Rice breeding in India: eight decades of journey towards enhancing the genetic gain for yield, nutritional quality, and commodity value

The contribution of rice breeding for ensuring food security in India is well known. Organized rice breeding is nearly eight decades old in the country which started with the establishment of Central Rice Research Institute at Cuttack in the year 1946. Thereafter, the rice breeding programmes have undergone several transformations to meet the needs of stakeholders at both regional and national level. For all the rice ecologies of the country, high yielding varieties were developed by deployment of the required genes. Initially the objectives were met only through phenotypic selections based on breeders' own skills. With time, the rice breeders of the country adopted the advances in the fields of science and technologies especially in the areas of plant sciences. From the initial phase of users of methodologies and materials developed elsewhere, the rice scientists of India have transformed themselves to discover useful genes from the vast germplasm resources of the country and utilize them as per the local requirements through marker assisted selection. Despite the progress made in last few decades, the genetic gain from breeding programmes is becoming stagnant over time and the increased yield in current years are now attributed more to production interventions. The rice breeders of India need to take advantage of the recent developments of speed breeding, whole genome sequences of various Oryza species, advanced phenomics and computational methods, high throughput genotyping platforms, tissue culture and genome editing tools etc. to shift from its current approach of "breeding by chance" to "breeding by design" and to bring significant improvements in the rate of genetic gain per generation.

Rice Blast Prevalence in Smallholder Rice Farmlands in Uganda

Rice blast disease remains the most important contributor to low and stagnated rice yields in Uganda. However, the role of the smallholder farming system in shaping the prevalence of the disease in the country is not known. In 2015B and 2016A, we surveyed smallholder rice farmlands in 27 districts of Uganda and recorded blast incidence, severity, and symptoms expression. Infected rice samples taken from the infected plants were sub-cultured on PDA media to confirm the pathogen and obtain isolates for the establishment of a core collection for breeding work. Rice blast prevalence in the districts varied from 50-100% and the national average stood at 72.61%, higher than that recorded five years ago. Mean incidence and severity varied significantly (< 0.001) with the highest incidence (96.8%) recorded in Luwero district and the least (21.3%) was recorded in the Amuru district. However, the eastern region recorded the highest average incidence (74.5%) followed by the central, the northern, and Mid-western regions. In the rice ecologies, the highest blast incidence was recorded in the rain-fed lowland rice (72.18%) followed by irrigated lowland (59.53%) and rain-fed upland rice (47.27%). This is the first report on the prevalence of blast in smallholder rice farmlands in Uganda and showed a higher prevalence of the disease.

Genetic Analysis and Molecular Identification of Virulence in Xanthomonas oryzae pv. oryzae Isolates

Bacterial leaf blight (BLB) of rice is a very destructive disease worldwide and is caused by Xanthomonas oryzae pv. oryzae (Xoo). The aim of the present study was to examine if the Xoo virulence pathotypes obtained using phenotypic pathotyping could be confirmed using molecular approach. After screening of 60 Operon primers with genomic DNA of two Xoo isolates (virulent pathotype, Vr, and mildly virulent pathotype, MVr), 12 Operon primers that gave reproducible and useful genetic information were selected and used to analyze 50 Xoo isolates from 7 West African countries. Genetic analysis revealed two major Xoo virulence genotypes (Mta and Mtb) with Mta having two subgroups (Mta1 and Mta2). Mta1 (Vr1) subgroup genotype has occurrence in six countries and Mta2 (Vr2) in three countries while Mtb genotype characterized mildly virulence (MVr) Xoo isolates present in five countries. The study revealed possible linkage and correlation between phenotypic pathotyping and molecular typing of Xoo virulence. Xoo virulence genotypes were known to exist within country and there was evidence of Xoo pathogen migration between countries. Durable resistance rice cultivars would need to overcome both Mta and Mtb Xoo virulence genotypes in order to survive after their deployment into different rice ecologies in West Africa.