Identification of High-Temperature Tolerant Lentil (Lens culinaris Medik.) Genotypes through Leaf and Pollen Traits

Abstract

Rising temperatures are proving detrimental for various agricultural crops. Cool-season legumes such as lentil (Lens culunaris Medik.) are 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 38 core lentil accessions were screened for heat stress tolerance by sowing 2 months later (first week of January; max/min temperature >32/20°C during the reproductive stage) than the recommended date of sowing (first week of November; max/min temperature <32/20°C during the reproductive stage). Screening revealed some promising heat-tolerant genotypes (IG2507, IG3263, IG3297, IG3312, IG3327, IG3546, IG3330, IG3745, IG4258, and FLIP2009) which can be used in a breeding program. Five heat-tolerant (HT) genotypes (IG2507, IG3263, IG3745, IG4258, and FLIP2009) and five heat-sensitive (HS) genotypes (IG2821, IG2849, IG4242, IG3973, IG3964) were selected from the screened germplasm and subjected to further analysis by growing them the following year under similar conditions to probe the mechanisms associated with heat tolerance. Comparative studies on reproductive function revealed significantly higher pollen germination, pollen viability, stigmatic function, ovular viability, pollen tube growth through the style, and pod set in HT genotypes under heat stress. Nodulation was remarkably higher (1.8–22-fold) in HT genotypes. Moreover, HT genotypes produced more sucrose in their leaves (65–73%) and anthers (35–78%) that HS genotypes, which was associated with superior reproductive function and nodulation. Exogenous supplementation of sucrose to in vitro-grown pollen grains, collected from heat-stressed plants, enhanced their germination ability. Assessment of the leaves of HT genotypes suggested significantly less damage to membranes (1.3–1.4-fold), photosynthetic function (1.14–1.17-fold) and cellular oxidizing ability (1.1–1.5-fold) than HS genotypes, which was linked to higher relative leaf water content (RLWC) and stomatal conductance (gS). Consequently, HT genotypes had less oxidative damage (measured as malondialdehyde and hydrogen peroxide concentration), coupled with a higher expression of antioxidants, especially those of the ascorbate–glutathione pathway. Controlled environment studies on contrasting genotypes further supported the impact of heat stress and differentiated the response of HT and HS genotypes to varying temperatures. Our studies indicated that temperatures >35/25°C were highly detrimental for growth and yield in lentil. While HT genotypes tolerated temperatures up to 40/30°C by producing fewer pods, the HS genotypes failed to do so even at 38/28°C. The findings attributed heat tolerance to superior pollen function and higher expression of leaf antioxidants.

Impact of heat stress during seed filling on seed quality and seed yield in lentil (Lens culinarisMedikus) genotypes

“…Our studies showed that heat stress at the time of seed filling drastically reduced the components of yield and quality of seeds in both heat‐tolerant (HT) and heat‐sensitive (HS) lentil genotypes. We previously reported the damaging effects of high temperature on traits related to pollen function in lentil, which were associated with pod set and seed yield . In the present study, we investigated the adverse effects of heat stress on seed quality in lentil genotypes using proximate analysis and other seed component analyses.…”

“…Lentil ( Lens culinaris Medikus) is a vital cool‐season crop that is highly sensitive to rising temperatures . Lentil requires low temperatures at the time of vegetative growth but warm temperatures to mature; optimum growth occurs from 18–30 °C .…”

Quantifying the Impact of Heat Stress on Pollen Germination, Seed Set, and Grain Filling in Spring Wheat

“…4. The observed decrease in pollen germination under heat stress at or during anthesis can be associated with damages to pollen physical structure, pollen wall composition, or lower energy (sugar) status (Jagadish et al, 2010;Jiang et al, 2015;Djanaguiraman et al, 2017a;Sita et al, 2017). 1) and grain filling (HS Grain-filling for 30 d in Exp.…”

Influence of drought and heat stress, applied independently or in combination during seed development, on qualitative and quantitative aspects of seeds of lentil (Lens culinarisMedikus) genotypes, differing in drought sensitivity

“…High temperature is frequently associated with reduced availability of water; hence, crops grown in tropical and subtropical environments need to be evaluated for their responses to the combination of heat and drought stress (Barnabás et al, ). The individual effects of heat and drought stress have been investigated in many crops (Shanker et al, ) including lentil (Sita et al, ); however, studies on their combined effects are less common, despite being strongly associated and having severe impact on growth and productivity of several crops (Cvikrová, Gemperlová, Martincová, & Vanková, ; Lipiec, Doussan, Nosalewicz, & Kondracka, ; Lobell et al, ; Nankishore & Farrell, ; Prasad, Pisipati, Momcilovic, & Ristic, ; Rollins et al, ; Shinohara & Leskovar, ). The occurrence of drought, accompanied by heat stress, is likely to increase in the near future (IPCC, ), which highlights the need to investigate crop responses to combined heat and drought stresses (Zandalinas, Mittler, Balfagon, Arbona, & Gomez‐Cadenaz, ).…”

“…Cool‐season food legumes are adapted to low and mild temperature environment and hence show high sensitivity to heat stress, as observed in chickpea (Kaushal et al, ) and lentil (Sita et al, ). Our earlier studies have indicated lentil ( L. culinaris Medikus) to be more sensitive than chickpea to high temperature, both at vegetative as well as reproductive stages (Bhandari et al, ; Sita et al, ). The optimum temperatures for lentil growth range from 18 to 30 °C (Sinsawat et al ; Roy, Tarafdar, Das, & Kundagrami, ), with warm temperatures needed for maturity.…”