Heat stress tolerance in peas (Pisum sativum L.): Current status and way forward

In the era of climate change, the overall productivity of pea (Pisum sativum L.) is being threatened by several abiotic stresses including heat stress (HS). HS causes severe yield losses by adversely affecting several traits in peas. A reduction in pod yield has been reported from 11.1% to 17.5% when mean daily temperature increase from 1.4 to 2.2°C. High-temperature stress (30.5-33°C) especially during reproductive phase is known to drastically reduce both seed yield and germination. HS during germination and early vegetative stage resulted in poor emergence and stunted plant growth along with detrimental effects on physiological functions of the pea plant. To combat HS and continue its life cycle, plants use various defense strategies including heat escape, avoidance or tolerance mechanisms. Ironically, the threshold temperatures for pea plant and its responses are inconsistent and not yet clearly identified. Trait discovery through traditional breeding such as semi leaflessness (afila), upright growing habit, lodging tolerance, lower canopy temperature and small seeded nature has highlighted their utility for greater adaptation under HS in pea. Screening of crop gene pool and landraces for HS tolerance in a targeted environment is a simple approach to identify HS tolerant genotypes. Thus, precise phenotyping using modern phenomics tools could lead to increased breeding efficiency. The NGS (next generation sequencing) data can be associated to find the candidate genes responsible for the HS tolerance in pea. In addition, genomic selection, genome wide association studies (GWAS) and marker assisted selection (MAS) can be used for the development of HS tolerant pea genotypes. Additionally, development of transgenics could be an alternative strategy for the development of HS tolerant pea genotypes. This review comprehensively covers the various aspects of HS tolerance mechanisms in the pea plant, screening protocols, omic advances, and future challenges for the development of HS tolerant genotypes

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Not AvailableThis study reports the development of a garden pea genotype ‘VRPM–901–5’ producing five flowers per peduncle at multiple flowering nodes, by using single plant selection approach from a cross ‘VL-8 × PC-531’. In addition, five other stable genetic stocks, namely VRPM-501, VRPM–502, VRPM–503, VRPM–901–3 and VRPSeL–1 producing three flowers per peduncle at multiple flowering nodes were also developed. All these unique genotypes were of either mid- or late- maturity groups. Furthermore, these multi-flowering genotypes were identified during later generations (F4 onward), which might be because of fixation of certain QTLs or recessive gene combinations. Surprisingly, a common parent PC–531, imparting multi-flowering trait in ten cross combinations was identified. Thus, the genotype PC–531 seems to harbor some recessive gene(s) or QTLs that in certain combination(s) express the multi-flowering trait. The interaction between genotype and environment showed that temperature (11–20°C) plays a key role in expression of the multi-flowering trait besides genetic background. Furthermore, the possible relationship between various multi-flowering regulatory genes such as FN, FNA, NEPTUNE, SN, DNE, HR and environmental factors was also explored, and a comprehensive model explaining the multi-flowering trait in garden pea is proposed.ICA

Gene-Based Resistance to <i>Erysiphe</i> Species Causing Powdery Mildew Disease in Peas (<i>Pisum sativum</i> L.)

Globally powdery mildew (PM) is one of the major diseases of the pea caused by Erysiphe pisi. Besides, two other species viz. Erysiphe trifolii and Erysiphe baeumleri have also been identified to infect the pea plant. To date, three resistant genes, namely er1, er2 and Er3 located on linkage groups VI, III and IV respectively were identified. Studies have shown the er1 gene to be a Pisum sativum Mildew resistance Locus ‘O’ homologue and subsequent analysis has identified eleven alleles namely er1–1 to er1–11. Despite reports mentioning the breakdown of er1 gene-mediated PM resistance by E. pisi and E. trifolii, it is still the most widely deployed gene in PM resistance breeding programmes across the world. Several linked DNA markers have been reported in different mapping populations with varying linkage distances and effectiveness, which were used by breeders to develop PM-resistant pea cultivars through marker assisted selection. This review summarizes the genetics of PM resistance and its mechanism, allelic variations of the er gene, marker linkage and future strategies to exploit this information for targeted PM resistance breeding in Pisum

Gene-Based Resistance to Erysiphe Species Causing Powdery Mildew Disease in Peas (Pisum sativum L.)

Not AvailableGlobally powdery mildew (PM) is one of the major diseases of the pea caused by Erysiphe pisi. Besides, two other species viz. Erysiphe trifolii and Erysiphe baeumleri have also been identified to infect the pea plant. To date, three resistant genes, namely er1, er2 and Er3 located on linkage groups VI, III and IV respectively were identified. Studies have shown the er1 gene to be a Pisum sativum Mildew resistance Locus ‘O’ homologue and subsequent analysis has identified eleven alleles namely er1–1 to er1–11. Despite reports mentioning the breakdown of er1 gene-mediated PM resistance by E. pisi and E. trifolii, it is still the most widely deployed gene in PM resistance breeding programmes across the world. Several linked DNA markers have been reported in different mapping populations with varying linkage distances and effectiveness, which were used by breeders to develop PM-resistant pea cultivars through marker assisted selection. This review summarizes the genetics of PM resistance and its mechanism, allelic variations of the er gene, marker linkage and future strategies to exploit this information for targeted PM resistance breeding in Pisum.Not Availabl

Development and characterization of penta-flowering and triple-flowering genotypes in garden pea (<i>Pisum sativum</i> L. var. <i>hortense</i>)

<div><p>This study reports the development of a garden pea genotype ‘VRPM–901–5’ producing five flowers per peduncle at multiple flowering nodes, by using single plant selection approach from a cross ‘VL-8 × PC-531’. In addition, five other stable genetic stocks, namely VRPM-501, VRPM–502, VRPM–503, VRPM–901–3 and VRPSeL–1 producing three flowers per peduncle at multiple flowering nodes were also developed. All these unique genotypes were of either mid- or late- maturity groups. Furthermore, these multi-flowering genotypes were identified during later generations (F₄ onward), which might be because of fixation of certain <i>QTLs</i> or recessive gene combinations. Surprisingly, a common parent PC–531, imparting multi-flowering trait in ten cross combinations was identified. Thus, the genotype PC–531 seems to harbor some recessive gene(s) or <i>QTLs</i> that in certain combination(s) express the multi-flowering trait. The interaction between genotype and environment showed that temperature (11–20°C) plays a key role in expression of the multi-flowering trait besides genetic background. Furthermore, the possible relationship between various multi-flowering regulatory genes such as <i>FN</i>, <i>FNA</i>, <i>NEPTUNE</i>, <i>SN</i>, <i>DNE</i>, <i>HR</i> and environmental factors was also explored, and a comprehensive model explaining the multi-flowering trait in garden pea is proposed.</p></div

Pictorial presentation of a compound raceme of the garden pea, resulting in two, three and five flowers per peduncle at specific nodes.

<p>Green arrows indicate indeterminate growth of the inflorescence stem (I; I1); Green ovals represent leaves; Yellow circles represent flowers; Pink triangles are stubs terminating at each secondary inflorescence (I₂) axis; VM: Vegetative meristem; IM: Inflorescence meristem; I1M: Primary inflorescence meristem; I₂M: Secondary inflorescence meristem; FM: Floral meristem; NFI: First node of flower initiation.</p

Multi-flowering lines.

<p>(a) three flowers per peduncle; (b) four flowers per peduncle; and (c) three and four pods per peduncle.</p