Rajender Singh Chhokar

Molecular Genotyping of Herbicide Resistance in P. minor: ACCase Resistance

Little seed canary grass (Phalaris minor Retz.) populations resistant to herbicides that inhibit acetyl-CoA carboxylase (ACCase) represent an increasingly important weed control problem in northern India. The objective of this study was to develop DNA-based markers to differentiate herbicide-resistant and herbicide-susceptible population of P. minor. Primers were designed to amplify the conserved region carrying two reported mutations Trp2027 to Cys and Ile2041 to Asn conferring ACCase inhibitor resistance in several grass weeds and subjected to single-strand conformational polymorphism (SSCP) to detect the mutations. Five distinctive electrophoretic patterns on non-denaturing PAGE were observed, and four patterns were found to be associated with ACCase herbicide resistance in P. minor. The PCR-SSCP test developed in this study confirmed 17 resistant populations to contain mutations in CT domain of ACCase gene. This is the first report of rapid and easy molecular diagnosis of ACCase herbicide-resistant and herbicide-sensitive population of P. minor through PCR-SSCP analysis.

Suitable wheat cultivars and seeding machines for conservation agriculture in rice-wheat and sugarcane-wheat cropping systems

Field investigations were conducted to improve the wheat yield and profitability through identification of suitable wheat cultivars and seeding machines under conservation agriculture (CA) after rice and sugarcane. For wheat seeding under CA after rice harvest with full residue retention, Turbo Happy Seeder (THS) was more appropriate, while in sugarcane ratoon with full trash, Rotary Disc Drill (RDD) was found suitable. Based on the research farm and farmer’s field experiments, the wheat grain yield was similar under conventional tillage (CT) and CA. Among 32 wheat varieties (28 aestivum and 4 durum) evaluated under timely sown conditions, no significant yield differences were observed under CT and CA. Among test cultivars, the best yielding were HD 2967, PBW 723, HDCSW 18, HI 8498, MPO 1215, UAS 428 and MACS 6222. Out these seven genotypes, three (HI 8498, MPO 1215 and UAS 428) were durum genotypes. For very late sown (20-25th January) and CA conditions after sugarcane harvest, five aestivum wheat varieties namely PBW 550, DBW 71, Raj 3765, WR 544 and WB 02 yielded 30.24, 33.80, 32.62, 32.46 and 27.54 q/ha, respectively. On an average, 31.8 q/ha additional wheat yield can be obtained when seeded in sugarcane ratoon using RDD. If we translate 50% sugarcane area across the wheat growing zone of India (1.0 mha) then we can have an additional wheat production of 3.2 mt/year. Both the crop establishment methods viz. no till (NT) with residue retention and conventional till (CT) wheat had similar yield levels but CA can have an additional profit of Rs 3125/ha due to reduction in tillage cost. The results clearly indicate that wheat productivity and production as well as profitability can be improved through right choice of cultivar, and seeding machinery for conservation agriculture in rice-wheat and sugarcane ratoon-wheat system.

Influence of Tillage, Cultivar, Seed Rate and Planting Geometry on Wheat Yield

Field experiments were conducted to improve the wheat yield through adjustments in seed rate, spacing and sowing method at Indian Institute of Wheat and Barley Research, Karnal, Haryana during Rabi seasons of 2008-09 to 2012-13. The results showed that by using the precision seed drilling, seed rate from present recommendations of 100 kg/ha can be reduced to 75 kg/ha, however further reduction in seed rate caused yield reductions. If we translate 25% saving across the wheat growing area of India (30 mha) then we can have a huge saving of about 7.5 x 105 ton per year of wheat seed. The yield improved as row spacing was reduced from 22.5 to 15 cm, although yield was not significantly different among 15, 17.5 and 20 cm row spacing. Among three varieties (PBW 550, PBW 502 and DBW 17) maximum yield was produced by PBW 550. Among three crop establishment methods viz. no till (NT), conventional till (CT) and bed planted wheat, the lowest yield was obtained in bed planted system, whereas NT and CT had similar yield levels. In 2 and 3 rows bed planted system, 3 rows yielded more compared to 2 row system. Yield improved with bidirectional (criss-cross) sowing (1⁄2 + 1⁄2 seed) compared to uni-directional sowing. The results of the present studies clearly indicate that wheat yield can be improved through right choice of cultivar, seed rate, spacing and crop establishment methods (Crisscross sowing).