Aims:To investigate the diversity of eco-distinct isolates of Magnaporthe oryzae for their morphological, virulence and molecular diversity and relative distribution of five Avr genes. Methods and Results:Fifty-two M. oryzae isolates were collected from different rice ecosystems of southern India. A majority of them (n = 28) formed a circular colony on culture media. Based on the disease reaction on susceptible cultivar (cv. HR-12), all 52 isolates were classified in to highly virulent (n = 28), moderately virulent (n = 11) and less-virulent (13) types. Among the 52 isolates, 38 were selected for deducing internal transcribed spacer (ITS) sequence diversity. For deducing phylogeny, another set of 36 isolates from other parts of the world was included, which yielded two distinct phylogenetic clusters. We identified eight haplotype groups and 91 variable sites within the ITS sequences, and haplotype-group-2 (Hap_2) was predominant (n = 24). The Tajima's and Fu's Fs neutrality tests exhibited many rare alleles. Furthermore, PCR analysis for detecting the presence of five Avr genes in the different M. oryzae isolates using Avr gene-specific primers in PCR revealed that Avr-Piz-t, Avr-Pik, Avr-Pia and Avr-Pita were present in 73.68%, 73.68%, 63.16% and 47.37% of the isolates studied, respectively; whereas, Avr-Pii was identified only in 13.16% of the isolates.Conclusions: Morpho-molecular and virulence studies revealed the significant diversity among eco-distinct isolates. PCR detection of Avr genes among the M. oryzae population revealed the presence of five Avr genes. Among them, Avr-Piz-t, Avr-Pik and Avr-Pia were more predominant. Significance and Impact of the Study:The study documented the morphological and genetic variability of eco-distinct M. oryzae isolates. This is the first study demonstrating the distribution of the Avr genes among the eco-distinct population of M. oryzae from southern India. The information generated will help plant breeders to select appropriate resistant gene/s combinations to develop blast disease-resistant rice cultivars. 7 MF716846.1 M. oryzae isolate AMA UOC-01 8 KT693184.1 M. oryzae strain UPM-PO Malaysia 9 KM249937.1 M. oryzae strain PO-FA01 10 MW042178.1 P. oryzae strain Pos-3 China 11 MW042177.1 P. oryzae strain Pos-2 12 MT588875.1 P. grisea isolate DW-2016-2 13 MW042176.1 P. oryzae strain Pos-1 14 MG642970.1 M. e grisea 15 MF946553.1 Pyricularia sp. strain F2 United Kingdom 16 MN203028.1 P. oryzae isolate T49 17 FN555121.1 M. oryzae 18 JX469384.1 M. oryzae culture-collection NFCCI:2605 India (NE) 19 MF678836.1 M. oryzae isolate Gudalur India (TN) 20 MF669475.1 M. oryzae isolate Nagaranai 21 MF668695.1 M. oryzae isolate Aduthurai 22 MF668692.1 M. oryzae isolate Maduranthakam 23 KM816799.1 M. oryzae strain w11-65 18S Korea 24 KM816801.1 M. oryzae strain w11-110 25 KM816797.1 M. oryzae strain w11-58 26 KM816796.1 M. oryzae strain w11-23 27 AB269937.1 M. grisea genes Japan 28 MT103091.1 P. oryzae isolate Mf3 Iran 29 MT103090.1 P. oryzae isolate Mb3 30 LC552959.1

No abstract

Rice is the most widely consumed cereal staple food for a significant part of the world, particularly in Asia. The Karnataka state of India is one of the highest rice producers, and it has a varied rice ecosystem from irrigated plains to rainfed hilly areas. The rice blast occurs at different severity in these ecosystems causing significant losses each year. The roving survey was carried out in the 120 villages of 18 districts distributed under five irrigated and two rainfed ecosystems of Karnataka during Kharif -2019. Within the irrigated ecosystems, the highest PDI was observed in the Kavery (50.85), followed by Varada (45.89), Bhadra (45.82), Tungabhadra (11.13), and Upper Krishna (10.58) command areas. In a rainfed ecosystem, the highest PDI was observed in the hilly ecosystem (53.38) and the least in the coastal ecosystem (3.73). Within 18 districts, the lowest PDI was observed in the Gadag district (1.68) of the Thungabhadra ecosystem, and the highest was observed in the Chikkamagalur district (81.60) of the hilly ecosystem. The disease was severe in the rainfed hilly ecosystem, followed by an irrigated and rainfed coastal ecosystem. This information is helpful in formulating the management strategies of rice blast in different rice ecosystems of Karnataka.

A new combination fungicide Tricyclazole 22.5% W/V (20.36% W/W) + Azoxystrobin 7.5% W/V (6.79% W/W) was tested against rice sheath blight diseases under field condition during Kharif 2015 and Rabi 2015-16. The combination fungicide Tricyclazole 22.5% W/V (20.36% W/W) + Azoxystrobin 7.5% W/V (6.79% W/W) at 1000 ml/ha was found effective against sheath blight diseases by recording least Percent Disease Index (PDI) of 14.44 during Kharif 2015 and 13.35 during Rabi 2015-16. Significant increase in grain yield (61.53 q/h) was also observed in the plots treated with Tricyclazole 22.5% W/V

Bacterial leaf blight (BLB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the significant constraints for rice production. A study was carried out to analyze the virulence, genetic diversity, and population structure of Xoo isolates collected from different rice ecosystems in Karnataka, India. The taxonomic identity of all 54 isolates was confirmed using a Xoo-specific PCR assay. The virulence assay on a set of twenty-eight near-isogenic differentials identified nine pathotype groups (KPthX-1 to KPthX-9). Among them, KPthX-6 was highly virulent, whereas KPthx-2 was less virulent. Differentials with four and five resistance (R) genes (Xa4 + xa5 + xa13 + Xa21, Xa4 + Xa7 + xa13 + Xa21, and Xa4 + xa5 + Xa7 + xa13 + Xa21) were effective against all the pathotypes. Further, genetic diversity was deduced using a universal marker set, JEL-1 and JEL-2, complementary to a conserved repetitive sequence IS1112. The amplicon size and numbers varied from 100 bp to 3 Kbp and 1 to 25. Based on the amplicon counts, Jaccard's co-efficient and phylogenetic analyses were carried out and categorized the 54 isolates into three clusters (I to III). Cluster II contains the maximum number of isolates ( 27), followed by cluster I (23 isolates) and cluster III (one isolate). The structure analysis categorized the isolates into five subgroups, viz SG1, SG2, SG3, SG4, and SG5 indicate the existence of five subpopulations. The present study has identified the genetic and virulence diversity of the Xoo population and reported the effective R gene/s for different rice ecosystems, which can be used in the breeding program for the eco-specific management of BLB of rice.