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Study the Heat Tolerance in Lentil Under Field Condition (2016--2017)

A. K. M. M. ALAM
Pulses Research Centre, RARS, BARI, Ishurdi, Pabna

Abstract/ Executive Summary:

Winter legumes lentil (Lens culinaris Medik.) is sensitive to even small increases in temperature during the reproductive stage, hence the need to explore the available germplasm for heat tolerance as well as its underlying mechanisms. In the present study, a set of 10 core lentil accessions were screened for heat stress tolerance by sowing 2 months later than the recommended date of sowing. Among the genotypes, G₃showed the highest number of pod/plant and yield/plant followed by G₄ and G₁₀ at late sown (LS2) under field conditions.

Keywords: Heat tolerant, Lentil, Germplasm

Location: PRSS, BARI Gazipur

Start Date: 00-00-2016

End Date: 00-00-2017

Program Area: Variety and Species

Commodity: Lentil

Objectives:

The objective of this study was to (a) screen the core lentil germplasm for heat tolerance and (b) understand the basis of heat tolerance using contrasting genotypes.

Methodology:

The seeds of ten lentil (Lens culinaris Medik.) genotypes were grown at PRSS, BARI Gazipur during 2016-17 in RCBD with three replications. Seeds of the lentil genotypes were sown in the field on three sowing dates: (1) 2^nd week of November (15/11/16) 2016 for normal sowing and (2) first week of December (5/12/16) 2016 and (3) 3^rd week of December (20/12/16) for late sowing to impose heat stress at the reproductive stage. For normal-sown plants, temperatures ranged from 22-30⁰C (maximum); 2^nd sowing temperatures ranged from 24.5-32⁰C (maximum) and 3rd sowing temperatures ranged from 26.5-34⁰C during the reproductive stage. Genotypes were sown on two sowing dates to ensure heat stress during reproductive growth. The plants were grown in the natural environment. Lentils are normally sown in November, the temperatures throughout reproductive development remain below 32?C/20?C; sowing in December would ensure that plants were exposed to heat stress (above >32/20⁰C). The observations were made on days to flowering, pollen viability; podding and maturity, pod number, unfilled pod and seed weight were recorded from randomly selected 10 plants per genotype in three replications (30 plants/genotype). The flowers were tagged and examined for pollen viability. In order to see the impact of late-sown conditions on seed size data were recorded on 100-SW under late- and normal-sown conditions.

Pollen Viability

Pollen viability was tested on terminal branch pollen grains with 0.5% acetocarmine/Alexander stain (Kaushal et al., 2013). The pollen grains were collected from flowers, which opened on the same day. The pollen grains collected from flowers were pooled and tested for their viability (Alexander, 1969). The pollen germination on the stigma and pollen tube growth was also examined. The flowers were collected 1–2 days after anthesis and fixed in acetic alcohol (1:3) for 24 h and then transferred to 8N NaOH for 6 h at 60⁰C for clearing purposes.

Source of Information: Annual Research Report 2016-2017, Pulses Research Centre, RARS, BARI, Ishurdi, Pabna

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Ten lentil genotypes were screened for heat tolerance at the reproductive stage on the basis of days to flowering, pollen viability, podding and maturity, pod number, unfilled pod and seed weight. Observations revealed that in normal-sown (NS) plants the days to maturity ranged from 92-102 across the screened genotypes, but in 92-105 days & 100-105 days in late-sown (LS1 and LS2) plants due to heat stress. On the basis of the number of pods/plant at a higher temperature, G₃ and G₄, showed more number of pods/plant at LS2 and thus showed highly heat tolerant. In the present investigation, we observed unfilled pods on the terminal branch which could be useful to select tolerant genotypes at a higher temperature. Late-sown plants produced fewer filled pods might be due to heat stress than NS plants. Among the different genotypes, the highest number of the filled pod was observed in G₁₀ at LS2 followed by G₉, G₂, and G8 which revealed that these genotypes are sensitive to terminal heat stress. Under LS conditions, the genotypes G₃, G₄ and G₆produced few unfilled pods compare to other genotypes. Besides these pollen viability and pollen tube growth were also observed. Most of the genotypes pollen was viable at late sown condition but they are failing to germinate. In the case of lentil optimum temperature for fertilization <32/20⁰C but LS2 genotypes stand > 32/20⁰ during the flowering and pod filling stage. Considering 100 seed weight and yield /plant G₃ and G₄ showed better performances under late shown conditions. We observed significantly higher unfilled pods for some genotypes, indicating the impacts of high temperature on pod formation. In legumes, high temperature during anthesis reduces seed set due to impaired pollen tube growth and fertilization. In the present investigation, impacts of high temperature were also observed on seed size. Seed size comparatively lower than other genotypes due to the efficient accumulation of photosynthesis in seeds during grain filling at higher temperatures. High temperature leads to pollen sterility and hence seed yield depends on the temperature during pollen development. In the present study, high pollen viability was observed for two genotypes (G₃ and G₄) and showed a highly positive correlation with the number of pods per plant. The present investigation shows that heat stress significantly affects yield-related traits and seed yield. Filled and unfilled pods on a single plant basis and on the terminal branch are important traits for phenotyping heat tolerance under field conditions.

Knowledge Management: Report/Proceedings