Peer review

Phosphorus (P) is an essential macro-nutrient required for growth and development of all crop plants including rice. Low availability of P in the soils manifests in terms of impeding crop growth leading to yield losses in rice. Adequate genetic variability for low soil P tolerance and also P use efficiency has been documented in rice and a major QTL called Pup1, conferring tolerance to low soil P has been identified, characterized and cloned from an Indian landrace, Kasalath. In the present study, a set of 98 germplasm lines collected from North-Eastern part of India were characterized for low soil P tolerance by screening them in a plot with low soil P (with available P < 2.0 kg ha−1) and also a plot with normal soil P (available P > 20 kg ha−1). The rice lines showed significantly high genetic variability for low soil P tolerance associated traits. Stress indices were estimated based on yield under normal and low soil P conditions and cluster analysis based on the stress indices; yield under normal and low soil P condition grouped the genotypes into highly tolerant, tolerant and sensitive to low soil P. Among the rice lines, 18 showed tolerance to low soil P (i.e. yield reduction < 70% in low soil P condition). The genotypic analysis based on Pup1 associated molecular markers revealed the presence of complete or partial Pup1 genomic region in most of the germplasm lines. Interestingly, a landrace called Wazuhophek was observed to be completely devoid of Pup1 and hence it can serve as novel source for low P tolerance.

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