Impact of nitrogen and phosphorus fertilizers on Cry1Ac protein contents in transgenic cotton

Application of different fertilizers to check the efficiency of expression of Bt (Bacillus thuringiensis) gene in one of the leading commercialized crops (cotton) against Lepidopteran species is of great concern. The expression of Cry protein level can be controlled by the improvement of nutrients levels. Therefore, the myth of response of Cry toxin to different combinations of NP fertilizers was explored in three Bt cotton cultivars. Combinations include three levels of nitrogen and three levels of phosphorus fertilizers. Immunostrips and Cry gene(s) specific primer based PCR (Polymerase Chain Reaction) analysis were used for the presence of Bt gene that unveiled the presence of Cry1Ac gene only. Further, the ELISA (enzyme-linked immunosorbent assay) kit was used to quantify the expression of Cry1Ac protein. Under various NP fertilizers rates, the level of toxin protein exhibited highly significant differences. The highest toxin level mean was found to be 2.3740 and 2.1732 µg/g under the treatment of N150P75 kg ha-1 combination while the lowest toxin level mean was found to be 0.9158 and 0.7641 µg/g at the N50P25 kg ha-1 level at 80 and 120 DAS (Days After Sowing), respectively. It was concluded from the research that the usage of NP fertilizers has a positive relation with the expression of Cry1Ac toxin in Bt cotton. We recommend using the N150P50 kg ha-1 level as the most economical and practicable fertilizer instead of the standard dose N100P50 kg ha-1 to get the desired level of Cry1Ac level for long lasting plant resistance (<1.5). The revised dose of fertilizer may help farmers to avoid the cross-resistance development in contradiction of insect pests.

Assessing Crop and Water Productivity Performance of Different Crops and Cropping Systems

Background: Freshwater in sufficient quantity and adequate quality is a prerequisite for human societies and natural ecosystems. To adequately feed 9.3 billion people in 2050, consumptive water use (i.e. transpired water) by all food and fodder crops needs to increase from its present estimated level of 7000 km3/year to 12,586 km3/year. However, fresh water resources are increasingly getting scarce because of increased competition among a multitude of users. Getting agriculture to perform with progressively smaller allocation of renewable water resources will remain a challenge on global scale. To meet the challenge there is an urgent need to improve the crop water productivity to ensure the sustainability of agriculture. Methods: An experiment was carried out at village Menawali, Hanumangarh, Rajasthan during both kharif and rabi seasons to assess productivity, economics, N-uptake and water use of different crops. An area of 187 ha comprising 25 farmers irrigated by common irrigation channels were selected to collect the information. The information required i.e. soil, crop management, growth, phonological, yields, water balance, N-uptake and water use efficiency of each crops were collected from 15 farmers. Bt-cotton and clusterbean of kharif and wheat and Indian mustard in rabi were prominent crops, cotton-wheat, cotton-mustard, clusterbean-wheat and clusterbean-mustard were major cropping sequences of the study region. Result: In kharif season, Bt-cotton gave higher economic yields than clusterbean and amongst rabi season crops, economic yields of wheat and mustard were 4255, 1778 kg/ha, respectively. The economic yield of cropping sequences varied from 3741-6514 kg/ha and were higher for cotton-wheat (6218 kg/ha), intermediate for clusterbean-wheat (5785 kg/ha) and lower for cotton-mustard (3741 kg/ha) and clusterbean-mustard (3308 kg/ha). The cotton-wheat (₹1181.2 mm) sequence had highest water use. Clusterbean-wheat cropping system recorded highest water productivity (16.5 kg/ha mm) followed by clusterbean-mustard (14.9 kg/ha mm). The clusterbean-mustard (₹456/ha mm) cropping sequence was most profitable and fetched highest net return followed by clusterbean-wheat (₹383/ha mm).

Assessing fitness costs of the resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to pyramided Cry1 and Cry2 insecticidal proteins on different host plants

Fall armyworm (FAW), Spodoptera frugiperda (Smith), is one of the major pests targeted by transgenic crops expressing insecticidal proteins from Bacillus thuringiensis (Bt) Berliner. However, FAW presents a high capacity to develop resistance to Bt protein-expressing crop lines, as reported in Brazil, Argentina, Puerto Rico and the southeastern U.S. Here, FAW genotypes resistant to pyramided maize events expressing Cry1F/Cry1A.105/Cry2Ab2 (P-R genotype) and Cry1A.105/Cry2Ab2 (Y-R genotype) from Brazil were used to investigate the interactions between non-Bt hosts (non-Bt maize, non-Bt cotton, millet and sorghum) and fitness costs. We also tested a FAW genotype susceptible to Bt maize and F1 hybrids of the resistant and susceptible genotypes (heterozygotes). Recessive fitness costs (i.e., costs affecting the resistant insects) were observed for pupal and neonate to adult survival of the P-R genotype on non-Bt cotton; larval developmental time of the P-R genotype on millet and sorghum; larval and neonate-to-adult developmental time of the Y-R genotype on non-Bt cotton and sorghum; the fecundity of the Y-R genotype on non-Bt cotton; and mean generation time of both resistant genotypes. However, on non-Bt cotton and non-Bt maize, the P-R genotype had a higher fitness (i.e., fitness benefits), displaying greater fecundity and rates of population increases than the Sus genotype. Non-recessive fitness costs (i.e., costs affecting heterozygotes) were found for fecundity and population increases on millet and sorghum. These findings suggest that, regardless of the disadvantages of the resistant genotypes in some hosts, the resistance of FAW to Cry1 and Cry2 Bt proteins is not linked with substantial fitness costs, and may persist in field conditions once present.

