However, in 2015 water use did not vary significantly between species. In both years the Pima species had greater boll retention, especially at nodes eight and above, and higher fiber quality compared to Upland, confirming previous reported quality differences between these two species. In addition, Pima’s fiber traits were observed to be less impacted by water deficit, and in some instances slight increases in quality were observed. While Uplands had negative impact to deficit irrigation especially for fiber length, strength, and uniformity under the highest water deficit. The Upland cultivars produced significantly greater lint yields compared with Pima with differences averaged across years of 1154 kg ha−1 and 504 kg ha−1 at the high and low irrigation levels, respectively. New, high yield-Pima cultivars are needed to create premium cotton lint to encourage producers evaluating Pima cotton as an alternative to Upland cotton production, as water availability declines.