Phenotyping and Genotype × Environment Interaction of Resistance to Leaffolder, Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae) in Rice

Rice leaffolder, Cnaphalocrocis medinalis is one of the key foliage feeding insects of great concern throughout Asia as it results in significant yield losses. High visibility of damage is triggering farmers to apply toxic pesticides for its management. Therefore, it is vital to identify new stable sources of resistance for leaffolder. Phenotyping of 160 recombinant inbred lines (RILs) of a cross between a resistant parent, W1263 and a susceptible parent, TN1 using a rapid field screening method for three seasons resulted in identification of nine RILs as stable sources of resistance to rice leaffolder. Phenotypic frequency distributions were found continuous indicating that the resistance is a quantitative trait governed by polygenes. Phenotypic data for three seasons were analyzed using Genotype and Genotype × Environment Interaction (GGE) analysis for identification of stable resistant lines. Additive main effect and multiplicative interaction (AMMI) analysis showed that 86.41% of the total sum of square of damaged leaf area was attributed to genotype (GEN) effect; 0.48% to environment (ENV) effects and 5.68% to genotype by environment (G × E) interaction effects. Damage area, damage score and leaf length showed very high broad-sense heritability across three environments. However, leaf width had low heritability indicating higher environment influence. Phylogenetic analysis grouped these 160 RILs and parents into five clusters based on resistant reaction. AMMI and GGE biplot analysis revealed that stable genotypes G8 (MP114) and G3 (MP108) with lower damage area and damage score can be utilized in developing cultivars with leaffolder resistance

Multiparent-Derived, Marker-Assisted Introgression Lines of the Elite Indian Rice Cultivar, ‘Krishna Hamsa’ Show Resistance against Bacterial Blight and Blast and Tolerance to Drought

Major biotic stresses viz., bacterial blight (BB) and blast and brown plant hopper (BPH) coupled with abiotic stresses like drought stress, significantly affect rice yields. To address this, marker-assisted intercross (IC) breeding involving multiple donors was used to combine three BB resistance genes—xa5, xa13 and Xa21, two blast resistance genes—Pi9 and Pi54, two BPH resistance genes—Bph20 and Bph21, and four drought tolerant quantitative trait loci (QTL)—qDTY1.1, qDTY2.1, qDTY3.1 and qDTY12.1—in the genetic background of the elite Indian rice cultivar ‘Krishna Hamsa’. Three cycles of selective intercrossing followed by selfing coupled with foreground selection and phenotyping for the target traits resulted in the development of 196 introgression lines (ILs) with a myriad of gene/QTL combinations. Based on the phenotypic reaction, the ILs were classified into seven phenotypic classes of resistance/tolerance to the following: (1) BB, blast and drought—5 ILs; (2) BB and blast—10 ILs; (3) BB and drought—9 ILs; (4) blast and drought—42 ILs; (5) BB—3 ILs; (6) blast—84 ILs; and (7) drought—43 ILs; none of the ILs were resistant to BPH. Positive phenotypic response (resistance) was observed to both BB and blast in 2 ILs, BB in 9 ILs and blast in 64 ILs despite the absence of corresponding R genes. Inheritance of resistance to BB and/or blast in such ILs could be due to the unknown genes from other parents used in the breeding scheme. Negative phenotypic response (susceptibility) was observed in 67 ILs possessing BB-R genes, 9 ILs with blast-R genes and 9 ILs harboring QTLs for drought tolerance. Complex genic interactions and recombination events due to the involvement of multiple donors explain susceptibility in some of the marker positive ILs. The present investigation successfully demonstrates the possibility of rapid development of multiple stress-tolerant/resistant ILs in the elite cultivar background involving multiple donors through selective intercrossing and stringent phenotyping. The 196 ILs in seven phenotypic classes with myriad of gene/QTL combinations will serve as a useful genetic resource in combining multiple biotic and abiotic stress resistance in future breeding programs

Germplasm Collection from Last Remnants of Rice Landrace Genetic Diversity in High Altitude Areas of Kashmir Himalayas

The aim of the present study was to know about past and present cultivation and status of rice landraces in Kashmir province of Indian Himalayan state of Jammu and Kashmir. Tremendous genetic diversity has existed in past in paddy fields throughout Kashmir especially in remote high altitude areas and more than 4 dozen named landraces have been recorded in the literature. Elderly farmers in their sixties and beyond still fondly remember these landraces and often recall quality attributes in many of these genetic resources. Most of the landraces have now disappeared from the local production system and only few are presently being cultivated and that too in a very small area. The reasons as to why farmers lost interest in these genetic resources and why few landraces are still popular in farmer fields have been discussed. Our study has revealed that variability in paddy fields has now been drastically reduced to few high altitude areas where also it is seriously endangered. We argue that collection of well adapted traditional varieties from these ‘last remnants of rice genetic diversity’ in Kashmir is an important task especially under prevailing uncertain social and climatic conditions to ensure a sustainable environment. 32 germplasm accessions of some landraces have been collected during our survey in these areas. These have been deposited in National Seed Gene Bank at NBPGR, New Delhi for conservation and characterization

Genetic analysis of early seedling vigour in Oryza glaberrima accessions under laboratory and direct-seeded rice conditions

Breeding for “weed competitive” cultivars is a prioritized goal under direct seeded rice (DSR) conditions for achieving higher grain yields. Early seedling vigour (ESV) is an imperative trait that imparts weed competitiveness through initial rapid growth and uniform crop establishment. African rice species Oryza glaberrima has been recognised as potential donors for weed competitive traits due to their early vegetative vigour. In the present study, 29 accessions of O. glaberrima were evaluated for early seedling vigour traits under laboratory and DSR conditions. Seedling vigour index-I and II estimated from the paper roll method under laboratory condition revealed that six O. glaberrima accessions (EC861796, EC861801, EC861804, EC861814, EC861819 and EC861820) had higher/similar seedling vigour indices than high vigour check Sabita. In addition, during Kharif 2017 and Rabi 2018, O. glaberrima accessions were phenotyped for nine ESV traits, e.g. seedling height, number of leaves/tillers, leaf area, shoot fresh/dry weight, absolute growth rate, specific leaf area and crop growth rate under DSR condition. Significant genetic variation and genotype × environment interaction was observed for ESV traits under DSR condition. The heritability estimates for ESV traits were ranging from low to high, indicating complex inheritance of the trait. The study identified six accessions of O. glaberrima (EC861787, EC861790, EC861792, EC861795, EC861819 and EC861820) as promising accessions with early seedling vigour based on mean performance in both seasons under direct seeded rice condition. Thus, our study demonstrated inherent nature of early seedling vigour in O. glaberrima and these promising accessions could be exploited for breeding weed-competitive rice cultivars