Indian scenario on the occurrence of a dreaded insect pest Pink bollworm, Pectinophora gossypiella on Bt cotton-A review

The pink bollworm, Pectinophora gossypiella, has become a significant production constraint on Bt cotton in India. This problem is unique to India because the pest has developed multi-fold resistance to Cry toxins in many Indian populations but not in other countries. Most Indian populations have developed multifold resistance to Cry 1 Ac and Cry 1Ac + Cry 2 Ab toxins. Year-round cultivation of long-duration Bt cotton hybrids on a large scale has a pronounced impact on the incidence. Also discussed other factors responsible for the occurrence of pink bollworm on Bt cotton in India. Insecticide Resistance Management (IRM) strategies implemented by different cotton-growing countries globally; the USA, India, and China had a significant impact on the interaction of pink bollworm on Bt cotton. Huge selection pressure resulted in resistance to Cry toxins. Time-tested IPM, if implemented on a community basis focusing on pheromones technology and closed season, will help sustain the cotton cultivation in India in the future. Thus, this review aims to congregate exhaustive information on the history, biology, resistance to Bt cotton, and Integrated Management (IPM) options for the Indian scenario, which would help researchers in their future endeavors.

Mutation in the Cadherin Gene Is a Key Factor for Pink Bollworm Resistance to Bt Cotton in China

Transgenic crops producing Bacillus thuringiensis (Bt) toxins are widely planted for insect control, but their efficacy may decrease as insects evolve resistance. Understanding the genetic basis of insect resistance is essential for developing an integrated strategy of resistance management. To understand the genetic basis of resistance in pink bollworm (Pectinophora gossypiella) to Bt cotton in the Yangtze River Valley of China, we conducted an F2 screening for alleles associated with resistance to the Bt (Cry1Ac) protein for the first time. A total of 145 valid single-paired lines were screened, among which seven lines were found to carry resistance alleles. All field parents in those seven lines carried recessive resistance alleles at the cadherin locus, including three known alleles, r1, r13 and r15, and two novel alleles, r19 and r20. The overall frequency of resistance alleles in 145 lines was 0.0241 (95% CI: 0.0106–0.0512). These results demonstrated that resistance was rare and that recessive mutation in the cadherin gene was the primary mechanism of pink bollworm resistance to Bt cotton in the Yangtze River Valley of China, which will provide a scientific basis for implementing targeted resistance management statics of pink bollworm in this region.

Economic Analysis of Parawilt Management in Bt-Cotton (Gossypium hirsutum L.) in Mansa District of South-western Punjab, India

Parawilt characterized by a sudden drooping of leaves followed by death of plants withinfew hours after rainfall or heavy irrigation has been the major physiological disorder affectingproductivity of Bt-Cotton (Gossypium hirsutum L.). We studied the effect of foliarapplication of cobalt chloride (@10 mg L-1 water) within 24-36 hours after appearance ofsymptoms on recovery rate, seed cotton yield and economics at farmers’ fields in Mansadistrict of south-western Punjab. The results of front line demonstrations revealed thatfoliar application of cobalt chloride resulted in significantly (p<0.05) higher seed cottonyield by ~9.1 per cent, compared with the control (no-spray). The mean gross returns(MGRs) increased significantly by Rs. 9620/- ha-1 in the demonstration plots. The higherbenefit-cost (B:C) ratio of 2.38 was observed for the demonstration plots, against 2.15 forthe control (no-spray). The foliar application of cobalt chloride resulted in higher averageproduction efficiency of 1.1 kg seed cotton yield ha-1 d-1 and average economic efficiencyof Rs. 65.7 ha-1 d-1, compared with the control. These results therefore, revealed that farmerscan effectively manage parawilt in Bt-cotton using foliar application of cobalt chloride andmay increase seed cotton yield and economic returns.

Effect of host plants on the oviposition preference of pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Pink bollworm (Pectinophora gossypiella (Saunders, 1843)) (Lepidoptera: Gelechiidae) is an important pest of cotton. We aimed to study the effect of different host plants on the oviposition preference of pink bollworm under laboratory conditions. Cotton (Bt and non-Bt), okra and hibiscus plants were used, which vary in morphological characteristics. Significant differences were observed in the density of trichomes and it is positively correlated with oviposition behaviour of pink bollworm. In a no-choice test, we recorded a higher number of eggs on Bt and non-Bt cotton plants. In two-, three- and four-choice experiments, pink bollworm preferred to deposit the maximum number of eggs on non-Bt cotton among other host plants. A substantially higher number of eggs were laid on Bt cotton in combinations with okra and hibiscus and a considerably lower number on non-Bt cotton. We recorded fewer numbers of eggs on hibiscus in all combinations. Overall, pink bollworm moths showed greater affinity towards non-Bt cotton plants and deposited the maximum number of eggs there. From the practical point of view, the development of cotton genotypes which are devoid or have a lesser density of trichomes may be a possible solution to reduce the pink bollworm egg load on cotton.