Agro-morphological Characteristics of Weedy Rice (Oryza sativa f. spontanea): A Precious Genetic Resource for Rice Improvement

Abstract

Weedy rice (Oryza sativa f. spontanea) is considered a feral crop wild relative (CWR) of cultivated rice (O. sativa) and has become common weeds of rice fields globally. Weedy rice has been generated either through hybridization or gene flow process between wild rice O. rufipogon and cultivated rice during domestication event. Weedy rice is a conspecific to cultivated rice under the family poaceae which are annual and self-pollinating plant. Weedy rice retains a wide range of diversity in the phenotypic features for adaptation in natural harsh climatic conditions. Many biotic and abiotic stresses tolerance traits have been accumulated slowly through natural evolution to withstand climatic fluctuation. Agromorphological traits were assessed in weedy rice including wild rice and cultivated rice following DUS test protocol for proper characterization and comparative studies. Physicochemical properties such as ASV, GT, GC and sensory based aroma were carried out for six rice genotypes. Phenol test conducted to categories the rice genotypes. Caryopsis ultrastructure was studied using SEM for more clarity in grain fine structural anatomy. Plant height in weedy rice is on average 94.40 cm, and in wild rice it is 120.19 cm. Flag leaf length is 33.69 cm in weedy rice, in case of wild rice it is 21.21cm. Thousand grain weight is 22.50 g in weedy rice whereas in wild rice it is only 13.50 g. Grain per panicle is high in weedy rice (117.10 grain/panicle) but very less in wild rice (39.80 grain/panicle). Weedy rice showed phenol positive reactivity due to presence of PPO (enzyme). Sadanunia was negative in phenol test, is a local aromatic variety. Starch granules mainly CSG ranges from 5.88 to 13.33 μm with irregular spherical structure in weedy rice. In wild rice, CSG is polyhedral structure without any angularity (5.45 μm to 16.26 μm in size). CSG are various shape and size, spherical to polyhedral with moderate angularity (3.53 to 13.748 μm in size) in Banni. PB is moderately present with less impression of PB (0.692 to 1.53 μm in diameter) in all the rice genotypes. It was detected that CSG ranges from polyhedral to spherical in shape and size from 3.53 to 23.07 μm. Both wild rice (O. rufipogon) and weedy rice (O. sativa f. spontanea) have long awn with barbed features (329.169 to 358.489 μm). Main aim of the present work is to explore the reservoir of natural variations in weedy rice based on agro-morphological characteristics and ultra-structure of the caryopsis under SEM and to utilize feral rice for the crop improvement program in near future. Therefore, it needs conservation through on farm in situ process and utilization in the breeding program to develop climate resilient high yielding improved rice varieties with quality grain for sustainable food security. This precious genetic resource of Oryza species is to be utilized in future breeding program to introgress the naturally occurring stress tolerance genes for both biotic and abiotic tolerance potentiality to develop climate ready rice varieties.