Some peas like it hot


Farm­ers across the world pro­duce be­tween 10 and 13 mil­lion tons of field pea every year. That makes it a top legume crop, just be­hind dry beans and chick­peas.

But as the global cli­mate changes and tem­per­a­tures con­tinue to rise, heat stress is be­com­ing a ma­jor lim­it­ing fac­tor for pea cul­ti­va­tion.

Pea blos­soms with­out pod as a re­sult of heatA new study in­di­cates that pea plants with some spe­cific traits – such as longer flow­er­ing time and higher pod num­bers – may be more re­sis­tant to heat stress.

The re­searchers also gained new in­sights into the ge­net­ics of heat tol­er­ance in pea.

“In some years, the older va­ri­eties of pea weren’t grow­ing very well be­cause of heat stress,” says Ros­alind Bueck­ert, lead au­thor of the study. “We wanted to find new va­ri­eties that have ro­bust and con­sis­tent yields in a warm­ing world.”

Ac­cord­ing to Bueck­ert, a plant sci­en­tist at the Uni­ver­sity of Saskatchewan, “tol­er­ance to heat stress in peas seems to be de­pen­dent on quite a few traits.” The study found that two traits, how­ever, are most im­por­tant: higher pod num­bers and longer flow­er­ing du­ra­tion.

Bueck­ert and her col­leagues Tom Warkentin and Shaom­ing Huang are the first to un­cover the lo­ca­tion of genes that af­fect heat stress.

“Heat stress means fewer flow­ers, fewer pods, and ul­ti­mately, lower yields,” says Bueck­ert. Va­ri­eties of pea that have more pods to be­gin with have higher yields af­ter a heat-stress event.

Sim­i­larly, “if a pea va­ri­ety flow­ers for a longer time, it has more op­por­tu­ni­ties to have a higher yield, even un­der heat stress,” says Bueck­ert. That’s be­cause the plant has more time to re­cover from ex­treme weather events dur­ing flow­er­ing.

But too long of a flow­er­ing time can lead to other prob­lems. “You need the right bal­ance of the veg­e­ta­tive and re­pro­duc­tive phases,” says Bueck­ert.

To de­ter­mine which traits are im­por­tant for heat re­sis­tance in peas, Bueck­ert and her col­leagues crossed two com­monly used va­ri­eties of pea, CDC Cen­ten­nial and CDC Sage. Then the re­searchers eval­u­ated more than a hun­dred new va­ri­eties of pea de­rived from this cross.

“By cross­ing two dif­fer­ent va­ri­eties of pea, you may be able to breed off­spring with traits be­yond those of ei­ther par­ent,” says Bueck­ert. For ex­am­ple, some of the off­spring tested in this study were more heat-re­sis­tant than ei­ther CDC Sage or CDC Cen­ten­nial.

The re­searchers cul­ti­vated these new va­ri­eties of pea for two grow­ing sea­sons in Saskatchewan.

One batch was seeded at a typ­i­cal time for pea cul­ti­va­tion, mid-May. A sec­ond batch was started in early June. These plants flow­ered later in the year when tem­per­a­tures are higher. This al­lowed the re­searchers to test for pea va­ri­eties that grew bet­ter and had higher yields in warmer weather.

“Iden­ti­fy­ing traits that make pea plants more re­sis­tant to heat stress is one piece of the puz­zle,” says Bueck­ert. The other piece is bet­ter un­der­stand­ing the ge­net­ics of these traits.

Tra­di­tion­ally, re­searchers used vis­i­ble traits, such as pod num­ber, to se­lect crop va­ri­eties that grow well in spe­cific en­vi­ron­ments. How­ever, map­ping out the per­ti­nent ge­netic in­for­ma­tion helps fo­cus the work. Re­searchers can iden­tify spe­cific ge­netic lo­ca­tions for a trait within the pea’s ge­netic map. From there, re­searchers can more re­li­ably se­lect crop va­ri­eties.

“The more work we can do with ge­netic lo­ca­tions and molec­u­lar tech­niques, the more ef­fi­cient we will be,” says Bueck­ert.

While flow­er­ing du­ra­tion and pod num­ber are the two most im­por­tant traits for heat re­sis­tance in peas, the re­searchers are also ex­am­in­ing other traits that can con­trib­ute. For ex­am­ple, “semi-leaf­less va­ri­eties of pea are bet­ter at deal­ing with heat stress than leafy va­ri­eties,” says Bueck­ert.

Fu­ture re­search will aim to iden­tify more of these traits, and fur­ther in­crease our un­der­stand­ing of the ge­netic ba­sis of heat re­sis­tance in peas.


Ex­treme heat has re­sulted in these pea blos­soms not pro­duc­ing a pod

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